Shape Deformation Research Articles

Parametrically excited shape distortion of a submillimeter bubble

The existence of finite amplitude shape distortion caused by parametrically excited surface instabilities for a gas bubble in water driven by a temporally periodic, spatially uniform pressure field in an axisymmetric geometry is investigated. Employing a nonlinear coupled system of equations which includes shape mode interactions to third order, the resultant spherical oscillations, translation, and shape distortion of the bubble are modelled, placing no restriction on the size of the spherical oscillations. The model accounts for viscous and thermal damping with compressibility effects. The existence of synchronous and higher order parametrically induced sustained, finite amplitude, periodic shape deformation is demonstrated. The excitement of an odd shape mode via the synchronous mechanism is shown to give rise to linear bubble self-propulsion. For larger driving amplitudes, it is shown that more than one shape mode can be parametrically excited at the same driving frequency but by different resonance mechanisms, leading to more involved shape deformation and the increased possibility of bubble self-propulsion.

Dimethyl sulfoxide mediated high-fidelity 3D printing of hydrogels

Owing to flexible structural design and rapid prototyping manufacturing, 3D printable hydrogels with solid-like and fluid-like characters have emerged as a promising candidate for biomedical engineering, soft robotics, and flexible electronics. However, existing 3D printing of hydrogel place substantial constraints on hydrogel high-fidelity of the printed hydrogel complex structures due to the shape deformation and collapse caused by water evaporation. Herein, we propose a mixed solvent printing strategy followed with water dialysis to achieve vat photopolymerization 3D printing of high-fidelity hydrogel structure by restraining water evaporation. Concretely, dimethyl sulfoxide (DMSO) is introduced into the hydrogel ink as co-solvent to improve the anti-dehydration performance during 3D printing. The as-prepared gels are then transformed into hydrogels with good fidelity and excellent performance through solvent exchange and water dialysis. Enabled by these characteristics, various functional devices with complex structures are demonstrated with the present high-fidelity 3D printing of diverse hydrogels. The solvent assisted high-fidelity hydrogel 3D printing protocol combining with the compatibility to various high-performance hydrogels is believed to be promising for wearable devices, wound dressings, electronic skin, and intelligent robots.

Normal deformation of a soft lipid-based microtube in response to the flow generated by a tangential motion of a nearby microbead

In this study, we experimentally examine the deformation of a micrometer-scale soft membrane in response to a periodic shear flow. We fabricate long and straight cylindrical-shaped soft microtubes from lipid bilayers as part of this study. A microtube with a diameter of about 1–5 μm is moved parallel to its longitudinal axes. At the same time, a polystyrene microbead, trapped by optical tweezers, is forced to stay near the external surface of the microtube. We study the induced shape deformation in the microtube for different shearing parameters. The effects related to the size of the bead, its distance to the surface of the microtube, and their relative speed are analyzed. The overall results qualitatively demonstrate the impact of shearing on the shape of the soft membrane.

Left atrial myocardial strain, assessed by the method of speckle-tracking echocardiography, as a marker of fibrosis in patients with ischemic stroke

Introduction. Cardioembolic stroke (CE) is one of the main etiopathogenetic subtypes of ischemic stroke and accounts for approximately 17% of all patients with ischemic stroke. Currently, there is a search for widely accessible radiological diagnostic methods that allow for the accurate diagnosis of left atrial (LA) dysfunction. Among these methods is transthoracic strain echocardiography (EchoCG), which provides additional information about the degree of deformation and change in shape of the LA during the cardiac cycle. To date, the association between strain EchoCG parameters and the severity of fibrotic changes in the LA among patients with CE remains unstudied.Objective. To evaluate the relationship between myocardial deformation parameters of the left atrium and the degree of fibrosis in patients with CE, as well as the impact of LA myocardial deformation changes on the prognosis of patients with CE.Materials and Methods. A prospective cross-sectional study included 132 patients who underwent evaluation and treatment in the Department of Emergency Neurology at the N.V. Sklifosovsky Research Institute for Emergency Medicine from 2020 to 2022. Group 1 consisted of 12 patients who died during hospitalization, while Group 2 comprised 120 patients who were discharged from the department after receiving treatment.Results. Deceased patients, compared to survivors, were characterized by the presence of LA myocardial remodeling. Statistically significant differences in LA myocardial deformation parameters were found between the study groups. Correlation analysis revealed statistically significant associations between LA myocardial deformation parameters and the severity of fibrotic changes. In the multifactorial logistic regression model, significant effects on the prognosis of patients were observed for LA strain peak systolic circumferential strain rate (LA-Scs) and LA strain peak systolic longitudinal strain rate (LA-Sls), with each 1% increase in the parameter associated with a 1.128-fold and 1.075-fold increase in the odds of a lethal outcome, respectively (OR: 1.128, 95% CI: 1.021–1.25, p = 0.017, and OR: 1.075, 95% CI: 1.009–1.15, p = 0.025).Conclusions. The conducted study established a strong correlation between LA myocardial deformation and LA fibrosis and the degree of fibrosis in the LA. LA myocardial deformation parameters can be used in risk stratification for the development of a lethal outcome in patients with CE.

Achieving high strength and energy absorption of novel 3D printed helical layered square honeycombs

Bionics shape design of cellular structures has the potential advantage of improving their both mechanical properties and energy absorption capabilities to the conventional honeycomb structures. In this article, inspired by square porous wood and DNA double helix, we demonstrate the creation of the novel helical layered square honeycombs (HLSHs) that simultaneously exhibit high strength and excellent energy absorption capacity. In-plane compression experiments and finite element simulations revealed that helical structure can effectively strengthen every unit cell to resist local stress concentration which always leads to rapid strain localization and finally followed by catastrophic collapse. Furthermore, the stiffness, strength and energy absorption capability can be continuously improved by increasing the number of helical layers. More specifically, the HLSH-4L (4 layers) exhibits higher collapse stress (∼176 %) and specific absorption energy (∼502 %) compared with that of regular square honeycomb (RESH). The investigation of deformation and failure behavior show that the helical structure can supply high cell-buckling resistance and facilitate the “X” shape deformation band. Besides, the helical structure also caused the transition of failure mechanisms from printing fibers tearing in RESH to layer cracking in HLSHs. This study can present insight into the design of lighter and stronger honeycomb.

DETERMINATION OF THE CALCULATED LENGTH OF THE COLUMNS TAKING INTO ACCOUNT THEIR FORM OF DEFORMATION AND UNEQUAL LOADING IN THE FRAME COMPOSITIOND

The coefficient of expansion of the columns, which are used in the warehouse of one-span frames with crane attachments, must depend on the shape of their deformation and the unequal attachment of the columns. At this time, the peculiarity of the current development of the frame is the fact that the most likely objectives can be achieved by only one column in the warehouse. If one of the columns (which has a heavy tap with a vantage) is subject to the maximum influx of constant force at the moment, then the longitudinal column of the same cut allows for the influx of significantly less force. The overall rigidity of the columns in the warehouse frame plays a vital role in the stability of the columns. In a transverse direction, two columns of one span of the workshop are connected by a crossbar into a frame system. The development of significant plastic deformations in one of the columns does not cause a loss of the column’s strength. The protruding column is becoming increasingly important. The regulation of the efficient operation of columns in warehouses allows for more rational design in accordance with current standards. The arrangement of the crazy work of unequally attractive columns in the warehouse can be characterized as a refinement of the first form of deformation. Meanwhile, under active pressure, the frame is deformed according to a mixed shape, which in addition to the first appears in the form of warehouses and other types of normative, effective form of deformation in action. The form of deformation of the frame is stimulated by the following main factors, and, as a rule, does not coincide with the first moisture form and does not predict it. Essentially, the structured combination includes a vantage that stimulates different moisture forms, and a vantage that fits on a similar frame that can be laid out in warehouses that stimulates a variety of moisture forms. The resulting form, due to the resistance of permanent forces in the plastic elements and the elasticity of the material, is a linear combination of warehouse forms and this form can be called mixed. The established principle of independence of action of forces can be distributed on the rod or rod system of storage in the warehouse, where the skin storage force is stimulated by those and other moisture forms. A method has been developed for assessing the durability of steel-curved columns of steel frames with crane attachments, which ensures the effective operation of differently attached columns in the warehouse and the shape of deformation under the action of active forces. The calculated lengths of the columns, determined for cross-sections with crane loads according to the proposed method, are smaller than the calculated lengths determined according to the standard method by 8-20%. Keywords: squeezed columns, gauge length, deformed form, making a column in a frame.

Effect of manufacturing process parameters on the compression and energy absorption properties of 4D-printed deformable honeycomb structure

Four-dimensional-printed deformable honeycombs can produce pro-programmed shape deformation and different properties under external stimuli, and the manufacturing process parameters are the dominant factors affecting the microstructure and properties of the manufactured honeycomb structures. Although many researchers have investigated the effects of manufacturing process parameters on the mechanical properties of printed materials, there is still a lack of research on the relationship between manufacturing process parameters and properties of honeycomb structures. Therefore, a novel honeycomb structures which has two configurations under temperature stimuli is proposed, and the optimum manufacturing processes for the printing of this honeycomb are selected considering the compression and energy absorption properties simultaneously. The novel honeycomb is designed and printed with fused deposition modeling technology, which have hexagonal configuration (Structure I) and semi-triangular configuration (Structure II) under external temperature stimulus. The energy absorption capacity of Structure I and compressive properties of Structure II are investigated under different manufacturing process parameters. The experimental results indicate that the layer thickness has the most significant impact on the mechanical performance of deformable honeycombs. The combination of a layer thickness of 0.2 mm, printing speed of 40 mm s−1, and 100% infill density are the best process parameters for the novel deformable honeycomb structures.

Deformable shape matching with multiple complex spectral filter operator preservation

Deformable shape matching with multiple complex spectral filter operator preservation

Active-compensation of systematic error for the 1000 mm aperture flat interferometer

Large-aperture elements would induce unnegligible systematic errors due to material inhomogeneity, manufacturing or gravity, that are difficult to correct in an extreme large aperture flat interferometer and result in reference wavefront distortion. We propose an active-compensation method for systematic errors by employing a deformable mirror into the interferometer to modulate reference wavefront. A mapping relationship between sag of the deformable mirror and reference wavefront error is derived by theory of matrix optics, and two interferometer optical paths are designed for whether the deformable mirror is located at the pupil or not. The algorithm for calculating and controlling the sag of a deformable mirror can eliminate the need for the deformable mirror to be positioned at the pupil in order to achieve controllable modulation of the wavefront. This algorithm has been validated through the intentional introduction of systematic errors into the 1000 mm aperture flat interferometer for effective compensation. Moreover, the optimization algorithm in Ansys Zemax is utilized to calculate the optimal solution for surface shape of the deformable mirror, treating it as a nominal value. The algorithm error is on the order of 10−6 mm, falling within the acceptable tolerance range for the deformable mirror's surface shape.

Reynolds number effect on the Lagrangian evolution of hairpin vortices in turbulent channel flow

The evolution and generation of hairpins are studied in a Lagrangian perspective in turbulent channel flows. Direct numerical simulation database of turbulent channel flow at friction Reynolds numbers R e τ = 590, 390, and 180 is employed to perform tracking and interpolation algorithms of fluid particles on hairpins. These particles are carefully selected using a vortex line identification technique developed to extract the hairpin's core line. Interesting results are observed regarding the Reynolds number impact on the evolution and regeneration of hairpins. As the Reynolds number increases, the head and the vortical tongues are compressed and aligned in the main flow direction and the hairpin structures tend to orient more horizontally. The deformation shape of hairpins using the strain state parameter, which is correlated with the dissipation rate, is analysed using the probability density function. Most phenomena related to the generation of secondary hairpins, including the existence of vortical tongues, occur in the range 35 ≲ y + ≲ 50 . The results reveal that the Lagrangian perspective is a proper technique to address the extension of vortical tongues, generation of the secondary hairpin, and stretch of hairpin legs.

Role of Shape Deformation of DNA-Binding Sites in Regulating the Efficiency and Specificity in Their Recognition by DNA-Binding Proteins.

Accurate transcription of genetic information is crucial, involving precise recognition of the binding motifs by DNA-binding proteins. While some proteins rely on short-range hydrophobic and hydrogen bonding interactions at binding sites, others employ a DNA shape readout mechanism for specific recognition. In this mechanism, variations in DNA shape at the binding motif resulted from either inherent flexibility or binding of proteins at adjacent sites are sensed and capitalized by the searching proteins to locate them specifically. Through extensive computer simulations, we investigate both scenarios to uncover the underlying mechanism and origin of specificity in the DNA shape readout mechanism. Our findings reveal that deformation in shape at the binding motif creates an entropy funnel, allowing information about altered shapes to manifest as fluctuations in minor groove widths. This signal enhances the efficiency of nonspecific search of nearby proteins by directing their movement toward the binding site, primarily driven by a gain in entropy. We propose this as a generic mechanism for DNA shape readout, where specificity arises from the alignment between the molecular frustration of the searching protein and the ruggedness of the entropic funnel governed by molecular features of the protein and arrangement of the DNA bases at the binding site, respectively.

AGAR - Attention Graph-RNN for Adaptative Motion Prediction of Point Clouds of Deformable Objects

This article focuses on motion prediction for point cloud sequences in the challenging case of deformable 3D objects, such as human body motion. First, we investigate the challenges caused by deformable shapes and complex motions present in this type of representation, with the ultimate goal of understanding the technical limitations of state-of-the-art models. From this understanding, we propose an improved architecture for point cloud prediction of deformable 3D objects. Specifically, to handle deformable shapes, we propose a graph-based approach that learns and exploits the spatial structure of point clouds to extract more representative features. Then, we propose a module able to combine the learned features in a adaptative manner according to the point cloud movements. The proposed adaptative module controls the composition of local and global motions for each point, enabling the network to model complex motions in deformable 3D objects more effectively. We tested the proposed method on the following datasets: MNIST moving digits, the Mixamo human bodies motions [ 15 ], JPEG [ 5 ] and CWIPC-SXR [ 32 ] real-world dynamic bodies. Simulation results demonstrate that our method outperforms the current baseline methods given its improved ability to model complex movements as well as preserve point cloud shape. Furthermore, we demonstrate the generalizability of the proposed framework for dynamic feature learning by testing the framework for action recognition on the MSRAction3D dataset [ 19 ] and achieving results on par with state-of-the-art methods.

The Corpus Callosum in Schizoaffective Disorder: A Shape Analysis Study

Objective: The corpus callosum is the largest white matter structure in the human brain that connects the cortical regions of both hemispheres. Diseases could lead to degenerative alterations in brain structures such as the corpus callosum (CC). Studies have associated CC abnormalities with Schizoaffective Disorder (SAD) symptoms. We predicted that there may be differences in the CC, an important structure connecting the two halves of the brain, in patients with SAD. The present study aims to analyze the CC of patients with statistical shape analysis (SSA) and compare the findings with healthy controls. Methods: Thirty-nine SAD patients and 39 healthy individuals (11 females and 28 males) of similar age that included subjects participated in the study. CC landmarks were marked on the mid-sagittal images of each participant. The mean ‘Procrustes’ point was determined, and shape deformations were analyzed with thin plate spline analysis. Results: Significant differences were observed between the shapes of CC in the two groups, and maximum CC deformation was observed in the posterior regions of SAD patients. There was no significant difference between the CC area of the SAD patients and the controls. Conclusion: In the present study, the maximum deformation was observed in the posterior region (isthmus and splenium) and the rostrum of the CC. The first CC region, the rostrum (+genu), connects prefrontal and premotor regions, which are associated with cognitive information (landmarks = 1, 7, 8, 9, 13, 15, and 12). The second area, the splenium, connects temporal and occipital cortical areas. These predominantly have auditory, peripheral, and central visual stimulation functions (landmarks = 5, 3, and 4). The current study could assist future studies on the etiology, diagnosis, and treatment of SAD.

Evaluation and Defect Detection in L-Shaped GFRP Laminates by Infrared Thermography.

Glass fiber-reinforced polymer (GFRP) laminates are used in many applications because of their availability, high mechanical properties, and cost-effectiveness. Fiber defects in the form of waviness or wrinkles can occur during the production of multilayered laminates. When curved laminates of significant thickness are produced, the likelihood of such defects increases. Studies have confirmed that fiber deformation during manufacture leads to a reduction in the mechanical properties of laminates. Therefore, early detection of such defects is essential. The main part of this paper deals with research into the possibility of using active infrared thermography to detect wrinkles in curved multilayered GFRP laminates. The size of the artificial wrinkles was assessed by analyzing scans and microimages. The shape deformations of the samples were evaluated by comparing the samples with the mold and the assumed nominal shape. The influence of the out-of-autoclave manufacturing process on the reduction in wrinkles formed without significantly affecting the internal structure of the laminate is presented in this work. This research demonstrated the ability to detect wrinkles in thick curved laminates using active infrared thermography. However, it also showed how the interpretation of the thermographic results is affected by the curvature of the structure, the lack of uniform heating, and the configuration of the thermographic setup.

Determination of muscle shape deformations of the tibialis anterior during dynamic contractions using 3D ultrasound.

In this paper, we introduce a novel method for determining 3D deformations of the human tibialis anterior (TA) muscle during dynamic movements using 3D ultrasound. An existing automated 3D ultrasound system is used for data acquisition, which consists of three moveable axes, along which the probe can move. While the subjects perform continuous plantar- and dorsiflexion movements in two different controlled velocities, the ultrasound probe sweeps cyclically from the ankle to the knee along the anterior shin. The ankle joint angle can be determined using reflective motion capture markers. Since we considered the movement direction of the foot, i.e., active or passive TA, four conditions occur: slow active, slow passive, fast active, fast passive. By employing an algorithm which defines ankle joint angle intervals, i.e., intervals of range of motion (ROM), 3D images of the volumes during movement can be reconstructed. We found constant muscle volumes between different muscle lengths, i.e., ROM intervals. The results show an increase in mean cross-sectional area (CSA) for TA muscle shortening. Furthermore, a shift in maximum CSA towards the proximal side of the muscle could be observed for muscle shortening. We found significantly different maximum CSA values between the fast active and all other conditions, which might be caused by higher muscle activation due to the faster velocity. In summary, we present a method for determining muscle volume deformation during dynamic contraction using ultrasound, which will enable future empirical studies and 3D computational models of skeletal muscles.

Analysis of knee-bending motion through three-dimensional scanning for advanced brace design

Knee braces have been increasing in popularity as a means to support joint stability and promote the healing process. In order to enhance the fit, comfort, and design of knee braces, this study investigates knee shape deformations across four knee-bending angles from 0° to 90°. Using three-dimensional (3D) scanning technology, the knee contours of 50 Asian males aged between 22 and 33 were examined. The reliability of the 3D measurements was validated through comparisons with tape measurements on the actual body. The analysis revealed a stretch of the skin covering the patella bone with a notable vertical strain of 19% and horizontal stretching of 7%. The circumference along the muscle belly at the thigh (15 cm above the center of the patella) and at the calf (7.5 cm below the center of the patella) showed no significant changes with different bending angles, and can be used as an indicator for sizing of knee braces. However, at the patella bone level, the bending of the knee from 0° to 90° increased the knee circumference by 6.4%. The results from sectional analysis showed the asymmetry and the lateral shifting of the knee joint during bending. The findings offer guidelines for the design and optimization of knee braces to address knee deformations and individual body shape variations.

On the Water Jet Quality at Part-Load Operation of Pelton turbines

Abstract Pelton turbines with multiple nozzles are characterised by their excellent performance over a wide operating range of mass flow rates. Thus, Pelton turbine manifolds must also be designed to deliver good flow quality to the nozzles at part-load operating conditions to accomplish the expectations. A reduced number of nozzles are opened at low mass flow rate operating conditions, where the choice of the open nozzles depends on the water jet quality generated at the individual nozzles. We investigate the flow phenomena occurring in the manifold with the operation of a reduced nozzle number employing numerical simulations to analyse beneficial nozzle opening selections. The turbulent two-phase flow is predicted by the Volume-Of-Fluid (VOF) approach and the k–ω SST turbulence closure model. Different nozzle operating scenarios are simulated, and the implications on the water jet quality, i.e. deviation and shape deformation, are reported. The results show that the free water jet quality criteria can change drastically at individual nozzle operating conditions because of the velocity changes at the branch line junctions.

Estimation of waveform deformation with the matched filter

In many particle physics experiments the data processing is based on the analysis of the digitized waveforms provided by the detector. While the waveform amplitude is usually correlated to the event energy, the shape may carry useful information for event discrimination. Thanks to the high signal to noise ratio they provide, matched filters are often applied. Their original design is however intended for the estimation of the waveform amplitude only. In this work we introduce an analytical extension of the original matched filter for the estimation of a possible shape deformation with respect to a reference template. The new filter is validated on simulations and, with respect to shape parameters calculated on unfiltered waveforms or derived from the original matched filter, it improves the discrimination capability by at least a factor 2 both at low and high signal to noise ratios, making it applicable to the data of several experiments.

Shape-Memory Polymers Based on Carbon Nanotube Composites.

For the past two decades, researchers have been exploring the potential benefits of combining shape-memory polymers (SMP) with carbon nanotubes (CNT). By incorporating CNT as reinforcement in SMP, they have aimed to enhance the mechanical properties and improve shape fixity. However, the remarkable intrinsic properties of CNT have also opened up new paths for actuation mechanisms, including electro- and photo-thermal responses. This opens up possibilities for developing soft actuators that could lead to technological advancements in areas such as tissue engineering and soft robotics. SMP/CNT composites offer numerous advantages, including fast actuation, remote control, performance in challenging environments, complex shape deformations, and multifunctionality. This review provides an in-depth overview of the research conducted over the past few years on the production of SMP/CNT composites with both thermoset and thermoplastic matrices, with a focus on the unique contributions of CNT to the nanocomposite's response to external stimuli.

93‐1: Invited Paper: Meta‐Elastomer for Biaxially Stretchable Displays Without Image Distortion

Stretchable displays are garnering attention due to their ability to undergo reversible shape deformation. However, due to Poisson's ratio, image distortion issues caused by undesired substrate deformations during stretching remain challenging. Here, we propose meta‐elastomers with biaxially zero Poisson's ratio for distortion‐free stretchable displays. To program the Poisson's ratio according to biaxial stretching, elastomeric mechanical metamaterial (MM) frames with a negative Poisson's ratio are integrated into an elastomer matrix. By leveraging competitive interactions between the elastomeric MM frame and elastomer matrix deformation, we have successfully implemented the biaxial near‐zero Poisson's ratio substrates.