Search Results (1,331)

Spasticity of the distal lower limb substantially impairs stance, gait, and quality of life in patients with upper motor neuron lesions. Although ultrasound-guided botulinum toxin A (BoNT-A) injections are increasingly employed, structured, muscle-specific visual guidance for the distal lower limb remains limited. This study provides a comprehensive guide for ultrasound-guided BoNT-A injections across ten key distal lower limb muscles: gastrocnemius, soleus, tibialis posterior, flexor hallucis longus, flexor digitorum longus, tibialis anterior, extensor hallucis longus, flexor digitorum brevis, flexor hallucis brevis, and extensor digitorum longus. For each muscle, we present (1) Anatomical positioning relative to osseous landmarks; (2) Sonographic identification cues and dynamic features; (3) Zones of intramuscular neural arborization optimal for injection; (4) Practical injection protocols derived from literature and clinical experience. High-resolution ultrasound images and dynamic videos illustrate real-life muscle behavior and guide injection site selection. This guide facilitates precise targeting by correlating sonographic signs with optimal injection zones, addresses common spastic patterns—including equinus, varus, claw toe, and hallux deformities—and integrates fascial anatomy with motor-point mapping. This article completes the Elias University Hospital visual series, providing clinicians with a unified framework for effective spasticity management to improve gait, posture, and patient autonomy. Full article

Permeability of fissured sorbing rocks, such as coal and shale, controls gas transport and is relevant to a variety of scientific problems and industrial processes. Multiple gas transport and rock deformation mechanisms affect permeability evolution, including gas rarefaction effects, gas-sorption-induced anisotropic matrix–fracture interaction, and anisotropic deformation induced by effective stress variation. In this paper, a generic anisotropic permeability model is proposed to address the impacts of the above mechanisms and effects. Specifically, the influence of matrix–fracture interactions on permeability evolution is depicted through the nonuniform matrix swelling caused by the gas diffusion process from fracture walls into the matrix. The following characteristics are also incorporated in this model: (1) anisotropic mechanical and swelling properties, (2) arbitrary box-shaped matrix blocks due to the anisotropic rock structure, (3) adsorbability variation of different matrix blocks because of complex rock compositions, (4) adsorption hysteresis, and (5) dynamic tortuosity. The directional permeability models are derived based on the anisotropic poroelasticity theory and anisotropic swelling equations considering adsorption hysteresis. We use a gas-invaded-volume ratio to describe the nonuniform swelling of matrix blocks. Additionally, swelling of blocks with different adsorption and mechanical properties are characterized by a volume-weighted function. Finally, the anisotropic tortuosity is defined as a power law function of effective porosity. The model is verified against experimental data. Results show that four-stage permeability evolution with time can be observed. Permeability evolution in different directions follows its own ways and depends on anisotropic swelling, mechanical properties, and structures, even when the boundary conditions are identical. Adsorption hysteresis controls the local shrinkage region. Tortuosity variation significantly affects permeability but has the smallest influence on the local swelling region. The existence of multiple matrix types complicates the permeability evolution behavior. Full article

Nanoparticle superlattices, periodic assemblies of nanoscale building blocks, offer opportunities to tailor mechanical behavior through controlled lattice geometry and interparticle interactions. Here, classical molecular dynamics simulations were performed to investigate the compressive responses of copper nanoparticle superlattices with face-centered cubic (FCC), hexagonal close-packed (HCP), body-centered cubic (BCC), and simple cubic (SC) arrangements, as well as disordered assemblies. The flow stresses span 0.5–1.5 GPa. Among the studied configurations, the FCC and HCP superlattices exhibit the highest strengths (~1.5 GPa), followed by the disordered assembly (~1.0 GPa) and the SC structure (~0.8 GPa), while the BCC superlattice exhibits the lowest strength (~0.5 GPa), characterized by pronounced stress drops and recoveries resulting from interfacial sliding. Atomic-scale analyses reveal that plastic deformation is governed by two coupled geometric factors: (i) the number of interparticle contact patches, controlling the density of dislocation sources, and (ii) their orientation relative to the loading axis, which dictates stress transmission and slip activation. A combined parameter integrating particle coordination number and contact orientation is proposed to rationalize the structure-dependent strength, providing mechanistic insight into the deformation physics of metallic nanoparticle assemblies. Full article

The deformation mechanism during the hot compression of PM nickel-based superalloy FGH99 and its micro-structural evolution, especially the evolution of γ’ phases, are the key factors affecting the final molding quality of aero-engine hot forged turbine disks. In this study, a new constitutive model of viscoplasticity with micro-structures as physical internal parameters were developed to simulate the hot compression behavior of FGH99 by incorporating the strengthening effect of the γ’ phase. The mechanical behavior of high-temperature (>1000 K) compressive deformation of typical superalloys under a wide strain rate (0.001~1 s⁻¹) is investigated using the Gleeble thermal-force dynamic simulation tester. The micro-structure after the hot deformation was characterized using EBSD and TEM. Work hardening as well as dynamic softening were observed in the hot compression tests. Based on the mechanical responses and micro-structural features, the model considered the coupled effects of dislocation density, DRX, and γ’ phase during hot flow. The model is programmed into a user subroutine based on the Fortran language and called in the simulation of the DEFORM-3D V6.1 software, thus realizing the multiscale predictive simulation of FGH99 alloy by combining macroscopic deformation and micro-structural evolution. The established viscoplastic constitutive model shows a peak discrepancy of 10.05% between its predicted hot flow stresses and the experimental values. For the average grain size of FGH99, predictions exhibit an error below 7.20%. These results demonstrate the high accuracy of the viscoplastic constitutive model developed in this study. Full article

Traditional single-layer water-lubricated rubber or plastic bearings suffer from water film rupture, excessive frictional losses, and insufficient load-carrying capacity, which limit performance and service life in marine propulsion and ocean engineering. To address these issues, this study introduces an innovative laminated bearing consisting of a rubber composite layer and an ultra-high-molecular-weight polyethylene (UHMWPE) layer. A three-dimensional dynamic model based on fluid–structure interaction theory is developed to evaluate the effects of eccentricity, rotational speed, and liner thickness on lubrication pressure, load capacity, deformation, stress–strain behavior, and frictional power consumption. The model also reveals how thickness matching governs load transfer and energy dissipation. Results indicate that eccentricity, speed, and thickness are key determinants of lubrication and structural response. Hydrodynamic pressure and load capacity rise with eccentricity above 0.8 or higher speeds, but frictional losses also intensify. The rubber layer performs optimally at a thickness of 5 mm, while excessive or insufficient thickness leads to stress concentration or reduced buffering. The UHMWPE layer exhibits optimal performance at 5–7 mm, with greater deviations resulting in increased stress and deformation. Proper thickness matching improves pressure distribution, reduces local stresses, and enhances energy dissipation, thereby strengthening bearing stability and durability. Full article

Polyurethane (PU), owing to its superior physicochemical properties, is considered an ideal modifier for asphalt. To improve the mechanical performance and service durability of asphalt pavements, PU-modified asphalts with varying dosages were prepared and evaluated through laboratory experiments and molecular dynamics simulations. Rheological, thermodynamic, and mechanical tests, as well as asphalt–aggregate adhesion energy calculations, were conducted to elucidate the modification mechanism, aging resistance, and interfacial behavior. The results showed that PU incorporation significantly enhanced rutting resistance at high temperatures, flexibility at low temperatures, and overall load-bearing capacity. Under ultraviolet and long-term aging, PU-modified asphalts exhibited notably lower performance degradation than base asphalt. At the molecular level, PU absorbed light fractions and formed a cross-linked network, reducing the free volume fraction and strengthening resistance to deformation. Moreover, PU substantially improved asphalt–aggregate adhesion energy, thereby reinforcing interfacial bonding. These findings provide theoretical insights and practical guidance for the optimal design and engineering application of PU-modified asphalt. Full article

This study presents an experimental investigation into the dynamic response and blast resistance of aluminum foam-cored sandwich panels with varied face sheet thicknesses under impulsive loading conditions. The primary focus is on analyzing how the thickness of front and back face sheets affects the deformation behavior and energy absorption capabilities of the sandwich panels. By employing a 3D digital image correlation (3D-DIC) system coupled with post-test analyses, the dynamic responses and permanent deformations were quantitatively characterized. Failure modes of the core layers, front face sheets, and back face sheets were identified and discussed. The results demonstrated that sandwich panels with thick front face sheets exhibited superior blast resistance and energy absorption performance than their thin-front counterparts under high localized impulsive loading. The findings provide important comparative insights about face sheet thickness distribution effects, though further studies with broader thickness variations are needed to establish comprehensive design guidelines. Full article

Scene Text Recognition (STR) faces significant challenges under complex degradation conditions, such as distortion, occlusion, and semantic ambiguity. Most existing methods rely heavily on language priors for correction, but effectively constructing language rules remains a complex problem. This paper addresses two key challenges: (1) The over-correction behavior of language models, particularly on semantically deficient input, can result in both recognition errors and loss of critical information. (2) Character misalignment in visual features, which affects recognition accuracy. To address these problems, we propose a Deformable-Alignment-based Dual Correction Mechanism (DADCM) for STR. Our method includes the following key components: (1) We propose a visually guided and language-assisted correction strategy. A dynamic confidence threshold is used to control the degree of language model intervention. (2) We designed a visual backbone network called SCRTNet. The net enhances key text regions through a channel attention module (SENet) and applies deformable convolution (DCNv4) in deep layers to better model distorted or curved text. (3) We propose a deformable alignment module (DAM). The module combines Gumbel-Softmax-based anchor sampling and geometry-aware self-attention to improve character alignment. Experiments on multiple benchmark datasets demonstrate the superiority of our approach. Especially on the Union14M-Benchmark, where the recognition accuracy surpasses previous methods by 1.1%, 1.6%, 3.0%, and 1.3% on the Curved, Multi-Oriented, Contextless, and General subsets, respectively. Full article

To mitigate explosion hazards arising from hydrogen leakage and subsequent mixing with air, the injection of inert gases can substantially diminish explosion risk. However, prevailing research has predominantly characterized inert gas dilution effects on explosion behavior under quiescent conditions, largely neglecting the turbulence-mediated explosion enhancement inherent to dynamic mixing scenarios. A comprehensive investigation was conducted on the combustion behavior of 30%, 50%, and 70% H₂-air mixtures subjected to jet-induced (CO₂, N₂, He) turbulent flow, incorporating quantitative characterization of both the evolving turbulent flow field and flame front dynamics. Research has demonstrated that both an increased H₂ concentration and a higher jet medium molecular weight increase the turbulence intensity: the former reduces the mixture molecular weight to accelerate diffusion, whereas the latter results in more pronounced disturbances from heavier molecules. In addition, when CO₂ serves as the jet medium, a critical flame radius threshold emerges where the flame propagation velocity decreases below this threshold because CO₂ dilution effects suppress combustion, whereas exceeding it leads to enhanced propagation as initial disturbances become the dominant factor. Furthermore, at reduced H₂ concentrations (30–50%), flow disturbances induce flame front wrinkling while preserving the spherical geometry; conversely, at 70% H₂, substantial flame deformation occurs because of the inverse correlation between the laminar burning velocity and flame instability governing this transition. Through systematic quantitative analysis, this study elucidates the evolutionary patterns of both turbulent fields and flame fronts, offering groundbreaking perspectives on H₂ combustion and explosion propagation in turbulent environments. Full article

In this study, the behavior of the spherical bearing component of the L-100 bridge part (AlfaTech LLC, Perm, Russia) is considered within the framework of a finite element model. The influence of the pattern of the coupling of the antifriction interlayer with the lower steel plate on the operation of the part is examined in terms of ideal contact, full adhesion, and frictional contact. The thickness of the antifriction interlayer varied from 4 to 12 mm. The dependencies of the contact parameters and the stress–strain state on the thickness were determined. Structurally modified polytetrafluoroethylene (PTFE) without AR-200 fillers was considered the material of the antifriction interlayer. The gradual refinement of the behavioral model of the antifriction material to account for structural and relaxation transitions was carried based on a wide range of experimental studies. The elastic–plastic and primary viscoelastic models of material behavior were constructed based on a series of homogeneous deformed-state experiments. The viscoelastic model of material behavior was refined using data from dynamic mechanical analysis over a wide temperature range [−40; +80] °C. In the first approximation, a model of the deformation theory of plasticity with linear elastic volumetric compressibility was identified. As a second approximation, a viscoelasticity model for the Maxwell body was constructed using Prony series. It was established that the viscoelastic model of the material allows for obtaining data on the behavior of the part with an error of no more than 15%. The numerical analog of the construction in an axisymmetric formulation can be used for the predictive analysis of the behavior of the bearing, including when changing the geometric configuration. Recommendations for the numerical modeling of the behavior of antifriction layer materials and the coupling pattern of the bearing elements are given in this work. A spherical bearing with an antifriction interlayer made of Arflon series material is considered for the first time. Full article

Thermal cycling test is one of the reliability tests, which are important for metal-ceramic layered composites (metallized ceramic substrates), a part in power modules. Since thermal cycles are within a large range of temperature, the test has only been performed using a thermal chamber. It limited the understanding of degradation mechanism in metallized ceramics substrates. Among NDE techniques, Digital Image Correlation (DIC) is a simple and effective method, enhanced by modern digital imaging technologies, enabling precise measurements of displacement, strain, deformation, and defects with a simple setup. In this paper, we combined some of our previous work to make a review to present a full analysis of a silicon metallized substrate under thermal cycling test (from beginning to fail) using DIC method. The main content is the application of DIC in evaluating the reliability of metallized silicon nitride (AMB-SN) substrates under thermal cycling with temperatures from −40 °C to 250 °C. Three key aspects of the AMB-SN substrate are presented, including (i) thermal strain characteristics before and after delamination, (ii) warpage and dynamic bending behavior across damage states, and (iii) stress–strain behavior of constituent materials. The review provides insights into degradation progress of the substrate and the role of Cu in substrate failure, and highlights DIC’s potential in ceramic composites, offering a promising approach for improving reliability test simulations and advancing digital transformation in substrate evaluation, ultimately contributing to enhanced durability in high-power applications. Full article

The paper presents an innovative theoretical concept of a bio-inspired soft gripper system with two parallel jaws, a fixed and a mobile one. It is conceived for gripping fragile or soft objects with complex, irregular shapes that are easily deformable. This novel gripper is designed for handling small objects of masses up to 0.5 kg. The maximum gripping stroke of the mobile jaw is 13.5 mm. The driving motor is a pneumatic muscle, an actuator with inherently compliant, spring-like behavior. Compliance is the feature responsible for the soft character of the gripper system, ensuring its passive adaptability to the nature of the object to be gripped. The paper presents the structural, kinematic, static, and dynamic models of the novel gripper system and describes the compliant behavior of the entire assembly. The results of the dynamic simulation of the gripper have confirmed the attaining of the imposed motion-related performance. Full article

Lattice structures are lightweight architected materials particularly suitable for aerospace and automotive applications due to their ability to combine mechanical strength with reduced mass. Among various topologies, Body-Centered Cubic (BCC) lattices are widely employed for their geometric regularity and favorable strength-to-weight ratio. Advances in Additive Manufacturing (AM) have enabled the precise and customizable fabrication of such complex architectures, reducing material waste and increasing design flexibility. This study investigates the low-velocity impact behavior of two polylactic acid (PLA)-based BCC lattice panels differing in strut diameter: BCC1.5 (1.5 mm) and BCC2 (2 mm). Experimental impact tests and finite element simulations were performed to evaluate their energy absorption ($EA$) capabilities. In addition to conventional global performance indices, a dimensionless parameter, $D^{\ast },$ is introduced to quantify the ratio between local plastic indentation and global displacement, allowing for a refined characterization of deformation modes and structural efficiency. Results show that BCC1.5 absorbs more energy than BCC2, despite the latter’s higher stiffness. This suggests that thinner struts enhance energy dissipation under dynamic loading. Despite minor discrepancies, numerical simulations provide accurate estimations of $EA$ and support the robustness of the $D^{\ast }$ index within the examined configuration, highlighting its potential to deformation heterogeneity. Full article

Isothermal hot compression tests were performed on an Al-4.8Cu-0.25Mg-0.32Mn-0.17Si alloy using a Gleeble-3500 thermomechanical simulator within the temperature range of 350–510 °C and strain rate range of 0.001–10 s⁻¹, achieving a true strain of 0.9. The constitutive equation and hot processing maps were established to predict the flow behavior of the alloy. The hot deformation mechanisms were investigated through microstructural characterization using inverse pole figure (IPF), grain boundary (GB), and grain orientation spread (GOS) analysis. The results demonstrate that both dynamic recovery (DRV) and dynamic recrystallization (DRX) occur during hot deformation. At high lnZ values (high strain rates and low deformation temperatures), discontinuous dynamic recrystallization (DDRX) dominates. Under middle lnZ conditions (low strain rate or high deformation temperature), both continuous dynamic recrystallization (CDRX) and DDRX are the primary mechanisms. Conversely, at low lnZ values (low strain rates and high temperatures), CDRX and geometric dynamic recrystallization (GDRX) become predominant. The DRX process in the Al-Cu-Mg alloy is controlled by the deformation temperature and strain rate. Full article

This work proposes a novel design configuration for an elasto-poro-hydrodynamic damper (EPHD damper) that consists of an imbibed, soft, elastic, porous material enclosed by a rubber membrane. The core innovation lies in the device’s ability to collect and re-imbibe expelled fluid during decompression, ensuring potential functionality and durability across repetitive loading cycles. Damping is achieved through the synergy of three mechanisms: friction of the membrane and of the piston with solid boundaries, squeeze flow inside the porous layer, and compression of the poro-elastic structure. The EPHD damper’s behavior was evaluated both theoretically and experimentally through quasi-static, low-speed compression tests, with dynamic evaluation being reserved for future work. A numerical model successfully validated stress-deformation behavior against experimental data, with a simplified analytical model providing a good approximation. The study also identifies that the piston–membrane friction coefficient significantly influences the EPHD damper’s performance. These findings provide a valuable framework for optimizing the design and expanding its potential application to repetitive damping systems. Full article