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We study experimentally and theoretically the dynamics of permanent paramagnetic chains and mixed clusters formed by permanent paramagnetic chains and paramagnetic particles under the influence of a time-varying magnetic field. First, we examine the dynamics of permanent chains at high frequencies (∼50 to 1000 Hz). These permanent chains exhibit continuous rotational motion with a frequency several orders of magnitude lower than that of the magnetic field. We develop a theoretical model that accurately describes the dependence of the rotational dynamics of chains on their length, as well as the amplitude and frequency of the external magnetic field in this high frequency regime. Next, we examine how cluster dynamics are affected by the presence of permanent chains. We show that the rotation of clusters composed of a high proportion of permanent chains is slowed down but remains qualitatively well described by the theoretical model we developed for homogeneous clusters of isotropic particles. We propose that the decrease in angular velocity for mixed clusters is due to the hardening of the cluster's 2D elastic modulus caused by the increase of the steric interaction parameter stemming from the presence of chemical links between particles in the chains. [ABSTRACT FROM AUTHOR]

We employed all-atom molecular dynamics simulations to explore the mechanical response of bending, twisting, and overwinding for double-stranded DNA (dsDNA). We analyzed the bending and twisting deformations, as well as their stiffnesses, using the tilt, roll, and twist modes under stretching force. Findings indicate that the roll and twist angles vary linearly with the stretching force but show opposite trends. The tilt, roll, and twist elastic moduli are considered constants, while the coupling between roll and twist modes slightly decreases under stretching force. The effect of the stretching force on the roll and twist modes, including both their deformations and elasticities, exhibits sequence-dependence, with symmetry around the base pair step. Furthermore, we examined the overwinding path and mechanism of dsDNA from the perspective of the stiffness matrix, based on the tilt, roll, and twist modes. The correlations among tilt, roll, and twist angles imply an alternative overwinding pathway via twist–roll coupling when dsDNA is stretched, wherein entropic contribution prevails. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the stress distribution along a premolar's root dentin, its post, and its post-luting agent when materials with different elastic moduli are used to fabricate one-piece post-and-cores in two different designs. Materials and Methods: Two 3D virtual models (for cylindrical and conical post designs) of a mandibular premolar restored with one-piece post-and-core restorations were obtained using a software. A total of eight post-and-core materials were tested: polyetheretherketone (PEEK), polyetherketoneketone (PEKK), glass fiber-reinforced polyetheretherketone (GFR-PEEK), carbon fiber-reinforced polyetheretherketone (CFR-PEEK), gold-palladium alloy (Au-Pd), titanium (Ti), zirconia (Zi), and chromium-nickel (Cr-Ni). Maximum principals stress (MPS) in the post, post-luting agent, and root dentin were determined. A load of 150 N was applied to the buccal cusp in the linguo-labial direction at an angle of 45 degrees oblique to the longitudinal axis of the crown. Results: The highest MPS value in post structure was observed with Cr-Ni material for both post designs. Similarly, the highest MPS value in the post-luting agent was observed for Cr-Ni, the material with the highest elastic modulus. However, in the root dentin, the highest value was observed in PEEK, the material with the lowest elastic modulus. Conclusions: Post material and design influenced the stress concentration in the post, post-luting agent, and root dentin. The stress at the root dentin was slightly higher for polymeric materials. Cylindrical post design revealed lower stresses than conical post design at root dentin for all post-and-core materials tested. [ABSTRACT FROM AUTHOR]

The lattice thermal conductivity stands as a pivotal thermos-physical parameter of high-entropy alloys; nonetheless, achieving precise predictions of the lattice thermal conductivity for high-entropy alloys poses a formidable challenge due to their complex composition and structure. In this study, machine learning models were built to predict the lattice thermal conductivity of AlCoCrNiFe high-entropy alloy based on molecular dynamic simulations. Our model shows high accuracy with R2, mean absolute percentage error, and root mean square error of the test set is 0.91, 0.031, and 1.128 W m−1 k−1, respectively. In addition, a high-entropy alloy with low a lattice thermal conductivity of 2.06 W m−1 k−1 (Al8Cr30Co19Ni20Fe23) and with a high lattice thermal conductivity of 5.29 W m−1 k−1 (Al0.5Cr28.5Co25Ni25.5Fe20.5) was successfully predicted, which shows good agreement with the results from molecular dynamics simulations. The mechanisms of the thermal conductivity divergence are further explained through their phonon density of states and elastic modulus. The established model provides a powerful tool for developing high-entropy alloys with the desired properties. [ABSTRACT FROM AUTHOR]

The motivation of the present study is to gain insights into the evolution of elastic properties of cemented tungsten carbides (WC) shock compressed to 100 GPa. Seven plate impact experiments—two front surface impact and five release wave overtake—are conducted to make simultaneous measurements of Hugoniot states and longitudinal sound speeds in shocked WC with 3.7wt.% cobalt binder. The sound speeds along with estimates for bulk sound speeds, obtained using the Birch–Murnaghan EoS, are analyzed to determine the elastic moduli—longitudinal, bulk, and shear—as a function of Hugoniot stress. The longitudinal and bulk sound speeds at Hugoniot states of interest are found to increase linearly with longitudinal stress. Consistent with the increase in sound speeds, the longitudinal and bulk moduli also increase with Hugoniot stress; however, the increase in longitudinal modulus is modest when compared to predictions of theoretical models that account for pressure and temperature dependence of elastic moduli, but with no damage. The shear moduli remain nearly constant at ∼ 318 GPa over the range of Hugoniot states investigated. These values are, however, much lower than those predicted by the Steinberg–Guinan model with no damage. Poisson's ratio decreases initially from its ambient value of 0.208 to ∼ 0.199 for Hugoniot stress ≤ 10 GPa indicating consolidation of the WC microstructure with low initial stress; however, with an increase in Hugoniot stress to ∼ 100 GPa, Poisson's ratio increases to ∼ 0.317, indicating degradation of shear moduli with increasing stress. The product of density and Grüneisen parameter (ρ Γ), after an initial spike, remains nearly constant for volumetric strains ≥ 0.07. The maximum average temperature rise is estimated to be ∼ 286 ° C at the highest Hugoniot stress employed in the study. [ABSTRACT FROM AUTHOR]

High-pressure treatment of oxide glasses can lead to significant alteration of various material properties such as increased density, ductility, and elastic moduli. In this study, a model of melt-quenched bulk silica glass was subject to high-pressure treatments (up to 16 GPa) using molecular dynamics simulations. The thermal conductivity of such prepared glass structures was determined using the equilibrium Green–Kubo method. We observed that, up to the pressure treatments of ∼ 6 GPa, the structure exhibits moderate density increase and a much steeper increase between 6 and 16 GPa, with associated density increase of fivefold silicon atoms. We also observed a noticeable increase (up to 20%) of the thermal conductivity in samples subjected to high-pressure treatments. The observed increases are somewhat, but not significantly, larger than those predicted by the minimum thermal conductivity model, accounting for density and elastic moduli increase. [ABSTRACT FROM AUTHOR]

To develop special insulating paper is of great significance to promote the service life of transformers. Using molecular simulation to guide the development of special insulating paper can greatly reduce the trial-and-error rate and waste of resources in traditional experiments. The effect of different types of polysilsesquioxane (POSS) on cellulose insulating paper was investigated by using molecular simulation. This paper investigated the thermal stability and mechanical properties and electrical characteristics of caged POSS, semi-caged POSS, and ladder-like POSS doped cellulose insulating paper. The results show that POSS with all types can enhance the performance of cellulose insulating paper, and ladder-like POSS possess the best modification effect. The glass transition temperature was increased by 58 K, and the bulk modulus, shear modulus, and elastic modulus of cellulose insulating paper doped with ladder-like POSS can improve up to 27.07%, 45.67%, and 41.28%, respectively. Meanwhile, the dielectric properties of ladder-like POSS modified insulating paper are also significantly improved. The findings of this paper propose a method for the preparation of ladder-like POSS modified insulating paper, which provides theoretical guidance for the experimental preparation of special insulating paper. [ABSTRACT FROM AUTHOR]

OBJECTIVE: The purpose of this study was to determine the in vitro effects of a single exposure of bupivacaine on the mechanical properties of bovine cartilage explants at 3 weeks. DESIGN: Femoral condyle articular cartilage explants were aseptically harvested from juvenile bovine stifle joints before being exposed to chondrogenic medium containing 0.50% (wt/vol) bupivacaine, 0.25% (wt/vol) bupivacaine, or no medication (control) for 1 hour. Explants were then washed and maintained in culture in vitro for 3 weeks before testing. Cell viability, tensile and compressive mechanical properties, histological properties, and biochemical properties were then assessed. RESULTS: Explants exhibited a dose-dependent decrease in mean tensile Youngs modulus with increasing bupivacaine concentration (9.86 MPa in the controls, 6.48 MPa in the 0.25% bupivacaine group [P = 0.048], and 4.72 MPa in the 0.50% bupivacaine group [P = 0.005]). Consistent with these results, collagen content and collagen crosslinking decreased with bupivacaine exposure as measured by mass spectrometry. Compressive properties of the explants were unaffected by bupivacaine exposure. Explants also exhibited a trend toward dose-dependent decreases in viability (51.2% for the controls, 47.3% for the 0.25% bupivacaine-exposed group, and 37.0% for the 0.50% bupivacaine-exposed group [P = 0.072]). CONCLUSIONS: Three weeks after 1-hour bupivacaine exposure, the tensile properties of bovine cartilage explants were significantly decreased, while the compressive properties remained unaffected. These decreases in tensile properties corresponded with reductions in collagen content and crosslinking of collagen fibers. Physicians should be judicious regarding the intra-articular administration of bupivacaine in native joints.

Alloying and site ordering play complementary roles in dictating a material's properties. However, deconvolving the impacts of these separate phenomena can be challenging. In this work, we simulate structures of Zn (Sn , Ge) N 2 with varied Sn content and site ordering to determine the impacts of order and composition on structural and electronic properties. We assess the formation enthalpy, lattice parameters, elastic constants, spontaneous polarization, and piezoelectric coefficients. In mostly disordered structures (order parameters ranging from 0.2 to 0.4), the formation enthalpy exhibits local extrema as a function of the order parameter, deviating from the more linear trends seen in both fully disordered and fully ordered systems. This anomalous deviation from the otherwise linear trend in formation enthalpy with order manifests in each of the other properties calculated. This range of order parameters of interest may be caused by a transition in the ordering of the quaternary material similar to phase changes seen in ternary compounds but stretched over a region inclduing 20% of the order parameter range. Most parameters calculated are more sensitive to order than to composition in the limited composition range tested; however, the lattice parameter c , piezoelectric coefficient e 33 , and elastic moduli C 12 , C 13 , and C 23 are more sensitive to composition. Of the properties compared, the piezoelectric coefficients are influenced most significantly by changes in both the composition and order parameter. Lattice parameters undergo the smallest changes with order and composition, but these small differences appear to impart large trends in the other properties. Better understanding the effects of disorder and group IV alloying in Zn (Sn , Ge) N 2 allows for more accurate modeling of characteristics of this material system for solid state lighting and other applications. [ABSTRACT FROM AUTHOR]

Many researchers observed enhanced water flow through carbon nanotubes (CNTs) and attributed the reason to large slips. Even after taking significant slip effects into account, there remain unaddressed observations of significant improvements in flow rates. As CNTS are deformable, we represent nanotubes with a deformable-wall using a linear pressure–area relationship. We assume lubrication assumption, and using the properties of nanoconfined water, we derive the model for deformable-nanotubes. We validated our derived model in its limiting cases with the previously reported results in the literature. We compare the predictions by our deformable-wall and rigid-wall model with the experimental results and the MD-simulation predictions by multiple literature studies. Many studies were well-predicted by the rigid-wall model with slips. However, we find that there are many studies with high porosity and thin wall tubes, where elasticity or deformability of the tube is essential in modeling, which is well-predicted by our deformable-wall model with slips. In our study, we focus on investigating the impact of two key factors: the deformability, and the slip length on the flow rate. We find that the flow rate inside the tube increases as the deformability increases or the thickness T and elastic modulus E of the tube-wall decrease). We also find that the flow rate in deformable tubes scales as m ˙ deformable ∼ 1 / α 0 for (Δ p / α A o ) ≪ 1 , m ˙ deformable ∼ 1 / α for (Δ p / α A o ) ∼ O (10 − 1) and m ˙ deformable ∼ α 2 for (Δ p / α A o ) ∼ O (1). Further, for a given deformability, the percentage change in flow rate in the smaller diameter of the tube is much larger than the larger diameter. As the tube diameter decreases for the given pressure, Δ m ˙ / m ˙ increases. We find that for rigid-tube, the flow rate varies m ˙ rigid ∼ Δ p , whereas for the deformable-tubes, the flow rate scales as m ˙ deformable ∼ Δ p 2 for (Δ p / α A o ) ∼ O (10 − 1) , and finally to m ˙ deformable ∼ Δ p 3 for (Δ p / α A o ) ∼ O (1). We further find that slip also significantly increases flow rate, but, deformability has more substantial effect. [ABSTRACT FROM AUTHOR]

This study uses molecular dynamics simulations to explore the mechanical behavior of a CoCrCuFeNi high-entropy alloy (HEA) with Σ5 and Σ13 grain boundaries (GBs) as well as without GBs and dislocation. The analysis focused on understanding the influence mechanisms of these grain boundaries on the mechanical behavior of the HEA. Our findings reveal that the atomic size disparity among the constituent elements induces lattice distortion, leading to deformation in HEAs. The determined elastic constants met Born stability requirements, ensuring mechanical stability across both the examined GBs. Higher elastic moduli were associated with increased strength and stiffness, particularly evident in HEAs with Σ5 GB, surpassing those of non-GB structures. Notably, GB Σ5 demonstrated enhanced strength and hardness, indicated by larger elastic moduli compared with those of non-GB structures. Conversely, GB Σ13 exhibited increased Cauchy pressure and Poisson and Pugh's ratios. The ductility of face-centered cubic HEAs was found to be significantly influenced by the GBs, affecting mechanical properties. The Kleinman parameter highlighted a bending-type bonding with reduced strength at the GBs. Machinability indices indicated high machinability of the CoCrCuFeNi alloy, further enhanced by the presence of the GBs. Direction-dependent parameters underscored the anisotropic nature of the HEA, mitigated by the GBs. Overall, this study elucidates the nuanced influence of different GBs on the mechanical properties of HEAs, offering valuable insights for materials design and applications. The results of this investigation shed light on HEAs with improved mechanical properties via GB engineering. [ABSTRACT FROM AUTHOR]

Under decompression, disordered solids undergo an unjamming transition where they become under-coordinated and lose their structural rigidity. The mechanical and vibrational properties of these materials have been an object of theoretical, numerical, and experimental research for decades. In the study of low-coordination solids, understanding the behavior and physical interpretation of observables that diverge near the transition is of particular importance. Several such quantities are length scales (ξ or l) that characterize the size of excitations, the decay of spatial correlations, the response to perturbations, or the effect of physical constraints in the boundary or bulk of the material. Additionally, the spatial and sample-to-sample fluctuations of macroscopic observables such as contact statistics or elastic moduli diverge approaching unjamming. Here, we discuss important connections between all of these quantities and present numerical results that characterize the scaling properties of sample-to-sample contact and shear modulus fluctuations in ensembles of low-coordination disordered sphere packings and spring networks. Overall, we highlight three distinct scaling regimes and two crossovers in the disorder quantifiers χz and χμ as functions of system size N and proximity to unjamming δz. As we discuss, χX relates to the standard deviation σX of the sample-to-sample distribution of the quantity X (e.g., excess coordination δz or shear modulus μ) for an ensemble of systems. Importantly, χμ has been linked to experimentally accessible quantities that pertain to sound attenuation and the density of vibrational states in glasses. We investigate similarities and differences in the behaviors of χz and χμ near the transition and discuss the implications of our findings on current literature, unifying findings in previous studies. [ABSTRACT FROM AUTHOR]

BackgroundThe calcaneal enthesis, an osseous footprint where the Achilles tendon seamlessly integrates with the bone, represents a complex interface crucial for effective force transmission. Bone adapts to mechanical stress and remodels based on the applied internal and external forces. This study explores the relationship between the elasticity of the Achilles tendon enthesis and the bone microstructure in the calcaneal crescent.MethodsIn total, 19 calcaneal-enthesis sections, harvested from 10 fresh-frozen human cadaveric foot-ankle specimens (73.8 ± 6.0 years old, seven female), were used in this study. Indentation tests were performed at the enthesis region, and Hayes' elastic modulus was calculated for each specimen. Micro-CT scanning was performed at 50-micron voxel size to assess trabecular bone microstructure within six regions of interest (ROIs) and the cortical bone thickness along the calcaneal crescent.ResultsSignificant Spearman correlations were observed between the enthesis elastic modulus and trabecular bone thickness in the distal entheseal (ROI 3) and proximal plantar (ROI 4) regions (R = 0.786 and 0.518, respectively).ConclusionThis study highlights the potential impacts of Achilles tendon enthesis on calcaneal bone microstructure, which was pronounced in the distal calcaneal enthesis, suggesting regional differences in load transfer mechanism that require further investigation.

The present work aims to elucidate the effect of process parameters and pin length on microstructure and the characteristics, distribution of intermetallic compounds (IMCs), and associated failure initiation and progress pattern of AA7075 friction stir lap weld (FSLW) joints prepared employing copper interlayer. FSLW joints obtained using various combinations of tool rotation (900 and 1200 rpm), weld speeds (63 and 98 mm/min), and pin lengths (3 mm and 4 mm) are tested for tensile shear strength, fracture behavior, and the influence of IMCs formed are appraised. Further, the elastic modulus and hardness of the IMCs and neighborhood are evaluated using nanoindentation tests to correlate with the joint performance. The non-uniform thickness of AlCu, Al2Cu, and Al4Cu9 IMCs is formed due to intermixing of Al and Cu whose thickness varied with process parameters. Higher elastic modulus and hardness are recorded at the IMCs. FSLW joint prepared with 1200 rpm tool rotation, 63 mm/min weld speed, and 4 mm pin length results in better joint formation and higher strength, wherein an IMC layer thickness of around 3–4.3 µm is measured near the hook region. [ABSTRACT FROM AUTHOR]

This paper studied the densification, phase composition, microstructure and properties of polycrystalline La 0.6 Ce 0.3 Pr 0.1 B 6 bulks prepared by SPS. The dense specimen (98.9 % in relative density) with the average grain size of 15.46 μm has been determined to be a CsCl-type single-phase substitutional solid solution without any impurities or other secondary phases. The homogenous elemental distributions of La, Ce and Pr have been confirmed by both microscale and nanoscale. The room temperature (RT) Vickers hardness (H v), indentation fracture toughness (K IC) and flexure strength of the dense specimen have been measured to be 23.0 GPa, 2.04 MPa m1/2 and 305.1 MPa, respectively. The Berkovich hardness (H B) and elastic modulus (E) of the dense specimen have been measured to be 30.0 GPa and 376.0 GPa, respectively, by nanoindentation tests at a maximum load of 40 mN. In comparison with the polycrystalline LaB 6 bulk, the lower work function Φ of 2.64 eV evaluated by UPS and the larger thermionic emission current densities measured at the same operating condition suggest that the polycrystalline La 0.6 Ce 0.3 Pr 0.1 B 6 bulk is a superior-performance thermionic cathode material. [ABSTRACT FROM AUTHOR]

Y 2 O 3 ceramics are increasingly recognized for their excellent vacuum stability and high-temperature chemical stability in the field of functional materials research. However, their poor thermal shock resistance renders them susceptible to spalling and damage during use, thus restricting further applications. To address this issue, the low thermal expansion coefficients of Y 2 SiO 5 materials were leveraged. Through an in situ reaction between SiO 2 and Y 2 O 3 , a Y 2 SiO 5 phase was generated that induced a thermal expansion mismatch with Y 2 O 3 , thereby enhancing the thermal shock resistance of the ceramic. Using Y 2 O 3 fine powder as the primary material, silica sol and nano-SiO 2 were selected as reactive silicon sources to prepare Y 2 O 3 –Y 2 SiO 5 composite ceramics at 1750 °C. The impact of the different silicon sources and Y 2 SiO 5 phase content on the microstructure, mechanical, and thermal properties of the composite ceramics was studied. The results demonstrated that the in situ formation of Y 2 SiO 5 significantly improved the thermal shock resistance of the composite ceramic. Specifically, increasing the SiO 2 content led to a gradual rise in the volume fraction of Y 2 SiO 5 formed between Y 2 O 3 grains, thereby increasing the residual flexural strength and enhancing the hardness and elastic modulus. The low thermal expansion coefficient of Y 2 SiO 5 reduced the overall thermal expansion coefficient of the composite material, thereby improving the thermal shock resistance. Moreover, the thermal expansion coefficient mismatch between the Y 2 O 3 and Y 2 SiO 5 phases induced numerous microcracks within the material, providing thermal stress relief within the microcracks and markedly improving the resistance of the ceramic to thermal shock. [ABSTRACT FROM AUTHOR]

Al 2 O 3 ceramic have excellent chemical inertness, superior heat resistance, and excellent corrosion resistance, so they are considered ideal materials for manufacturing high-performance components such as thermal end devices in aerospace, heat dissipation panels in electronic communication, and exhaust filters in the automotive industry. Digital Light Processing (DLP) is a useful technology to fabricate complex Al 2 O 3 ceramic components. However, the size shrinkage effect of DLP-fabricated components need to be investigated deeply before its further application. In this work, we utilized DLP technology to fabricate Al 2 O 3 ceramic honeycomb structures and systematically investigated their microstructure, size shrinkage, and mechanical properties. Our findings revealed that the Al 2 O 3 ceramic grains exhibit flake-like structures with an average diameter of 1–2 μm, and the ceramic particles are tightly bonded. The shrinkage rates in the X and Y axes were 7.54 % and 7.42 %, respectively, while the Z-axis exhibited a more significant shrinkage of 13.04 %. This anisotropic shrinkage in different direction was attributed to accumulation of the interlayer bonding under gravity action during debinding and sintering process. The compressive stress-strain curve of the honeycomb structures demonstrated a typical brittle compressive behavior, including elastic, stress plateau, and brittle fracture stages. The honeycomb structures exhibited an elastic modulus of 54.49 ± 1.22 MPa and a compressive strength of 10.22 ± 0.42 MPa. The fracture analysis indicated that the fractures region of honeycomb structures initiated at the corners of the honeycomb structures, indicating their easy-broken compared to the walls. These findings provide valuable guidance for the high-precision and high-performance manufacturing of complex Al 2 O 3 ceramic components. [ABSTRACT FROM AUTHOR]

[Display omitted] Low mechanical strength is still the key question for collagen hydrogel consisting of nanofibrils as hard tissue repair scaffolds with no loss of biological function. In this work, novel collagen nanofibrous hydrogels with high mechanical strength were fabricated based on the pre-protection of trisodium citrate masked Zr(SO 4) 2 solution for collagen self-assembling nanofibrils and then further coordination with Zr(SO 4) 2 solution. The mature collagen nanofibrils with d -period were observed in Zr(IV) mediated collagen hydrogels by AFM when the Zr(IV) concentration was ≥ 10 mmol/L, and the distribution of zirconium element was uniform. Due to the coordination of Zr(IV) with ─COOH, ─NH 2 and ─OH within collagen and the tighter entanglement of collagen nanofibrils, the elastic modulus and compressive strength of Zr(IV) mediated collagen nanofibrous hydrogel were 208.3 and 1103.0 kPa, which were approximate 77 and 12 times larger than those of pure collagen hydrogel, respectively. Moreover, the environmental stability such as thermostability, swelling ability and biodegradability got outstanding improvements and could be regulated by Zr(IV) concentration. Most importantly, the resultant hydrogel showed excellent biocompatibility and even accelerated cell proliferation. [ABSTRACT FROM AUTHOR]

Flexible perovskite solar cells (FPSCs) have gained considerable attention for potential applications in portable and wearable electronics. However, the design principles governing FPSCs remain incompletely understood. In this study, two critical factors—thermal conductivity and elastic modulus—that significantly influence the thermal and mechanical stabilities of FPSCs are identified. Achieving stress‐less conditions is crucial for enhancing the performance of FPSCs. To address this, a liquid crystal elastomer (LCE) is employed as a buffer interlayer to effectively mitigate residual thermal stress. This is achieved by improving the thermal conductivity of the electron transport layer from 0.76 to 1.07 W mK−1 and softening the perovskite layer, reducing the Young's modulus from 50 to 42 GPa. The optimized thin films are utilized in both rigid and flexible PSCs, resulting in efficiencies of 24.5% and 22.8%, respectively. Remarkably, these devices demonstrated excellent thermal stability, with unpackaged LCE rigid PSCs retaining 85.6% of their initial efficiency after 504 h of aging at 85 °C. Moreover, robust mechanical stability in FPSCs is exhibited, with 88.4% of the original efficiency retained after 5400 bending cycles. This investigation elucidates the profound impact of thermal conductivity and Young's modulus on the efficiency and stability of flexible electronics. [ABSTRACT FROM AUTHOR]

Ion‐gels, with inherent flexibility, tunable conductivity, and multi‐stimulus response, have attracted significant attention in flexible/wearable electronics. However, the design of ion‐gels that exhibit both strength and toughness is challenging. In this study, a novel ion‐gel design is proposed that mimics the hierarchical meshing structure of leaves in combination with ion hybridization. Polyacrylamide (PAM) is incorporated in TEMPO oxidized cellulose nanofibers (TOCNFs) clusters by in situ polymerization, generating a hydrogel with micro/nanoscale entangled networks. Replacement of water by a metal halide ionic liquid ([BMIm]ZnxCly) in the hydrogel resulted in the formation of an ion hybrid network with supramolecular interactions. The integration of the PAM/TOCNF polymer network with [BMIm]ZnxCly resulted in ion‐gels with high strength (5.9 MPa), toughness (22 MJ m−3), and enhanced elastic modulus (30 MPa) combined with non‐flammability, heat and cold resistance. While having fast responsiveness (36 ms) of sensing signal and stability of power supply even at 4000 cycle collisions. Stable signal output even at high (200 °C) /sub‐zero temperatures. The proposed strategy offers a new approach to the material design of flexible/wearable electronics. [ABSTRACT FROM AUTHOR]

This study investigates the effect of aging temperature on the physical properties of Fe–40.32Ni–5.51Cr–2.63Ti–0.47Al–0.55Mn–0.40Si–0.016C (wt.%) alloy using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, a physical-property measurement system, and a dilatometer, among others. After a solution treatment, the microstructure of the experimental alloy was composed of the γ phase. The aging process involved the precipitation of the γ' and η phases to regulate the Elinvar effect. No martensite or ferrite phases were observed in either the solid-solution or aged samples using X-ray diffraction and transmission electron microscopy. The Elinvar effect for traditional Fe–Ni–Cr ferromagnetic Elinvar alloys is related to spontaneous magnetisation, resulting in spontaneous volume magnetostriction. The inflection temperature of the elastic modulus exceeded the Curie temperature. The larger the precipitation amount, the weaker the ΔE effect, and the larger the Young's modulus value. For a holding time of 2 h, the amount of precipitation was maximised at an aging temperature of 650 °C, while Young's modulus and its temperature coefficient achieved maxima of 190 GPa and 9.0 × 10⁻5 °C⁻1, respectively. In addition, the lattice constant at room temperature indirectly reflects the amount of precipitation. Young's modulus, the temperature coefficient of Young's modulus, the Curie temperature, and the linear-expansion coefficient obeyed an approximately parabolic law as functions of the lattice constant or its reciprocal. Moreover, Young's modulus and its temperature coefficient can be estimated using the Curie temperature and linear-expansion coefficient, respectively. [ABSTRACT FROM AUTHOR]

The estimation of mechanical and physical properties of coal reservoirs is important for the successful exploration and development of coalbed methane (CBM). Unlike conventional sandstone reservoirs, coal reservoirs exhibit greater sensitivity to stress, resulting in distinct mechanical and physical behaviors. In this study, uniaxial compression tests were performed on both low-rank and high-rank coal samples under different moisture conditions to reveal the mechanical and physical property changes with stress. The results indicate that during axial stress loading (up to 2.8 MPa), axial strain initially increases rapidly and subsequently at a slower rate, with an axial strain of 0.13–0.25% observed at the maximum axial stress. The instantaneous Young's modulus increases linearly before stabilizing, ranging from 618.01 to 4861.10 MPa, while the Poisson's ratio remains relatively constant or increases linearly, ranging from 0.002 to 0.165. This results in a negative exponential decrease in both porosity and permeability, with maximum reductions of 1.77–4.21% and 5.38–12.25%, respectively. The mechanical properties of coal are influenced by both the cementation effect of water at low water saturation and the softening effect at high water saturation, which results in axial strain decreases and then increases as the water saturation increases. Concurrently, the elastic modulus initially increases and then decreases, while the Poisson's ratio exhibits a less pronounced change or tends to increase. Consequently, there is a trend in which porosity and permeability first increase and then decrease. In addition, during stress unloading, the influence of water in coal induces a notable strain hysteresis phenomenon in water-containing coal samples, and this phenomenon is more obvious in the low-rank coals. [ABSTRACT FROM AUTHOR]

Hybrid fiber‐reinforced composite sandwich panels with multi‐layer polyurethane cores are widely applied in aerospace, automotive, construction, and shipbuilding industries. This study aims to investigate the buckling performance of composite structures with varying numbers of polyurethane cores. To achieve this, the buckling loads of these structures are determined using an energy method, microscopic mechanics method, and the first‐order zigzag kinematic model. The accuracy of the equation employed in the algorithm is validated using the finite element method. Additionally, we conduct a parametric analysis to examine the influence of various parameters on the buckling performance of the structures. The results indicate that an effective strategy for improving the critical buckling loads of the hybrid fiber‐reinforced composite sandwich plate involves strategically placing fibers and matrix materials with higher elastic modulus on the skin layer. Moreover, the critical buckling load is notably influenced by the number and positioning of polyurethane layers, as well as the fiber content. Highlights: An analytical model is established to predict the buckling behavior.The correctness of the model was verified using the finite element method.Effects of structural parameters on buckling performance were investigated. [ABSTRACT FROM AUTHOR]

Acoustic black hole (ABH), as a new wave manipulation technique, shows excellent applications in vibration and noise reduction of structures. Nowadays, most ABHs use materials with a fixed elastic modulus, limiting their low-frequency performance. Herein ABH plates with variable elastic modulus (VM-ABH) is designed, and its vibration and acoustic radiation characteristics are investigated by using numerical analysis. The results show that the vibration response of VM-ABH has a decrease of 5–13.2 dB relative to that of the uniform texture ABH (UT-ABH) in the frequency range of 10–5000 Hz, and the degree of energy aggregation is significantly improved. Moreover, the sound pressure level was reduced by 3.6 dB. Meanwhile, by linearly varying the elastic modulus in the center region of the VM-ABH, the effects of gradient index and terminal elastic modulus on the damping characteristics and dynamic response are revealed. The research results provide new objects for the study of vibration and noise reduction of ABH. [ABSTRACT FROM AUTHOR]

ABSTRACT Rock masses in alpine regions inevitably undergo freeze–thaw (F–T) cycles, which affects the safety of infrastructure such as slopes, with shear failure being a significant concern. This study investigates the Mode II fracture behavior of F–T treated granite via the short core in compression (SCC) test, analyzing the related physical properties and mechanical properties while also discussing F–T damage mechanism at a microscopic level. Results reveal that as F–T cycles increase, the dynamic elastic modulus and P‐wave velocity decrease, whereas porosity and backbone fractal dimension of pore scale increase, indicating a transition towards a large‐scale pore. Mode II fracture toughness decreased by 31.19% and fracture process zone width increased by 248.49% with F–T cycles rising from 0 to 80, and related fractal dimension of surface morphology also increased by 11.17%. Microscopic observation reveals the microstructure deterioration induced by F–T treatment, indicating the correlation between microscopic damage and macroscopic fracture properties. [ABSTRACT FROM AUTHOR]

Long-term cyclic loading can have a significant effect on the modulus of sand, and the influence on saturated coral sand has yet to be established. In this paper, the significant influence of non-plastic fines content (FC) and relative density (D r) on dynamic elastic modulus (E) of saturated coral sand has been evaluated by a series of cyclic triaxial drainage tests. The results show that the dynamic elastic modulus increases rapidly at the beginning of loading; then the growth slows down and finally stabilizes. In general, the development of E is influenced collectively by FC, D r and cyclic stress ratio (CSR). The initial dynamic elastic modulus E d-1 and steady-state dynamic elastic modulus E d-s increase with the increase of D r, and decrease as FC increases. The linear fitting equations are given by introducing the equivalent skeleton void ratio esk*. Furthermore, the relative dynamic elastic modulus E r is defined as the ratio of E d-N to E d-s, and the prediction equation for E r was developed to provide a basis for the engineering mechanical parameters of coral sands under long-term loads. [ABSTRACT FROM AUTHOR]

Man‐made ceramics generally undergo harsh manufacturing conditions (e.g., high‐temperature sintering). In contrast, mineral structures with superior mechanical strength are generated in organisms under mild biocompatible conditions. Herein, it is reported that ceramic objects can be directly produced and strengthened by drying purely inorganic gels (PIGs), mimicking the biological tactic of fabricating continuous monoliths from hydrated amorphous precursors. The overall process is easy and biocompatible in that solutions of common iron and molybdate salts are mixed to generate a PIG, consisting of 80 wt% liquid water and amorphous mineral nanoparticles (hydrated iron molybdate: FeMo2H7O11), which, upon drying under mild temperature, turns into a residual stress‐strengthened ceramic block that displays a high mechanical performance (with a hardness/elastic modulus of 1.7/17.5 GPa). Analogous to the well‐known Prince Rupert's drop reinforced by residual stress upon quenching, the uneven volume shrinkage from the outside inwards during dehydration builds up residual stress that enables amorphous mineral fusion (with the assistance of hydration water) and strengthening. Furthermore, a dramatic bandgap reduction is achieved in the dried objects due to local structural changes of the Fe atoms under residual stress. This PIG‐dehydration approach holds promise for green ceramic manufacturing and offers insights into biomineralization puzzles. [ABSTRACT FROM AUTHOR]

Polymer colloidal crystals (PCCs) have been widely explored as acoustic and optical metamaterials and as templates for nanolithography. However, fabrication impurities and fragility of the self‐assembled structures are critical bottlenecks for the device's efficiency and applications. We have demonstrated that temperature‐assisted pressure [T,p]$T,p]$ annealing results in the mechanical strengthening of PCCs, which improves with the annealing temperature. Here, the enhancement of elastic properties and morphological features of self‐assembled PCC's is evaluated using Brillouin light scattering and scanning electron microscopy. The pressure‐induced effects on the vibrational modes of PCCs are also illustrated at temperatures well below the polymer glass transition. While the PCCs colloid constituents display reversibility, the PCC material is strongly irreversible in the performed thermodynamic cycle. The effective elastic modulus enhances from 0.7 GPa for the pristine sample to 0.8 GPa, solely by pressure annealing at room temperature. [T,p]$T,p]$ annealing at higher temperatures leads to a maximum effective elastic modulus of 1.7 GPa, more than twice the value in the pristine sample. Above a cross‐over pressure, pc(≈${{p}_{c\ }}( \approx $725 bar at 348 K), the PCCs respond elastically and, hence, reversibly to pressure changes. [ABSTRACT FROM AUTHOR]

Organic photodetectors (OPDs) hold immense promise for stretchable and wearable applications, but their photoactive films demonstrate brittleness, stiffness, and mechanical instability, posing challenges for future applications. Herein, the nanoconfinement effect is reported to substantially improve the stretchability and mechanical stability while reducing the stiffness of photoactive films, simultaneously maintaining the high light detection performance. The microstructure, mechanical properties, and photoelectric performance of the quaternary blend films with varying elastomer contents are thoroughly characterized. Additionally, the elastic modulus of quaternary blends can be accurately predicted by the Coran–Patel model. Cyclic tensile tests demonstrate enhanced mechanical stability, resulting in a specific detectivity of the quaternary blend with the nanoconfinement effect being 19 times higher than that of the ternary blend after 200 cycles. Overall, this study provides novel insights into constructing stretchable blend films for wearable electronics. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper investigates the influence of indenter shape and rock texture on the crack growth properties and rock hardness. For this purpose, two different rock specimens such as basalt and marble with various textures were prepared and tested by Vickers indentation hardness device with rhombus indenter shape under two different temperatures of 35°C and 100°C. Concurrent with the experimental test, Vickers indentation simulations have been done on three calibrated rock models with nine different indenter shapes. The tensile strength of marble was 8 MPa, while basalt had a tensile strength of 10.8 MPa. Regarding compressive strength, marble exhibited 71 MPa, whereas basalt had a compressive strength of 153 MPa. Marble and basalt had elastic moduli of 45 and 95 GPa, respectively. The physical loading was applied vertically at a rate of 0.004 mm/min. The rock's texture and temperature significantly impact Vickers indentation hardness. Penetration by the Vickers indenter creates an elastic‐plastic stress field, leading to radial cracks due to exceeding the critical stress level. Ring cracks are caused by bulging of the test material and nested cracks directly under the indentation due to high shear and bending stresses in the region. The indentation shape affected the extent of the damage zone below it, leading to increased crack growth with smaller indentation diameters. The radial fracture number increased when the cross‐section changed from circular to quadrilateral shape. The crack growth and damage zone area increased with higher rock temperature due to increased rock brittleness. [ABSTRACT FROM AUTHOR]

ABSTRACT Functionally graded coating (FGC) has played a pivotal role in numerous engineering applications owing to its exceptional properties. This work proposes a novel elastohydrodynamic lubrication (EHL) model with FGC, in which the elastic deformation and stress are computed using influence coefficients (ICs) and discrete convolution‐fast Fourier transform (DC‐FFT) algorithm. Comparisons are made with homogeneous EHL solutions and finite element analysis (FEA) to validate its accuracy. The study systematically explores how coating elastic modulus, coating thickness and substrate elastic modulus influence contact and lubrication behaviours. The developed model is expected to establish a theoretical framework for FGC material design, enhancing the performance of friction pairs. [ABSTRACT FROM AUTHOR]

To assess the impact of elastic gradients formed among restorative material, cement, and substrate on the fracture resistance of tri-layer restorative systems. Four CAD/CAM materials were utilized, two glass-ceramics (IPS e.max CAD, Vita Suprinity) and two resin-ceramic hybrids (Vita Enamic, Lava Ultimate). Their fracture resistance was examined by biaxial flexure (n = 8) and Hertzian indentation (n = 10) tests. Statistical analysis was conducted using ANOVA and Tukey tests (p = 5 %). Finite element analysis (FEA) was employed to simulate the Hertzian indentation test and elucidate the stress-fields formed on the intaglio surface below the loading area. The biaxial flexural strength (MPa) of glass-ceramics exceeded the hybrid materials (e.max 417a, Suprinity 230b, Enamic 138c, and Lava Ultimate 183bc). Conversely, the load-bearing capacity (N) of the materials bonded to dentin analog demonstrated the opposite trend, with the hybrid materials achieving superior results (e.max 830 C, Suprinity 660D, Enamic 1822B, and Lava Ultimate 2593 A). The stress-fields observed by FEA were coherent with the experimental results for Hertzian flexural stresses (MPa): e.max 501 A, Suprinity 342 C, Enamic 406B, whereas no tensile stress was observed at the intaglio surface of Lava Ultimate. Detailed analysis of the fracture resistance of the tri-layer restorative systems showed that the elastic gradients play a more significant role than the flexural strength of the restorative materials. The coherence of the elastic moduli between the restorative material and supporting structures results in reduced tensile stress concentration at the intaglio surface beneath the loading area and enhances the ability to withstand load. • The biaxial flexural strength of glass-ceramics exceeds that of the hybrid materials. • When bonded to "dentin", the load-bearing capacity is greater for hybrid materials. • When bonded to "dentin", no flexural stress is observed for Lava Ultimate. • Elastic gradients are critical to the fracture resistance of restorative materials. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the degree of conversion (%), flexural strength (MPa), elastic modulus (GPa), compressive strength (MPa), Knoop microhardness (KHN), post-gel shrinkage (%) and prediction of ideal concentration of cholesteryl methacrylate (CM) in experimental resins. Four formulations were manipulated (F): F1, control group, (0 % CM); F2 (15 % CM); F3 (19.8 % CM) and F4 (30 % CM). Bis-GMA and CM percentages were determined using Statistica™ software. For the degree of conversion test, Raman spectroscopy was used. To testing flexural strength, elastic modulus and compressive strength, a universal testing machine was used. For the Knoop microhardness test five indentations were made in each sample. Post-gel shrinkage was determined using the strain gauge method. Statistica™ software processed all data obtained in this study. Results were submitted to one-way ANOVA and Tukey's post hoc tests (α = 0.05). Better performance was observed for F2 (15 % CM) and F3 (19,8 % CM) for degree of conversion, elastic modulus and post-gel shrinkage. For Knoop microhardness F2 (15 % CM), F3 (19,8 % CM) and F4 (30 % CM) showed higher values than F1 (0 % CM). For flexural strength F1 (0 % CM) and F3 (19,8 %) were similar and F4 showed the lowest values and for compressive strength F1 (0 % CM) showed the highest values. For mixture designs analysis data, concentrations ≤ 25 % of CM would provide better results. Addition of CM at concentrations lower than 30 % contributed to a significant increase in the degree of conversion, microhardness values, elastic modulus and reduction of post-gel shrinkage. • Cholesteryl methacrylate proved to be a promising polymer for improving composites. • An endocyclic double bond can be an additional site for photochemical cycloaddition. • Concentrations ≤ 25 % cholesteryl methacrylate enhance composite resins. • Post-gel shrinkage performed better with 15 %, 19.8 % and 30 % cholesteryl methacrylate. • Knoop microhardness was higher with 15 %, 19.8 %, and 30 % cholesteryl methacrylate. [ABSTRACT FROM AUTHOR]

This study highlights the impact of low amounts of MoS2 quantities on composite performance by examining the effects of ultrasonication exfoliated MoS2 at different loadings (0.1–0.5 wt%) on the mechanical and tribological parameters of epoxy composites. Even at low concentrations, the ultrasonication and exfoliation procedures greatly improve the dispersion of MoS2 in the epoxy matrix, enabling its efficient incorporation into the tribofilm during sliding. Optimum mechanical properties were demonstrated by the MoS2/epoxy composite at 0.3 wt%, including a modulus of elasticity of 0.86 GPa, an ultimate tensile strength of 61.88 MPa, and a hardness of 88.0 Shore D, representing improvements of 61.5%, 35.45%, and 16.21%, respectively. Corresponding tribological tests revealed that high sliding velocity (10 N load, 0.2 m/s) resulted in a 44.07% reduction in the coefficient of friction and an 86.29% reduction in wear rate compared to neat epoxy. The enhanced tribological performance is attributed to the efficient removal and incorporation of MoS2 into the tribofilm, where it acts as a solid lubricant that significantly reduces friction and wear. Even though an ultra-low amount of filler concentration was added to the composite, a unique finding was the high MoS2 content in the tribofilm at higher sliding speeds, enhancing lubrication and wear protection. This study establishes that even ultralow MoS2 content, when uniformly dispersed, can profoundly improve the mechanical and tribological properties of epoxy composites, offering a novel approach to enhancing wear resistance. [ABSTRACT FROM AUTHOR]

Red blood cells respond to fluctuations in blood plasma pH by changing the rate of biochemical and physical processes that affect the specific functions of individual cells. This study aimed to analyze the effect of pH changes on red blood cell morphology and structure. The findings revealed that an increase or decrease in pH above or below the physiological level of pH 7.4 results in the transformation of discocytes into echinocytes and causes significant alterations in the membrane, including its roughness, cytoskeleton structure, and the cell's elastic modulus. Furthermore, the study shown a strong connection between critical acidosis and alkalosis with increased intracellular reactive oxygen species production. [ABSTRACT FROM AUTHOR]

Scanning probe microscopy (SPM) is a versatile tool for studying a wide range of materials. It is well suited for investigating living matter, for example, in single-cell neutrophil studies. SPM has been extensively utilized to analyze cell physical properties, providing detailed insights into their structural and functional characteristics at the nanoscale. Its long-standing application in this field highlights its essential role in cell biology and immunology research, significantly contributing to understanding cellular mechanics and interactions. In this review, we discuss the application of SPM techniques, specifically atomic force microscopy (AFM) and scanning ion-conductance microscopy (SICM), to study the fundamental functions of neutrophils. In addition, recent advances in the application of SPM in single-cell immunology are discussed. The application of these techniques allows for obtaining data on the morphology, topography, and mechanical and electrochemical properties of neutrophils with high accuracy. [ABSTRACT FROM AUTHOR]

The material properties and structural characteristics of ballistic composites are crucial to their ballistic performance. A numerical model of a 1.1 g FSP penetrating a UHMWPE target plate was established in this paper. The numerical results show that the failure process of the body armor target plate primarily involves shear failure, interlayer delamination, and tensile failure. Based on this, further research was conducted on the influence of material properties and structural characteristics on the ballistic limit velocity of the UHMWPE armor plate. Furthermore, the study evaluates the effects of elastic modulus, tensile strength, shear strength, number of layers, and interlayer strength on the ballistic limit velocity of UHMWPE body armor. The findings reveal that the ballistic limit velocity is most sensitive to changes in shear strength, with variation rates ranging from −18% to +11%, showing an approximate positive correlation, while the elastic modulus has the smallest impact on ballistic limit velocity, with variation rates ranging from −2% to +4%. Additionally, appropriate interlayer strength can improve the ballistic limit velocity of the body armor to a certain extent. This study provides theoretical methods and recommendations for optimizing anti-penetration performance of UHMWPE body armor. [ABSTRACT FROM AUTHOR]

A dense monolithic SiC/(Hf0.25Ta0.25Zr0.25Nb0.25)C/C high-entropy ceramic nanocomposite was prepared using a polymer-derived ceramic (PDC) method combined with spark plasma sintering (SPS). The microstructural evolution and mechanical properties of the obtained nanocomposites were characterized by X-ray diffractometer (XRD), transmission electron microscope (TEM), scanning-electron microscope (SEM), and nanoindentation. The results indicate that the phase composition of SiC/(Hf0.25Ta0.25Zr0.25Nb0.25)C/C can be adjusted by modifying the metal content of the single-source precursor (SSP) through molecular design. The resulting precursor exhibits an exceptionally high ceramic yield, with mass retention of over 90% at 1100 °C, which guarantees the densification of the final SiC/(Hf0.25Ta0.25Zr0.25Nb0.25)C/C composites. The PDC route facilitates the in situ formation of a high-entropy phase within the ceramic matrix under low temperature pyrolysis conditions. Combined with SPS, a dense monolithic SiC/(Hf0.25Ta0.25Zr0.25Nb0.25)C/C nanocomposite was obtained, exhibiting an open porosity of 0.41 vol%, nano-hardness of 27.47 ± 0.46 GPa, elastic modulus of 324.00 ± 13.60 GPa, and fracture toughness of 3.59 ± 0.24 MPa·m0.5, demonstrating excellent mechanical properties. [ABSTRACT FROM AUTHOR]

Nickel foam offers excellent conductivity, a high surface area, and lightweight structure, making it ideal for applications, like battery electrodes, catalysts, and filtration systems. Its durability and corrosion resistance further enhance its performance in various industries. However, few studies focus on the tensile anisotropy of nickel foam and its tensile fracture process. In this study, the anisotropic tensile behavior of nickel foam with varying relative densities has been investigated, along with its tensile fracture behavior using in situ techniques. The tensile properties of nickel foams show strong anisotropy due to the flattening process in the production process. The results show that the tensile properties, including the yield strength, tensile strength, and elastic modulus, increase with the increasing relative density, while the elongation percentage has no relationship with the relative density. The experiment data on tensile strength are in agreement with Gibson's formula and Liu's formula. In situ tensile tests are conducted to explore the microscopic fracture mechanism of nickel foam. The results show that the struts of nickel foam are tensile fractures or shear fractures near the joints, and the fracture process of struts is clearly recorded and analyzed. This study is significant as it provides critical insights into the anisotropic tensile behavior of nickel foam and fracture mechanism, enabling the optimization of production processes and broadening its potential applications. [ABSTRACT FROM AUTHOR]

Purpose: To compare the mechanical properties of human annulus fibrosus obtained by forceps versus bistoury and observe whether the measurement could be affected by forceps sampling method. Methods: In this study, the mechanical properties of the the extracellular matrix (ECM) of human annulus fibrosus, including elastic modulus and stiffness, were investigated using atomic force microscope (AFM). Tissue was obtained from patients during operation using a bistoury or nucleus pulposus forceps. Tissues obtained with the nucleus pulposus forceps were considered as the forceps group and those obtained with a bistoury were considered as the bistoury group. Results: There was no significant difference observed between the forceps and bistoury group according to histological staining. The elastic modulus of the forceps group was 0.41 ± 0.08 MPa, and that of bistoury group was 0.53 ± 0.13 MPa, and the difference between the two groups was statistically significant (p < 0.05). The stiffness of the forceps group was 0.024 ± 0.003 N/m, and that of the bistoury group was 0.037 ± 0.003 N/m, and the difference between the two groups was statistically significant (p < 0.05). Conclusion: The results indicate that the forceps sampling method has a substantial negative effect on the micromechanical properties of the ECM of the annulus fibrosus. Bistoury sampling method is recommended as the experimental subject for exploring the micromechanics mechanisms of cervical degenerative disease. [ABSTRACT FROM AUTHOR]

Background: The skin is the largest organ of the human body and serves distinct functions in protecting the body. The viscoelastic properties of the skin play a key role in supporting the skin‐healing process, also it may be changed due to some skin diseases. Propose: In this study, high‐frequency ultrasound (HFUS) elastography based on a Lamb wave model was used to noninvasively assess the viscoelastic anisotropy of human skin. Method: Elastic waves were generated through an external vibrator, and the wave propagation velocity was measured through 40 MHz ultrafast HFUS imaging. Through the use of a thin‐layer gelatin phantom, HFUS elastography was verified to produce highly accurate estimates of elasticity and viscosity. In a human study involving five volunteers, viscoelastic anisotropy was assessed by rotating an ultrasound transducer 360°. Results: An oval‐shaped pattern in the elasticity of human forearm skin was identified, indicating the high elastic anisotropy of skin; the average elastic moduli were 24.90 ± 6.63 and 13.64 ± 2.67 kPa along and across the collagen fiber orientation, respectively. The average viscosity of all the recruited volunteers was 3.23 ± 0.93 Pa·s. Conclusions: Although the examined skin exhibited elastic anisotropy, no evident viscosity anisotropy was observed. [ABSTRACT FROM AUTHOR]

Traditional methods for measuring single-cell mechanical characteristics face several challenges, including lengthy measurement times, low throughput, and a requirement for advanced technical skills. To overcome these challenges, a novel machine learning (ML) approach is implemented based on the convolutional neural networks (CNNs), aiming at predicting cells' elastic modulus and constitutive equations from their deformations while passing through micro-constriction channels. In the present study, the computational fluid dynamics technology is used to generate a dataset within the range of the cell elastic modulus, incorporating three widely-used constitutive models that characterize the cellular mechanical behavior, i.e., the Mooney-Rivlin (M-R), Neo-Hookean (N-H), and Kelvin-Voigt (K-V) models. Utilizing this dataset, a multi-input convolutional neural network (MI-CNN) algorithm is developed by incorporating cellular deformation data as well as the time and positional information. This approach accurately predicts the cell elastic modulus, with a coefficient of determination R2 of 0.999, a root mean square error of 0.218, and a mean absolute percentage error of 1.089%. The model consistently achieves high-precision predictions of the cellular elastic modulus with a maximum R2 of 0.99, even when the stochastic noise is added to the simulated data. One significant feature of the present model is that it has the ability to effectively classify the three types of constitutive equations we applied. The model accurately and reliably predicts single-cell mechanical properties, showcasing a robust ability to generalize. We demonstrate that incorporating deformation features at multiple time points can enhance the algorithm's accuracy and generalization. This algorithm presents a possibility for high-throughput, highly automated, real-time, and precise characterization of single-cell mechanical properties. [ABSTRACT FROM AUTHOR]

Based on the local resonance theory, the vibration isolation performance of four-component periodic pile barriers consisting of a matrix, an outer pipe, an inner pipe, and a pile core was investigated using the finite element method (FEM). This configuration is contrasted with traditional three-component periodic pile barriers, which are composed of a matrix, a pipe, and a pile core. The four-component systems demonstrate significantly broader bandgaps compared to three-component systems. To validate the efficiency of the FEM, model test on pile barriers were conducted, facilitating a comparison between the FEM and experimental observations of bandgap characteristics. Additionally, the effects of the outer pipe's density, elastic modulus, and thickness on the complete bandgap characteristics were comprehensively studied within the four-component structure. It is found that the broadest vibration isolation band gaps occur under hexagonal arrangement pattern. In square and hexagonal lattice configurations, the density, elastic modulus, and thickness of the outer pipe pile's pile have predominantly influenced the upper bound frequency (UBF). There has been a positive correlation between the elastic modulus and the UBF, while the density and thickness have shown inverse relationships. Moreover, there exists a elastic modulus threshold, marking a transition in the displacement mode of the UBF, from the outer irreducible Brillouin zone (M or X) to the inner zone (Γ). Once the threshold is exceeded, both the vibration displacement mode and the width of bandgap remain substantially unchanged. The results obtained in the present paper are very useful for the design and application of periodic pile barriers in ambient vibration reduction. [ABSTRACT FROM AUTHOR]

As one of the hotspots in rock mechanics research, coal rock's dynamic tensile properties are crucial to the parameter selection of blasting engineering, mechanism studies of rock burst disasters, and stability control. The stress states of coal rock during indirect tension with Brazilian splitting and direct tension with split Hopkinson tensile bar (SHTB) were compared using numerical simulations, revealing the superiority of the direct-tension test. On this basis, systematic dynamic direct-tension tests of coal rock under the strain rates (124 to 247 s−1) were carried out utilizing the improved SHTB, and quasi-static tensile tests were performed for comparison. The results reveal that the connection mode of using high-strength adhesive paste specimens and gradient reinforcement with steel wire mesh is reliable for SHTB tests. However, the stress equilibrium is no longer satisfied if the strain rate exceeds 300 s−1, and the layered fracture of the specimen will occur. With an increase in strain rate, the dynamic elastic modulus increases linearly, the dynamic tensile strength tends to increase as an exponential function, and the dynamic increase factor (DIF) tends to increase linearly in two stages. The DIF grows slowly once the strain rate is over 180 s−1 and the dynamic ultimate tensile strength of the coal rock lies around 8 MPa. Finally, based on the improved Zhu–Wang–Tang (ZWT) model and the introduction of dynamic damage factor, the unified damage constitutive equation that can describe the strain rate effect under dynamic tension of coal rock is constructed. Moreover, the rationality of the constitutive parameter value is verified. Highlights: Superiority of direct tension test over Brazilian disk tensile test is revealed Functional relationship between tensile DIF and strain rate of coal rock isobtained Unified damage constitutive model of coal rock under dynamic tension isconstructed [ABSTRACT FROM AUTHOR]

To prevent economic losses caused by borehole breakout during coalbed methane extraction, it is essential to understand the mechanisms of borehole deformation and the distribution patterns of stress-induced fractures. However, previous research efforts have failed to address these aspects adequately. This article investigates the geometry nature of borehole breakout in pre-loaded coal samples under various factors using the discrete element method (DEM). The results revealed significant distinctions in borehole breakout behaviour between coal and other geological materials. In the case of coal, the geometry of breakout is particularly pronounced during the initial stages of failure. However, as stress differentials intensify, the geometry undergoes relatively minimal alterations compared to other rock formations, suggesting a relatively weak sensitivity. The geometry of the borehole breakout in the coal seam widened and deepened as the stress difference increased and the coal elastic modulus decreased. The breakout volume first increased significantly and remained stable as the stress difference increased. A critical threshold line is proposed to represent the macroscopic failure of coal rock caused by drilling, considering the combined effects of elastic modulus and stress differential. The region below the threshold line represents the trend of macroscopic failure after drilling instability, while the region above the threshold line indicates a stable trend. The findings of this study have practical implications for engineering applications. Highlights: Various factors (stress difference, borehole size, coal elastic modulus) influence the geometry nature of borehole breakout in coal. Breakout depth and breakout width in simulated coal rock show a linear positive correlation with stress differences. Borehole deformation in coal seams is apparent once it occurs but shows lower sensitivity to the in-situ stress difference compared to sandstone and limestone,. A decisive criterion for determining whether borehole breakout leads to macroscopic fracture in coal rock is suggested by considering the joint impact of elastic modulus and stress difference. [ABSTRACT FROM AUTHOR]

Opalinus Clay is a stratified shale that exhibits anisotropic deformation properties. In this work, the transversely isotropic deformation parameters of Opalinus Clay are summarized from recent undrained triaxial test campaigns. Relatively consistent values are found for Poisson's ratios representing different orientations, regardless of the lithofacies and the effective confining stresses used in the tests. Pressuremeter tests were performed at the Mont Terri Rock Laboratory in two boreholes perpendicular and parallel to bedding, respectively. The elastic moduli normal to the borehole wall (borehole moduli) are determined using unloading data obtained at multiple diametric caliper axes and exhibit strong anisotropy for the tests in the borehole parallel to bedding. The anisotropic borehole moduli are predicted based on Amadei and Savage's (Int J Rock Mech Min Sci 28:383–396, 1991. https://doi.org/10.1016/0148-9062(91)90077-Y) analytical solution using the laboratory-derived Poisson's ratios and the shear modulus derived from pressuremeter tests in the borehole perpendicular to bedding. The prediction overestimates the magnitude of the borehole moduli but underestimates their anisotropic ratio compared to that from pressuremeter measurement. Drilling a borehole parallel to the bedding of Opalinus Clay is known to induce a local borehole damage zone preferentially developed normal to bedding. The results from a finite element analysis that incorporates this local damage are in better agreement with the pressuremeter measurement. Highlights: The elastic parameters of Opalinus Clay assessed from laboratory triaxial tests show transversely isotropic (TI) properties with reasonably consistent Poisson's ratios but large scatters of Young's moduli. The elastic moduli determined from pressuremeter tests in boreholes with orientations perpendicular and parallel to the bedding of Opalinus Clay also indicate the TI properties. The anisotropic elastic response observed from the pressuremeter tests can be explained using Amadei and Savage's (1991) solution with laboratory-derived Poisson's ratios. A numerical solution further incorporating the local borehole damage better predicts the anisotropic elastic response from the pressuremeter tests. [ABSTRACT FROM AUTHOR]

Xiyu conglomerate, widely distributed in the Xinjiang province of China, plays a crucial role in tunnel construction given its mechanical properties under freeze–thaw cycles. Composed mainly of gravel and cementing material, the heterogeneity in the mechanical properties of Xiyu conglomerate results in a damage evolution mechanism under freeze–thaw cycles distinct from that of common rocks. In accordance with the local climatic conditions, this study conducted instantaneous uniaxial monotonic loading and cyclic loading–unloading tests on Xiyu conglomerate specimens with varying freeze–thaw cycle numbers. The relationship between fundamental physical–mechanical properties of Xiyu conglomerate (porosity, P-wave velocity, uniaxial compressive strength, elastic modulus, etc.) and the number of freeze–thaw cycles was analyzed. Deformation characteristics and energy evolution patterns under cyclic loading–unloading for different freeze–thaw cycle numbers were investigated. Computed tomography (CT) scanning experiments were employed to analyze the crack propagation mechanism of Xiyu conglomerate specimens under freeze–thaw damage conditions. In response to observed anomalies in Xiyu conglomerate, our study developed a novel damage evolution model, integrating experimental insights to precisely quantify the combined impacts of freeze–thaw cycles and cyclic loading–unloading. This model not only reflects the unique characteristics of Xiyu conglomerate but also offers new theoretical perspectives on understanding its degradation process. The findings of this research contribute theoretical support to tunnel construction projects in the Xinjiang region of China. Highlights: Research reveals how Xiyu conglomerates respond to natural freeze-thaw cycles. Analyzing Xiyu conglomerate deformation and energy during freeze-thaw and cyclic loading. Developing a dissipated energy based freeze-thaw damage evolution model. Using CT scans to explore freeze-thaw damage mechanisms of inhomogeneous Xiyu conglomerate. [ABSTRACT FROM AUTHOR]

Original coal reservoir contains massive free and adsorbed methane, that directly affects the mechanical properties and permeability of coal with its unique dual effects, which may, thus, promote the gestation and occurrence of mine gas disasters. Mining disturbance and borehole drainage can facilitate the plastic rupture of surrounding rock mass, which would result in the gas migration law becoming more complex that, in turn, would be difficult to explain based on classical elastic deformation theory. Therefore, understanding elastoplastic deformation behavior and gas migration law relating to coal under engineering disturbance is crucial for preventing gas disasters. First, when mechanical and adsorption induced effects of gas on coal are considered, a concept of effective total pore pressure has been proposed. From which, calculation of plastic deformation in accordance with non-associated flow rule, a constitutive model that considered elastoplastic deformation (EPC Model) was established to simulate deformation and failure characteristics. Following that, a permeability jump coefficient was introduced to describe the sudden increase in permeability following damage and failure in coal, and an elastoplastic damage-permeability model (EPDP Model) was further deduced on basis of cubic law. Finally, through triaxial compression-seepage experimental data to verify the established EPC Model and EPDP Model. The results revealed that gas would weaken coal's mechanical properties (peak strength and elastic modulus) by changing its microstructure, whose deterioration would become more obvious with an increase of gas pressure. The changes to the permeability curve were of an "S" type, which showed a good corresponding relationship with the change trends relating to whole stress–strain curve. Both the EPC Model and the EPDP Model exhibited satisfactory matching effects with experimental data. Furthermore, EPDP Model was popularized and applied, with its universality being verified by the experimental data relating to a reduction in pore pressure seepage. This research will provide a new thinking for ensuring safe and efficient production in coal mines. Highlights: When the double effect of gas on coal were examined, Terzaghi's effective stress principle was modified appropriately, and a concept of effective total pore pressure has been proposed. The plastic strain on coal during triaxial compression was calculated, and an elastoplastic constitutive model that investigated gas action was further deduced. A permeability jump coefficient was introduced to describe permeability change following damage and failure to coal, thereby, making it possible to establish a damage-permeability model during elastoplastic deformation. The damage-permeability model was simplified appropriately, in order for it to be suitable to be employed as a classical elastic permeability model appropriate during CBM extraction stage, with its application scope of the permeability model being extended. [ABSTRACT FROM AUTHOR]