Search

Biomolecular condensates are viscoelastic materials defined by time-dependent, sequence-specific complex shear moduli. Here, we show that viscoelastic moduli can be computed directly using a generalization of the Rouse model that leverages information regarding intra- and inter-chain contacts, which we extract from equilibrium configurations of lattice-based Metropolis Monte Carlo (MMC) simulations of phase separation. The key ingredient of the generalized Rouse model is a graph Laplacian that we compute from equilibrium MMC simulations. We compute two flavors of graph Laplacians, one based on a single-chain graph that accounts only for intra-chain contacts, and the other referred to as a collective graph that accounts for inter-chain interactions. Calculations based on the single-chain graph systematically overestimate the storage and loss moduli, whereas calculations based on the collective graph reproduce the measured moduli with greater fidelity. However, in the long time, low-frequency domain, a mixture of the two graphs proves to be most accurate. In line with the theory of Rouse and contrary to recent assertions, we find that a continuous distribution of relaxation times exists in condensates. The single crossover frequency between dominantly elastic vs dominantly viscous behaviors does not imply a single relaxation time. Instead, it is influenced by the totality of the relaxation modes. Hence, our analysis affirms that viscoelastic fluid-like condensates are best described as generalized Maxwell fluids. Finally, we show that the complex shear moduli can be used to solve an inverse problem to obtain the relaxation time spectra that underlie the dynamics within condensates. This is of practical importance given advancements in passive and active microrheology measurements of condensate viscoelasticity. [ABSTRACT FROM AUTHOR]

β-LiGaO2 with a wurtzite-like crystal structure is a direct ultra-wide bandgap semiconductor. Similar to many wide bandgap oxides, the valence band of LiGaO2 is predominantly composed of O-2p orbital, leading to a low valence band position, drastically limiting its applications. In this work, we employ first-principles calculations to demonstrate that adding a small amount of Bi into LiGaO2 to form the highly mismatched Li(Ga1−xBix)O2 alloys can dramatically modulate the valence band compositions. Compared to LiGaO2, the valence band maximum of the alloys is significantly elevated, and a fully occupied intermediate valence band appears, further raising the valence band positions. Despite the appearance of intermediate valence bands that significantly reduce the alloys' bandgap, the bandgap remains over 3.10 eV, ensuring visible light transparency. With increasing Bi composition in the alloys, the bulk modulus increases while the shear modulus gradually decreases, which improves the ductility. Moreover, the compliant elastic constants of the alloys indicate mechanical stability. These findings suggest that Li(Ga1−xBix)O2 alloys are promising flexible transparent conductive oxides, offering valuable insights for future applications. [ABSTRACT FROM AUTHOR]

The boson peak in the terahertz vibrational spectrum carries information about nano-heterogeneities in the shear modulus in glass formers. Its evolution upon heating or cooling in a supercooled liquid state may shed light on the temperature dependence of heterogeneities. For this purpose, an analysis of the light scattering spectra of supercooled glycerol in the spectral range of the boson peak and fast relaxation was carried out and the parameters of the boson peak in the temperature range 180–330 K were determined. The temperature dependent frequency of the boson peak was then expressed in terms of the mean-square amplitude of the shear modulus fluctuations. This was done using the heterogeneous elasticity theory in combination with the perturbation theory on small fluctuations and Ioffe–Regel criterion for transverse vibrations in glass formers. The contribution of structural relaxation effects to phonon damping becomes significant with increasing temperature. It is shown here that structural relaxation largely determines the temperature dependence of the mean-square fluctuations of the shear modulus at high temperatures. By solving the inverse problem, the temperature dependence of shear modulus fluctuations was obtained. It shows a rapid decrease above ∼250 K with a linear extrapolation going to zero at the so-called Arrhenius temperature TA = 350 K. Comparison with literature data on the Landau–Placzek ratio shows that they have a similar temperature dependence at T < TA, which is explained by the appearance of nanometer scale spatial heterogeneities below TA. This is confirmed by the temperature dependence of the amplitude of the boson peak. [ABSTRACT FROM AUTHOR]

In this work, the Common Model of Multi-phase Strength and Equation of State (CMMP) model was applied to tin. Specifically, calibrations of the strength-specific elements of the CMMP foundation were developed with a combination of experiments and theory, and then the model was validated experimentally. The first element of the foundation is a multi-phase analytic treatment of the melt temperature and the shear modulus for the solid phases. These models were parameterized for each phase based on ab initio calculations using the software VASP (Vienna Ab initio Simulations Package) based on density functional theory. The shear modulus model for the ambient β phase was validated with ultrasonic sound speed measurements as a function of pressure and temperature. The second element of the foundation is a viscoplastic strength model for the β phase, upon which strength for inaccessible higher-pressure phases can be scaled as necessary. The stress–strain response of tin was measured at strain rates of 10 − 3 to 3 × 10 3 s − 1 and temperatures ranging from 87 to 373 K. The Preston–Tonks–Wallace (PTW) strength model was fit to that data using Bayesian model calibration. For validation, six forward and two reverse Taylor impact experiments were performed at different velocities to measure large plastic deformation of tin at strain rates up to 10 5 s − 1 . The PTW model accurately predicted the deformed shapes of the cylinders, with modest discrepancies attributed to the inability of PTW to capture the effects of twinning and dynamic recrystallization. Some material in the simulations of higher velocity Taylor cylinders reached the melting temperature, thus testing the multiphase model because of the presence of a second phase, the liquid. In simulations using a traditional modeling approach, the abrupt reduction of strength upon melt resulted in poor predictions of the deformed shape and non-physical temperatures. With CMMP, the most deformed material points evolved gradually to a mixed solid–liquid but never a fully liquid state, never fully lost strength, stayed at the melt temperature as the latent heat of fusion was absorbed, and predicted the deformed shape well. [ABSTRACT FROM AUTHOR]

The boson peak (BP), a low-energy excess in the vibrational density of states over the Debye contribution, is often identified as a characteristic of amorphous solid materials. Despite decades of efforts, its microscopic origin still remains a mystery. Recently, it has been proposed, and corroborated with simulations, that the BP might stem from intrinsic localized modes involving one-dimensional (1D) string-like excitations ("stringlets"). We build on a theory originally proposed by Lund that describes the localized modes as 1D vibrating strings, but we specify the stringlet size distribution to be exponential, as observed in simulations. We provide an analytical prediction for the BP frequency ωBP in the temperature regime well below the observed glass transition temperature Tg. The prediction involves no free parameters and accords quantitatively with prior simulation observations in 2D and 3D model glasses based on inverse power law potentials. The comparison of the string model to observations is more uncertain when compared to simulations of an Al–Sm metallic glass material at temperatures well above Tg. Nonetheless, our stringlet model of the BP naturally reproduces the softening of the BP frequency upon heating and offers an analytical explanation for the experimentally observed scaling with the shear modulus in the glass state and changes in this scaling in simulations of glass-forming liquids. Finally, the theoretical analysis highlights the existence of a strong damping for the stringlet modes above Tg, which leads to a large low-frequency contribution to the 3D vibrational density of states, observed in both experiments and simulations. [ABSTRACT FROM AUTHOR]

Grafting polymer chains to the surface of nanoparticles overcomes the challenge of nanoparticle dispersion within nanocomposites and establishes high-volume fractions that are found to enable enhanced material mechanical properties. This study utilizes coarse-grained molecular dynamics simulations to quantify how the shear modulus of polymer-grafted nanoparticle (PGN) systems in their glassy state depends on parameters such as strain rate, nanoparticle size, grafting density, and chain length. The results are interpreted through further analysis of the dynamics of chain conformations and volume fraction arguments. The volume fraction of nanoparticles is found to be the most influential variable in deciding the shear modulus of PGN systems. A simple rule of mixture is utilized to express the monotonic dependence of shear modulus on the volume fraction of nanoparticles. Due to the reinforcing effect of nanoparticles, shortening the grafted chains results in a higher shear modulus in PGNs, which is not seen in linear systems. These results offer timely insight into calibrating molecular design parameters for achieving the desired mechanical properties in PGNs. [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]

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]

We report results on the mechanical and structural response to shear deformation of nanodiamond superstructures in interlayer-bonded twisted bilayer graphene (IB-TBG) and interlayer-bonded graphene bilayers with randomly distributed individual interlayer C–C bonds (RD-IBGs) based on molecular-dynamics simulations. We find that IB-TBG nanodiamond superstructures subjected to shear deformation undergo a brittle-to-ductile transition (BDT) with increasing interlayer bond density (nanodiamond fraction). However, RD-IBG bilayer sheets upon shear deformation consistently undergo brittle failure without exhibiting a BDT. We identify, explain, and characterize in atomic-level detail the different failure mechanisms of the above bilayer structures. We also report the dependence of the mechanical properties, such as shear strength, crack initiation strain, toughness, and shear modulus, of these graphene bilayer sheets on their interlayer bond density and find that these properties differ significantly between IB-TBG nanodiamond superstructures and RD-IBG sheets. Our findings show that the mechanical properties of interlayer-bonded bilayer graphene sheets, including their ductility and the type of failure they undergo under shear deformation, can be systematically tailored by controlling interlayer bond density and distribution. These findings contribute significantly to our understanding of these 2D graphene-based materials as mechanical metamaterials. [ABSTRACT FROM AUTHOR]

This work employs density functional theory calculations to investigate the structural, hydrogen storage, mechanical, electronic, optical, and bonding characteristics of perovskite hydrides KNaX 2 H 6 (X = Mg, Ca) for potential hydrogen storage applications. Negative formation energies, positive phonon dispersions, and appropriate tolerance factor values confirm the thermodynamic, dynamic, and cubic structural stability of these compounds. KNaMg 2 H 6 exhibits a promising gravimetric hydrogen storage capacity of 5.19%, while KNaCa 2 H 6 shows 4.09%. Both compounds display semiconducting behavior with indirect energy band gaps of 3.31 eV and 3.17 eV, respectively. Key mechanical properties, including bulk modulus, shear modulus, and Poisson's ratio, were evaluated using computed elastic constants. The desorption temperature for KNaMg 2 H 6 , determined to be 470.4 K, renders it suitable for practical applications. Partial Bader charge analysis reveals both ionic and slightly covalent bonding interactions. Optical analysis demonstrates strong ultraviolet absorption capabilities with a redshift in the absorption spectrum. The computed properties indicate these materials hold promise for hydrogen storage applications. • DFT study of KNaX 2 H 6 (Y Mg, Ca) perovskites for H 2 storage applications. • KNaX 2 H 6 (Y Mg, Ca) hydrides are mechanically and thermodynamically stable. • KNaX 2 H 6 (Y Mg, Ca) hydrides are semiconductors in nature. • The gravimetric ratios are found 5.19% for KNaMg 2 H 6 and 4.09% for KNaCa 2 H 6. [ABSTRACT FROM AUTHOR]

The structural, electronic, elastic, optical, phonon, and thermo-physical properties of the tetragonal X 2 CoH 5 (X = Ca, Sr) hydrogen storage compounds were thoroughly examined using first-principles calculations. The negative formation enthalpies (−76.03 kJ/mol.H 2 for Ca 2 CoH 5 and −72.55 kJ/mol.H 2 for Sr 2 CoH 5) highlight the structural stability of these materials. Phonon calculations revealed no imaginary frequency modes, confirming the dynamic stability of X 2 CoH 5. The mechanical stability of Ca 2 CoH 5 and Sr 2 CoH 5 was evidenced by the compliance of the elastic constants with Born stability criteria. The electronic band structure indicates that Ca 2 CoH 5 and Sr 2 CoH 5 are direct bandgap semiconductors with narrow bandgaps of ∼ 0.27 and 0.34 eV, respectively. The appraisal of Poisson's ratio (ν = 0.22 for X = Ca and 0.23 for Sr) and Pugh's ratio (B/G = 1.47 for X = Ca and 1.56 for Sr) suggests that both metal hydrides exhibit brittle mechanical behavior. Moreover, 3D plots of Young's modulus (E), shear modulus (G), linear compressibility (β), and Poisson's ratio (ν) uncover anisotropy within X 2 CoH 5. The hydrogen storage capabilities were scrutinized, and the present materials feature excellent volumetric hydrogen density (95.65 gH 2 l −1 for Ca 2 CoH 5 and 80.24 gH 2 l −1 for Sr 2 CoH 5), moderate gravimetric hydrogen density (3.38 wt% for Ca 2 CoH 5 and 2.06 wt% for Sr 2 CoH 5) and high hydrogen desorption temperature (584 K for Ca 2 CoH 5 and 558 K for Sr 2 CoH 5). Notably, the obtained volumetric hydrogen densities are in line with the volumetric capacity criteria set by the U.S. Department of Energy (DOE) for 2025. Finally, the optical and thermo-physical characteristics of X 2 CoH 5 compounds were also investigated in this work. • New X 2 CoH 5 (X = Ca and Sr) hydrides were studied using first-principles calculations. • The X 2 CoH 5 compounds are thermodynamically, dynamically and mechanically stable. • X 2 CoH 5 hydrides display semiconductor behavior, brittleness, and elastic anisotropy. • The Gravimetric capacity was calculated as 3.38 wt% for Ca 2 CoH 5 2.06 wt% for Sr 2 CoH 5. [ABSTRACT FROM AUTHOR]

The strontium based hydrides XSrH 3 (X = Cs , Fr) are investigated in current study using first principles calculations for hydrogen storage applications. The obtained lattice constants for CsSrH 3 and FrSrH 3 are 4.88 Å and 4.74 Å respectively. The gravimetric hydrogen storage capacity ( C wt %) for CsSrH 3 and FrSrH 3 is 1.33% and 0.95%. The optimized lattice constants are utilized to compute elastic constants and mechanical parameters. The Young's modulus, bulk modulus and shear modulus for FrSrH 3 is larger than that of CsSrH 3 revealing the greater mechanical strength of FrSrH 3. The investigations of band structures and density of states indicating the semiconducting nature of with gaps 2.95 eV, 2.52 eV with PBE-GGA and 5.40 eV, 4.54 eV with TB-mBJ for CsSrH 3 and FrSrH 3 respectively. The dynamical stability for both hydrides is confirmed from phonon properties. The thermodynamic parameters are calculated under the variation of temperature and pressure. The heat capacities, volume, entropy and thermal expansion coefficient increase with temperature and decrease with pressure. • The gravimetric hydrogen storage of XSrH 3 (X = Cs, Fr) is explored for the first time. • The elastic, mechanical and transport properties of XSrH 3 (X = Cs, Fr) are investigated. • The PBE-GGA and TB-mBJ methods are used to explore band structures and optical properties. [ABSTRACT FROM AUTHOR]

This study focuses on the relationship between porosity, surface roughness, microstructure, strength, and thermal properties, as well as their effect on the bioactivity and biodegradability of fabricated akermanite (AK; Ca 2 MgSi 2 O 7) bioceramic scaffolds. Firstly, we prepared the AK nanopowders using the mechanical activation method, mixed them with varying proportions of space-holder agent (NaCl), specifically 15, 20, 30, 40, and 50 vol%, and sintered them at 1200 °C to create porous scaffolds. We investigated the physical properties and microstructure using the Archimedes method and field emission scanning electron microscopy (FE-SEM), respectively. The mechanical properties in terms of microhardness, compressive strength, longitudinal modulus, Young's modulus, bulk modulus, and shear modulus were measured. The bioactivity and biodegradability of prepared scaffolds were assessed after soaking in simulated body fluid (SBF) for 10 days by FE-SEM and inductively coupled plasma-atomic emission spectroscopy (ICP-AES), respectively. The results revealed that porous scaffolds with suitable mechanical properties, bioactivity, and biodegradability were prepared. The porosity had a significant impact on the mechanical and biodegradability of the investigated scaffolds. It reduced mechanical properties slightly while improving bioactivity and biodegradability. The microstructure study displayed that all scaffolds formed apatite layer on their surfaces. This is because of good bioactivity and the suitable porosity level of AK. The obtained findings provide promising prospects for the future use of AK in bone tissue engineering. [ABSTRACT FROM AUTHOR]

In this paper, anisotropic magnetorheological (MR) elastomers have been prepared using a magneto-thermal coupling process. The composition of these elastomers includes a silicone rubber matrix, carbonyl iron particles (CIP), and assorted additives. We have conducted experimental and modeling studies to analyze the dynamic mechanical properties of MREs under varying conditions of temperatures, magnetic field strengths, displacement amplitudes, and frequencies. Furthermore, to explore the variations in shear storage modulus and loss factor under diverse loading conditions, two MRE vibration mitigation devices with varying CIP weight fractions have been prepared and tested in shear mode. The findings indicate that the MRE devices exhibit pronounced temperature-dependent and magnetorheological effects. Notably, both the shear storage modulus and loss factor increase with rising magnetic field strength, excitation frequency, and CIP weight fraction, whereas they decrease as ambient temperature and displacement amplitude rise. Building on these results, a modified fractional order derivative microstructure (MFMS) model which integrates the molecular chain network of MREs with the temperature–frequency equivalence principle has been proposed to predict and characterize the dynamic viscoelastic properties of MREs under various working conditions. A comparative analysis of experimental and model-calculated data confirms that the proposed model accurately describes the dynamic viscoelastic properties of MREs. [ABSTRACT FROM AUTHOR]

Here we define and report the relationship between the maximum seismic magnitude (M) and injection volume (ΔV) through fluid-injection fault-reactivation experiments and analysis. This relationship incorporates the in situ shear modulus (G) and fault pre-stress as a fraction of the strength drop (c), expressed as M = c/(1-c) GΔV. Injection response defines a sigmoidal relation in M − Δ V space with unit gradient limbs linked by an intermediate up-step. Both laboratory observations and analysis for a rigid fault with slip limited to the zone of pressurization show trajectories of cumulative M − Δ V that evolve at a gradient of unity, are offset in order of increasing pre-stress and are capable of step changes in moment with shear reactivation at elevated critical-stresses – key features apparent in field observations. The model and confirmatory laboratory observations explain the occurrence of some triggered earthquakes at EGS sites significantly larger than expected relative to injection volumes and based on previous models. Through fluid-injection fault-reactivation experiments and analysis, the authors here define and report the relationship between the maximum seismic magnitude and injection volume for fluid-injection triggered earthquakes. [ABSTRACT FROM AUTHOR]

The mechanical properties of the sclera play a critical role in supporting the ocular structure and maintaining its shape. However, non-invasive measurements to quantify scleral biomechanics remain challenging. Recently introduced multi-directional optical coherence elastography (OCE) combined with an air-coupled ultrasound transducer for excitation of elastic surface waves was used to estimate phase speed and shear modulus in ex vivo rabbit globes (n = 7). The scleral phase speed (12.1 ± 3.2 m/s) was directional-dependent and higher than for corneal tissue (5.9 ± 1.4 m/s). In the tested locations, the sclera proved to be more anisotropic than the cornea by a factor of 11 in the maximum of modified planar anisotropy coefficient. The scleral shear moduli, estimated using a modified Rayleigh-Lamb wave model, showed significantly higher values in the circumferential direction (65.4 ± 31.9 kPa) than in meridional (22.5 ± 7.2 kPa); and in the anterior zone (27.3 ± 9.3 kPa) than in the posterior zone (17.8 ± 7.4 kPa). The multi-directional scanning approach allowed both quantification and radial mapping of estimated parameters within a single measurement. The results indicate that multi-directional OCE provides a valuable non-invasive assessment of scleral tissue properties that may be useful in the development of improved ocular models, the evaluation of potential myopia treatment strategies, and disease characterization and monitoring. [ABSTRACT FROM AUTHOR]

The traditional specific storage coefficient (Ss) was defined under two assumptions. One is that aquifer rock deforms only in the vertical direction, and the other is that the average rock stress remains unchanged. Consequently, Ss is irrelevant to the shear modulus of rock (G). In this paper, the Biot theory is used to derive a new specific storage coefficient (Ss∗) with the natural deformation of rock. Ss∗ appears to be relevant to G. Compressed glass beads and Berea sandstone are used for illustration. At frequencies lower than 10 kHz, the equation of groundwater flow with Ss∗ yields the same phase velocity and quality factor as the Biot theory, and therefore, it is capable of accurately predicting fluid pressure diffusion in the low‐frequency regime. The results also show that Ss is 16%–17% higher than Ss∗. In conclusion, the latter one is superior to the former in its consistency with the Biot theory and unconstraint by the aforementioned two assumptions. [ABSTRACT FROM AUTHOR]

In this paper, the bending, dynamic responses and multi-objective optimization of the pyramidal lattice sandwich plate are studied. Initially, the paper calculates the equivalent elasticity moduli and equivalent shearing moduli of pyramid lattice core. Then, the kinematic relations between the plate and the pyramid grid core are established by using the improved FSDT. The governing differential equations and the conditions for boundaries are deduced from the Hamilton principle, and solved by using Navier’s method. To validate that the theoretical model is accurate, the paper compares the center deflection and natural frequency derived from theoretical calculations with the experimental and finite element results. In detail, this paper studies the influence of the number of single cells, thickness ratio, and lattice rod radius on the bending and free vibration behavior. Then, the key elements are chosen as design parameters. Next, the space of design variables is explored using the hybrid PSO-GWO algorithm to find Pareto optimal solutions. The optimum number of single cells, thickness ratio and radius of the pyramid lattice sandwich plates are finally derived to satisfy the conflicting desired objectives of maximizing natural frequency and minimizing center displacement and mass. The results show that the proposed equivalent model can predict the static bending and dynamic responses of pyramidal lattice sandwich plate well. In order to satisfy maximizing natural frequency and minimizing center displacement and mass, different Pareto optimal solutions are given for different design options by using the hybrid PSO-GWO algorithm. [ABSTRACT FROM AUTHOR]

The structural, mechanical, optical, thermo-physical, and electronic properties of the monoclinic XGaH 5 (X = Ba, Ca, and Mg) used as hydrogen storage material were investigated in detail using the ab initio technique. Gravimetric hydrogen densities (5.1 wt % for the MgGaH 5 , 4.4 wt % for the CaGaH 5 , and 2.38 wt % for the BaGaH 5), hydrogen desorption temperatures (29.05 K for the MgGaH 5 , 175.56 K for the CaGaH 5 , and 218.36 K for the BaGaH 5) and enthalpies of formation (−0.039 eV/atom for the MgGaH 5 , -0.237 eV/atom for the CaGaH 5 and -0.296 eV/atom for the BaGaH 5) of these compounds were also calculated. As a result of electronic band structure calculations, band gap values for BaGaH 5 , CaGaH 5 , and MgGaH 5 were obtained as 3.08 eV, 4.05 eV, and 3.61 eV, respectively. It is clear from the high band gap values that all three materials have insulator character. The second-order independent elastic constant values, which provide information about the hardness and mechanical stability of the materials, were calculated. The elastic constant values showed that XGaH 5 is mechanically stable. Hardness parameters such as bulk modulus, shear modulus, B/G ratio (1.19 for the MgGaH 5 , 1.11 for the CaGaH 5 , and 1.68 for the BaGaH 5), Young's modulus, and Poisson's ratio were also calculated using elastic constant values. According to the B/G ratio, all three structures were found to be brittle materials. From Poisson's ratio (0.17 for the MgGaH 5 , 0.15 for the CaGaH 5 , and 0.25 for the BaGaH 5), the atoms in XGaH 5 compounds are connected by covalent bonds. Besides, the formation enthalpies of the materials were calculated, and it was concluded that all three compounds could be synthesized in the laboratory. In addition, some optical properties of XGaH 5 such as dielectric function, conductivity, reflectivity, and absorption were also calculated. Finally, thermo-physical properties were calculated for XGaH 5 compounds. • First-principles calculations to investigate XGaH 5 materials for hydrogen storage applications. • XGaH 5 (X = Ba, Ca, and Mg) compounds are found to be mechanically stable and brittle. • The desorption temperature values for MgGaH 5 , CaGaH 5 , and BaGaH 5 are 29.05 K, 175.56 K, and 218.36 K, respectively • MgGaH 5 5.1 wt % has a higher gravimetric hydrogen densities. [ABSTRACT FROM AUTHOR]

A set of creative formulation is introduced to estimating the small-strain shear modulus (Gmax) of various sandy soils through the measurement of well-controlled laboratory tests combined with the analysis of experimental data published in the literature. The influences of normalized effective confining pressure ( σ c0 ′ /Pa), void ratio (e), and fines contents (FC) on the values of Gmax are revealed through a series of bender element measurements. Through introducing the equivalent skeleton void ratio ( e sk ∗ ) to describe the intergranular contact state of sandy soils with FC less than a threshold value (FCth), a remarkable finding is that the stress exponent n, characterizing the increase rate of Gmax with increasing σ c0 ′ , is a soil-specific constant and a linear function of the synthesizing material parameter ( C u s C u f ) in log-scale. Another remarkable finding is that a virtually unique form of the correlation between Gmax/( σ c0 ′ /Pa)n and e sk ∗ exists. An unified form of the binary packing material-based Gmax prediction formulation for different types of sandy soils is established. The three coefficients of the proposed Gmax expression in form of explicit equations can be simply determined using some basic index properties of clean sand and pure fines. In this regard, the proposed Gmax prediction formulation provides a significant advantage in the determination of Gmax and associated shear wave velocity Vs of sandy soils in practice. [ABSTRACT FROM AUTHOR]

The objective of this study is to recognize and characterize the nanoscale phase modulus mapping of the asphalt film in pavement mixture cores using atomic force microscopy quantitative nanomechanical technology. The pavement core samples from the upper and middle layers of four highways and laboratory samples were taken as the research object. The phase modulus–macro property correlation of recovered asphalt was analyzed using mathematical statistics. The results showed that the pavement core samples had more significant multi-phase and diversified phase characteristics compared to lab samples. This indicated that the asphalt in the pavement core had an obvious phase separation phenomenon due to aging. The phase modulus of each sample was distributed across a relatively wide numerical range, and there were also many numerical points with large fluctuations. Especially for the mixture sample containing SBS (Styrene-Butadiene-Styrene)-modified asphalt, the phase modulus distribution mappings presented a multi-peak phenomenon. Hence, considering the distribution characteristics of the data, the box plot method was introduced. Compared with quantified results from laboratory samples, the phase modulus of SBS-modified asphalt increased by 0.96 times, 1.18 times and 1.15 times, and that of base asphalt increased by 0.59 times, 0.56 times, 0.42 times, 1.24 times and 0.39 times, respectively. This indicates that the aging degree of asphalt in the upper layer was generally greater than that of the asphalt in the middle layer and that there was an aging gradient in the direction of pavement depth. All points were within the 95% confidence band in terms of correlation fitting, indicating a better fitting effect between phase modulus and complex shear modulus, as well as between phase modulus and penetration. This research provides innovative ideas for future multi-scale numerical simulation and cross-scale performance model development of asphalt binders. [ABSTRACT FROM AUTHOR]

This study delved into the utilization of chamotte particles in varying contents (0–50 wt%) as reinforcing agents in both fresh and hardened states within potassium‐based geopolymer (KGP) composites. Although the previous research predominantly underscored the high‐temperature stability of chamotte in composites subjected to extreme conditions, this study focuses on expanding their potential applications at ambient temperature. The experimental findings showed that the flowability of the pastes experienced a slight reduction up to 20 wt% chamotte, followed by a substantial decrease, ultimately resulting in complete shape retention at 50 wt%. Squeeze flow and standard rheological tests supported these observations, revealing elevated work‐to‐squeeze values peaking at 1.3 J. X‐ray diffraction data showed that crystallinity prevailed in chamotte, establishing its efficacy as a nonreactive reinforcement. In the hardened state, the inclusion of chamotte enhanced the mechanical properties of the composites, specifically compressive, flexural, and splitting tensile strengths, reaching up to 61.7, 13.2, and 5.6 MPa, respectively. Young's modulus (E) and shear modulus (G) also exhibited an upward trend with increasing chamotte content, reaching values of up to 17.7 and 7.7 GPa at 50 wt%, respectively. Scanning electron microscopy (SEM) analysis validated particle interlocking and crack‐bridging mechanisms. In general, this study highlights the effectiveness of chamotte particles in improving the mechanical properties of KGP composites at room temperature. It also emphasizes the necessity of considering the mentioned parameters in the design of particulate‐reinforced geopolymer compositions for diverse applications. [ABSTRACT FROM AUTHOR]

During the production and transport of reclaimed asphalt pavement (RAP), the diffusion of recycled aged asphalt binder and virgin asphalt binder can significantly affect the mechanical properties of the virgin and aged asphalt binder system. Therefore, a thorough understanding of the diffusion behavior of virgin and aged asphalt binder system is essential for the production of RAP. In this study, a diffusion model of the virgin and aged asphalt binder system was established based on the Fick's law to calculate the complex shear modulus (|GT*|) of the system. The calculated |GT*| values were then compared with the measured values (|GD*|) obtained from the dynamic shear rheological (DSR) test. molecular dynamics (MD) simulations were also carried out to investigate the diffusion behavior of the virgin and aged asphalt binder system and to compare the simulated and calculated values of the diffusivity (D). The influence of different asphalt binder layers and saturates, aromatics, resins, and asphaltenes (SARA) on the diffusion behavior of the system was also analyzed. The results show that the |GT*| values calculated by the diffusion model are in good correlation with the |GD*| values measured by the DSR test at different temperatures and times. Furthermore, the diffusivity of virgin asphalt binder was found to be smaller than that of the four individual components, suggesting that the colloid structure and intermolecular interactions of asphalt binder play a crucial role in its diffusion behavior. Practical Applications: Asphalt pavement is a common form of pavement, but it can be seen in life that asphalt pavement often has diseases such as cracks and potholes. The cause of some pavement diseases is the decrease of the performance of asphalt binder in the pavement. Under the action of natural factors, the phenomenon that the performance of asphalt binder gradually changes with time is called asphalt aging. Therefore, if the principle of asphalt aging can be mastered, the influencing factors of asphalt aging can be clarified, and a rejuvenator that can restore the performance of aged asphalt binder to the greatest extent can be designed. It can delay the aging rate of asphalt binder and improve the durability of asphalt pavement, conversely, it can also effectively recycle and renovate old asphalt pavement, reuse waste asphalt concrete, and reduce the waste of resources. This article mainly uses molecular dynamics simulation to achieve the preceding purpose. The result is helpful in providing guidance for the production of RAP in practical application. [ABSTRACT FROM AUTHOR]

Generic models for estimating the earthquake-induced displacement of Earth slopes are developed based on a numerical approach. A number of 14,112 slope models with different configurations of slope geometry and soil property parameters are developed to represent generic Earth slopes. Thousands of slope dynamic analyses are then conducted in FLAC to estimate the coseismic slope displacements. Based on the displacements calculated, 18 ground-motion intensity measures (IMs) and eight slope variables are considered as candidate predictor variables to develop predictive displacement models using the light gradient boosting machine (LightGBM). Comparative results indicate that yield acceleration (Ky) and Arias intensity (AI) are the most efficient scalar variables in regressing the displacements. Based on the efficiency, sufficiency, and computability criteria, the vector IMs of (AI, peak ground velocity) and (AI, peak ground acceleration), together with Ky and initial shear modulus, are regarded as the preferable predictor variables, respectively. Two sets of predictive displacement models are thus proposed using the preferable variables via the LightGBM- and polynomial-based approaches, respectively. The aleatory variability in predicting the slope displacement for the polynomial models is approximately 15%–30% larger than that of the LightGBM models, indicating that the predictive performance of the LightGBM models is superior to the polynomial models. [ABSTRACT FROM AUTHOR]

• Contact vibration model between a rigid punch and a half-space with hysteretic damping considering couple stress is studied. • The size effect has a pronounced impact on the peak effect of the dynamic contact stiffness and reciprocal receptance. • The real parts of the reciprocal receptance and dynamic contact stiffness are sensitive to the internal friction. This paper investigates the contact vibration between a rigid spherical indenter and a half-space with hysteretic damping within the framework of the couple stress theory. Firstly, the static contact pressure is determined by using the integral least square approach. Subsequently, the dynamic contact pressure is obtained through the perturbation technology, and the dynamic contact displacement is obtained by employing the Hankel transform. Finally, the receptance is obtained and the dynamic contact stiffness is deduced by adopting approximate dynamic displacement boundary conditions under the assumption of a sufficiently small oscillation force. Parametric studies are presented to clarify the effects of the characteristic material length, Poisson's ratio, shear modulus, and internal friction on the reciprocal receptance and dynamic contact stiffness. The results obtained reveal that the size effect has a pronounced effect on the peak values of the dynamic contact stiffness and reciprocal receptance. Furthermore, the present work provides a useful theoretical framework for applying contact resonance microscopy techniques to micro-structured materials. [ABSTRACT FROM AUTHOR]

The curing cycle of natural rubber (NR) with a conventional accelerated sulfur system (CV) generally exhibits three phases. The induction phase, the crosslinking phase, and the reversion phase. Prolonged curing of NR/CV system even at a temperature of 150 °C can show reversion. Many research reports are available in the literature with reference to the reversion behavior and the subsequent network modifications of natural rubber with accelerated sulfur. However, the literature regarding post-reversion curing behavior is scanty. This article describes the post-reversion upturn of natural rubber with a conventional accelerator sulfur system at a higher curing temperature. A network rebuilding after collapsing the initially formed network due to reversion was identified as the primary reason for the post-reversion upturn. The dynamic rheological testing capability of the Rubber Process Analyzer (RPA) was employed to characterize the network formed during curing, reversion and post-reversion phases. The cure-strain sweep data from the RPA indicated that the shear storage modulus (G′) of the broken network increased due to the post-reversion upturn. The chemical crosslink densities of the samples were also found to increase due to the upturn curing behavior. From these experimental results and the information conceived from the previous literature, two plausible mechanisms have been proposed to interpret the post-reversion upturn cure behavior. [ABSTRACT FROM AUTHOR]

In offshore engineering, soft clay foundations supporting infrastructure are subjected to significant multidirectional cyclic shear stresses due to earthquake or storm loads. To explore the undrained multidirectional cyclic behavior of foundation clays under critical loading conditions, a series of tests were conducted using a variable-direction dynamic cyclic shear system. By controlling the amplitude ratio (η) of two mutually perpendicular shear stresses in the horizontal plane, both unidirectional and multidirectional cyclic shear stress paths were achieved. The shear strength, stiffness, and pore water pressure are presented and discussed by considering the effects of η and cyclic stress ratio (CSR). The results suggest that the increase of CSR and η accelerates the cyclic failure, stiffness degradation, and pore water pressure accumulation of the clay specimens. An η-independent cyclic strength curve is established by normalizing the CSR to 0.755η. Although η hardly affects the shear modulus in the x direction (Gx) during the first cycle and at failure, it affects the parameter (χ) governing the shape of the stiffness degradation curve. Additionally, a model is proposed for predicting the evolution of normalized residual pore water pressure with respect to the number of cycles, wherein the parameter d remains unaffected by CSR and η. [ABSTRACT FROM AUTHOR]

Uneven settlement of the strata induced by ground fissure activity trigger great damage to a shield tunnel crossing a ground fissure zone. It is of great significance for the safe maintenance of tunnels to accurately predict the mechanical response of the tunnel structure under the dislocation of a ground fissure. In this paper, an analytical solution of mechanical behaviors of a shield tunnel crossing an active ground fissure zone is proposed. The shield tunnel-strata interaction in a ground fissure site is simplified as a Timoshenko beam placed on a Vlasov foundation. The governing differential equation and the closed-form solution for an equivalent shield tunnel subjected to additional load induced by the dislocation of ground fissure are derived. The proposed solution is adopted to analyze the mechanical behaviors of a shield tunnel, including tunnel displacement, rotation, bending moment, and shear force. The results of a model test and a numerical model are provided to verify the rationality of the proposed analytical solutions. Finally, a parameter sensitivity analysis about the additional load forms, the compression and shear modulus of the foundation, and the shear stiffness coefficients of the tunnel are conducted. The result shows that the form and value of the additional load has a large impact on the deformation and a slight impact on the internal forces of the tunnel. The foundation compression modulus determines the constraint effect of the strata, and the deformation and internal force response of a tunnel decrease with the increasing foundation shear modulus. In addition, the increase of shear coefficient enhances the shear stiffness of a tunnel, but largely increases the internal force as well. [ABSTRACT FROM AUTHOR]

Flexural vibration (FV), torsional vibration (TV), static torsion (ST), longitudinal vibration (OAV), and tension (OAT) of 45° off-axis tests of flat pieces of cardboards were analyzed to determine the in-plane shear modulus (IPSM) using samples of various widths. The analyses were performed with simulations using the finite element method (FEM) for models with and without lamination and physical experiments using cardboard samples. For the FV, TV, and ST tests, the IPSM was calculated using binary search (BS) and linear regression (LR). The FEM results suggest that the IPSM values obtained from the TV and ST test simulations were affected by lamination. In contrast, the effect of lamination was not clear in the FV, OAV, and OAT test simulations. The coefficient of variation obtained from the FV experiments was often larger than that obtained from other tests. Despite this variation, the FV test is more attractive than the other tests because the experiments could be performed easily, and the effect of lamination could be reduced. [ABSTRACT FROM AUTHOR]

Featured Application: Real-time monitoring of the elastic properties of materials during the printing process. This study demonstrated the potential of a non-destructive evaluation (NDE) method to assess the elastic properties of materials printed under various parameters. A database was created documenting the relationship between the elastic properties (Young's modulus, shear modulus, and Poisson's ratio) of PLA (polylactic acid) materials and selected printing parameters such as temperature, speed, and layer height. PLA, which is widely used in additive manufacturing, offers convenient testing conditions due to its less demanding control compared to materials like metals. Ultrasonic testing was conducted on specimens printed under different nozzle temperatures, speeds, and layer heights. The results indicated that an increase in the printing temperature corresponded to an increase in material density and elastic properties of the material. In contrast, an increase in layer height led to a decrease in both density and the elastic properties of the material. Variations in the nozzle speed had a negligible effect on density and did not show a notable effect on the elastic moduli. This study demonstrated that ultrasonic testing is effective in measuring the elastic properties of PLA materials and shows the potential of real-time ultrasonic NDE. [ABSTRACT FROM AUTHOR]

This paper presents the torsional behavior of reinforced concrete beams strengthened with carbon fiber-reinforced polymer (CFRP) sheets. Assorted retrofit schemes are implemented with variable widths and number of single- and double-layer CFRP U-wraps. After loading 27 beams (three unstrengthened and 24 strengthened), test data were collected to investigate the efficacy of those U-wrap configurations. The width and layer of the bonded sheets dominate the capacity of the beams, whereas the number of the U-wraps in the longitudinal direction is an insignificant attribute. Although the CFRP retrofit decreases structural ductility, the placement of the U-wraps impedes stiffness-reduction rates, reduces twist angles, and redistributes torque-induced stresses. The identified characteristic effective shear modulus of the strengthened beams demarcates the pattern of energy drops, which are related to the degree of brittleness in failure. As far as effective strains are concerned, the applicability of existing equations is appraised, and a new expression is proposed through reliability theory and stochastic simulations. [ABSTRACT FROM AUTHOR]

This study aimed to develop an alternative approach to characterise the linear viscoelastic behaviour of asphalt binders. A rheogram model was firstly proposed based on the Carreau–Yasuda model; its accuracy was substantiated by high R2 values. The dynamic shear modulus master curve model was then obtained using the relationship between the magnitude of complex viscosity and dynamic shear modulus and the two definitions of the time-temperature shift factor. Afterwards, the phase angle master curve model was derived according to the approximate Kramers–Kronig relation. The proposed approach was demonstrated to be capable of accurately characterising the linear viscoelastic behaviour of selected asphalt binders. In addition, the predicted zero shear viscosity (ZSV) could be potentially employed to evaluate the asphalt binder rutting resistance. Compared with the widely-used Christensen-Anderson-Marasteanu (CAM) model, the developed master curves models were better at constructing the phase angle master curves of selected asphalt binders. [ABSTRACT FROM AUTHOR]

Megathrusts at convergent plate boundaries generate the largest and some of the most hazardous earthquakes on Earth. However, their physical properties, including those influencing fault slip accumulation and release and earthquake‐related surface displacements, are still poorly constrained at critical depths. Here, we combine seismic imaging and geodetic modeling to investigate the structure and mechanical behavior of the Main Himalayan Thrust fault (MHT) in the center of the 2015 Mw 7.8 Gorkha rupture in Nepal. Our results from two independent observations consistently suggest the presence of a channel associated with the MHT with high compliance (shear modulus as low as ∼4 GPa) and strain anisotropy (stiffer in the vertical orientation than in the horizontal), likely arising from a weak subducting layer with north‐dipping foliation. Such mechanical heterogeneity significantly influences the quantification of short‐term fault kinematics and associated earthquake potential, with implications on across‐scale dynamics of plate boundaries in Himalaya and elsewhere. Plain Language Summary: The Main Himalayan Thrust fault marks the boundary where the Indian continent slides beneath the Eurasian plate, causing earthquakes like the 2015 magnitude 7.8 event in Nepal. Subsurface images constructed using seismic waves suggest a weak layer surrounding the fault. However, we show that the seismic signature of this layer changes depending on the direction in which the seismic waves travel through it. We compare this information on the subsurface structure to insights from static surface motions during the earthquake. We find that the fit to the motion is poor when we assume the subsurface rock around the fault has the same strength in both horizontal and vertical orientations. The fit improves when we assume the near‐fault rock is stronger under vertical compression than under horizontal compression. This assumption also helps explain the images constructed using seismic waves. We suggest that a strong oriented rock fabric develops in a channel around the plate boundary. The presence of this fabric may have influenced our estimates of fault slip before, during and after great earthquakes. Accurately describing this behavior is crucial for understanding the earthquake potential of plate boundary faults. Key Points: Seismic imaging suggests a Main Himalayan Thrust‐associated low‐velocity channel with north‐dipping anisotropic foliationModeling of InSAR and GNSS data together suggests a weak channel with anisotropic rigidity whose orientation matches seismic constraintsThe weak anisotropic plate boundary may be related to S‐C fabrics and influence the margin geodynamics on different time scales [ABSTRACT FROM AUTHOR]

This study establishes a theoretical framework for analyzing the lateral oscillation of marine pipe piles. The additional mass model is introduced herein to consider the inertial fluctuation effect of the soil plug. Analytical mathematical methods are used to determine the complex impedance variation of the pile over a range of frequency effects. An investigation is performed to determine how the presence of soil plugs changes the lateral complex stiffness and natural frequency of pipe piles. Additionally, comparisons of the applicability of the plane strain model and continuous medium model have been conducted to enable the easy use of the theoretical model. The main conclusions can be drawn as (1) if the fluctuation inertia effect of the soil plug is not taken into consideration, the dynamic active length and the dynamic stiffness of the pipe pile will be underestimated; (2) for the soft soil, the plane strain model may give rise to substantial calculation errors attributed to them regardless of the vertical continuity of the soil, nevertheless, the calculation error decreases rapidly with the increase of soil shear modulus and vibration frequency. [ABSTRACT FROM AUTHOR]

Dynamic mechanical spectroscopy is a common analysis for polymers. Rectangular specimens are usually used for measurement in the solid state due to their easy designing. However, in reason of the non‐symmetric shape of sample, rectangular specimens do not experience linear stress on their all body, leading to overestimation of shear modulus. Corrections are required to determine the right shear modulus. In this present work, straight shear modulus determination is carried out using specimens with a cylindrical shape. The reliability of the technique is described on a biosourced polymer materials made of thermoplastic starch, plasticized by glycerol, choline chloride/urea mixture (ChCl/U), 1‐ethyl‐3‐methylimidazolium chloride ([EMIM]Cl) and 1‐ethyl‐3‐imidazolium acetate ([EMIM]Ac). The technique is shown to be particularly interesting to avoid any additional shaping of the specimens prior to measurements, that can be detrimental to their properties (evaporation, degradation). A comparison between cylinder and rectangular specimen has also been made to illustrate the interest of cylinder clamping on biosourced polymer material. [ABSTRACT FROM AUTHOR]

In this paper, we present studies relating to the structural, electronic, magnetic and mechanical properties of TiHfFeX (X = Al , Ga, In) full Heusler alloys. We will use the GGA-PBE, TB-mBj, GGA-PBEsol, and GGA-WC approximation implemented in the density functional of the theory as integrated into the Wien2k software. However, the full Heusler alloys studied are considered in the ferromagnetic phase for different structural stabilities of the TiHfFeAl, TiHfFeGa and TiHfFeIn phases. types I, II or III, respectively. Calculation of band structures and total electron density of states shows that these alloys can both exhibit topologically non-trivial semi-metallic characteristics with energy bandgaps of 0.010 eV, 0.014 eV and 0.018 eV. The electronic stability of 'such a Heusler structure will have nothing to do with its mechanical stability. Calculations reveal that the systems exhibit semi-metallic ferromagnetism. The elastic constants and the associated elastic moduli confirm its stability given by different elastic constants namely the Cauchy pressure, Poisson's ratio, the anisotropy factor, Young's modulus and the shear modulus. [ABSTRACT FROM AUTHOR]

An elastic instability model of polymer cylinder subject to surface tension is studied by energy functional analysis. The no‐classical boundary conditions and equilibrium equation are derived by introducing stress double harmonic function. The criteria of instability with surface tension contribution are deduced by substituting stress solution into boundary conditions. The results show that the criterion equation of elastic instability is relevant to the radius and intrinsic scale and instable wavelength or wavenumber of cylinder. Therefore, the relation between shear modulus and surface tension has the same trend comparing with the result of Barrierès' et al. This study provides insights into the instability of polymer and has important implications for the development of nanoscale cylindrical element in micro electro mechanical systems (MEMS) or nano electro mechanical systems (NEMS). [ABSTRACT FROM AUTHOR]

Metamaterials are artificially created materials or structures with properties not found in nature. They encompass electromagnetic, acoustic, and mechanical metamaterials, which are particularly significant in applied engineering. Mechanical metamaterials exhibit unique mechanical properties such as vanishing shear modulus, negative Poisson's ratio, negative compressibility, etc. This paper reviews the most commonly used mechanical metamaterials and discusses their applications in the field of applied engineering, specifically in vibration isolation, energy absorption, and vibration reduction. The prospects for future developments in this field are also presented. [ABSTRACT FROM AUTHOR]

There is a significant difference between the simulation effect and the actual effect in the design process of maize straw-breaking equipment due to the lack of accurate simulation model parameters in the breaking and processing of maize straw. This article used a combination of physical experiments, virtual simulation, and machine learning to calibrate the simulation parameters of maize straw. A bimodal-distribution discrete element model of maize straw was established based on the intrinsic and contact parameters measured via physical experiments. The significance analysis of the simulation parameters was conducted via the Plackett–Burman experiment. The Poisson ratio, shear modulus, and normal stiffness of the maize straw significantly impacted the peak compression force of the maize straw and steel plate. The steepest-climb test was carried out for the significance parameter, and the relative error between the peak compression force in the simulation test and the peak compression force in the physical test was used as the evaluation index. It was found that the optimal range intervals for the Poisson ratio, shear modulus, and normal stiffness of the maize straw were 0.32–0.36, 1.24 × 108–1.72 × 108 Pa, and 5.9 × 106–6.7 × 106 N/m3, respectively. Using the experimental data of the central composite design as the dataset, a GA–BP neural network prediction model for the peak compression force of maize straw was established, analyzed, and evaluated. The GA–BP prediction model's accuracy was verified via experiments. It was found that the ideal combination of parameters was a Poisson ratio of 0.357, a shear modulus of 1.511 × 108 Pa, and a normal stiffness of 6.285 × 106 N/m3 for the maize straw. The results provide a basis for analyzing the damage mechanism of maize straw during the grinding process. [ABSTRACT FROM AUTHOR]

The new generation of impact-resistant materials should be lightweight and flexible. For this purpose, various additives, such as shear thickening gels (STG) are synthesized and incorporated into these materials. In this article, it has been tried to develop a new method for synthesizing new shear -thickening gels (n-STG). This new method involves dispersing Polyvinyl alcohol (PVA) solution into the STG polymer matrix. Unlike previous studies that used PDMS, and boric acid as fixed materials in the preparation of STG, this work introduces PVA as a new auxiliary material in the PDMS and boric acid polymer matrix. At first, different percentages of PVA solution in distilled water (DW) were prepared. After a series of experiments, PVA (14%) was well combined with the polymer matrix. In this way, by changing the mass ratio of PVA (14%) to pyroboric acid (P-BA) and PVA (14%) to polydimethylsiloxane (PDMS), 7 values of (1:6) to (7:6) were tested. When the ratio of PVA (14%) to P-BA is greater than 1:6, it lacks STG properties. However, when the ratio of PVA (14%) to PDMS changed from 1:6 to 6:6, shear thickening gel properties were observed and the samples were named n-STG. The maximum shear storage modulus (G'max) of n-STG samples first increases and then decreases, reaching a maximum value of 0.55 MPa. The resilience elasticity test demonstrated that the rebound percentage value of the n-STG-5 sample was 22.6% higher than the STG sample without PVA, due to its higher shear storage modulus. This study showed that PVA in the STG polymer matrix improves polymer chain cross-linking and performance due to its n-STG stimulus–response property. [ABSTRACT FROM AUTHOR]

As a large area of SBS-modified asphalt pavement entered the maintenance period, the aging and rejuvenation of SBS-modified asphalt have attracted attention in recent years. In order to further study the rejuvenation of aged SBS-modified asphalt, both rheological experiments and quantum mechanical simulations were used. Complex shear modulus (G*) and phase angle (δ) were used to analyze the rejuvenation effect of aged SBS-modified asphalt. Electron density, binding energy (Ebinding), and charge transfer number (Qtransfer) were used to observe the process of rejuvenation in aged SBS-modified asphalt. The results show that compared to asphalt components, SBS polymer was the least stable and most susceptible to breaking. After oxidative aging, SBS polymer with its aging products could impair the rejuvenation in aged asphalt. The interaction between aromatic components in rejuvenator and asphaltenes in aged asphalt was unstable and could be influenced by asphalt aging level. The interaction between heavy component molecules in aged asphalt with saturate component molecules in rejuvenator are closer than those with aromatic components molecules. The binding energies between saturate components in rejuvenator and asphaltenes in aged asphalt could be served as an evaluation indicator of rejuvenation. [ABSTRACT FROM AUTHOR]

Two hypotheses divide experts on determining the effective properties of composite materials using multi–scale homogenization methods. The first hypothesis states that multi-scale homogenization methods can ensure the direct determination of effective properties, at the macro level, of composite materials from a single representation of the medium at the lowest possible scale that allows for a good representation of all heterogeneities. The second hypothesis states that the determination cannot be ensured directly from a single scale but rather through multistep homogenization where each step represents the medium at a different scale from the lowest to the macroscale. To answer this question, a rigorous study is carried out; it includes calculating the two effective elastic properties, bulk, and shear moduli of three phases of a multi–layered sphere composite model by studying three phases. A multistep homogenization method is used to determine the effective properties of the composite and the obtained results are compared with those of the direct homogenization. Two different studies are considered: the first is based on an analytical model and the second on the numerical homogenization based on finite element calculation. To consider the effect of some influential parameters, several situations are treated by the combination of the variation of the volume fractions of the three phases and their property contrasts. The analytical calculations are performed using the Python 3.10 commercial software. It could be concluded that the effective elastic properties obtained either by the multistep or by the direct homogenization show no significant difference. [ABSTRACT FROM AUTHOR]

First principles calculations have been performed using full potential linearized augmented plane wave, FP‐LAPW, within Wien2k to elucidate structural, elastic, mechanical, phonon, electronic and optical properties of lead free halide perovskites AgXF3(X=Be,Ca)$$ {\mathrm{AgXF}}_3\left(\mathrm{X}=\mathrm{Be},\mathrm{Ca}\right) $$. The energy volume curve fitting is used to examine structural stability. For structural optimization and mechanical properties, we employed Perdew–Burke–Ernzerhof generalized gradient approximation and PBEsol, revised for solids, exchange and correlation functional. The optimized lattice constant of AgBeF3$$ {\mathrm{AgBeF}}_3 $$ and AgCaF3$$ {\mathrm{AgCaF}}_3 $$ is 3.631 and 4.349Å. The elastic constant C11$$ {\mathrm{C}}_{11} $$, C12$$ {\mathrm{C}}_{12} $$ and C44$$ {\mathrm{C}}_{44} $$ are computed to extract different mechanical parameters like Poisson's ratio, Pugh's ratio, bulk modulus, shear modulus, Young's modulus, anisotropic ratio, Cauchy pressure and shear constant. The mechanical parameters exhibit greater structural, mechanical and dynamical stability of AgBeF3$$ {\mathrm{AgBeF}}_3 $$ than AgCaF3$$ {\mathrm{AgCaF}}_3 $$. The electronic and optical properties are calculated by using TB‐mBJ and SCAN potentials in addition to PBEsol. The electronic band gap of AgBeF3$$ {\mathrm{AgBeF}}_3 $$ and AgCaF3$$ {\mathrm{AgCaF}}_3 $$ is 4.71 and 6.01 eV with TB‐mBJ and both perovskites are indirect band gap materials. The optical response of these perovskites against wide range of incident electromagnetic radiation is assessed by calculating absorption, reflection, optical conductivity, dielectric constant, energy loss function and refraction. Strong absorption, high optical conductivity and low reflectivity indicates that AgBeF3$$ {\mathrm{AgBeF}}_3 $$ and AgCaF3$$ {\mathrm{AgCaF}}_3 $$ are promising materials for photovoltaic applications. [ABSTRACT FROM AUTHOR]

We consider a nonlinear transmission problem for a Bresse beam, which consists of two parts, damped and undamped. The mechanical damping in the damping part is present in the shear angle equation only, and the damped part may be of arbitrary positive length. We prove the well-posedness of the corresponding system in energy space and establish the existence of a regular global attractor under certain conditions on the nonlinearities and coefficients of the damped part only. Besides, we study the singular limits of the problem under consideration when curvature tends to zero, or curvature tends to zero, and simultaneously shear moduli tend to infinity and perform numerical modeling for these processes. [ABSTRACT FROM AUTHOR]

Underground soil in coastal areas is often affected by various dynamic effects such as earthquakes, construction, and waves. In order to study the influence of stress path on the dynamic characteristics of silty clay, resonance column tests were conducted on undisturbed samples of silty clay at different depths in the Yancheng area under cyclic stress paths. The results show that stress history has a significant impact on the response of soil dynamic parameters, and there is a significant difference between the maximum dynamic shear modulus Gmax and dynamic shear modulus G of the soil between loading and unloading paths; When the confining pressure is between 0~80 kPa, Gmax rapidly increases and variability decreases; The geological age and burial depth play an important role in the variation of soil dynamic parameters. As the burial depth increases, the difference between Gmax under different stress paths and G when the confining pressure changes continuously expands. When the geological age changes, G shows a significant increase; Propose a fitting relationship between the maximum dynamic shear modulus and confining pressure based on experiments, and provide fitting results for silty clay with different stress histories, providing reference for engineering design and construction in Yancheng and related coastal areas. [ABSTRACT FROM AUTHOR]

Studies of the mechanical response behavior of slate and the establishment of corresponding damage-ontological relationships are crucial for improving safety and avoiding disasters in construction projects. For the study reported in this paper, we first assumed that slate is a transverse isotropic body. Next, to characterize disparities in elastic characteristics between axial and radial orientations, we introduced five distinct elastic parameters for these two directions. Specifically, these parameters were Young's modulus E1, Poisson's coefficient v1 (associated with parallel bedding planes), Young's modulus E2, Poisson's coefficient v2, and shear modulus G2 (associated with perpendicular bedding planes). We then established a statistical damage-evolution equation for transverse isotropic slate based on a lognormal distribution, and we constructed a statistical damage-constitutive model for laminated slate under three-way stress by considering the shear–slip deformation and closure deformation of the laminated surface. Finally, we demonstrated the effectiveness of our model by comparing its output data with results obtained in triaxial compression tests on slate. We found that the differential stress–strain curves obtained from the model and the tests were in good agreement in the peak front. Average relative errors of 15.62% and 16.19% were recorded for cases of 5 Mpa and 10 Mpa of enclosing pressure, respectively. The rationality of the established transverse isotropic slate damage-constitutive relationship was therefore proved. [ABSTRACT FROM AUTHOR]

Exposure to mechanical stimuli such as pressure and stretching prompts the skin to undergo physiological adaptations to accommodate and distribute applied forces, a process known as mechanotransduction. Mechanotherapy, which leverages mechanotransduction, shows significant promise across various medical disciplines. Traditional methods, such as massage and compression therapy, effectively promote skin healing by utilizing this mechanism, although they require direct skin contact. This study introduces a novel contactless modality, Shear Wave Stimulation (SWS), and evaluates its efficacy compared to traditional massage in eliciting responses from human skin and fascia. Fifteen healthy volunteers received SWS, while another fifteen volunteers received massage. Tests of skin mechanical properties revealed significant enhancements in skin shear modulus for both methods, showing an increase of approximately 20%. Additionally, deformation analysis of ultrasound images showed distinct responses of the skin and fascia to the two stimuli. SWS induced extension in the dermis (∼18%), hypodermis (∼16%), and fascia (∼22%) along the X and Y axes. In contrast, massage compressed the skin layers, reducing the dermis by around 15% and the hypodermis by about 8%, while simultaneously stretching the superficial fascia by approximately 8%. The observed extension across the entire skin with SWS highlights its potential as a groundbreaking contactless approach for promoting skin healing. Furthermore, the differing responses in blood flow reaffirm the distinct stimulation modes of SWS and massage. These findings establish a foundation for future innovative skin therapy modalities. [ABSTRACT FROM AUTHOR]

Groundwater level tidal analysis is a powerful technique to monitor aquifer's permeability and hence its change over time. Earthquakes are known to affect aquifer's properties, in their vicinity through static stress changes but also further away through dynamic stresses. Most often changes are in the form of permeability increases, but sometimes decreases; the changes can be either permanent or transient. These observations are relatively well documented but the physical processes behind these changes are not well understood. By combining solid‐earth and barometric tidal groundwater level responses in a borehole in a coherent poroelastic theoretical framework, and a bi‐layer hydrogeological model, we recover a 15 years‐long time series evolution of aquifer transmissivity and shear modulus. This study showcases the full potential of the tidal analysis method, coupling pore pressure diffusion and rock deformation, at the frontier of hydrogeology and rock physics. This unprecedented measurement of permeability and shear modulus evolution by tidal analysis reveals, during interseismic period, high sensitivity of this shallow aquifer to effective stress, and thus to pore pressure. Thanks to additional finite element simulation of seismic wave propagation, we explore the different mechanisms affecting permeability and shear modulus in the studied fractured andesite aquifer. This study confirms the predominant role of seismic dynamic stresses, and more precisely of dynamic shear stresses, in the change of permeability following an earthquake. Plain Language Summary: Tidal oscillations of groundwater level, observable in boreholes all around the world, are information‐rich signals for hydrogeologist to infer the properties of surrounding aquifers, and how they evolve over time. Most importantly, it allows to monitor aquifer permeability and how it evolves under the influence of earthquakes, especially through static stresses changes or seismic wave propagation. Here we push the limits of what tidal analysis can reveal by also retrieving the shear modulus of the studied aquifer. This new observable, combined with the computation of regional earthquakes stresses, allows us to understand better how aquifer properties are modified by earthquakes. The analysis reveals first that dynamic shear stresses are the most probable cause of permeability changes, and second that the sensitivity of our fractured aquifer permeability to pore pressure is high. Key Points: The 15‐years' time series of permeability and shear modulus of the aquifer is deduced from the analysis of solid earth and barometric tidesCo‐seismic irreversible changes of fractured aquifer permeability are induced by earthquakes dynamic shear stressesInterseismic permeability variations of the aquifer are controlled by pore pressure, that is, the hydraulic head [ABSTRACT FROM AUTHOR]