Modulus Data Research Articles

Mechanical and thermal properties versus effective cubic lattice constant in Cu2-II-IV-VI4 quaternary compounds

The present work aims to study the dependence of the bulk modulus B and the Debye temperature θD with the effective cubic lattice constant aeff of some Cu2-II-IV-VI4 compounds. We are also studied the correlation between the bulk modulus B, the Debye temperature θD, the microhardness H and the melting point Tm.The fits of the data of the bulk modulus B and the Debye temperature θD versus the effective cubic lattice constant aeff show that B of Cu2-II-IV-VI4 semiconducting materials decreases almost linearly with increase of the effective cubic lattice constant aeff, while that of Debye Temperature θD decreases exponentially with a rising of the effective cubic lattice constant aeff. The coefficients of the correlation were found at around -0.78 for the bulk modulus B, and at around -0.94 for the Debye temperature, respectively.For the bulk modulus B, the best fit was obtained using the following expression: B = - 596.52 aeff + 393.4, where B is expressed in GPa, and aeff in nm, while that of θD is: θD = 165.46 + 3.8 exp (-57.2 aeff), respectively. The average error on the estimation of B was found at around 10%, while that on the estimation of θD is only around 4.5%, respectively. Our expressions perhaps used with high accurate to predict the bulk modulus B and the Debye temperature θD of other quaternary Cu2-II-IV-VI4 semiconducting materials.

Towards room-temperature and above magnetoelectricity in CoFe2O4/Cr2O3 core/shell nanoparticles

This work provides an effective approach to increase the magnetoelectric (ME) operating temperature of primordial sesqui oxide Cr2O3. The CoFe2O4 (core)/Cr2O3 (shell) nanoparticles with varying molar fractions are prepared via the sol-gel auto-combustion method. The phase-purity and coating induced micro-strains in core as well as shell have been validated from the Rietveld refinement of x-ray diffraction data, and are complementary to the Fourier transform infrared spectroscopy and Raman spectroscopy studies. Transmission electron microscopy measurement confirms the core/shell configuration of the nanoparticles. The magnetization measurements suggest screening of ferromagnetic interaction of CoFe2O4 (core) due to Cr2O3 shell over it, such that core/shell nanoparticles respond like single domain particles. A careful inspection of the impedance and modulus data suggest single relaxation in the studied frequency/temperature range for all the compositions. Both, the relaxation and the conduction processes are found to be polaronic obeying Mott variable range hopping mechanism. Direct ME measurements on these samples manifests the presence of linear magnetoelectricity for temperature as high as 400 K―a hallmark of enhancement in ME operating temperature of parental Cr2O3 phase and therefore widen its scope to meet the necessity of ME based potential applications.

Automated ultrasound measurements of lateral abdominal muscles under controlled breathing phases

Background and objectivesA breathing phase during ultrasound measurements of the lateral abdominal muscles (LAMs) are usually indirectly controlled by visual inspection of the position of the transversus abdominis (TrA) muscle. This is due to the lack of devices to directly control airflow that are connected to the ultrasound in order to automatically and simultaneously freeze ultrasound images at the programmed breathing phase. Such indirect control may be related with potential measurement error because LAMs are respiratory muscles. Thus, the aim of this study was to present a newly developed and automatic measurement procedure to directly control airflow and at the same time automatically collect ultrasound images at the programed breathing phase. Additionally, it was decided to compare LAMs measurements obtained manually by the examiner and with an external device controlling the peak phase of tidal inspiration and expiration and compare the elasticity and thickness measurements between tidal inspiration and expiration in young participants. MethodsThe study was carried out on 10 healthy youth. The thickness and shear modulus were measured by an Aixplorer ultrasound scanner. The measurements were obtained manually by the examiner and with a newly developed external device controlling the peak phases of tidal inspiration and expiration. ResultsA significant difference in external/internal oblique thickness between the expiration and inspiration phases depended on the measurement procedure. The TrA thickness was similar during inspiration and expiration. During inspiration, the TrA shear modulus was higher than during expiration, and the TrA shear modulus depended on the measurement procedure. ConclusionAlthough the raw LAMs thickness and external/internal oblique thickness/shear modulus data were similar, the measurement procedure may affect the interpretation of the results. The TrA shear modulus is the most vulnerable to errors related to the measurement procedure. Construction of this study device controlling airflow and automatically collecting ultrasound images at the selected breathing phase seems to be promising in future studies considering measurements of respiratory muscles in a strictly defined breathing phase.

Revisiting a non-parametric reconstruction of the deceleration parameter from combined background and the growth rate data

The cosmic deceleration parameter q has been reconstructed in a non-parametric way using various combinations of recent observational datasets. The Pantheon compilation of the Supernova (SN) distance modulus data, the Cosmic Chronometer (CC) measurements of the Hubble parameter including the full systematics and the Baryon Acoustic Oscillation (BAO) data have been considered in this work. The redshift z t , where the transition from a past decelerated to a late-time accelerated phase of evolution occurs, is estimated from the reconstructed q . The possible effect of a non-zero spatial curvature from the Planck 2020 estimate is checked. The outcome of including different H 0 measurements from recent Planck 2020 and Riess 2021 probes having a maximum discrepancy at the 4 . 2 σ level, is investigated. Results indicate that the transition from a past decelerated phase to the late-time accelerated phase occurs within the redshift range 0 . 5 < z < 1 . The reconstructed q is observed to have a non-monotonic evolution in case of the combined CC and SN data for z > 1 , which becomes oscillatory on introducing the BAO data. To investigate the effect of matter perturbations, the growth rate data from the Redshift-Space Distortions (RSD) are utilized in reconstructing q . Using the O m ( z ) diagnostic, we draw inferences on the validity of Λ CDM as a consistency check. The Λ CDM model is well consistent and included at the 2 σ level in the domain of all the reconstructions.

Study of the Durability Damage of Ultrahigh Toughness Fiber Concrete Based on Grayscale Prediction and the Weibull Model

The purpose of this research is to investigate the durability damage law for ultrahigh toughness cementitious composites (UHTCCs) under freeze–thaw environments and impact resistance. In this study, UHTCCs with fiber length-to-diameter ratios of 5/30, 8/30, 12/20, 12/30 and 12/48 were tested for impact resistance and freeze–thaw cycles. The freeze–thaw cycle process and impact resistance process for UHTCC are comprehensively analyzed and evaluated in terms of mass loss, compressive strength loss, relative dynamic elastic modulus loss and impact resistance number. The freeze–thaw damage prediction model for the relative dynamic elastic modulus of the UHTCC is established based on the regularity of the measured data for the relative dynamic elastic modulus of UHTCC and also on the GM(1,1) power model. The accuracy and reliability of the GM(1,1) power model is analyzed using the relative error, absolute correlation degree, mean variance and probability of small errors. According to the evolution law of the impact resistance number of the UHTCC, the impact damage prediction model for UHTCC is established based on the Weibull distribution model, and the accuracy of the model is analyzed by using the decision coefficient R2. The results show that UHTCC has high durability performance, and the durability performance of UHTCC at a length-diameter ratio of 12/48 is optimal. The freeze–thaw damage evolution model and impact damage evolution model established in this research are sufficiently realistic, the average relative error of the GM(1,1) power model is less than 5%, and the coefficient of determination R2 of the Weibull distribution model is greater than 0.93, which effectively reflects the damage development process for concrete under freeze–thaw and impact environment with high fitting accuracy.

A stochastic gradient descent approach with partitioned-truncated singular value decomposition for large-scale inverse problems of magnetic modulus data

We propose a stochastic gradient descent approach with partitioned-truncated singular value decomposition (SVD) for large-scale inverse problems of magnetic modulus data. Motivated by a uniqueness theorem in gravity inverse problem and realizing the similarity between gravity and magnetic inverse problems, we propose to solve the level-set function modeling the volume susceptibility distribution from the nonlinear magnetic modulus data. To deal with large-scale data, we employ a mini-batch stochastic gradient descent approach with random reshuffling when solving the optimization problem of the inverse problem. We propose a stepsize rule for the stochastic gradient descent according to the Courant–Friedrichs–Lewy condition of the evolution equation. In addition, we develop a partitioned-truncated SVD algorithm for the linear part of the inverse problem in the context of stochastic gradient descent. Numerical examples illustrate the efficacy of the proposed method, which turns out to have the capability of efficiently processing large-scale measurement data for the magnetic inverse problem. A possible generalization to the inverse problem of deep neural network is discussed at the end.

Electric conductivity and dielectric relaxation properties of BiFeO3-YMnO3 solid solution

This manuscript presents a systematic study of conductivity and dielectric relaxations in the solid solution of (BiFeO3)1-x -(YMnO3)x for compositional range (0.0 ≤ x ≤ 0.2) as function of frequency, temperature, and magnetic field. The samples have been synthesized by combustion method. The thermal activations of dc-conductivity and relaxation time obey Arrhenius behavior for, x = 0.0, 0.025, 0.05 but follow variable range hopping of small polarons above, x ≥ 0.075 with activation energy 0.45 eV. The compositional time-temperature superposition of dielectric modulus data suggests that conduction mechanism changes with composition. The bulk capacitance decreases with increase in magnetic field.

Effect of Water on Mechanical Properties of Coal Measures Mudstone Using Nanoindentation

Mudstone rich in clay minerals exhibits an obvious water-induced weakening effect, and the mechanical properties of mudstone are significantly affected by the groundwater. To investigate the effect of water on mechanical characteristics of mudstone at microscale, a series of uniaxial compression and nanoindentation tests were conducted on mudstone specimens at different moisture contents. Microscale measurements are upscaled to estimate the corresponding magnitudes at the macroscale using the Mori-Tanaka method. The results showed that the indentation modulus varied significantly, from as low as 0.2 GPa to a quite high value of 125 GPa, indicating a strongly heterogeneous distribution of mudstone. The water illustrated a significant effect on the microscale mechanical properties of water-sensitivity minerals like clay minerals. The water-sensitivity minerals occupied the highest proportion of the mudstone and were believed to play an important role in the mechanical properties of mudstone. For water-bearing specimens, the comparison with elastic modulus data obtained from common method indicated similar values as those predicted by homogenization method. The results of this study indicated that nanoindentation technique is a feasible experimental technique to assess the macroscale mechanical properties of rock materials.

Research on the Combination of Firefly Intelligent Algorithm and Asphalt Material Modulus Back Calculation.

The modulus of asphalt pavement material is a necessary parameter for the design, strength measuring and stability evaluation of asphalt pavement. To get more precise test data for asphalt pavement material modulus, a new modulus back calculation method is proposed in this article, named as the Firefly Asphalt Back Calculation Method (FABCM). This novel method uses the firefly optimization algorithm, which is a kind of particle swarm intelligence algorithm imitating the information transfer process among fireflies. To demonstrate the reliability and stability of FABCM, and to study the feasibility of multi-parameter modulus back calculation methods, this article used theoretical deflection curves calculated by BISAR3.0 and the actual measurement data of deflection curves and vertical pressures on the subgrade top surfaces on the full-scale test circular track in the Research Institute of Highway, Ministry of Transport (RIOHTrack) to conduct a modulus back calculation. The results show that FABCM only takes 0.5–1 s for each calculation, and the back calculation errors in the verification of FABCM are mostly smaller than 1%, which means that the firefly optimization algorithm was modified effectively in this article. Moreover, this article also indicates some key factors influencing the accuracy of modulus back calculation, and several reasonable suggestions to the application of modulus back calculation.

Multilayer Microstructure Characterization of the Interfacial Transition Zone between Polymer-Modified Magnesium Phosphate Cement and Portland Cement

Magnesium phosphate cement (MPC) as a fast-setting material has been widely used in the rapid repair of cement concrete pavement. A decisive role was played in the bonding performance of the repair interface between MPC and portland cement concrete (PCC) except for the high early strength and good durability of MPC. Premising the MPC as the rapid repair material for PCC, the characterization and analysis of the interface performance are studied. The data of elastic modulus for the interfacial transition zone (ITZ) is measured by nanoindentation technology while the mechanical properties firstly. The heterogeneity and stratification in the ITZ were characterized by the combination of Raman spectroscopy and nanoindentation test. The content of each material composition was explored with scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS) experiment and X-ray diffraction (XRD) analysis. Additionally, the adhesion-like substances in the cracks, observed by SEM images in the ITZ, inferred a certain self-healing ability of the polymer-modified magnesium phosphate cement (PMPC). Finally, the elastic modulus of ITZ was simulated by DIGIMAT version 2019.1 software, indicating that the single-layer microstructure analysis is feasible for obtaining elastic modulus of the ITZ without hydration stratification, while the multilayer microstructure analysis is necessary for obtaining elastic modulus of the ITZ with the hydration stratification.

Mechanical properties and damage analysis of S-glass: A reactive molecular dynamics study

Glass fibers are widely used as reinforcements in composites for applications ranging from lightweight and damage tolerant structures to protective materials providing high levels of energy absorption during ballistic impact. Understanding the atomistic origin of mechanical response and damage modes under various strain rate loading conditions is important to improve the properties of glass fibers. In this paper, molecular dynamics (MD) simulations with a reactive potential relate the composition of S-glass fiber to the mechanical properties and progressive damage mechanisms. Stress-strain response of Magnesium Aluminosilicate S-glass fiber using our newly developed Mg/Al/Si/O ReaxFF interatomic potential is predicted from 1e7/s to 1e15/s. Overall strain rate dependent modulus and strength data exhibit a characteristic S-shaped curve on a semi-log plot indicating strain rate dependent properties followed by a steep rise in properties at approximately 1e12/s to a strain rate-independent plateau. Detailed analysis of the atomic structure during high strain rate tensile loading provides insight into the dependency of properties on the rate of atomistic reconstruction, suggesting that the characteristic time-to-reconstruct is an important factor governing strain rate-dependent progressive damage. The origin of the higher modulus of S-glass over silica arises from electrostatic interactions associated with Al-O and Mg-O bonds in S-glass. Investigation on Al-O-Mg, Mg-BO/NBO interaction, and Al/Si-O ring structure indicates that the reconstruction of local structure leads to a more ductile-type response and progressive damage evolution in S-glass fiber than silica glass . In addition, we introduce a methodology to construct stress-strain response for low strain rates (1E-3/s) from a series of high strain rate loading to prescribed strain levels followed by stress-relaxation to an equilibrium stress level. The method is computationally efficient, and the results agree with the quasi-static modulus of both S-glass and silica.

Effect of Base Oil and Thickener on Texture and Flow of Lubricating Greases: Insights from Bulk Rheometry, Optical Microrheology and Electron Microscopy

The structure and flow behavior of lubricating greases depend on the base oil and the type and concentration of the dissolved thickener. In this study, the linear viscoelastic properties of greases were characterized by combining oscillatory shear and squeeze flow covering a broad frequency range (0.1–105 rad s−1). Multiple-particle tracking (MPT) microrheology and scanning electron microscopy (SEM) provided further insight into local viscoelastic properties and sample structure on a submicron-length scale. The type and viscosity of the base oil did not affect the absolute value of the complex viscosity and the filament shape formed by a given thickener. High-frequency shear modulus data, however, indicated that the thickener lithium 12-hydroxystearate formed stiffer networks/filaments in poly-α-olefins than in mineral oils. As expected, the viscosity increased with increased thickener concentrations, but microscopy and high-frequency rheometry revealed that the thickness, length, and stiffness of the individual filaments did not change. In mineral oil, the 12-hydroxystearate thickeners yielded higher viscosity than the corresponding stearates with the same metal ion. The filamentous lithium thickeners created stronger networks than the roundish aggregates formed by magnesium and zinc stearate. Network mesh sizes varying between approximately 100 nm and 300 nm were consistently determined from SEM image analysis and MPT experiments. The MPT experiments further disclosed the existence of gel-like precursors of approximately 130 µm at thickener concentrations far below the critical value at which a sample-spanning network resulting in a characteristic grease texture is formed.

Impact of Improved Density on Pavement Design Response for Low-Volume Roads/Non-Primary Routes

Hughes said “Compaction is the single most important factor that affects pavement performance in terms of durability, fatigue life, resistance to deformation, strength, and moisture damage.” Past research studies have shown that a 1% decrease in air voids was estimated to improve the fatigue performance of asphalt pavements between 8.2% and 43.8%. Tran et al. quoted: “A 1% decrease in air voids was estimated to extend the service by conservatively 10% .” The objective of this research study is to show the impact of varying density properties using the concept of expected life difference. Fatigue life will be evaluated using the traditional fatigue life prediction equations and an advanced mechanistic empirical model (i.e., AASHTO Pavement ME). Dynamic modulus is the main input for conducting a pavement analysis and/or design when using AASHTO Pavement ME. The dynamic modulus data was generated from an extensive laboratory density study sponsored by Kentucky Transportation Cabinet. The air voids of the dynamic modulus samples varied from 11.4% to 3.9%. This study forms a framework for a highway agency, city, and county engineer if they are looking for an engineering solution as to why they should improve their in-place density specifications and what that impact is, using mechanistic empirical design procedures.

Constraining the curvature density parameter in cosmology

The cosmic curvature density parameter has been constrained in the present work independent of any background cosmological model. The reconstruction is performed adopting the non-parametric Gaussian Processes (GP). The constraints on $\Omega_{k0}$ are obtained via a Markov Chain Monte Carlo (MCMC) analysis. Late-time cosmological probes viz., the Supernova (SN) distance modulus data, the Cosmic Chronometer (CC) and the radial Baryon Acoustic Oscillations ($r$BAO) measurements of the Hubble data have been utilized for this purpose. The results are further combined with the data from redshift space distortions (RSD) which studies the growth of large scale structure in the universe. The only \textit{a priori} assumption is that the universe is homogeneous and isotropic, described by the FLRW metric. Results indicate that a spatially flat universe is well consistent in 2$\sigma$ within the domain of reconstruction $0<z<2$ for the background data. On combining the RSD data we find that the results obtained are consistent with spatial flatness mostly within 2$\sigma$ and always within 3$\sigma$ in the domain of reconstruction $0<z<2$.

Thermal Change Affects Flexural and Thermal Properties of Fused Deposition Modeling Poly(Lactic Acid) and Compression Molding Poly(Methyl Methacrylate).

Polylactic acid (PLA) is one of the most widely used materials in three-dimensional (3D) printing technology due to its multiple advantages such as biocompatibility and biodegradable. However, there is still a lack of study on 3D printing PLA for use as a denture base material. The goal of this study was to compare 3D printing PLA to traditional poly(methyl methacrylate) (PMMA) as a denture basis. The PMMA (M) and PLA (L) specimens were fabricated by compression molding, and fuse deposition modeling technique, respectively. Each specimen group was divided into three different temperature groups of 25°C (25), 37°C (37), and 55°C (55). The glass transition temperature (Tg) of raw materials and specimen was investigated using differential scanning calorimetry. The heat deflection temperature (HDT) of each material was also observed. The data of flexural strength and flexural modulus were analyzed with two-way analysis of variance, and Tukey honestly significant difference. The Tg and HDT data, on the other hand, were descriptively analyzed. The results showed that PLA had lower flexural strength than PMMA in all temperature conditions, while the PMMA 25°C (M25) and PMMA 37°C (M37) obtained the highest mean values. PLA 25°C (L25) and PLA 37°C (L37) had significant higher flexural modulus than the other groups. However, the flexural properties of L55 could not be observed, which may be explained by Tg and HDT of PLA. PLA only meets the flexural modulus requirement, although it was greater than flexural modulus of PMMA. On the other hand, PMMA can meet both good flexural strength and modulus requirement. However, increase in temperature could reduce flexural strength and flexural modulus of PMMA and PLA.

Analytical and numerical results for the elasticity and adhesion of elastic films with arbitrary Poisson’s ratio and confinement

ABSTRACT We present an approximate, analytical treatment for the linearly elastic response of a film with arbitrary Poisson's ratio , which is indented by a flat cylindrical punch while resting on a rigid foundation. Our approach is based on a simple scaling argument allowing the vast changes of the elastomer’s effective modulus with the ratio of film height and indenter radius to be described with a compact, analytical expression. This yields exact asymptotics for large and small reduced film heights , whereby it also reproduces the observation that has a pronounced minimum for at . Using Green’s function molecular dynamics (GFMD), we demonstrate that the predictions for are reasonably correct and generate accurate reference data for effective modulus and pull-off force. GFMD also reveals that the nature of surface instabilities occurring during stable crack growth as well as the crack initiation itself depend sensitively on the way how continuum mechanics is terminated at small scales, that is, on parameters beyond the two dimensionless numbers and defining the continuum problem.

Predicting glass properties by using physics- and chemistry-informed machine learning models

Physics- and chemistry-informed machine learning (ML) models were trained by using descriptors in the element physical and chemical properties domain, which include stoichiometric, elemental-property-based, valance orbital occupation, and ionicity features. Young's modulus, shear modulus and electrical resistivity (ρ) data for a group of oxide glasses were used to train artificial neural network (ANN), support vector machine (SVM), and random forest (RF) models. In comparison with experimental values, the ANN performs the best in predicting elastic moduli, whereas the RF is the best in predicting the temperature dependence of ρ in terms of the coefficient of determination (R2) value. The benefits of the ML models using descriptors in the element physical and chemical properties domain were demonstrated by revealing the relationships between the predicted glass properties and their first and second important features through a grid search.

Linear viscoelastic response of semi-circular asphalt sample based on digital image correlation and XFEM

Asphalt mixtures behave as linear viscoelastic materials when subjected to loading conditions that are similar to pavement operating conditions. Thus, this study proposed a novel method for extracting the linear viscoelastic properties of asphalt mixture at 25 °C using digital image correlation and repeated-load semi-circular bending (SCB) test. Digital image correlation was utilised successfully for extracting creep compliance using semi-circular samples under repeated loading conditions. A fractional time-dependent viscoelastic element converted the creep compliance data into relaxation modulus. The extracted relaxation modulus data were verified by simulating the viscoelastic response of control and modified asphalt mixtures using the extended finite element model (XFEM). The findings presented in this paper showed that digital image correlation has a high potential for bridging the gap between experimental and simulation work. The strain map provided by the prediction model was compatible with the DIC strain.

Effect of evolving physical constants on type Ia supernova luminosity

ABSTRACT Type Ia supernovae, SNeIa, are used as standard candles in cosmology to determine the distances of the galaxies harbouring them. We show that the luminosity of an SNIa depends on its distance from us when physical constants (the speed of light c, the gravitational constant G, and the Planck constant h) are permitted to evolve. It is because the Chandrasekhar mass of the white dwarf that explodes to create SNIa depends on the values of the constants at the epoch the SNIa is formed. We show that the SNeIa luminosities could be about four times higher in the past than they are now. Thus, the luminosity distance estimation of the earliest SNeIa could be off by up to a factor of 2. Cosmological parameters, determined with this correction applied to the redshift versus distance modulus data base (Pantheon SNeIa), are not very different from those from the standard ΛCDM model without this correction, except for the dark-energy density and the curvature energy density; the latter increases at the cost of the former. Variations of the constants are given by $\dot{G}/G = \ 3.90 \ ( { \pm 0.04} ) \times {10^{ - 10}}\ {\rm y{r^{ - 1}}}$and $\dot{c}/c = \dot{h}/h\ = \ 1.30\ ( { \pm 0.01} ) \times {10^{ - 10}}\ {\rm y{r^{ - 1}}}$ at present. These variations are valid only when $G,\ c,\ $and$\ h$ are permitted to vary concurrently rather than individually.

A Cylindrical Grip Type of Tactile Device Using Magneto-Responsive Materials Integrated with Surgical Robot Console: Design and Analysis.

This paper proposes a cylindrical grip type of tactile device that is effectively integrated to a surgical robot console so that a surgeon can easily touch and feel the same stiffness as the operating organs. This is possible since the yield stress (or stiffness) of magnetic-responsive materials can be tuned or controlled by the magnetic field intensity. The proposed tactile device consists of two main parts: a magnetorheological elastomer (MRE) layer and a magnetorheological fluid (MRF) core. The grip shape of the device to be positioned on the handle part of the master of the surgical robot is configured and its operating principle is discussed. Then, a couple of equations to calculate the stiffness from the gripping force and the field-dependent yield stress of MRF are derived and integrated using the finite element analysis (FEA) model. After simulating the stiffness of the proposed tactile device as a function of the magnetic field intensity (or current), the stiffnesses of various human organs, including the liver and heart, are calculated from known data of an elastic modulus. It is demonstrated from comparative data between calculated stiffness from human tissues and simulated stiffness from FEA that the proposed tactile device can generate sufficient stiffness with a low current level to recognize various human organs which are significantly required in the surgical robot system.