Search results for "Modulus"
showing 10 items of 491 documents
Curve packing and modulus estimates
2018
A family of planar curves is called a Moser family if it contains an isometric copy of every rectifiable curve in $\mathbb{R}^{2}$ of length one. The classical "worm problem" of L. Moser from 1966 asks for the least area covered by the curves in any Moser family. In 1979, J. M. Marstrand proved that the answer is not zero: the union of curves in a Moser family has always area at least $c$ for some small absolute constant $c > 0$. We strengthen Marstrand's result by showing that for $p > 3$, the $p$-modulus of a Moser family of curves is at least $c_{p} > 0$.
Determination of Young’s modulus of Sb2S3 nanowires by in situ resonance and bending methods
2016
In this study we address the mechanical properties of Sb2S3 nanowires and determine their Young’s modulus using in situ electric-field-induced mechanical resonance and static bending tests on individual Sb2S3 nanowires with cross-sectional areas ranging from 1.1·104 nm2 to 7.8·104 nm2. Mutually orthogonal resonances are observed and their origin explained by asymmetric cross section of nanowires. The results obtained from the two methods are consistent and show that nanowires exhibit Young’s moduli comparable to the value for macroscopic material. An increasing trend of measured values of Young’s modulus is observed for smaller thickness samples.
Monoclinic model shear zones
1998
Abstract Although many ductile shear zones are supposed to have developed by approximately simple shear flow, some must have formed under different conditions. A few types of such ‘non-simple shear zones’ have been proposed in the literature such as transpression-, transtension- and stretching-shear zones. This paper presents a full three-dimensional kinematic model of shear zones with monoclinic flow geometry. Monoclinic shear zone types can be classified according to flow parameters, and according to the geometry and orientation of accumulating finite strain. Modelling of finite strain accumulation shows that a number of unusual and potentially problematic structural features may develop …
A machine learning approach to determine airport asphalt concrete layer moduli using heavy weight deflectometer data
2021
An integrated approach based on machine learning and data augmentation techniques has been developed in order to predict the stiffness modulus of the asphalt concrete layer of an airport runway, from data acquired with a heavy weight deflectometer (HWD). The predictive model relies on a shallow neural network (SNN) trained with the results of a backcalculation, by means of a data augmentation method and can produce estimations of the stiffness modulus even at runway points not yet sampled. The Bayesian regularization algorithm was used for training of the feedforward backpropagation SNN, and a k-fold cross-validation procedure was implemented for a fair performance evaluation. The testing p…
Compressive behavior of short high-strength concrete columns
2010
Abstract The focus of the present paper is the compressive response of short high strength reinforced concrete members. Members have square transverse cross-sections and they are reinforced with longitudinal steel bars and transverse stirrups. A preliminary analysis to check the stability condition of longitudinal bars was made to verify that buckling occurs after yielding in compression. Prescriptions on required diameter and spacing of stirrups are given. In the following, a model is presented which allows us to evaluate the confinement pressures exercised by transverse steel and by longitudinal bars during the loading process taking into account the interaction of the stirrups with the i…
Influence of steel reinforcements on the behavior of compressed high strength R.C. circular columns
2012
Abstract In the present paper the focus is on the compressive response of short high strength reinforced concrete members having circular transverse cross-sections and reinforced with longitudinal steel bars and transverse spirals or hoops. An analytical model is proposed which allows one to estimate the confinement pressures exerted by transverse steel and by longitudinal bars during the loading process, taking into account the interaction of the hoops or spirals with the inner core both in the plane of the transverse steel and in the space between two successive hoops. Yielding of steel spirals or hoops and longitudinal bars including buckling phenomena and damage to the concrete core are…
Synthesis and High-Pressure Study of Corundum-Type In2O3
2015
This work reports the high-pressure and high-temperature (HP-HT) synthesis of pure rhombohedral (corundum-type) phase of indium oxide (In2O3) from its most stable polymorph, cubic bixbyite-type In2O3, using a multianvil press. Structural and vibrational properties of corundum-type In2O3 (rh-In2O3) have been characterized by means of angle-dispersive powder X-ray diffraction and Raman scattering measurements at high pressures which have been compared to structural and lattice dynamics ab initio calculations. The equation of state and the pressure dependence of the Raman-active modes of the corundum-type phase are reported and compared to those of corundum (α-Al2O3). It can be concluded that …
Measuring (biological) materials mechanics with atomic force microscopy. 2. Influence of the loading rate and applied force (colloidal particles)
2020
Atomic force microscopy (AFM) is the most often used tool to study the mechanical properties of eukaryotic cells. Due to their complex assembly, cells show viscoelastic properties. When performing experiments, one has to consider the influence of both loading rate and maximum load on the measured mechanical properties. Here, we employed colloidal particles of various sizes (from 2 to 20 μm diameter) to perform force spectroscopy measurements on endothelial cells at loading rates varying from 0.1 to 50 μm/s, and maximum loads ranging from 1 to 25 nN. We were able to determine the non-linear dependence of cell viscoelastic properties on the loading rate which followed a weak power law. In add…
Interpretation of EXAFS in ReO3using molecular dynamics simulations
2009
Temperature dependent Re L3-edge EXAFS signals from perovskite-type cubic ReO3 have been successfully interpreted using a combination of classical NVT molecular dynamics (MD) and ab initio multiple-scattering approach. The force field model, required for MD simulations, has been determined by fitting the Re-O and O-O pairwise interatomic potentials to a set of experimental data (lattice parameter, elastic constants and bulk modulus) and phonon frequencies, theoretically calculated from the first principles at high symmetry points of the Brillouin zone. The MD simulations reproduce well the anisotropy of thermal vibration for oxygen atoms and confirm a deviation of the mean Re-O-Re angle fro…
Relations between the cohesive energy, atomic volume, bulk modulus and sound velocity in metals
2011
By analysing the experimental data available in the literature, it has been found that the bulk modulus B of metals is proportional to the cohesive energy density Ec/V. For metals which start to melt having the close packed structure A1 or A3 the proportionality factor in the forementioned correlation is distinctly greater than that for metals melting from the A2 type structure. The existence of the correlation between the bulk modulus and the cohesive energy density leads to another, hitherto unrevealed correlation between the sound velocity, cohesive energy and the molar mass of metals: u2 ~ Ec/μ.