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Showing papers on "Elasticity (economics) published in 2013"


Journal ArticleDOI
TL;DR: The application of virtual elements to linear elasticity problems, for both the compressible and the nearly incompressible case, is discussed.
Abstract: We discuss the application of virtual elements to linear elasticity problems, for both the compressible and the nearly incompressible case. Virtual elements are very close to mimetic finite differences (see, for linear elasticity, [L. Beirao da Veiga, M2AN Math. Model. Numer. Anal., 44 (2010), pp. 231--250]) and in particular to higher order mimetic finite differences. As such, they share the good features of being able to represent in an exact way certain physical properties (conservation, incompressibility, etc.) and of being applicable in very general geometries. The advantage of virtual elements is the ductility that easily allows high order accuracy and high order continuity.

463 citations


Journal ArticleDOI
TL;DR: This review focuses on ultrasound-based elasticity imaging methods that generate an acoustic radiation force to induce tissue displacements that can be performed noninvasively during routine exams to provide either qualitative or quantitative metrics of tissue elasticity.
Abstract: The development of ultrasound-based elasticity imaging methods has been the focus of intense research activity since the mid-1990s. In characterizing the mechanical properties of soft tissues, these techniques image an entirely new subset of tissue properties that cannot be derived with conventional ultrasound techniques. Clinically, tissue elasticity is known to be associated with pathological condition and with the ability to image these features in vivo; elasticity imaging methods may prove to be invaluable tools for the diagnosis and/or monitoring of disease. This review focuses on ultrasound-based elasticity imaging methods that generate an acoustic radiation force to induce tissue displacements. These methods can be performed noninvasively during routine exams to provide either qualitative or quantitative metrics of tissue elasticity. A brief overview of soft tissue mechanics relevant to elasticity imaging is provided, including a derivation of acoustic radiation force, and an overview of the various acoustic radiation force elasticity imaging methods.

281 citations


Journal ArticleDOI
TL;DR: Tissue elasticity, Et, increases daily for heart to 1-2 kPa by embryonic day 4 (E4), and although this is ~10-fold softer than adult heart, the beating contractions of E4 cardiomyocytes prove optimal at ~Et,E4 both in vivo and in vitro.

172 citations


Journal ArticleDOI
TL;DR: The first-principles alloy theory predicts that at room temperature the paramagnetic NiCoFeCrAlx high entropy alloys adopt the face centered cubic (fcc) structure for x less than or similar to 0.60 and...
Abstract: First-principles alloy theory predicts that at room temperature the paramagnetic NiCoFeCrAlx high entropy alloys adopt the face centered cubic (fcc) structure for x less than or similar to 0.60 and ...

158 citations


Journal ArticleDOI
TL;DR: In this paper, the equivalence between nonlocal and gradient elasticity models is investigated by making reference to one-dimensional boundary value problems equipped with two integral stress-strain laws proposed by Eringen (2002).

155 citations


Journal ArticleDOI
TL;DR: In this article, an approach coupling ab initio calculations and linear elasticity theory is proposed to obtain the properties of an isolated point defect for reduced supercell sizes for three problematic cases: the self-interstitial in zirconium, clusters of selfinterstitials in iron, and the neutral vacancy in silicon.
Abstract: Modeling point defects at an atomic scale requires careful treatment of the long-range atomic relaxations. This elastic field can strongly affect point defect properties calculated in atomistic simulations because of the finite size of the system under study. This is an important restriction for ab initio methods which are limited to a few hundred atoms. We propose an original approach coupling ab initio calculations and linear elasticity theory to obtain the properties of an isolated point defect for reduced supercell sizes. The reliability and benefit of our approach are demonstrated for three problematic cases: the self-interstitial in zirconium, clusters of self-interstitials in iron, and the neutral vacancy in silicon.

153 citations


Journal ArticleDOI
TL;DR: In this article, a single-phase high-entropy alloys were investigated using the exact muffin-tin orbitals (EMTO) method in combination with the coherent potential approximation (CPA).
Abstract: Single-phase high-entropy alloys are investigated using the exact muffin-tin orbitals (EMTO) method in combination with the coherent potential approximation (CPA). Choosing the paramagnetic face-ce ...

143 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that the blowup of the gradient can be characterized by a singular function defined by the single layer potential of an eigenfunction corresponding to the eigenvalue 1/2 of a Neumann-Poincare type operator defined on the boundaries of the inclusions.
Abstract: When holes or hard elastic inclusions are closely located, stress which is the gradient of the solution to the anti-plane elasticity equation can be arbitrarily large as the distance between two inclusions tends to zero. It is important to precisely characterize the blow-up of the gradient of such an equation. In this paper we show that the blow-up of the gradient can be characterized by a singular function defined by the single layer potential of an eigenfunction corresponding to the eigenvalue 1/2 of a Neumann–Poincare type operator defined on the boundaries of the inclusions. By comparing the singular function with the one corresponding to two disks osculating to the inclusions, we quantitatively characterize the blow-up of the gradient in terms of explicit functions. In electrostatics, our results apply to the electric field, which is the gradient of the solution to the conductivity equation, in the case where perfectly conducting or insulating inclusions are closely located.

136 citations


Journal ArticleDOI
TL;DR: The present model can be used for free vibration analysis of single-walled carbon nanotubes with essential, natural and nonlinear boundary conditions.

124 citations


Journal ArticleDOI
TL;DR: In this article, a test program is carried out to develop information about the mechanical properties of fiber-reinforced self-compacting concrete (FRSCC) and four SCC mixes are considered in the test program.
Abstract: Fiber-reinforced self-compacting concrete (FRSCC) is a high-performance building material that combines positive aspects of fresh properties of self-compacting concrete (SCC) with improved characteristics of hardened concrete as a result of fiber addition. Considering these properties, the application ranges of both FRSCC and SCC can be covered. A test program is carried out to develop information about the mechanical properties of FRSCC. For this purpose, four SCC mixes – plain SCC, steel, polypropylene, and hybrid FRSCC – are considered in the test program. The properties include compressive and splitting tensile strengths, moduli of elasticity and rupture, compressive stress–strain curve, and energy dissipated under compression. These properties are tested at 3, 7, 14, 28, 56, and 91 days. Relationships are established to predict the compressive and splitting tensile strengths, moduli of elasticity and rupture, compressive stress–strain curve, and energy dissipated under compression. The models provide predictions matching the measurements.

121 citations


Journal ArticleDOI
TL;DR: In this article, there is no evidence that differences in supply elasticity caused cross-sectional variation among U.S. housing markets in the severity of the 2000s housing cycle.
Abstract: There is no evidence that differences in supply elasticity caused cross-sectional variation among U.S. housing markets in the severity of the 2000s housing cycle. This is true in three sets of empirical specifications: a first that assumes identical demand changes in the 2000s across markets, a second that proxies for supply elasticity and demand changes in the 2000s with estimates based on price and quantity changes in the 1980s and a third that uses physical and regulatory constraints to proxy for supply elasticity and uses state fixed effects to capture variation in demand conditions.

Journal ArticleDOI
TL;DR: In this article, a size-dependent nonclassical Bernoulli-Euler beam model based on the strain gradient elasticity is proposed for piezoelectric nanowires.
Abstract: A size-dependent nonclassical Bernoulli–Euler beam model based on the strain gradient elasticity is proposed for piezoelectric nanowires. The governing equations and the corresponding boundary conditions are naturally derived from the variational principle. Different from the classical piezoelectric beam theory, the electric field–strain gradient coupling and the strain gradient elasticity are both taken into account. Static bending problem of a cantilever piezoelectric nanobeam is solved to illustrate the effect of strain gradient. The present model contains material length scale parameters and can capture the size dependent piezoelectricity and elasticity for nanoscale piezoelectric structures. The numerical results reveal that the deflections predicted by the present model are smaller than that by the classical beam theory and the effective electromechanical coupling coefficient is dramatic enhanced by the electric field–strain gradient coupling effect. However, the differences in both the deflections and effective EMC coefficient between the two models are very significant when the beam thickness is very small; they are diminishing with the increase of the beam thickness. This model is helpful for understanding the electromechanically coupling mechanism and in designing piezoelectric nanowires based devices.

Journal ArticleDOI
TL;DR: In this paper, the authors use a model of isotropic floppy elastic networks and show that such networks present a phonon gap for frequencies smaller than a frequency ω* governed by coordination, and that the elastic response is characterized, and in some cases localized, on a length scale that diverges as the gap vanishes.
Abstract: Gels of semi-flexible polymers, network glasses made of low valence elements, softly compressed ellipsoid particles and dense suspensions under flow are examples of floppy materials. These systems present collective motions with almost no restoring force. To study theoretically and numerically the frequency-dependence of the response of these materials and the length scales that characterize their elasticity, we use a model of isotropic floppy elastic networks. We show that such networks present a phonon gap for frequencies smaller than a frequency ω* governed by coordination, and that the elastic response is characterized, and in some cases localized, on a length scale that diverges as the phonon gap vanishes (with a logarithmic correction in the two dimensional case). lc also characterizes velocity correlations under shear, whereas another length scale l* ∼ 1/ω* controls the effect of pinning boundaries on elasticity. We discuss the implications of our findings for suspension flows, and the correspondence between floppy materials and amorphous solids near unjamming, where lc and l* have also been identified but where their roles are not fully understood.

Journal ArticleDOI
24 May 2013-Langmuir
TL;DR: In this article, a linear stability analysis confirmed that this long wavelength instability (λ ∼ 7H) is due to an elastocapillary effect, the implementation of which required direct measurements of the surface tension and the elasticity of the gel.
Abstract: An adhesively stressed thin film of a soft hydrogel confined between two rigid flat substrates autoroughens with its dominant wavelength (λ) exhibiting pronounced dependence on the film thickness (H). A linear stability analysis confirmed that this long wavelength instability (λ ∼ 7H) is due to an elastocapillary effect, the implementation of which required direct measurements of the surface tension and the elasticity of the gel. The surface tension of the gel was estimated from the fundamental spherical harmonic of a hemispherical cap of the gel that was excited by an external noise. The shear modulus (μ) of the gel was determined from its resonant shear mode in a confined geometry. During the course of this study, it was found that a high density steel ball submerges itself inside the gel by balancing its excess weight with the accumulated strain induced elastic force that allows another estimation of its elastic modulus. The large ratio (1.8 mm) of the surface tension to its elasticity ascertains the r...

Journal ArticleDOI
TL;DR: In this paper, the vibration behavior of single-walled carbon nanotubes based on three-dimensional theory of elasticity is studied, where the nonlocal parameter is incorporated into all constitutive equations in three dimensions and governing equations of motion are reduced to the ordinary differential equations in thickness direction by using Fourier series expansion in axial and circumferential direction.
Abstract: This paper studies vibration behavior of single-walled carbon nanotubes based on three-dimensional theory of elasticity To accounting for the size effect of carbon nanotubes, nonlocal theory is adopted to the shell model The nonlocal parameter is incorporated into all constitutive equations in three dimensions Governing differential equations of motion are reduced to the ordinary differential equations in thickness direction by using Fourier series expansion in axial and circumferential direction The state equations obtained from constitutive relations and governing equations are solved analytically by making use of the state space method A detailed parametric study is carried out to show the influences of the nonlocal parameter, thickness-to-radius ratio and length-to-radius ratio Results reveal that excluding small-scale effects caused decreasing accuracy of natural frequencies Furthermore, the obtained closed form solution can be used to assess the accuracy of conventional two-dimensional theories

Journal ArticleDOI
TL;DR: A model of wave propagation following impulsive excitation in an incompressible, transversely isotropic (TI) material such as muscle is developed and complex structure that agrees quantitatively with the theoretical model is demonstrated.

Journal ArticleDOI
TL;DR: A continuum mechanics-based model of stromal elasticity is developed based on orientation information extracted and synthesized from both X-ray scattering studies and SHG imaging, and the significance of the 3-D lamella orientation in the mechanics of the human cornea is demonstrated.
Abstract: Examining the cross-section of the human cornea with second harmonic-generated (SHG) imaging shows that many lamellae do not lie parallel to the cornea's anterior surface but have inclined trajectories that take them through the corneal thickness with a depth-dependent distribution. A continuum mechanics-based model of stromal elasticity is developed based on orientation information extracted and synthesized from both X-ray scattering studies and SHG imaging. The model describes the effects of inclined lamella orientation by introducing a probability function that varies with depth through the stroma, which characterizes the range and distribution of lamellae at inclined angles. When combined with the preferred lamellar orientations found from X-ray scattering experiments, a fully 3-D representation of lamella orientation is achieved. Stromal elasticity is calculated by a weighted average of individual lamella properties based on the spatially varying 3-D orientation distribution. The model is calibrated with in vitro torsional shear experiments and in vivo indentation data and then validated with an in vitro inflation study. A quantitative explanation of the experimentally measured depth dependence of mechanical properties emerges from the model. The significance of the 3-D lamella orientation in the mechanics of the human cornea is demonstrated by investigating and contrasting the effects of previous modeling assumptions made on lamella orientation.

Journal ArticleDOI
TL;DR: In this article, a model for anisotropic linear elastodynamics which allows for the body to have a doubly porous structure was studied and it was shown that the solution to the boundary-initial value problem for this material is unique.

Journal ArticleDOI
TL;DR: In this article, a new variational multiscale framework for finite strain incompressible elasticity is presented, which includes the classical F ¯ method as a particular subclass, and an error estimation procedure for nonlinear elasticity that emanates naturally from within the present multi-scale framework.

Journal ArticleDOI
TL;DR: Numerical experiments are presented to demonstrate that the IFE solution converges optimally for both compressible and nearly incompressible materials.

Journal ArticleDOI
TL;DR: In this article, the lower bound on the Poisson's ratio for isotropic materials from linear elasticity theory is derived from the relationship between? and the bulk and shear moduli.
Abstract: The lower bound customarily cited for Poisson's ratio ?, ?1, is derived from the relationship between ? and the bulk and shear moduli in the classical theory of linear elasticity. However, experimental verification of the theory has been limited to materials having ????0.2. From consideration of the longitudinal and biaxial moduli, we recently determined that the lower bound on ? for isotropic materials from this theory is actually . Herein we generalize this result, first by analyzing expressions for ? in terms of six common elastic constants, and then by considering arbitrary strains. The results corroborate that for classical linear elasticity to be applicable. Of course, a few materials exist for which ??

Journal ArticleDOI
TL;DR: In this paper, the Papkovitch-Neuber potential functions, Fourier transforms and Bessel functions are utilized in the formulation of the surface elasticity theory for the half-space and half-plane contact problems.
Abstract: Analytical solutions for the problems of an elastic half-space and an elastic half-plane subjected to a distributed normal force are derived in a unified manner using the general form of the linearized surface elasticity theory of Gurtin and Murdoch. The Papkovitch–Neuber potential functions, Fourier transforms and Bessel functions are utilized in the formulation. The newly obtained solutions are general and reduce to the solutions for the half-space and half-plane contact problems based on classical linear elasticity when the surface effects are not considered. Also, existing solutions for the half-space and half-plane contact problems based on simplified versions of Gurtin and Murdoch’s surface elasticity theory are recovered as special cases of the current solutions. By applying the new solutions directly, Boussinesq’s flat-ended punch problem, Hertz’s spherical punch problem and a conical punch problem are solved, which lead to depth-dependent hardness formulas different from those based on classical elasticity. The numerical results reveal that smoother elastic fields and smaller displacements are predicted by the current solutions than those given by the classical elasticity-based solutions. Also, it is shown that the out-of-plane displacement and stress components strongly depend on the residual surface stress. In addition, it is found that the new solutions based on the surface elasticity theory predict larger values of the indentation hardness than the solutions based on classical elasticity.

Journal ArticleDOI
23 Oct 2013-PLOS ONE
TL;DR: The results provide basic and significant information about the suitable selection of physical and physiological cues and show that cell elasticity increases with increasing culture density only in MDCK epithelial cells.
Abstract: Atomic force microscopy provides a novel technique for differentiating the mechanical properties of various cell types. Cell elasticity is abundantly used to represent the structural strength of cells in different conditions. In this study, we are interested in whether physical or physiological cues affect cell elasticity in Atomic force microscopy (AFM)-based assessments. The physical cues include the geometry of the AFM tips, the indenting force and the operating temperature of the AFM. All of these cues show a significant influence on the cell elasticity assessment. Sharp AFM tips create a two-fold increase in the value of the effective Young’s modulus (Eeff) relative to that of the blunt tips. Higher indenting force at the same loading rate generates higher estimated cell elasticity. Increasing the operation temperature of the AFM leads to decreases in the cell stiffness because the structure of actin filaments becomes disorganized. The physiological cues include the presence of fetal bovine serum or extracellular matrix-coated surfaces, the culture passage number, and the culture density. Both fetal bovine serum and the extracellular matrix are critical for cells to maintain the integrity of actin filaments and consequently exhibit higher elasticity. Unlike primary cells, mouse kidney progenitor cells can be passaged and maintain their morphology and elasticity for a very long period without a senescence phenotype. Finally, cell elasticity increases with increasing culture density only in MDCK epithelial cells. In summary, for researchers who use AFM to assess cell elasticity, our results provide basic and significant information about the suitable selection of physical and physiological cues.

Journal ArticleDOI
TL;DR: In this paper, the nonlinear transverse vibration response of bilayer graphene sheets in thermal environments was investigated by using molecular dynamics simulation and nonlocal elasticity, and the results showed that the stacking sequence has a small effect, while the aspect ratio has a moderate effect.

Journal ArticleDOI
TL;DR: In this article, the authors estimate the price and income elasticities of demand for gasoline in China and obtain a range from − 0.882 to −0.579 for the intermediate-run price elasticity.

Journal ArticleDOI
TL;DR: In this article, the authors derived fundamental solutions for two-and three-dimensional linear isotropic size-dependent couple stress elasticity based upon the decomposition of displacement fields into dilatational and solenoidal components.

Journal ArticleDOI
TL;DR: This paper studied how the elasticity of labor supply to the firm changes between economic contractions and economic expansions, and found that the labor supply is lower during recessions than during expansions, providing evidence of differential wage setting power over the business cycle.

Journal ArticleDOI
TL;DR: An h-analysis of the preconditioner for the primal formulation of compressible elasticity yields an optimal convergence rate bound that is scalable in the number of subdomains and is linear in the ratio between subdomain and overlap sizes.

Journal ArticleDOI
TL;DR: This paper derived a link between hours worked prior to retirement, the intertemporal elasticity of substitution for labor (IES), and the size of the nonconvexities, which is robust to allowing for credit constraints and human capital accumulation by younger workers.
Abstract: We consider two life cycle models of labor supply that use nonconvexities to generate retirement. In each case we derive a link between hours worked prior to retirement, the intertemporal elasticity of substitution for labor (IES), and the size of the nonconvexities. This link is robust to allowing for credit constraints and human capital accumulation by younger workers and suggests values for the IES that are .75 or higher. (JEL D91, J22, J24, J26)

Journal ArticleDOI
TL;DR: In this article, the authors presented the results of experimental study on compressive strength and secant modulus of elasticity of high strength concrete (HSC) containing different levels of silica fume, ground pumice, ground Pumice and silica Fume together with ground PUMICE.