International Nuclear Information System (INIS)
Chand, F.
2010-01-01
Exact fourth-order constants of motion are investigated for three-dimensional classical and quantum Hamiltonian systems. The rationalization method is utilized to obtain constants of motion for classical systems. Constants of motion for quantum systems are obtained by adding quantum correction terms, computed using Moyal's bracket, to the corresponding classical counterparts. (author)
REDUCED ISOTROPIC CRYSTAL MODEL WITH RESPECT TO THE FOURTH-ORDER ELASTIC MODULI
Directory of Open Access Journals (Sweden)
O. Burlayenko
2018-04-01
Full Text Available Using a reduced isotropic crystal model the relationship between the fourth-order elastic moduli of an isotropic medium and the independent components of the fourth-order elastic moduli tensor of real crystals of various crystal systems is found. To calculate the coefficients of these relations, computer algebra systems Redberry and Mathematica for working with high order tensors in the symbolic and explicit form were used, in light of the overly complex computation. In an isotropic medium, there are four independent fourth order elastic moduli. This is due to the presence of four invariants for an eighth-rank tensor in the three-dimensional space, that has symmetries over the pairs of indices. As an example, the moduli of elasticity of an isotropic medium corresponding to certain crystals of cubic system are given (LiF, NaCl, MgO, CaF2. From the obtained results it can be seen that the reduced isotropic crystal model can be most effectively applied to high-symmetry crystal systems.
Strain fluctuations and elastic constants
Energy Technology Data Exchange (ETDEWEB)
Parrinello, M.; Rahman, A.
1982-03-01
It is shown that the elastic strain fluctuations are a direct measure of elastic compliances in a general anisotropic medium; depending on the ensemble in which the fluctuation is measured either the isothermal or the adiabatic compliances are obtained. These fluctuations can now be calculated in a constant enthalpy and pressure, and hence, constant entropy, ensemble due to recent develpments in the molecular dynamics techniques. A calculation for a Ni single crystal under uniform uniaxial 100 tensile or compressive load is presented as an illustration of the relationships derived between various strain fluctuations and the elastic modulii. The Born stability criteria and the behavior of strain fluctuations are shown to be related.
Elastic constants from microscopic strain fluctuations
Sengupta; Nielaba; Rao; Binder
2000-02-01
Fluctuations of the instantaneous local Lagrangian strain epsilon(ij)(r,t), measured with respect to a static "reference" lattice, are used to obtain accurate estimates of the elastic constants of model solids from atomistic computer simulations. The measured strains are systematically coarse-grained by averaging them within subsystems (of size L(b)) of a system (of total size L) in the canonical ensemble. Using a simple finite size scaling theory we predict the behavior of the fluctuations as a function of L(b)/L and extract elastic constants of the system in the thermodynamic limit at nonzero temperature. Our method is simple to implement, efficient, and general enough to be able to handle a wide class of model systems, including those with singular potentials without any essential modification. We illustrate the technique by computing isothermal elastic constants of "hard" and "soft" disk triangular solids in two dimensions from Monte Carlo and molecular dynamics simulations. We compare our results with those from earlier simulations and theory.
Experimental determination of third-order elastic constants of diamond.
Lang, J M; Gupta, Y M
2011-03-25
To determine the nonlinear elastic response of diamond, single crystals were shock compressed along the [100], [110], and [111] orientations to 120 GPa peak elastic stresses. Particle velocity histories and elastic wave velocities were measured by using laser interferometry. The measured elastic wave profiles were used, in combination with published acoustic measurements, to determine the complete set of third-order elastic constants. These constants represent the first experimental determination, and several differ significantly from those calculated by using theoretical models.
Theory of the change of elastic constants by interstitials
International Nuclear Information System (INIS)
Breuer, N.; Dederichs, P.H.; Lehmann, C.; Leibfried, G.; Scholz, A.
1975-01-01
The theory of the change of elastic constants by point-defects, in particular by interstitials, is briefly summarized. The typical effects of spring changes in a defect lattice on the elastic data are discussed qualitatively. Numerical results for the change of elastic constants by self-interstitials and vacancies are given and compared with experimental data for Cu and Al
Scalar-tensor theory of fourth-order gravity
International Nuclear Information System (INIS)
Accioly, A.J.; Goncalves, A.T.
1986-04-01
A scalar-tensor theory of fourth-order gravity is considered. Some cosmological consequences, due to the presence of the scalar field, as well as of metric derivatives higher than second order, are analysed. In particular, upperbpunds are obtained for the coupling constant α and for the scale factor of the universe, respectively. The discussion is restricted to Robertson-Walker universes. (Author) [pt
Elastic constants of diamond from molecular dynamics simulations
International Nuclear Information System (INIS)
Gao Guangtu; Van Workum, Kevin; Schall, J David; Harrison, Judith A
2006-01-01
The elastic constants of diamond between 100 and 1100 K have been calculated for the first time using molecular dynamics and the second-generation, reactive empirical bond-order potential (REBO). This version of the REBO potential was used because it was redesigned to be able to model the elastic properties of diamond and graphite at 0 K while maintaining its original capabilities. The independent elastic constants of diamond, C 11 , C 12 , and C 44 , and the bulk modulus were all calculated as a function of temperature, and the results from the three different methods are in excellent agreement. By extrapolating the elastic constant data to 0 K, it is clear that the values obtained here agree with the previously calculated 0 K elastic constants. Because the second-generation REBO potential was fit to obtain better solid-state force constants for diamond and graphite, the agreement with the 0 K elastic constants is not surprising. In addition, the functional form of the second-generation REBO potential is able to qualitatively model the functional dependence of the elastic constants and bulk modulus of diamond at non-zero temperatures. In contrast, reactive potentials based on other functional forms do not reproduce the correct temperature dependence of the elastic constants. The second-generation REBO potential also correctly predicts that diamond has a negative Cauchy pressure in the temperature range examined
Elastic constants and internal friction of fiber-reinforced composites
International Nuclear Information System (INIS)
Ledbetter, H.M.
1982-01-01
We review recent experimental studies at NBS on the anisotropic elastic constants and internal friction of fiber-reinforced composites. Materials that were studied include: boron-aluminum, boron-epoxy, graphite-epoxy, glass-epoxy, and aramid-epoxy. In all cases, elastic-constant direction dependence could be described by relationships developed for single crystals of homogeneous materials. Elastic stiffness and internal friction were found to vary inversely
Horizon thermodynamics in fourth-order gravity
Directory of Open Access Journals (Sweden)
Meng-Sen Ma
2017-03-01
Full Text Available In the framework of horizon thermodynamics, the field equations of Einstein gravity and some other second-order gravities can be rewritten as the thermodynamic identity: dE=TdS−PdV. However, in order to construct the horizon thermodynamics in higher-order gravity, we have to simplify the field equations firstly. In this paper, we study the fourth-order gravity and convert it to second-order gravity via a so-called “Legendre transformation” at the cost of introducing two other fields besides the metric field. With this simplified theory, we implement the conventional procedure in the construction of the horizon thermodynamics in 3 and 4 dimensional spacetime. We find that the field equations in the fourth-order gravity can also be written as the thermodynamic identity. Moreover, we can use this approach to derive the same black hole mass as that by other methods.
On a fourth order superlinear elliptic problem
Directory of Open Access Journals (Sweden)
M. Ramos
2001-01-01
Full Text Available We prove the existence of a nonzero solution for the fourth order elliptic equation $$Delta^2u= mu u +a(xg(u$$ with boundary conditions $u=Delta u=0$. Here, $mu$ is a real parameter, $g$ is superlinear both at zero and infinity and $a(x$ changes sign in $Omega$. The proof uses a variational argument based on the argument by Bahri-Lions cite{BL}.
Temperature dependence of grain boundary free energy and elastic constants
International Nuclear Information System (INIS)
Foiles, Stephen M.
2010-01-01
This work explores the suggestion that the temperature dependence of the grain boundary free energy can be estimated from the temperature dependence of the elastic constants. The temperature-dependent elastic constants and free energy of a symmetric Σ79 tilt boundary are computed for an embedded atom method model of Ni. The grain boundary free energy scales with the product of the shear modulus times the lattice constant for temperatures up to about 0.75 the melting temperature.
X-Ray Elastic Constants for Cubic Materials
Energy Technology Data Exchange (ETDEWEB)
Malen, K
1974-10-15
The stress-strain relation to be used in X-ray stress measurements in anisotropic texture-free media is studied. The method for evaluation of appropriate elastic constants for a cubic medium is described. Some illustrative numerical examples have been worked out including line broadening due to elastic anisotropy. The elastic stress and strain compatibility at grain boundaries is taken into account using Kroner's method. These elastic constants obviously only apply when no internal stresses due to plastic deformation are present. The case of reorientation of free interstitials in the stress field can be taken into account
A first-principles approach to finite temperature elastic constants
Energy Technology Data Exchange (ETDEWEB)
Wang, Y; Wang, J J; Zhang, H; Manga, V R; Shang, S L; Chen, L-Q; Liu, Z-K [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States)
2010-06-09
A first-principles approach to calculating the elastic stiffness coefficients at finite temperatures was proposed. It is based on the assumption that the temperature dependence of elastic stiffness coefficients mainly results from volume change as a function of temperature; it combines the first-principles calculations of elastic constants at 0 K and the first-principles phonon theory of thermal expansion. Its applications to elastic constants of Al, Cu, Ni, Mo, Ta, NiAl, and Ni{sub 3}Al from 0 K up to their respective melting points show excellent agreement between the predicted values and existing experimental measurements.
X-Ray Elastic Constants for Cubic Materials
Energy Technology Data Exchange (ETDEWEB)
Malen, K.
1974-10-15
The stress-strain relation to be used in X-ray stress measurements in anisotropic texture-free media is studied. The method for evaluation of appropriate elastic constants for a cubic medium is described. Some illustrative numerical examples have been worked out including line broadening due to elastic anisotropy. The elastic stress and strain compatibility at grain boundaries is taken into account using Kroner's method. These elastic constants obviously only apply when no internal stresses due to plastic deformation are present. The case of reorientation of free interstitials in the stress field can be taken into account
X-Ray Elastic Constants for Cubic Materials
International Nuclear Information System (INIS)
Malen, K.
1974-10-01
The stress-strain relation to be used in X-ray stress measurements in anisotropic texture-free media is studied. The method for evaluation of appropriate elastic constants for a cubic medium is described. Some illustrative numerical examples have been worked out including line broadening due to elastic anisotropy. The elastic stress and strain compatibility at grain boundaries is taken into account using Kroner's method. These elastic constants obviously only apply when no internal stresses due to plastic deformation are present. The case of reorientation of free interstitials in the stress field can be taken into account
A first-principles approach to finite temperature elastic constants
International Nuclear Information System (INIS)
Wang, Y; Wang, J J; Zhang, H; Manga, V R; Shang, S L; Chen, L-Q; Liu, Z-K
2010-01-01
A first-principles approach to calculating the elastic stiffness coefficients at finite temperatures was proposed. It is based on the assumption that the temperature dependence of elastic stiffness coefficients mainly results from volume change as a function of temperature; it combines the first-principles calculations of elastic constants at 0 K and the first-principles phonon theory of thermal expansion. Its applications to elastic constants of Al, Cu, Ni, Mo, Ta, NiAl, and Ni 3 Al from 0 K up to their respective melting points show excellent agreement between the predicted values and existing experimental measurements.
Analiticity in fourth-order wave equations
International Nuclear Information System (INIS)
Bollini, C.G.; Giambiagi, J.J.
1987-01-01
In this paper it is presented, through a familiar example (δ-function potential in one dimension), the analytic properties of Jost functions associated with fourth-order equations. It is shown how to construct the Jost functions and the two discontinuity matrices associated with the line of singularities. The latter divide the complex k-plane in eight regions of analiticity. One of these matrices is related to the asymptotic behaviour of the scattering state. The other is not. Both are necessary to solve the inverse problem. Besides the usual poles related to bound states there are also other poles associated with total reflexion
Analiticity in fourth order wave equations
International Nuclear Information System (INIS)
Bollini, C.G.
1987-01-01
Through a familiar example (δ-function potential in one dimension) the analytic properties of Jost functions associated with fourth order equations are presented. It is shown how to construct the Jost functions and the two discontinuities matrices associated to the line of singularities. The latter divide the complex k-plane in eight regions of analiticity. One of these matrices is related to the asymptotic behaviour of scattering state. The other is not. Both being necessary to solve the inverse problem. Besides the usual poles related to bound states there are also other poles associated with total reflexion. (Author) [pt
Chaotic behaviour of a fourth-order autonomous electric circuit
International Nuclear Information System (INIS)
Koliopanos, Ch.L.; Kyprianidis, I.M.; Stouboulos, I.N.; Anagnostopoulos, A.N.; Magafas, L.
2003-01-01
The chaotic dynamics of a fourth-order autonomous nonlinear electric circuit was studied by measuring its response in the form of chaotic time series. The circuit consists of two active elements, one linear negative conductance and one nonlinear resistor exhibiting a symmetrical piecewise-linear v-i characteristic and two capacitances C 1 and C 2 , which serve as the control parameters of the system. From the experimental time series the minimum embedding dimensions m min =4, correlation dimensions ν, with positive noninteger values, and Kolmogorov entropies, tending to constant positive values, were determined by numerical evaluation for the examined states of the system
Solving Variable Coefficient Fourth-Order Parabolic Equation by ...
African Journals Online (AJOL)
Solving Variable Coefficient Fourth-Order Parabolic Equation by Modified initial guess Variational ... variable coefficient fourth order parabolic partial differential equations. The new method shows rapid convergence to the exact solution.
Estimation of effective elastic constants for grid plate
International Nuclear Information System (INIS)
Shibanuma, Kiyoshi; Kuriyama, Masaaki; Okumura, Yoshikazu
1980-07-01
This article contains a method of estimation for the effective elastic constants of a grid plate, which is a flat perforated plate with pipes for cooling. The elastic constants of the grid plate are formulated for two symmetric axes. In the case of using OFCu(E 0 = 12500 kg/mm 2 , ν 0 = 0.34) as the material of the grid, the results are given as follows. E sub(L) = 3180 kg/mm 2 , E sub(T) = 3860 kg/mm 2 upsilon sub(LT) = 0.12, upsilon sub(TL) = 0.15 (author)
Elasticity Constants of a Two-Phase Tungsten Thin Film
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Mohamed Fares Slim
2018-05-01
Full Text Available The IET was used to determine the macroscopic elasticity constants of the multiphase coating. In order to determine the macroscopic elasticity constants of the film firstly, a critical assessment of Young’s modulus determination was done by comparing all the models proposed in the literature. The best model was identified and a study was performed to identify and quantify the most influent factors on the global uncertainty. Secondly, an enhanced formulation to determine the shear modulus of coating by IET was developed. The methodology was applied on a tungsten thin film deposited by DC magnetron sputtering.
Dynamic measurements of the elastic constants of glass wool
DEFF Research Database (Denmark)
Tarnow, Viggo
2005-01-01
. But a new mechanical design, which reduces mechanical resonance, is described. The measurements were carried out in atmospheric air at normal pressure, and this causes an oscillatory airflow in the sample. To obtain the elastic constants, the influence of the airflow was subtracted from the data by a new...
New singularities in nonrelativistic coupled channel scattering. II. Fourth order
International Nuclear Information System (INIS)
Khuri, N.N.; Tsun Wu, T.
1997-01-01
We consider a two-channel nonrelativistic potential scattering problem, and study perturbation theory in fourth order for the forward amplitude. The main result is that the new singularity demonstrated in second order in the preceding paper I also occurs at the same point in fourth order. Its strength is again that of a pole. copyright 1997 The American Physical Society
Single-crystal elastic constants of natural ettringite
Speziale, Sergio
2008-07-01
The single-crystal elastic constants of natural ettringite were determined by Brillouin spectroscopy at ambient conditions. The six non-zero elastic constants of this trigonal mineral are: C11 = 35.1 ± 0.1 GPa, C12 = 21.9 ±0.1 GPa, C13 = 20.0 ± 0.5 GPa, C14 = 0.6 ± 0.2 GPa, C33 = 55 ± 1 GPa, C44 = 11.0 ± 0.2 GPa. The Hill average of the aggregate bulk, shear modulus and the polycrystal Young\\'s modulus and Poisson\\'s ratio are 27.3 ± 0.9 GPa, 9.5 ± 0.8 GPa, 25 ± 2 GPa and 0.34 ± 0.02 respectively. The longitudinal and shear elastic anisotropy are C33/C11 = 0.64 ± 0.01 and C66/C44 =0.60 ± 0.01. The elastic anisotropy in ettringite is connected to its crystallographic structure. Stiff chains of [Al(OH)6]3- octahedra alternating with triplets of Ca2+ in eight-fold coordination run parallel to the c-axis leading to higher stiffness along this direction. The determination of the elastic stiffness tensor can help in the prediction of the early age properties of cement paste when ettringite crystals precipitate and in the modeling of both internal and external sulfate attack when secondary ettringite formation leads to expansion of concrete. © 2008 Elsevier Ltd. All rights reserved.
Single-crystal elastic constants of natural ettringite
Speziale, Sergio; Jiang, Fuming; Mao, Zhu; Monteiro, Paulo J.M.; Wenk, Hans-Rudolf; Duffy, Thomas S.; Schilling, Frank R.
2008-01-01
The single-crystal elastic constants of natural ettringite were determined by Brillouin spectroscopy at ambient conditions. The six non-zero elastic constants of this trigonal mineral are: C11 = 35.1 ± 0.1 GPa, C12 = 21.9 ±0.1 GPa, C13 = 20.0 ± 0.5 GPa, C14 = 0.6 ± 0.2 GPa, C33 = 55 ± 1 GPa, C44 = 11.0 ± 0.2 GPa. The Hill average of the aggregate bulk, shear modulus and the polycrystal Young's modulus and Poisson's ratio are 27.3 ± 0.9 GPa, 9.5 ± 0.8 GPa, 25 ± 2 GPa and 0.34 ± 0.02 respectively. The longitudinal and shear elastic anisotropy are C33/C11 = 0.64 ± 0.01 and C66/C44 =0.60 ± 0.01. The elastic anisotropy in ettringite is connected to its crystallographic structure. Stiff chains of [Al(OH)6]3- octahedra alternating with triplets of Ca2+ in eight-fold coordination run parallel to the c-axis leading to higher stiffness along this direction. The determination of the elastic stiffness tensor can help in the prediction of the early age properties of cement paste when ettringite crystals precipitate and in the modeling of both internal and external sulfate attack when secondary ettringite formation leads to expansion of concrete. © 2008 Elsevier Ltd. All rights reserved.
Identification of elastic, dielectric, and piezoelectric constants in piezoceramic disks.
Perez, Nicolas; Andrade, Marco A B; Buiochi, Flavio; Adamowski, Julio C
2010-12-01
Three-dimensional modeling of piezoelectric devices requires a precise knowledge of piezoelectric material parameters. The commonly used piezoelectric materials belong to the 6mm symmetry class, which have ten independent constants. In this work, a methodology to obtain precise material constants over a wide frequency band through finite element analysis of a piezoceramic disk is presented. Given an experimental electrical impedance curve and a first estimate for the piezoelectric material properties, the objective is to find the material properties that minimize the difference between the electrical impedance calculated by the finite element method and that obtained experimentally by an electrical impedance analyzer. The methodology consists of four basic steps: experimental measurement, identification of vibration modes and their sensitivity to material constants, a preliminary identification algorithm, and final refinement of the material constants using an optimization algorithm. The application of the methodology is exemplified using a hard lead zirconate titanate piezoceramic. The same methodology is applied to a soft piezoceramic. The errors in the identification of each parameter are statistically estimated in both cases, and are less than 0.6% for elastic constants, and less than 6.3% for dielectric and piezoelectric constants.
Hydrostatic pressure dependence of elastic constants for lead fluoride crystal
International Nuclear Information System (INIS)
Singh, R.K.; Rao, C.N.
1988-10-01
The variations of the second order elastic constants (SOEC) and longitudinal and shear moduli with hydrostatic pressure for the lead fluoride have been investigated theoretically, for the first time, by means of a three-body force potential (TBP) model. The significance of three-body interactions (TBI) has been clearly demonstrated in these investigations. The present TBP model has reproduced the pressure derivatives of the SOEC of PbF more satisfactorily than the shell model and other model calculations. (author). 24 refs, 3 figs, 2 tabs
Oscillation criteria for fourth-order nonlinear delay dynamic equations
Directory of Open Access Journals (Sweden)
Yunsong Qi
2013-03-01
Full Text Available We obtain criteria for the oscillation of all solutions to a fourth-order nonlinear delay dynamic equation on a time scale that is unbounded from above. The results obtained are illustrated with examples
Quasipotential in the fourth order of perturbation theory
International Nuclear Information System (INIS)
Bojkova, N.A.; Dvoeglazov, V.V.; Tyukhtyaev, Yu.N.; Faustov, R.N.
1992-01-01
The quasipotential in the fourth order of perturbation theory is calculated in the Coulomb gauge for the unequal mass particles. It could be used for the future calculations of energy spectra in two-body systems. 15 refs.; 1 fig
On a class of fourth order linear recurrence equations
Directory of Open Access Journals (Sweden)
Sui-Sun Cheng
1984-01-01
Full Text Available This paper is concerned with sequences that satisfy a class of fourth order linear recurrence equations. Basic properties of such sequences are derived. In addition, we discuss the oscillatory and nonoscillatory behavior of such sequences.
Stresses and elastic constants of crystalline sodium, from molecular dynamics
International Nuclear Information System (INIS)
Schiferl, S.K.
1985-02-01
The stresses and the elastic constants of bcc sodium are calculated by molecular dynamics (MD) for temperatures to T = 340K. The total adiabatic potential of a system of sodium atoms is represented by pseudopotential model. The resulting expression has two terms: a large, strictly volume-dependent potential, plus a sum over ion pairs of a small, volume-dependent two-body potential. The stresses and the elastic constants are given as strain derivatives of the Helmholtz free energy. The resulting expressions involve canonical ensemble averages (and fluctuation averages) of the position and volume derivatives of the potential. An ensemble correction relates the results to MD equilibrium averages. Evaluation of the potential and its derivatives requires the calculation of integrals with infinite upper limits of integration, and integrand singularities. Methods for calculating these integrals and estimating the effects of integration errors are developed. A method is given for choosing initial conditions that relax quickly to a desired equilibrium state. Statistical methods developed earlier for MD data are extended to evaluate uncertainties in fluctuation averages, and to test for symmetry. 45 refs., 10 figs., 4 tabs
Determination of the elastic constants of portlandite by Brillouin spectroscopy
Speziale, S.; Reichmann, H.J.; Schilling, F.R.; Wenk, H.R.; Monteiro, P.J.M.
2008-01-01
The single crystal elastic constants Cij and the shear and adiabatic bulk modulus of a natural portlandite (Ca(OH)2) crystal were determined by Brillouin spectroscopy at ambient conditions. The elastic constants, expressed in GPa, are: C11 = 102.0(± 2.0), C12 = 32.1(± 1.0), C13 = 8.4(± 0.4), C14 = 4.5(± 0.2), C33 = 33.6(± 0.7), C44 = 12.0(± 0.3), C66 = (C11-C12)/2 = 35.0(± 1.1), where the numbers in parentheses are 1σ standard deviations. The Reuss bounds of the adiabatic bulk and shear moduli are K0S = 26.0(± 0.3) GPa and G0 = 17.5(± 0.4) GPa, respectively, while the Voigt bounds of these moduli are K0S = 37.3(± 0.4) GPa and G0 = 24.4(± 0.3) GPa. The Reuss and Voigt bounds for the aggregate Young's modulus are 42.8(± 1.0) GPa and 60.0(± 0.8) GPa respectively, while the aggregate Poisson's ratio is equal to 0.23(± 0.01). Portlandite exhibits both large compressional elastic anisotropy with C11/C33 = 3.03(± 0.09) equivalent to that of the isostructural hydroxide brucite (Mg(OH)2), and large shear anisotropy with C66/C44 = 2.92(± 0.12) which is 11% larger than brucite. The comparison between the bulk modulus of portlandite and that of lime (CaO) confirms a systematic linear relationship between the bulk moduli of brucite-type simple hydroxides and the corresponding NaCl-type oxides. © 2008 Elsevier Ltd. All rights reserved.
Symmetries and integrability of a fourth-order Euler-Bernoulli beam equation
International Nuclear Information System (INIS)
Bokhari, Ashfaque H.; Zaman, F. D.; Mahomed, F. M.
2010-01-01
The complete symmetry group classification of the fourth-order Euler-Bernoulli ordinary differential equation, where the elastic modulus and the area moment of inertia are constants and the applied load is a function of the normal displacement, is obtained. We perform the Lie and Noether symmetry analysis of this problem. In the Lie analysis, the principal Lie algebra which is one dimensional extends in four cases, viz. the linear, exponential, general power law, and a negative fractional power law. It is further shown that two cases arise in the Noether classification with respect to the standard Lagrangian. That is, the linear case for which the Noether algebra dimension is one less than the Lie algebra dimension as well as the negative fractional power law. In the latter case the Noether algebra is three dimensional and is isomorphic to the Lie algebra which is sl(2,R). This exceptional case, although admitting the nonsolvable algebra sl(2,R), remarkably allows for a two-parameter family of exact solutions via the Noether integrals. The Lie reduction gives a second-order ordinary differential equation which has nonlocal symmetry.
Ab Initio Simulation Beryllium in Solid Molecular Hydrogen: Elastic Constant
Guerrero, Carlo L.; Perlado, Jose M.
2016-03-01
In systems of inertial confinement fusion targets Deuterium-Tritium are manufactured with a solid layer, it must have specific properties to increase the efficiency of ignition. Currently there have been some proposals to model the phases of hydrogen isotopes and hence their high pressure, but these works do not allow explaining some of the structures present at the solid phase change effect of increased pressure. By means of simulation with first principles methods and Quantum Molecular Dynamics, we compare the structural difference of solid molecular hydrogen pure and solid molecular hydrogen with beryllium, watching beryllium inclusion in solid hydrogen matrix, we obtain several differences in mechanical properties, in particular elastic constants. For C11 the difference between hydrogen and hydrogen with beryllium is 37.56%. This may produce a non-uniform initial compression and decreased efficiency of ignition.
Determination of the elastic constants of portlandite by Brillouin spectroscopy
Speziale, S.
2008-10-01
The single crystal elastic constants Cij and the shear and adiabatic bulk modulus of a natural portlandite (Ca(OH)2) crystal were determined by Brillouin spectroscopy at ambient conditions. The elastic constants, expressed in GPa, are: C11 = 102.0(± 2.0), C12 = 32.1(± 1.0), C13 = 8.4(± 0.4), C14 = 4.5(± 0.2), C33 = 33.6(± 0.7), C44 = 12.0(± 0.3), C66 = (C11-C12)/2 = 35.0(± 1.1), where the numbers in parentheses are 1σ standard deviations. The Reuss bounds of the adiabatic bulk and shear moduli are K0S = 26.0(± 0.3) GPa and G0 = 17.5(± 0.4) GPa, respectively, while the Voigt bounds of these moduli are K0S = 37.3(± 0.4) GPa and G0 = 24.4(± 0.3) GPa. The Reuss and Voigt bounds for the aggregate Young\\'s modulus are 42.8(± 1.0) GPa and 60.0(± 0.8) GPa respectively, while the aggregate Poisson\\'s ratio is equal to 0.23(± 0.01). Portlandite exhibits both large compressional elastic anisotropy with C11/C33 = 3.03(± 0.09) equivalent to that of the isostructural hydroxide brucite (Mg(OH)2), and large shear anisotropy with C66/C44 = 2.92(± 0.12) which is 11% larger than brucite. The comparison between the bulk modulus of portlandite and that of lime (CaO) confirms a systematic linear relationship between the bulk moduli of brucite-type simple hydroxides and the corresponding NaCl-type oxides. © 2008 Elsevier Ltd. All rights reserved.
Is the Armington Elasticity Really Constant across Importers?
Yilmazkuday, Hakan
2009-01-01
This paper shows that the Armington elasticity, which refers to both the elasticity of substitution across goods and the price elasticity of demand under the assumption of a large number of varieties, systematically changes from one importer country to another in an international trade context. Then a natural question to ask is "What determines the Armington elasticity?" The answer comes from the distinction between the elasticity of demand with respect to the destination price (i.e., the Arm...
Benthic macroinvertebrate community of a fourth order stream in ...
African Journals Online (AJOL)
cinthia
Full Length Research Paper. Benthic macroinvertebrate community of a fourth order stream in Kashmir Himalaya, India. Shazia Habib1* and A.R. Yousuf2. 1Department of Environmental Science, University of Kashmir, Srinagar, India. 2National Green Tribunal, Government of India, India. Received 31 December, 2013; ...
Fourth-order discrete anisotropic boundary-value problems
Directory of Open Access Journals (Sweden)
Maciej Leszczynski
2015-09-01
Full Text Available In this article we consider the fourth-order discrete anisotropic boundary value problem with both advance and retardation. We apply the direct method of the calculus of variations and the mountain pass technique to prove the existence of at least one and at least two solutions. Non-existence of non-trivial solutions is also undertaken.
Fourth Order Nonlinear Intensity and the corresponding Refractive ...
African Journals Online (AJOL)
Nonlinear effects occur whenever the optical fields associated with one or more intense light such as from laser beams propagating in a crystal are large enough to produce polarization fields. This paper describes how the fourth order nonlinear intensity and the corresponding effective refractive index that is intensity ...
International Nuclear Information System (INIS)
Hauk, V.; Kockelmann, H.
1979-01-01
Methods of calculation are developed for determination of single crystal elastic compliance or stiffness constants of cubic and hexagonal materials from mechanical and X-ray elastic constants of polycrystals. The calculations are applied to pure, cubic iron and hexagonal WC. There are no single crystal constants in the literature for WC, because no single crystals suitable for measurement are available. (orig.) [de
International Nuclear Information System (INIS)
Reshak, Ali H.; Jamal, Morteza
2012-01-01
Highlights: ► A new package for calculating elastic constants of orthorhombic structure is released. ► The package called ortho-elastic. ► It is compatible with [FP-(L)APW+lo] method implemented in WIEN2k code. ► Several orthorhombic structure compounds were used to test the new package. ► Elastic constants calculated using this package show good agreement with experiment. - Abstract: A new package for calculating the elastic constants of orthorhombic structure is released. The package called ortho-elastic. The formalism of calculating the ortho-elastic constants is described in details. The package is compatible with the highly accurate all-electron full-potential (linearized) augmented plane-wave plus local orbital [FP-(L)APW+lo] method implemented in WIEN2k code. Several orthorhombic structure compounds were used to test the new package. We found that the calculated elastic constants using the new package show better agreement with the available experimental data than the previous theoretical results used different methods. In this package the second-order derivative E ″ (ε) of polynomial fit E=E(ε) of energy vs strains at zero strain (ε=0), used to calculate the orthorhombic elastic constants.
Rotation curves of galaxies by fourth order gravity
International Nuclear Information System (INIS)
Stabile, A.; Scelza, G.
2011-01-01
We investigate the radial behavior of galactic rotation curves by a Fourth Order Gravity adding also the dark matter component. The Fourth Order Gravity is a theory of gravity described by Lagrangian generalizing the one of Hilbert-Einstein containing a generic function of the Ricci scalar, the Ricci and Riemann tensor. A systematic analysis of rotation curves, in the Newtonian Limit of theory, induced by all galactic substructures of ordinary matter is shown. This analysis is presented for Fourth Order Gravity with and without dark matter. The outcomes are compared with respect to the classical outcomes of General Relativity. The gravitational potential of pointlike mass is the usual potential corrected by two Yukawa terms. The rotation curve is higher or also lower than curve of General Relativity if in the Lagrangian the Ricci scalar square is dominant or not with respect to the contribution of the Ricci tensor square. The theoretical spatial behaviors of rotation curve are compared with the experimental data for the Milky Way and the galaxy NGC 3198. Although the Fourth Order Gravity gives more rotational contributions, in the limit of large distances the Keplerian behavior is ever present, and it is missing only if we add the dark matter component. However by modifying the theory of gravity, consequently, also the spatial description of dark matter could undergo a modification and the free parameters of model can assume different values. After an analytical discussion of theoretical behaviors and the comparing with experimental evidence we can claim that any Fourth Order Gravity is not successful to explain the galactic rotation curves. In the last part of paper we analyze the gravitational potential induced by Lagrangian containing only powers of Ricci scalar. In this case we find an inconsistency in the boundary conditions in the passage from matter to the vacuum.
Evaluation of elastic constants of materials using the frequency spectrum
International Nuclear Information System (INIS)
Silva Neto, Ramiro J. da; Baroni, Douglas B.; Bittencourt, Marcelo de S.Q.
2015-01-01
The characterization of materials made with the support of non-destructive techniques has great importance in industrial applications. The ultrasonic techniques are distinguished by good resolution to measure small variations of wave velocities as a result of changes in the character suffered by a particular material. In general these ultrasonic techniques are studied in the time domain, which represents an experimental difficulties when thin materials are analyzed, as well as to attenuate the ultrasonic signal drastically. An ultrasonic technique that uses the frequency domain is used in this study aiming to provide good time measurements to calculate the elastic constants of the first order in an aluminum alloy 6351. With the aid of a statistical approach was possible to have good results of tests performed when compared by a time domain technique already well explored in Ultrasound works produced in the Nuclear Engineering Institute Laboratory (LABUS / IEN) and also presented in most of the package, in good agreement with the theoretical model established in literature and used to validate the experiment, which was found in the results with good approximation. The relevance of this work in the nuclear area is associated with the interest to know the mechanical properties of structural components of the nuclear industry, which is currently studied as a rule, resorting to the computer simulations or previously during the operation of the system. (author)
Evaluation of elastic constants of materials using the frequency spectrum
Energy Technology Data Exchange (ETDEWEB)
Silva Neto, Ramiro J. da; Baroni, Douglas B.; Bittencourt, Marcelo de S.Q., E-mail: ramirobd@gmail.com [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Departamento de Materiais Nucleares. Laboratorio de Ultrassom
2015-07-01
The characterization of materials made with the support of non-destructive techniques has great importance in industrial applications. The ultrasonic techniques are distinguished by good resolution to measure small variations of wave velocities as a result of changes in the character suffered by a particular material. In general these ultrasonic techniques are studied in the time domain, which represents an experimental difficulties when thin materials are analyzed, as well as to attenuate the ultrasonic signal drastically. An ultrasonic technique that uses the frequency domain is used in this study aiming to provide good time measurements to calculate the elastic constants of the first order in an aluminum alloy 6351. With the aid of a statistical approach was possible to have good results of tests performed when compared by a time domain technique already well explored in Ultrasound works produced in the Nuclear Engineering Institute Laboratory (LABUS / IEN) and also presented in most of the package, in good agreement with the theoretical model established in literature and used to validate the experiment, which was found in the results with good approximation. The relevance of this work in the nuclear area is associated with the interest to know the mechanical properties of structural components of the nuclear industry, which is currently studied as a rule, resorting to the computer simulations or previously during the operation of the system. (author)
Fourth-Order Spatial Correlation of Thermal Light
International Nuclear Information System (INIS)
Wen Feng; Zhang Xun; Sun Jia; Song Jian-Ping; Zhang Yan-Peng; Xue Xin-Xin
2014-01-01
We investigate the fourth-order spatial correlation properties of pseudo-thermal light in the photon counting regime, and apply the Klyshko advanced-wave picture to describe the process of four-photon coincidence counting measurement. We deduce the theory of a proof-of-principle four-photon coincidence counting configuration, and find that if the four randomly radiated photons come from the same radiation area and are indistinguishable in principle, the fourth-order correlation of them is 24 times larger than that when four photons come from different radiation areas. In addition, we also show that the higher-order spatial correlation function can be decomposed into multiple lower-order correlation functions, and the contrast and visibility of low-order correlation peaks are less than those of higher orders, while the resolutions all are identical. This study may be useful for better understanding the four-photon interference and multi-channel correlation imaging
Electroencephalography in ellipsoidal geometry with fourth-order harmonics.
Alcocer-Sosa, M; Gutierrez, D
2016-08-01
We present a solution to the electroencephalographs (EEG) forward problem of computing the scalp electric potentials for the case when the head's geometry is modeled using a four-shell ellipsoidal geometry and the brain sources with an equivalent current dipole (ECD). The proposed solution includes terms up to the fourth-order ellipsoidal harmonics and we compare this new approximation against those that only considered up to second- and third-order harmonics. Our comparisons use as reference a solution in which a tessellated volume approximates the head and the forward problem is solved through the boundary element method (BEM). We also assess the solution to the inverse problem of estimating the magnitude of an ECD through different harmonic approximations. Our results show that the fourth-order solution provides a better estimate of the ECD in comparison to lesser order ones.
New Efficient Fourth Order Method for Solving Nonlinear Equations
Directory of Open Access Journals (Sweden)
Farooq Ahmad
2013-12-01
Full Text Available In a paper [Appl. Math. Comput., 188 (2 (2007 1587--1591], authors have suggested and analyzed a method for solving nonlinear equations. In the present work, we modified this method by using the finite difference scheme, which has a quintic convergence. We have compared this modified Halley method with some other iterative of fifth-orders convergence methods, which shows that this new method having convergence of fourth order, is efficient.
Asymptotic integration of a linear fourth order differential equation of Poincaré type
Directory of Open Access Journals (Sweden)
Anibal Coronel
2015-11-01
Full Text Available This article deals with the asymptotic behavior of nonoscillatory solutions of fourth order linear differential equation where the coefficients are perturbations of constants. We define a change of variable and deduce that the new variable satisfies a third order nonlinear differential equation. We assume three hypotheses. The first hypothesis is related to the constant coefficients and set up that the characteristic polynomial associated with the fourth order linear equation has simple and real roots. The other two hypotheses are related to the behavior of the perturbation functions and establish asymptotic integral smallness conditions of the perturbations. Under these general hypotheses, we obtain four main results. The first two results are related to the application of a fixed point argument to prove that the nonlinear third order equation has a unique solution. The next result concerns with the asymptotic behavior of the solutions of the nonlinear third order equation. The fourth main theorem is introduced to establish the existence of a fundamental system of solutions and to precise the formulas for the asymptotic behavior of the linear fourth order differential equation. In addition, we present an example to show that the results introduced in this paper can be applied in situations where the assumptions of some classical theorems are not satisfied.
Chiral 2π exchange at fourth order and peripheral NN scattering
International Nuclear Information System (INIS)
Entem, D.R.; Machleidt, R.
2002-01-01
We calculate the impact of the complete set of two-pion exchange contributions at chiral fourth order (also known as next-to-next-to-next-to-leading order) on peripheral partial waves of nucleon-nucleon scattering. Our calculations are based upon the analytical studies by Kaiser. It turns out that the contribution of fourth order is substantially smaller than the one of third order, indicating convergence of the chiral expansion. We compare the prediction from chiral pion exchange with the corresponding one from conventional meson theory as represented by the Bonn full model and find, in general, good agreement. Our calculations provide a sound basis for investigating the issue whether the low-energy constants determined from πN lead to reasonable predictions for NN
Elastic constants of a Laves phase compound: C15 NbCr2
International Nuclear Information System (INIS)
Ormeci, A.; Chu, F.; Wills, J.M.; Chen, S.P.; Albers, R.C.; Thoma, D.J.; Mitchell, T.E.
1997-01-01
The single-crystal elastic constants of C15 NbCr 2 have been computed by using a first-principles, self-consistent, full-potential total energy method. From these single-crystal elastic constants the isotropic elastic moduli are calculated using the Voigt and Reuss averages. The calculated values are in fair agreement with the experimental values. The implications of the results are discussed with regards to Poisson's ratio and the direction dependence of Young's modulus
Low-temperature monocrystal elastic constants of Fe-19Cr-10Ni
International Nuclear Information System (INIS)
Ledbetter, H.M.
1984-01-01
By a pulse-echo-overlap ultrasonic method, we determined the monocrystal elastic constants (C 11 , C 12 , C 44 ) of an Fe-19Cr-10Ni alloy between 295 and 4 K. In composition this laboratory alloy approximates a technological austenitic stainless steel: AISI 304. Many previous studies on polycrystalline steels found a low-temperature magnetic phase transition that affects physical properties, including elastic constants. At the transition, anomalies occur in all polycrystal elastic constants: Young's modulus, shear modulus, bulk modulus, and Poisson's ratio. The present study found that the transition, near 50 K, does not affect one monocrystal elastic constant: C 44 , the resistance to shear on a (100) plane in a [100]-type direction. We interpret this new observation from the viewpoint of a Born-type lattice model. Also, we comment about the relationship between the elastic-constant changes and the low-temperature magnetic state
Directory of Open Access Journals (Sweden)
Eryi Hu
2016-01-01
Full Text Available The ultrasonic nondestructive method is introduced into the elastic constants measurement of metal material. The extraction principle of Poisson’s ratio, elastic modulus, and shear modulus is deduced from the ultrasonic propagating equations with two kinds of vibration model of the elastic medium named ultrasonic longitudinal wave and transverse wave, respectively. The ultrasonic propagating velocity is measured by using the digital correlation technique between the ultrasonic original signal and the echo signal from the bottom surface, and then the elastic constants of the metal material are calculated. The feasibility of the correlation algorithm is verified by a simulation procedure. Finally, in order to obtain the stability of the elastic properties of different metal materials in a variable engineering application environment, the elastic constants of two kinds of metal materials in different temperature environment are measured by the proposed ultrasonic method.
Dynamical Properties in a Fourth-Order Nonlinear Difference Equation
Xianyi Li; Yunxin Chen
2010-01-01
The rule of trajectory structure for fourth-order nonlinear difference equation xn+1=(xan−2+xn−3)/(xan−2xn−3+1), n=0,1,2,…, where a∈[0,1) and the initial values x−3,x−2,x−1,x0∈[0,∞), is described clearly out in this paper. Mainly, the lengths of positive and negative semicycles of its nontrivial solutions are found to occur periodically with prime period 15. The rule is 4+,3−,1+,2−,2+,1−,1+, 1&#x...
Elastic constants of stressed and unstressed materials in the phase-field crystal model
Wang, Zi-Le; Huang, Zhi-Feng; Liu, Zhirong
2018-04-01
A general procedure is developed to investigate the elastic response and calculate the elastic constants of stressed and unstressed materials through continuum field modeling, particularly the phase-field crystal (PFC) models. It is found that for a complete description of system response to elastic deformation, the variations of all the quantities of lattice wave vectors, their density amplitudes (including the corresponding anisotropic variation and degeneracy breaking), the average atomic density, and system volume should be incorporated. The quantitative and qualitative results of elastic constant calculations highly depend on the physical interpretation of the density field used in the model, and also importantly, on the intrinsic pressure that usually pre-exists in the model system. A formulation based on thermodynamics is constructed to account for the effects caused by constant pre-existing stress during the homogeneous elastic deformation, through the introducing of a generalized Gibbs free energy and an effective finite strain tensor used for determining the elastic constants. The elastic properties of both solid and liquid states can be well produced by this unified approach, as demonstrated by an analysis for the liquid state and numerical evaluations for the bcc solid phase. The numerical calculations of bcc elastic constants and Poisson's ratio through this method generate results that are consistent with experimental conditions, and better match the data of bcc Fe given by molecular dynamics simulations as compared to previous work. The general theory developed here is applicable to the study of different types of stressed or unstressed material systems under elastic deformation.
Pseudospectral collocation methods for fourth order differential equations
Malek, Alaeddin; Phillips, Timothy N.
1994-01-01
Collocation schemes are presented for solving linear fourth order differential equations in one and two dimensions. The variational formulation of the model fourth order problem is discretized by approximating the integrals by a Gaussian quadrature rule generalized to include the values of the derivative of the integrand at the boundary points. Collocation schemes are derived which are equivalent to this discrete variational problem. An efficient preconditioner based on a low-order finite difference approximation to the same differential operator is presented. The corresponding multidomain problem is also considered and interface conditions are derived. Pseudospectral approximations which are C1 continuous at the interfaces are used in each subdomain to approximate the solution. The approximations are also shown to be C3 continuous at the interfaces asymptotically. A complete analysis of the collocation scheme for the multidomain problem is provided. The extension of the method to the biharmonic equation in two dimensions is discussed and results are presented for a problem defined in a nonrectangular domain.
Calculation of elastic constants of BCC transition metals: tight-binding recursion method
International Nuclear Information System (INIS)
Masuda, K.; Hamada, N.; Terakura, K.
1984-01-01
The elastic constants of BCC transition metals (Fe, Nb, Mo and W) are calculated by using the tight-binding d band and the Born-Mayer repulsive potential. Introducing a small distortion characteristic to C 44 (or C') elastic deformation and calculating the energy change up to second order in the atomic displacement, the shear elastic constants C 44 and C' are determined. The elastic constants C 11 and C 12 are then calculated by using the relations B=1/3(C 11 + 2C 12 ) and C'=1/2(C 11 -C 12 ), where B is the bulk modulus. In general, the agreement between the present results and the experimental values is satisfactory. The characteristic elasticity behaviour, i.e. the strong Nsub(d) (number of d electrons) dependence of the observed anisotropy factor A=C 44 /C', will also be discussed. (author)
Brain source localization using a fourth-order deflation scheme
Albera, Laurent; Ferréol, Anne; Cosandier-Rimélé, Delphine; Merlet, Isabel; Wendling, Fabrice
2008-01-01
A high resolution method for solving potentially ill-posed inverse problems is proposed. This method named FO-D-MUSIC allows for localization of brain current sources with unconstrained orientations from surface electro- or magnetoencephalographic data using spherical or realistic head geometries. The FO-D-MUSIC method is based on i) the separability of the data transfer matrix as a function of location and orientation parameters, ii) the Fourth Order (FO) virtual array theory, and iii) the deflation concept extended to FO statistics accounting for the presence of potentially but not completely statistically dependent sources. Computer results display the superiority of the FO-D-MUSIC approach in different situations (very closed sources, small number of electrodes, additive Gaussian noise with unknown spatial covariance, …) compared to classical algorithms. PMID:18269984
Mechanical Properties and Elastic Constants Due to Damage Accumulation and Amorphization in SiC
International Nuclear Information System (INIS)
Gao, Fei; Weber, William J.
2004-01-01
Damage accumulation due to cascade overlap, which was simulated previously, has been used to study the changes of elastic constants, bulk and elastic moduli as a function of dose. These mechanical properties generally decrease with increasing dose, and the rapid decrease at low-dose level indicates that point defects and small clusters play an important role in the changes of elastic constants rather than topological disorder. The internal strain relaxation has no effect on the elastic constants, C11 and C12, in perfect SiC, but it has a significant influence on all elastic constants calculated in damaged SiC. The elastic constants in the cascade-amorphized (CA) SiC decrease about 19%, 29% and 46% for C11, C12 and C44, respectively. The bulk modulus decrease 23% and the elastic modulus decreases 29%, which is consistent with experimental measurements. The stability of both the perfect SiC and CA-SiC under hydrostatic tension has been also investigated. All mechanical properties in the CA-SiC exhibit behavior similar to that in perfect SiC, but the critical stress at which the CA-SiC becomes structurally unstable is one order of magnitude smaller than that for perfect SiC
Determination of the dynamic elastic constants of recycled aggregate concrete
Tsoumani, A. A.; Barkoula, N.-M.; Matikas, T. E.
2015-03-01
Nowadays, construction and demolition waste constitutes a major portion of the total solid waste production in the world. Due to both environmental and economical reasons, an increasing interest concerning the use of recycled aggregate to replace aggregate from natural sources is generated. This paper presents an investigation on the properties of recycled aggregate concrete. Concrete mixes are prepared using recycled aggregates at a substitution level between 0 and 100% of the total coarse aggregate. The influence of this replacement on strengthened concrete's properties is being investigated. The properties estimated are: density and dynamic modulus of elasticity at the age of both 7 and 28 days. Also, flexural strength of 28 days specimens is estimated. The determination of the dynamic elastic modulus was made using the ultrasonic pulse velocity method. The results reveal that the existence of recycled aggregates affects the properties of concrete negatively; however, in low levels of substitution the influence of using recycled aggregates is almost negligible. Concluding, the controlled use of recycled aggregates in concrete production may help solve a vital environmental issue apart from being a solution to the problem of inadequate concrete aggregates.
Elastic constants of a Laves phase compound: C15 NbCr{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Ormeci, A. [Koc Univ., Istanbul (Turkey)]|[Los Alamos National Lab., NM (United States); Chu, F.; Wills, J.M.; Chen, S.P.; Albers, R.C.; Thoma, D.J.; Mitchell, T.E. [Los Alamos National Lab., NM (United States)
1997-04-01
The single-crystal elastic constants of C15 NbCr{sub 2} have been computed by using a first-principles, self-consistent, full-potential total energy method. From these single-crystal elastic constants the isotropic elastic moduli are calculated using the Voigt and Reuss averages. The calculated values are in fair agreement with the experimental values. The implications of the results are discussed with regards to Poisson`s ratio and the direction dependence of Young`s modulus.
Elastic constants of the C15 laves phase compound NbCr2
International Nuclear Information System (INIS)
Chu, F.; He, Y.; Thoma, D.J.; Mitchell, T.E.
1995-01-01
Elastic properties of a solid are important because they relate to various fundamental solid-state phenomena such as interatomic potentials, equations of state, and phonon spectra. Elastic properties are also linked thermodynamically with specific heat, thermal expansion, Debye temperature, and Gruneisen parameter. Most important, knowledge of elastic constants is essential for many practical applications related to the mechanical properties of a solid as well: load-deflection, thermoelastic stress, internal strain (residual stress), sound velocities, dislocation core structure, and fracture toughness. In order to understand better the physical properties and deformation behavior of the C15 compound NbCr 2 , the authors have studied its elastic properties in this paper. In Section 2, the experimental methods are described, including the preparation of the sample and the measurement of the elastic constants. In Section 3, the experimental results are presented and the implications of these experimental results are discussed. Conclusions are drawn in Section 4
OSCILLATION CRITERIA FOR A FOURTH ORDER SUBLINEAR DYNAMIC EQUATION ON TIME SCALE
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
Some new criteria for the oscillation of a fourth order sublinear and/or linear dynamic equation on time scale are established. Our results are new for the corresponding fourth order differential equations as well as difference equations.
Elastic-constant systematics in f.c.c. metals, including lanthanides-actinides
Energy Technology Data Exchange (ETDEWEB)
Ledbetter, Hassel [Mechanical Engineering Department, University of Colorado, Boulder, Colorado 80309 (United States); Migliori, Albert [Los Alamos National Laboratory (E536), Los Alamos, New Mexico 87545 (United States)
2008-01-15
For f.c.c. metals, using Blackman's diagram of dimensionless elastic-constant ratios, we consider the systematics of physical properties and interatomic bonding. We focus especially on the lanthanides-actinides La, Ce, Yb, Th, U, Pu, those for which we know some monocrystal elastic constants. Their behavior differs from the other f.c.c. metals, and all except La show a negative Cauchy pressure, contrary to most f.c.c. metals, which show a positive Cauchy pressure. Among the lanthanides-actinides, {delta}-Pu stands apart, consistent with its many odd physical properties. Based on elastic-constant correlations, we suggest that {delta}-Pu possesses a strong s-electron interatomic-bonding component together with a covalent component. Elastically, {delta}-Pu shows properties similar to Yb. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Surface acoustic waves and elastic constants of InN epilayers determined by Brillouin scattering
Energy Technology Data Exchange (ETDEWEB)
Jimenez-Rioboo, R.J.; Prieto, C. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, Madrid (Spain); Cusco, R.; Domenech-Amador, N.; Artus, L. [Institut Jaume Almera, Consell Superior d' Investigacions Cientifiques (CSIC), Lluis Sole i Sabaris s.n., Barcelona, Catalonia (Spain); Yamaguchi, T.; Nanishi, Y. [Faculty of Science and Engineering, Ritsumeikan University, Noji-Higashi, Kusatsu, Shiga (Japan)
2012-06-15
The surface acoustic wave velocity in InN has been experimentally determined by means of Brillouin scattering experiments on c - and m -face epilayers. From simulations based on the Green's function formalism we determine the shear elastic constants c{sub 66} and c{sub 44} and propose a complete set of elastic constants for wurtzite InN. The analysis of the sagittal and azimuthal dependence of the surface acoustic wave velocity indicates a slightly different elastic behavior of the m -face sample that basically affects the c{sub 44} elastic constant. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Analysis of competitive power market with constant elasticity function
International Nuclear Information System (INIS)
Nguyen, D.H.M.; Wong, K.P.
2003-01-01
A solution method, for competitive power markets formulated as a Cournot game, that allows equilibrium to be determined without an explicit model of aggregated demand is presented. The method determines market equilibrium for all feasible demand conditions and thus provides a perspective on the market, independent of representative demand function, that reveals the inherent tendencies of producers in the market. Numerical solutions are determined by use of the new controlled genetic algorithm and constraint handling techniques. The solutions give production and demand elasticity distributions of the market at any feasible equilibrium price and volume. The solution distributions evaluated for the market with unspecified demand functions, were found to be consistent with previous results obtained from markets with specific demand functions. The ability of the new approach to all, and arbitrary, solutions allow specific markets to be examined, as well as very general observations to be made. Generally it was observed that: no inherent price constraint exists; price is more volatile for low volumes and high prices; market dominance and power are unaffected by price; and inelastic demand can give rise to equilibrium with lower price than responsive demand. (Author)
The relationship between elastic constants and structure of shock waves in a zinc single crystal
Krivosheina, M. N.; Kobenko, S. V.; Tuch, E. V.
2017-12-01
The paper provides a 3D finite element simulation of shock-loaded anisotropic single crystals on the example of a Zn plate under impact using a mathematical model, which allows for anisotropy in hydrostatic stress and wave velocities in elastic and plastic ranges. The simulation results agree with experimental data, showing the absence of shock wave splitting into an elastic precursor and a plastic wave in Zn single crystals impacted in the [0001] direction. It is assumed that the absence of an elastic precursor under impact loading of a zinc single crystal along the [0001] direction is determined by the anomalously large ratio of the c/a-axes and close values of the propagation velocities of longitudinal and bulk elastic waves. It is shown that an increase in only one elastic constant along the [0001] direction results in shock wave splitting into an elastic precursor and a shock wave of "plastic" compression.
The modified Black-Scholes model via constant elasticity of variance for stock options valuation
Edeki, S. O.; Owoloko, E. A.; Ugbebor, O. O.
2016-02-01
In this paper, the classical Black-Scholes option pricing model is visited. We present a modified version of the Black-Scholes model via the application of the constant elasticity of variance model (CEVM); in this case, the volatility of the stock price is shown to be a non-constant function unlike the assumption of the classical Black-Scholes model.
Determination of mass density, dielectric, elastic, and piezoelectric constants of bulk GaN crystal.
Soluch, Waldemar; Brzozowski, Ernest; Lysakowska, Magdalena; Sadura, Jolanta
2011-11-01
Mass density, dielectric, elastic, and piezoelectric constants of bulk GaN crystal were determined. Mass density was obtained from the measured ratio of mass to volume of a cuboid. The dielectric constants were determined from the measured capacitances of an interdigital transducer (IDT) deposited on a Z-cut plate and from a parallel plate capacitor fabricated from this plate. The elastic and piezoelectric constants were determined by comparing the measured and calculated SAW velocities and electromechanical coupling coefficients on the Z- and X-cut plates. The following new constants were obtained: mass density p = 5986 kg/m(3); relative dielectric constants (at constant strain S) ε(S)(11)/ε(0) = 8.6 and ε(S)(11)/ε(0) = 10.5, where ε(0) is a dielectric constant of free space; elastic constants (at constant electric field E) C(E)(11) = 349.7, C(E)(12) = 128.1, C(E)(13) = 129.4, C(E)(33) = 430.3, and C(E)(44) = 96.5 GPa; and piezoelectric constants e(33) = 0.84, e(31) = -0.47, and e(15) = -0.41 C/m(2).
Energy Technology Data Exchange (ETDEWEB)
Seo, Ho Geon; Song, Dong Gi; Jhang, Kyoung Young [Hanyang University, Seoul (Korea, Republic of)
2016-04-15
Measurement of elastic constants is crucial for engineering aspects of predicting the behavior of materials under load as well as structural health monitoring of material degradation. Ultrasonic velocity measurement for material properties has been broadly used as a nondestructive evaluation method for material characterization. In particular, pulse-echo method has been extensively utilized as it is not only simple but also effective when only one side of the inspected objects is accessible. However, the conventional technique in this approach measures longitudinal and shear waves individually to obtain their velocities. This produces a set of two data for each measurement. This paper proposes a simultaneous sensing system of longitudinal waves and shear waves for elastic constant measurement. The proposed system senses both these waves simultaneously as a single overlapped signal, which is then analyzed to calculate both the ultrasonic velocities for obtaining elastic constants. Therefore, this system requires just half the number of data to obtain elastic constants compared to the conventional individual measurement. The results of the proposed simultaneous measurement had smaller standard deviations than those in the individual measurement. These results validate that the proposed approach improves the efficiency and reliability of ultrasonic elastic constant measurement by reducing the complexity of the measurement system, its operating procedures, and the number of data.
International Nuclear Information System (INIS)
Seo, Ho Geon; Song, Dong Gi; Jhang, Kyoung Young
2016-01-01
Measurement of elastic constants is crucial for engineering aspects of predicting the behavior of materials under load as well as structural health monitoring of material degradation. Ultrasonic velocity measurement for material properties has been broadly used as a nondestructive evaluation method for material characterization. In particular, pulse-echo method has been extensively utilized as it is not only simple but also effective when only one side of the inspected objects is accessible. However, the conventional technique in this approach measures longitudinal and shear waves individually to obtain their velocities. This produces a set of two data for each measurement. This paper proposes a simultaneous sensing system of longitudinal waves and shear waves for elastic constant measurement. The proposed system senses both these waves simultaneously as a single overlapped signal, which is then analyzed to calculate both the ultrasonic velocities for obtaining elastic constants. Therefore, this system requires just half the number of data to obtain elastic constants compared to the conventional individual measurement. The results of the proposed simultaneous measurement had smaller standard deviations than those in the individual measurement. These results validate that the proposed approach improves the efficiency and reliability of ultrasonic elastic constant measurement by reducing the complexity of the measurement system, its operating procedures, and the number of data
Diffraction plane dependency of elastic constants in ferritic steel in neutron stress measurement
International Nuclear Information System (INIS)
Hayashi, M.; Ishiwata, M.; Minakawa, N.; Funahashi, S.
1993-01-01
Neutron diffraction measurements have been made to investigate the elastic properties of the ferritic steel obtained from socket weld. The Kroner elastic model is found to account for the [hkl]-dependence of Young's modulus and Poisson's ratio in the material. Maps of residual stress are later to be made by measuring lattice strain from shifts in the (112) diffraction peak, for which the diffraction elastic constants the herein found to be E=243±5GPa and ν=0.28±0.01. (author)
Change of elastic constants induced by point defects in hop crystals
International Nuclear Information System (INIS)
Tome, C.
1979-10-01
An approximate model is developed to calculate the change of elastic constants induced by point defects in hcp metals, supposed the defect configuration is known. General expressions relating the change of elastic moduli to the final atomic coordinates and to the defect force field are derived using the specific symmetry of the defect. Explicit calculations are done for Mg. The predicted change of elastic moduli turns out to be negative for vacancies and trigonal interstitials while for hexagonal interstitials a positive change is predicted. Compatibility with experimental data would suggest that the trigonal configuration is the stable one. (author)
International Nuclear Information System (INIS)
Haldipur, P.; Margetan, F. J.; Thompson, R. B.
2006-01-01
Single-crystal elastic stiffness constants are important input parameters for many calculations in material science. There are well established methods to measure these constants using single-crystal specimens, but such specimens are not always readily available. The ultrasonic properties of metal polycrystals, such as velocity, attenuation, and backscattered grain noise characteristics, depend in part on the single-crystal elastic constants. In this work we consider the estimation of elastic constants from UT measurements and grain-sizing data. We confine ourselves to a class of particularly simple polycrystalline microstructures, found in some jet-engine Nickel alloys, which are single-phase, cubic, equiaxed, and untextured. In past work we described a method to estimate the single-crystal elastic constants from measured ultrasonic velocity and attenuation data accompanied by metallographic analysis of grain size. However, that methodology assumes that all attenuation is due to grain scattering, and thus is not valid if appreciable absorption is present. In this work we describe an alternative approach which uses backscattered grain noise data in place of attenuation data. Efforts to validate the method using a pure copper specimen are discussed, and new results for two jet-engine Nickel alloys are presented
Ultrasonic Determination of the Elastic Constants of Epoxy-natural Fiber Composites
Valencia, C. A. Meza; Pazos-Ospina, J. F.; Franco, E. E.; Ealo, Joao L.; Collazos-Burbano, D. A.; Garcia, G. F. Casanova
This paper shows the applications ultrasonic through-transmission technique to determine the elastic constants of two polymer-natural fiber composite materials with potential industrial application and economic and environmental advantages. The transversely isotropic coconut-epoxy and fique-epoxy samples were analyzed using an experimental setup which allows the sample to be rotated with respect to transducers faces and measures the time-of-flight at different angles of incidence. Then, the elastic properties of the material were obtained by fitting the experimental data to the Christoffel equation. Results show a good agreement between the measured elastic constants and the values predicted by an analytical model. The velocities as a function of the incidence angle are reported and the effect of the natural fiber on the stiffness of the composite is discussed.
Pressure derivatives of the second-order elastic constants of strontium, barium, and lead nitrate
International Nuclear Information System (INIS)
Bedi, S.S.; Verma, M.P.
1980-01-01
An interpretation is given of the measured results on the pressure derivatives of second-order elastic constants (SOEC) of strontium barium, and lead nitrate crystallizing in the fluorite type structure from the Lundquist potential. Potential parameters are determined from the experimental values of SOEC and the equilibrium condition
Elastic constants and Debye temperature of wz-AlN and wz-GaN ...
Indian Academy of Sciences (India)
DOI: 10.1007/s12043-014-0785-7; ePublication: 5 September 2014. Abstract. First-principles calculations .... For calculating elastic stiffness constants, C11, C12, C13, C33 and C44, we have taken ..... 89, 5815 (2001). [2] G Chris, Van de Walle ...
Temperature variation of higher-order elastic constants of MgO
Indian Academy of Sciences (India)
series of strains using Taylor's series expansion. The coefficients of quadratic, cu- ... as thermal expansion, specific heat at higher temperature, temperature variation of ultrasonic velocity and attenuation, .... such studies have an impression that linear variation of elastic constant is true. The experimental study shows that ...
Naresh, P; Hitesh, C; Patel, A; Kolge, T; Sharma, Archana; Mittal, K C
2013-08-01
A fourth order (LCLC) resonant converter based capacitor charging power supply (CCPS) is designed and developed for pulse power applications. Resonant converters are preferred t utilize soft switching techniques such as zero current switching (ZCS) and zero voltage switching (ZVS). An attempt has been made to overcome the disadvantages in 2nd and 3rd resonant converter topologies; hence a fourth order resonant topology is used in this paper for CCPS application. In this paper a novel fourth order LCLC based resonant converter has been explored and mathematical analysis carried out to calculate load independent constant current. This topology provides load independent constant current at switching frequency (fs) equal to resonant frequency (fr). By changing switching condition (on time and dead time) this topology has both soft switching techniques such as ZCS and ZVS for better switching action to improve the converter efficiency. This novel technique has special features such as low peak current through switches, DC blocking for transformer, utilizing transformer leakage inductance as resonant component. A prototype has been developed and tested successfully to charge a 100 μF capacitor to 200 V.
Proposal for Ultrasonic Technique for evaluation elastic constants in UO2 pellets
International Nuclear Information System (INIS)
Lopes, Alessandra Susanne Viana Ragone; Baroni, Douglas Brandao; Bittencourt, Marcelo de Siqueira Queiroz; Souza, Mauro Carlos Lopes
2015-01-01
Pellets of uranium dioxide are used as fuel in nuclear power reactors, in which are exposed to high thermal gradients. This high energy will initiate fusion in the central part of the pellet. The expansion of the uranium dioxide pellets, resulting from fission products, can cause fissures or cracks, therefore, the study of their behavior is important. This work aims to develop and propose an ultrasonic technique to evaluate the elastic constants of UO 2 pellets. However, because of the difficulties in handling nuclear material, we proposed an initial study of alumina specimens. Alumina pellets are also ceramic material and their porosity and dimensions are in the similar range of dioxide uranium pellets. They also are used as thermal insulation in the fuel rods, operating under the same conditions. They were fabricated and used in two different sets of 10 alumina pellets with densities of 92% and 96%. The developed ultrasonic technique evaluates the traveling time of ultrasonic waves, longitudinal and transverse, and correlates the observed time and the elastic constants of the materials. Equations relating the speed of the ultrasonic wave to the elastic modulus, shear modulus and Poisson's ratio have led to these elastic constants, with graphics of correlation that showed excellent agreement with the literature available for Alumina. In view of the results and the ease of implementation of this technique, we believe that it may easily be used for dioxide uranium pellets, justifying further studies for that application. (author)
The Pricing of European Options Under the Constant Elasticity of Variance with Stochastic Volatility
Bock, Bounghun; Choi, Sun-Yong; Kim, Jeong-Hoon
This paper considers a hybrid risky asset price model given by a constant elasticity of variance multiplied by a stochastic volatility factor. A multiscale analysis leads to an asymptotic pricing formula for both European vanilla option and a Barrier option near the zero elasticity of variance. The accuracy of the approximation is provided in a rigorous manner. A numerical experiment for implied volatilities shows that the hybrid model improves some of the well-known models in view of fitting the data for different maturities.
PPN-limit of Fourth Order Gravity inspired by Scalar-Tensor Gravity
Capozziello, S.; Troisi, A.
2005-01-01
Based on the {\\it dynamical} equivalence between higher order gravity and scalar-tensor gravity the PPN-limit of fourth order gravity is discussed. We exploit this analogy developing a fourth order gravity version of the Eddington PPN-parameters. As a result, Solar System experiments can be reconciled with higher order gravity, if physical constraints descending from experiments are fulfilled.
ON THE INSTABILITY OF SOLUTIONS TO A NONLINEAR VECTOR DIFFERENTIAL EQUATION OF FOURTH ORDER
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
This paper presents a new result related to the instability of the zero solution to a nonlinear vector differential equation of fourth order.Our result includes and improves an instability result in the previous literature,which is related to the instability of the zero solution to a nonlinear scalar differential equation of fourth order.
The elastic constants and anisotropy of superconducting MgCNi3 and CdCNi3 under different pressure
Feng, Huifang; Wu, Xiaozhi; Gan, Liyong; Wang, Rui; Wei, Qunyi
2013-01-01
The second-order elastic constants (SOECs) and third-order elastic constants (TOECs) of MgCNi3 and CdCNi3 are presented by using first-principles methods combined with homogeneous deformation theory. The Voigt-Reuss-Hill (VRH) approximation are used
Fourth-order perturbative extension of the single-double excitation coupled-cluster method
International Nuclear Information System (INIS)
Derevianko, Andrei; Emmons, Erik D.
2002-01-01
Fourth-order many-body corrections to matrix elements for atoms with one valence electron are derived. The obtained diagrams are classified using coupled-cluster-inspired separation into contributions from n-particle excitations from the lowest-order wave function. The complete set of fourth-order diagrams involves only connected single, double, and triple excitations and disconnected quadruple excitations. Approximately half of the fourth-order diagrams are not accounted for by the popular coupled-cluster method truncated at single and double excitations (CCSD). Explicit formulas are tabulated for the entire set of fourth-order diagrams missed by the CCSD method and its linearized version, i.e., contributions from connected triple and disconnected quadruple excitations. A partial summation scheme of the derived fourth-order contributions to all orders of perturbation theory is proposed
Modelling and simulation of multi-phase effects on X-ray elasticity constants
Freour, S; Guillen, R; François, M X
2003-01-01
This paper deals with the calculation of X-ray Elasticity Constants (XEC) of phases embedded in multi-phase polycrystals. A three scales (macroscopic, pseudo-macroscopic, mesoscopic) model based on the classical self-consistent formalism is developed in order to analyse multi-phase effects on XEC values. Simulations are performed for cubic or hexagonal crystallographic structure phases embedded in several two-phases materials. In fact, it is demonstrated that XEC vary with the macroscopic stiffness of the whole polycrystal. In consequence, the constants of one particular phase depend on the elastic behaviour and the volume fraction of all the phases constituting the material. Now, XEC play a leading role in pseudo-macroscopic stresses determination by X-Ray Diffraction (XRD) methods. In this work, a quantitative analysis of the multi-phase effects on stresses determination by XRD methods was performed. Numerical results will be compared and discussed. (Abstract Copyright [2003], Wiley Periodicals, Inc.)
Castagnède, Bernard; Jenkins, James T.; Sachse, Wolfgang; Baste, Stéphane
1990-03-01
A method is described to optimally determine the elastic constants of anisotropic solids from wave-speeds measurements in arbitrary nonprincipal planes. For such a problem, the characteristic equation is a degree-three polynomial which generally does not factorize. By developing and rearranging this polynomial, a nonlinear system of equations is obtained. The elastic constants are then recovered by minimizing a functional derived from this overdetermined system of equations. Calculations of the functional are given for two specific cases, i.e., the orthorhombic and the hexagonal symmetries. Some numerical results showing the efficiency of the algorithm are presented. A numerical method is also described for the recovery of the orientation of the principal acoustical axes. This problem is solved through a double-iterative numerical scheme. Numerical as well as experimental results are presented for a unidirectional composite material.
First-principles elastic constants and phonons of delta-Pu
DEFF Research Database (Denmark)
Söderlind, P.; Landa, A.; Sadigh, B.
2004-01-01
Elastic constants and zone-boundary phonons of delta-plutonium have been calculated within the density-functional theory. The paramagnetic state of delta-Pu is modeled by disordered magnetism utilizing either the disordered local moment or the special quasirandom structure techniques. The anomalo......Elastic constants and zone-boundary phonons of delta-plutonium have been calculated within the density-functional theory. The paramagnetic state of delta-Pu is modeled by disordered magnetism utilizing either the disordered local moment or the special quasirandom structure techniques....... The anomalously soft C-' as well as a large anisotropy ratio (C-44/C-') of delta-Pu is reproduced by this theoretical model. Also the recently measured phonons for delta-Pu compare relatively well with their theoretical counterpart at the zone boundaries....
Energy Technology Data Exchange (ETDEWEB)
Bouchet, J M [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires
1969-03-01
We present an apparatus with which we have measured the Young's modulus and the Poisson's ratio of several compounds from the resonance frequency of cylinders in the temperature range 0 deg. C-700 deg. C. We especially studied the elastic constants of plutonium and measured for the first time to our knowledge the Young's modulus of Pu{sub {delta}} and Pu{sub {epsilon}}. E{sub {delta}} 360 deg. C = 1.6 10{sup 11} dy/cm{sup 2}; E{sub {epsilon}} 490 deg. C = 1.1 10{sup 11} dy/cm{sup 2}, {sigma}{sub {epsilon}} = 0.25 {+-} 0.03 Using our results, we have calculated the compressibility, the Debye temperature, the Grueneisen constant and the electronic specific heat of Pu{sub {epsilon}}. (author) [French] Nous decrivons un appareil qui permet de mesurer les constantes elastiques (module de Young et module de Poisson) jusqu'a 700 deg. C a partir des frequences de resonance de barreaux cylindriques. Nous avons plus specialement etudie le plutonium et determine pour la premiere fois a notre connaissance le module de Young des phases {delta} et {epsilon}: E{sub {delta}} 360 deg. C = 1.6 10{sup 11} dy/cm{sup 2}; E{sub {epsilon}} 490 deg. C = 1.1 10{sup 11} dy/cm{sup 2}, {sigma}{sub {epsilon}} = 0.25 {+-} 0.03 Nos mesures nous ont permis de calculer la compressibilite, la temperature de Debye, la constante de Gruneisen et la chaleur specifique electronique de Pu{sub {epsilon}}. (auteur)
Azarnavid, Babak; Parand, Kourosh; Abbasbandy, Saeid
2018-06-01
This article discusses an iterative reproducing kernel method with respect to its effectiveness and capability of solving a fourth-order boundary value problem with nonlinear boundary conditions modeling beams on elastic foundations. Since there is no method of obtaining reproducing kernel which satisfies nonlinear boundary conditions, the standard reproducing kernel methods cannot be used directly to solve boundary value problems with nonlinear boundary conditions as there is no knowledge about the existence and uniqueness of the solution. The aim of this paper is, therefore, to construct an iterative method by the use of a combination of reproducing kernel Hilbert space method and a shooting-like technique to solve the mentioned problems. Error estimation for reproducing kernel Hilbert space methods for nonlinear boundary value problems have yet to be discussed in the literature. In this paper, we present error estimation for the reproducing kernel method to solve nonlinear boundary value problems probably for the first time. Some numerical results are given out to demonstrate the applicability of the method.
Three-body interactions and the elastic constants of hcp solid 4He
Barnes, Ashleigh L.; Hinde, Robert J.
2017-09-01
The effect of three-body interactions on the elastic properties of hexagonal close packed solid 4He is investigated using variational path integral (VPI) Monte Carlo simulations. The solid's nonzero elastic constants are calculated, at T = 0 K and for a range of molar volumes from 7.88 cm3/mol to 20.78 cm3/mol, from the bulk modulus and the three pure shear constants C0, C66, and C44. Three-body interactions are accounted for using our recently reported perturbative treatment based on the nonadditive three-body potential of Cencek et al. Previous studies have attempted to account for the effect of three-body interactions on the elastic properties of solid 4He; however, these calculations have treated zero point motions using either the Einstein or Debye approximations, which are insufficient in the molar volume range where solid 4He is characterized as a quantum solid. Our VPI calculations allow for a more accurate treatment of the zero point motions which include atomic correlation. From these calculations, we find that agreement with the experimental bulk modulus is significantly improved when three-body interactions are considered. In addition, three-body interactions result in non-negligible differences in the calculated pure shear constants and nonzero elastic constants, particularly at higher densities, where differences of up to 26.5% are observed when three-body interactions are included. We compare to the available experimental data and find that our results are generally in as good or better agreement with experiment as previous theoretical investigations.
A fluctuation method to calculate the third order elastic constants in crystalline solids
Energy Technology Data Exchange (ETDEWEB)
Chen, Zimu [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Qu, Jianmin, E-mail: j-qu@northwestern.edu [Department of Civil and Environmental Engineering, Department of Mechanical Engineering, Northwestern University, Evanston, Illinois 60208 (United States)
2015-05-28
This paper derives exact expressions of the isothermal third order elastic constants (TOE) in crystalline solids in terms of the kinetic and potential energies of the system. These expressions reveal that the TOE constants consist of a Born component and a relaxation component. The Born component is simply the third derivative of the system's potential energy with respect to the deformation, while the relaxation component is related to the non-uniform rearrangements of the atoms when the system is subject to a macroscopic deformation. Further, based on the general expressions derived here, a direct (fluctuation) method of computing the isothermal TOE constants is developed. Numerical examples of using this fluctuation method are given to compute the TOE constants of single crystal iron.
Mining for elastic constants of intermetallics from the charge density landscape
Energy Technology Data Exchange (ETDEWEB)
Kong, Chang Sun; Broderick, Scott R. [Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011 (United States); Jones, Travis E. [Molecular Theory Group, Colorado School of Mines, Golden, CO 80401 (United States); Loyola, Claudia [Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011 (United States); Eberhart, Mark E. [Molecular Theory Group, Colorado School of Mines, Golden, CO 80401 (United States); Rajan, Krishna, E-mail: krajan@iastate.edu [Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011 (United States)
2015-02-01
There is a significant challenge in designing new materials for targeted properties based on their electronic structure. While in principle this goal can be met using knowledge of the electron charge density, the relationships between the density and properties are largely unknown. To help overcome this problem we develop a quantitative structure–property relationship (QSPR) between the charge density and the elastic constants for B2 intermetallics. Using a combination of informatics techniques for screening all the potentially relevant charge density descriptors, we find that C{sub 11} and C{sub 44} are determined solely from the magnitude of the charge density at its critical points, while C{sub 12} is determined by the shape of the charge density at its critical points. From this reduced charge density selection space, we develop models for predicting the elastic constants of an expanded number of intermetallic systems, which we then use to predict the mechanical stability of new systems. Having reduced the descriptors necessary for modeling elastic constants, statistical learning approaches may then be used to predict the reduced knowledge-based required as a function of the constituent characteristics.
Single-crystal elastic constants of a plutonium-gallium alloy
International Nuclear Information System (INIS)
Moment, R.L.
1976-01-01
The single-crystal elastic constants of a plutonium-1 wt % gallium alloy were determined at room temperature by measuring ultrasonic sound-wave velocities. The three independent elastic constants of this face-centered cubic delta-phase alloy were determined from the longitudinal and the two shear-wave velocities, all along a direction. Their values are C 11 =3.628, C 12 =2.673 and C 44 =3.359 in units of 10 10 N/m 2 ; the respective errors are estimated to be 1%, 1%, and 0.3 %. The Zener anisotropy ratio is 7.03, almost twice that known for any other fcc metal, and falls among the ratios for the body centered cubic alkali metals, which are noted for their high elastic anisotropy. Polycrystalline elastic constants calculated from the single-crystal data are Young's modulus E=4.064, the shear modulus G=1.596 and the bulk modulus (reciprocal compressibility) B=2.991, all in units of 10 10 N/m 2 , and Poisson's ratio γ=0.27. These values of E and G are both lower than those obtained by Taylor, Linford and Dean from measurements on polycrystalline specimens. Within a single crystal, the longitudinal sound velocity varies with direction by a factor of 1.4 and the transverse velocity by a factor of 2.6. The maximum Young's modulus (along ) was 5.4 times larger than the minimum (along ). The Debye temperature was calculated to be 105.7 K at 293 K and estimated to be 114 K at 0.K. (Auth.)
International Nuclear Information System (INIS)
Phadke, Sushil; DShrivastava, B; Dagaonkar, N; Mishra, Ashutosh
2012-01-01
The homogeneous continuous materials are widely used for many structural applications. Migrations of atoms or molecules are the mechanism of mechanical and kinetic processes in materials for their synthesis processing as well as for their structural evolutions. The elastic constant of solids provides valuable information on their mechanical and dynamical properties. In particular, they provide information on the stability and stiffness of materials. In the present study author investigated relation between elastic constant and temperature in Borassus Flabellifier 'BF' wood part. Determination of elastic properties of material is based on the longitudinal wave's velocities via ultrasonic methods. The resonant frequencies of the specimens were measured by Ultrasonic Interferometer (for solids) dual frequency using longitudinal cubic piezoelectric crystal of quartz of frequency 123.62 KHz. The temperature variations from room temperature were done by PID control unit, Mittal Enterprises, New Delhi, India. Characterization of the samples was done by scanning electron microscope (SEM) Model JEOL JSM5400 at 5.0kvx750, 10 μm.
Estimation of parameters of constant elasticity of substitution production functional model
Mahaboob, B.; Venkateswarlu, B.; Sankar, J. Ravi
2017-11-01
Nonlinear model building has become an increasing important powerful tool in mathematical economics. In recent years the popularity of applications of nonlinear models has dramatically been rising up. Several researchers in econometrics are very often interested in the inferential aspects of nonlinear regression models [6]. The present research study gives a distinct method of estimation of more complicated and highly nonlinear model viz Constant Elasticity of Substitution (CES) production functional model. Henningen et.al [5] proposed three solutions to avoid serious problems when estimating CES functions in 2012 and they are i) removing discontinuities by using the limits of the CES function and its derivative. ii) Circumventing large rounding errors by local linear approximations iii) Handling ill-behaved objective functions by a multi-dimensional grid search. Joel Chongeh et.al [7] discussed the estimation of the impact of capital and labour inputs to the gris output agri-food products using constant elasticity of substitution production function in Tanzanian context. Pol Antras [8] presented new estimates of the elasticity of substitution between capital and labour using data from the private sector of the U.S. economy for the period 1948-1998.
Gogu, C.; Haftka, R.; LeRiche, R.; Molimard, J.; Vautrin, A.; Sankar, B.
2008-11-01
The basic formulation of the least squares method, based on the L2 norm of the misfit, is still widely used today for identifying elastic material properties from experimental data. An alternative statistical approach is the Bayesian method. We seek here situations with significant difference between the material properties found by the two methods. For a simple three bar truss example we illustrate three such situations in which the Bayesian approach leads to more accurate results: different magnitude of the measurements, different uncertainty in the measurements and correlation among measurements. When all three effects add up, the Bayesian approach can have a large advantage. We then compared the two methods for identification of elastic constants from plate vibration natural frequencies.
X-ray elastic constants in textured Zr-base materials
International Nuclear Information System (INIS)
Ortiz, M.; Pochettino, A.A.; Lebrun, J.L.; Maeder, G.
1993-01-01
A general method for the calculation of the X-ray elastic constants (XREC) for textured hexagonal close-packed (hcp) materials was developed by using the orientation distribution function (ODF) and the Reuss hypothesis. This method was applied to textured zirconium (Zr) sheets and zircaloy 4 (Zry 4) extruded tubes. For these samples, where the elastic anisotropy is not very strong, an 'isotropic approximation' method is proposed using the ODF data. In that case, the classical XREC 1/2S 2 and S, values are calculated and experimentally verified for (10 bar 14) diffracting planes. Theoretical XREC values are also given for different (hkil) that could be chosen according to the experimental conditions, considering texture effects on diffracting peak intensities
Thermodynamic and classical instability of AdS black holes in fourth-order gravity
International Nuclear Information System (INIS)
Myung, Yun Soo; Moon, Taeyoon
2014-01-01
We study thermodynamic and classical instability of AdS black holes in fourth-order gravity. These include the BTZ black hole in new massive gravity, Schwarzschild-AdS black hole, and higher-dimensional AdS black holes in fourth-order gravity. All thermodynamic quantities which are computed using the Abbot-Deser-Tekin method are used to study thermodynamic instability of AdS black holes. On the other hand, we investigate the s-mode Gregory-Laflamme instability of the massive graviton propagating around the AdS black holes. We establish the connection between the thermodynamic instability and the GL instability of AdS black holes in fourth-order gravity. This shows that the Gubser-Mitra conjecture holds for AdS black holes found from fourth-order gravity
Optimizing lengths of confidence intervals: fourth-order efficiency in location models
Klaassen, C.; Venetiaan, S.
2010-01-01
Under regularity conditions the maximum likelihood estimator of the location parameter in a location model is asymptotically efficient among translation equivariant estimators. Additional regularity conditions warrant third- and even fourth-order efficiency, in the sense that no translation
Stability and square integrability of solutions of nonlinear fourth order differential equations
Directory of Open Access Journals (Sweden)
Moussadek Remili
2016-05-01
Full Text Available The aim of the present paper is to establish a new result, which guarantees the asymptotic stability of zero solution and square integrability of solutions and their derivatives to nonlinear differential equations of fourth order.
International Nuclear Information System (INIS)
Wang, Zhuqing; Stoica, Alexandru D.; Ma, Dong; Beese, Allison M.
2016-01-01
In this work, diffraction and single-crystal elastic constants of Inconel 625 have been determined by means of in situ loading at room and elevated temperatures using time-of-flight neutron diffraction. Theoretical models proposed by Voigt, Reuss, and Kroner were used to determine single-crystal elastic constants from measured diffraction elastic constants, with the Kroner model having the best ability to capture experimental data. The magnitude of single-crystal elastic moduli, computed from single-crystal elastic constants, decreases and the single crystal anisotropy increases as temperature increases, indicating the importance of texture in affecting macroscopic stress at elevated temperatures. The experimental data reported here are of great importance in understanding additive manufacturing of metallic components as: diffraction elastic constants are required for computing residual stresses from residual lattice strains measured using neutron diffraction, which can be used to validate thermomechanical models of additive manufacturing, while single-crystal elastic constants can be used in crystal plasticity modeling, for example, to understand mechanical deformation behavior of additively manufactured components.
Energy Technology Data Exchange (ETDEWEB)
Wang, Zhuqing [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Stoica, Alexandru D. [Chemical and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Ma, Dong, E-mail: dongma@ornl.gov [Chemical and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Beese, Allison M., E-mail: amb961@psu.edu [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States)
2016-09-30
In this work, diffraction and single-crystal elastic constants of Inconel 625 have been determined by means of in situ loading at room and elevated temperatures using time-of-flight neutron diffraction. Theoretical models proposed by Voigt, Reuss, and Kroner were used to determine single-crystal elastic constants from measured diffraction elastic constants, with the Kroner model having the best ability to capture experimental data. The magnitude of single-crystal elastic moduli, computed from single-crystal elastic constants, decreases and the single crystal anisotropy increases as temperature increases, indicating the importance of texture in affecting macroscopic stress at elevated temperatures. The experimental data reported here are of great importance in understanding additive manufacturing of metallic components as: diffraction elastic constants are required for computing residual stresses from residual lattice strains measured using neutron diffraction, which can be used to validate thermomechanical models of additive manufacturing, while single-crystal elastic constants can be used in crystal plasticity modeling, for example, to understand mechanical deformation behavior of additively manufactured components.
Energy Technology Data Exchange (ETDEWEB)
Berryman, J. G.
2012-03-01
While the well-known Voigt and Reuss (VR) bounds, and the Voigt-Reuss-Hill (VRH) elastic constant estimators for random polycrystals are all straightforwardly calculated once the elastic constants of anisotropic crystals are known, the Hashin-Shtrikman (HS) bounds and related self-consistent (SC) estimators for the same constants are, by comparison, more difficult to compute. Recent work has shown how to simplify (to some extent) these harder to compute HS bounds and SC estimators. An overview and analysis of a subsampling of these results is presented here with the main point being to show whether or not this extra work (i.e., in calculating both the HS bounds and the SC estimates) does provide added value since, in particular, the VRH estimators often do not fall within the HS bounds, while the SC estimators (for good reasons) have always been found to do so. The quantitative differences between the SC and the VRH estimators in the eight cases considered are often quite small however, being on the order of ±1%. These quantitative results hold true even though these polycrystal Voigt-Reuss-Hill estimators more typically (but not always) fall outside the Hashin-Shtrikman bounds, while the self-consistent estimators always fall inside (or on the boundaries of) these same bounds.
Block Hybrid Collocation Method with Application to Fourth Order Differential Equations
Directory of Open Access Journals (Sweden)
Lee Ken Yap
2015-01-01
Full Text Available The block hybrid collocation method with three off-step points is proposed for the direct solution of fourth order ordinary differential equations. The interpolation and collocation techniques are applied on basic polynomial to generate the main and additional methods. These methods are implemented in block form to obtain the approximation at seven points simultaneously. Numerical experiments are conducted to illustrate the efficiency of the method. The method is also applied to solve the fourth order problem from ship dynamics.
A fourth order spline collocation approach for a business cycle model
Sayfy, A.; Khoury, S.; Ibdah, H.
2013-10-01
A collocation approach, based on a fourth order cubic B-splines is presented for the numerical solution of a Kaleckian business cycle model formulated by a nonlinear delay differential equation. The equation is approximated and the nonlinearity is handled by employing an iterative scheme arising from Newton's method. It is shown that the model exhibits a conditionally dynamical stable cycle. The fourth-order rate of convergence of the scheme is verified numerically for different special cases.
The elastic constants of V2O3 in the insulating phase
International Nuclear Information System (INIS)
Yelon, W.B.; Keem, J.E.
1979-01-01
The initial slopes of the acoustic phonon dispersion curves in (Vsub(0.98)Crsub(0.02)) 2 O 3 have been measured at room temperature in several of the high symmetry directions by inelastic neutron scattering. From these data several sound velocities and four independent elastic constants have been determined. Although the Cr doped specimen is in the insulating phase and pure V 2 O 3 is metallic, these results are in good agreement with recent data obtained by ultrasonic measurements on pure V 2 O 3 . (author)
Energy Technology Data Exchange (ETDEWEB)
Ghosh, G., E-mail: g-ghosh@northwestern.edu [Department of Materials Science and Engineering, Robert R. McCormick School of Engineering and Applied Science, Northwestern University, 2220 Campus Drive, Evanston, IL 60208-3108 (United States)
2015-08-15
A comprehensive computational study of elastic properties of cementite (Fe{sub 3}C) and its alloyed counterparts (M{sub 3}C (M = Al, Co, Cr, Cu, Fe, Hf, Mn, Mo, Nb, Ni, Si, Ta, Ti, V, W, Zr, Cr{sub 2}FeC and CrFe{sub 2}C) having the crystal structure of Fe{sub 3}C is carried out employing electronic density-functional theory (DFT), all-electron PAW pseudopotentials and the generalized gradient approximation for the exchange-correlation energy (GGA). Specifically, as a part of our systematic study of cohesive properties of solids and in the spirit of materials genome, following properties are calculated: (i) single-crystal elastic constants, C{sub ij}, of above M{sub 3}Cs; (ii) anisotropies of bulk, Young’s and shear moduli, and Poisson’s ratio based on calculated C{sub ij}s, demonstrating their extreme anisotropies; (iii) isotropic (polycrystalline) elastic moduli (bulk, shear, Young’s moduli and Poisson’s ratio) of M{sub 3}Cs by homogenization of calculated C{sub ij}s; and (iv) acoustic Debye temperature, θ{sub D}, of M{sub 3}Cs based on calculated C{sub ij}s. We provide a critical appraisal of available data of polycrystalline elastic properties of alloyed cementite. Calculated single crystal properties may be incorporated in anisotropic constitutive models to develop and test microstructure-processing-property-performance links in multi-phase materials where cementite is a constituent phase.
Directory of Open Access Journals (Sweden)
Dellinger J.
2006-12-01
Full Text Available Inverting a set of core-sample traveltime measurements for a complete set of 21 elastic constants is a difficult problem. If the 21 elastic constants are directly used as the inversion parameters, a few bad measurements or an unfortunate starting guess may result in the inversion converging to a physically impossible solution . Even given perfect data, multiple solutions may exist that predict the observed traveltimes equally well. We desire the inversion algorithm to converge not just to a physically possible solution, but to the best(i. e. most physically likely solution of all those allowed. We present a new parameterization that attempts to solve these difficulties. The search space is limited to physically realizable media by making use of the Kelvin eigenstiffness-eigentensor representation of the 6 x 6 elastic stiffness matrix. Instead of 21 stiffnesses, there are 6 eigenstiffness parametersand 15 rotational parameters . The rotational parameters are defined using a Lie-algebra representation that avoids the artificial degeneracies and coordinate-system bias that can occur with standard polar representations. For any choice of these 21 real parameters, the corresponding stiffness matrix is guaranteed to be physically realizable. Furthermore, all physically realizable matrices can be represented in this way. This new parameterization still leaves considerable latitude as to which linear combinations of the Kelvin parameters to use, and how they should be ordered. We demonstrate that by careful choice and ordering of the parameters, the inversion can be relaxedfrom higher to lower symmetry simply by adding a few more parameters at a time. By starting from isotropy and relaxing to the general result in stages (isotropy, transverse isotropy, orthorhombic, general, we expect that the method should find the solution that is closest to isotropy of all those that fit the data. L'inversion d'un ensemble de mesures du temps de parcours d
International Nuclear Information System (INIS)
Wu, Szu-Ying; Tsai, Bor-Jiun; Chen, Jien-Jong
2015-01-01
In this study, a 3-D automatic elastic-plastic finite element mesh generator is established to accurately predict the J-integral value of an arbitrary reducer with a constant-depth internal circumferential surface crack under bending and axial force. The contact pairs are used on the crack surfaces to simulate the actual contact behaviors of the crack model under loadings. In order to verify the accuracy of the proposed elastic-plastic finite element model for a reducer with a surface crack, the cracked straight pipe models are generated according to a special modeling procedure for a flawed reducer. The J-integral values along the crack front of surface crack are calculated and compared with the straight pipe models which have been verified in the previous published studies. Based on the comparison of computed results, good agreements are obtained to show the accuracy of present numerical models. More confidence on using the 3-D elastic-plastic finite element analysis for reducers with internal circumferential surface cracks can be thus established in this work
Optimal determination of the elastic constants of woven 2D SiC/SiC composite materials
International Nuclear Information System (INIS)
Mouchtachi, A; Guerjouma, R El; Baboux, J C; Rouby, D; Bouami, D
2004-01-01
For homogeneous materials, the ultrasonic immersion method, associated with a numerical optimization process mostly based on Newton's algorithm, allows the determination of elastic constants for various synthetic and natural composite materials. Nevertheless, a principal limitation of the existing optimization procedure occurs when the considered material is at the limit of the homogeneous hypothesis. Such is the case of the woven bidirectional SiC matrix and SiC fibre composite material. In this study, we have developed two numerical methods for the determination of the elastic constants of the 2D SiC/SiC composite material (2D SiC/SiC). The first one is based on Newton's algorithm: the elastic constants are obtained by minimizing the square deviation between experimental and calculated velocities. The second method is based on the Levenberg-Marquardt algorithm. We show that these algorithms give the same results in the case of homogeneous anisotropic composite materials. For the 2D SiC/SiC composite material, the two methods, using the same measured velocities, give different sets of elastic constants. We then note that the Levenberg-Marquardt algorithm enables a better convergence towards a global set of elastic constants in good agreement with the elastic properties, which can be measured using classical quasi-static methods
A Fourth Order Formulation of DDM for Crack Analysis in Brittle Solids
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Abolfazl Abdollahipour
2017-01-01
Full Text Available A fourth order formulation of the displacement discontinuity method (DDM is proposed for the crack analysis of brittle solids such as rocks, glasses, concretes and ceramics. A fourth order boundary collocation scheme is used for the discretization of each boundary element (the source element. In this approach, the source boundary element is divided into five sub-elements each recognized by a central node where the displacement discontinuity components are to be numerically evaluated. Three different formulating procedures are presented and their corresponding discretization schemes are discussed. A new discretization scheme is also proposed to use the fourth order formulation for the special crack tip elements which may be used to increase the accuracy of the stress and displacement fields near the crack ends. Therefore, these new crack tips discretizing schemes are also improved by using the proposed fourth order displacement discontinuity formulation and the corresponding shape functions for a bunch of five special crack tip elements. Some example problems in brittle fracture mechanics are solved for estimating the Mode I and Mode II stress intensity factors near the crack ends. These semi-analytical results are compared to those cited in the fracture mechanics literature whereby the high accuracy of the fourth order DDM formulation is demonstrated.
Compensating amplitude-dependent tune-shift without driving fourth-order resonances
Ögren, J.; Ziemann, V.
2017-10-01
If octupoles are used in a ring to correct the amplitude-dependent tune-shift one normally tries to avoid that the octupoles drive additional resonances. Here we consider the optimum placement of octupoles that only affects the amplitude-dependent tune-shift, but does not drive fourth-order resonances. The simplest way turns out to place three equally powered octupoles with 60 ° phase advance between adjacent magnets. Using two such octupole triplets separated by a suitable phase advance cancels all fourth-order resonance driving terms and forms a double triplet we call a six-pack. Using three six-packs at places with different ratios of the beta functions allows to independently control all amplitude-dependent tune-shift terms without exciting additional fourth-order resonances in first order of the octupole excitation.
Conservative fourth-order time integration of non-linear dynamic systems
DEFF Research Database (Denmark)
Krenk, Steen
2015-01-01
An energy conserving time integration algorithm with fourth-order accuracy is developed for dynamic systems with nonlinear stiffness. The discrete formulation is derived by integrating the differential state-space equations of motion over the integration time increment, and then evaluating...... the resulting time integrals of the inertia and stiffness terms via integration by parts. This process introduces the time derivatives of the state space variables, and these are then substituted from the original state-space differential equations. The resulting discrete form of the state-space equations...... is a direct fourth-order accurate representation of the original differential equations. This fourth-order form is energy conserving for systems with force potential in the form of a quartic polynomial in the displacement components. Energy conservation for a force potential of general form is obtained...
Lunt, A. J. G.; Xie, M. Y.; Baimpas, N.; Zhang, S. Y.; Kabra, S.; Kelleher, J.; Neo, T. K.; Korsunsky, A. M.
2014-08-01
Yttria Stabilised Zirconia (YSZ) is a tough, phase-transforming ceramic that finds use in a wide range of commercial applications from dental prostheses to thermal barrier coatings. Micromechanical modelling of phase transformation can deliver reliable predictions in terms of the influence of temperature and stress. However, models must rely on the accurate knowledge of single crystal elastic stiffness constants. Some techniques for elastic stiffness determination are well-established. The most popular of these involve exploiting frequency shifts and phase velocities of acoustic waves. However, the application of these techniques to YSZ can be problematic due to the micro-twinning observed in larger crystals. Here, we propose an alternative approach based on selective elastic strain sampling (e.g., by diffraction) of grain ensembles sharing certain orientation, and the prediction of the same quantities by polycrystalline modelling, for example, the Reuss or Voigt average. The inverse problem arises consisting of adjusting the single crystal stiffness matrix to match the polycrystal predictions to observations. In the present model-matching study, we sought to determine the single crystal stiffness matrix of tetragonal YSZ using the results of time-of-flight neutron diffraction obtained from an in situ compression experiment and Finite Element modelling of the deformation of polycrystalline tetragonal YSZ. The best match between the model predictions and observations was obtained for the optimized stiffness values of C11 = 451, C33 = 302, C44 = 39, C66 = 82, C12 = 240, and C13 = 50 (units: GPa). Considering the significant amount of scatter in the published literature data, our result appears reasonably consistent.
Energy Technology Data Exchange (ETDEWEB)
Lunt, A. J. G., E-mail: alexander.lunt@eng.ox.ac.uk; Xie, M. Y.; Baimpas, N.; Korsunsky, A. M. [Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ (United Kingdom); Zhang, S. Y.; Kabra, S.; Kelleher, J. [ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Harwell, Oxford OX11 0QX (United Kingdom); Neo, T. K. [Specialist Dental Group, Mount Elizabeth Orchard, 3 Mount Elizabeth, #08-03/08-08/08-10, Singapore 228510 (Singapore)
2014-08-07
Yttria Stabilised Zirconia (YSZ) is a tough, phase-transforming ceramic that finds use in a wide range of commercial applications from dental prostheses to thermal barrier coatings. Micromechanical modelling of phase transformation can deliver reliable predictions in terms of the influence of temperature and stress. However, models must rely on the accurate knowledge of single crystal elastic stiffness constants. Some techniques for elastic stiffness determination are well-established. The most popular of these involve exploiting frequency shifts and phase velocities of acoustic waves. However, the application of these techniques to YSZ can be problematic due to the micro-twinning observed in larger crystals. Here, we propose an alternative approach based on selective elastic strain sampling (e.g., by diffraction) of grain ensembles sharing certain orientation, and the prediction of the same quantities by polycrystalline modelling, for example, the Reuss or Voigt average. The inverse problem arises consisting of adjusting the single crystal stiffness matrix to match the polycrystal predictions to observations. In the present model-matching study, we sought to determine the single crystal stiffness matrix of tetragonal YSZ using the results of time-of-flight neutron diffraction obtained from an in situ compression experiment and Finite Element modelling of the deformation of polycrystalline tetragonal YSZ. The best match between the model predictions and observations was obtained for the optimized stiffness values of C11 = 451, C33 = 302, C44 = 39, C66 = 82, C12 = 240, and C13 = 50 (units: GPa). Considering the significant amount of scatter in the published literature data, our result appears reasonably consistent.
Hahn, Steven; Arapan, Sergiu; Harmon, Bruce; Eriksson, Olle
2011-03-01
Conventional first principle methods for calculating lattice dynamics are unable to calculate high temperature thermophysical properties of materials containing modes that are entropically stabilized. In this presentation we use a relatively new approach called self-consistent ab initio lattice dynamics (SCAILD) to study the hcp to bcc transition (1530 K) in beryllium. The SCAILD method goes beyond the harmonic approximation to include phonon-phonon interactions and produces a temperature-dependent phonon dispersion. In the high temperature bcc structure, phonon-phonon interactions dynamically stabilize the N-point phonon. Fits to the calculated phonon dispersion were used to determine the temperature dependence of the elastic constants in the hcp and bcc phases. Work at the Ames Laboratory was supported by the Department of Energy-Basic Energy Sciences under Contract No. DE-AC02-07CH11358.
Temperature dependence of bulk modulus and second-order elastic constants
International Nuclear Information System (INIS)
Singh, P.P.; Kumar, Munish
2004-01-01
A simple theoretical model is developed to investigate the temperature dependence of the bulk modulus and second order elastic constants. The method is based on the two different approaches viz. (i) the theory of thermal expansivity formulated by Suzuki, based on the Mie-Gruneisen equation of state, (ii) the theory of high-pressure-high-temperature equation of state formulated by Kumar, based on thermodynamic analysis. The results obtained for a number of crystals viz. NaCl, KCl, MgO and (Mg, Fe) 2 SiO 4 are discussed and compared with the experimental data. It is concluded that the Kumar formulation is far better that the Suzuki theory of thermal expansivity
Seeley-Gilkey coefficients for the fourth-order operators on a Riemannian manifold
International Nuclear Information System (INIS)
Gusynin, V.P.
1989-01-01
A new covariant method for computing the coefficients in the heat kernel expansion is suggested. It allows one to calculate Seeley-Gilkey coefficients for both minimal and nonminimal differential operators acting on a vector bundle over a Riemannian manifold. The coefficients for the fourth-order minimal operators in arbitrary dimension of the space are calculated. In contrast to the second-order operators the coefficients for the fourth-order (and higher) operators turn out to be essentially dependent on the space dimension. The algorithmic character of the method suggested allows one to calculate coefficients by computer using the analytical calculation system. 19 refs.; 1 fig
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Khalil Ben Haddouch
2016-04-01
Full Text Available In this work we will study the eigenvalues for a fourth order elliptic equation with $p(x$-growth conditions $\\Delta^2_{p(x} u=\\lambda |u|^{p(x-2} u$, under Neumann boundary conditions, where $p(x$ is a continuous function defined on the bounded domain with $p(x>1$. Through the Ljusternik-Schnireleman theory on $C^1$-manifold, we prove the existence of infinitely many eigenvalue sequences and $\\sup \\Lambda =+\\infty$, where $\\Lambda$ is the set of all eigenvalues.
Determination of elastic constants of fuels plates based on uranium by ultrasound testing
International Nuclear Information System (INIS)
Moreira Castro, Martin Ignacio
2015-01-01
Current nuclear reactors use as U-235 U-enriched compounds enriched with U-235, requiring U-alloys that increase the amount of atoms available for nuclear fission in a convenient way. This study was carried out on fuel plates manufactured in the Chilean Nuclear Energy Commission, whose cores are composed of a dispersed mixture Al-U_3Si_2 and Al-U_7Mo, with different densities of uranium, covered by a coating of Al6061. The objective was to characterize elastically and classify the fuel plates analyzed. Specifically, five Al-U_3Si_2 fuel plates with 1.7 gU/cm"3, eight A-U_3Si_2 with 3.4 gU/cm"3, five of A-l U_3Si_2 with 4.8 gU/cm"3 were successfully studied. The apparent elastic constants (Young and Shear modules, and Poisson coefficient) were determined in the area where the fuel is located (MEAT) by means of an ultrasound sampling technique, thus being able to characterize them and classify them according to their composition. The behavior of the elastic constants generally shows a tendency to decrease as the amount of U_3Si_2 particles dispersed in the MEAT zone of the fuel plates increases. In addition, the non-destructive test method used made it possible to detect several differences between the fuel plates analyzed, such as the amount of reduction in rolling, among others. Additionally, six experimental fuel miniplates were analyzed whose meat were formed by a dispersion of the Al-UMo type, specifically: two of Al-U_7Mo with 6.0 gU/cm"3, two of Al-U_7Mo with 7.0 gU/ cm"3 and two of Al-U_7Mo with 8.0 gU/cm"3. The response of the U-Mo fuel miniplates against this technique was not good, so several ideas were proposed to improve this situation
Effect of plastic deformation and strain history on X-ray elastic constants
International Nuclear Information System (INIS)
Iadicola, Mark A.; Foecke, Tim
2005-01-01
The use of X-ray diffraction to measure residual stress in a crystalline material is well known. This method is currently being reapplied to the surface measurement of in situ stresses during biaxial straining of sheet metal specimens. This leads to questions of precision and calibration of the method through plastic deformation. Little is known of the change, with plastic work, in the X-ray elastic constants (XECs) that are required by the technique for stress measurement. Experiments to determine the formability of various materials using this stress measurement technique in conjunction with a typical Marciniak test (with the Raghavan variation of specimen shapes) have been performed assuming a constant value for XECs. New results of calibration experiments are presented which admit the possibility of variation of the XECs with plastic strain history and initial texture of the material. Adjustment of the data from the previously performed formability experiments is shown. Additionally, various phenomena are captured including initial yielding, change of XECs with plastic strain level (both with uniaxial and biaxial strain histories), and some of the effects of texture on the technique. This technique has potential application in verification of the assumptions made during other standard testing methods (in-plane biaxial specimen geometries and bulge testing), verifying stress predictions from finite element analyses (i.e. benchmarking experiments such as BM3), analysis of stress states in localized deformation (yield point effects), and tracking of the effect of prestraining on material formability through the process of multistage forming
Korkmaz, Erdal
2017-01-01
In this paper, we give sufficient conditions for the boundedness, uniform asymptotic stability and square integrability of the solutions to a certain fourth order non-autonomous differential equations with delay by using Lyapunov's second method. The results obtained essentially improve, include and complement the results in the literature.
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Erdal Korkmaz
2017-06-01
Full Text Available Abstract In this paper, we give sufficient conditions for the boundedness, uniform asymptotic stability and square integrability of the solutions to a certain fourth order non-autonomous differential equations with delay by using Lyapunov’s second method. The results obtained essentially improve, include and complement the results in the literature.
Multiple periodic solutions for a fourth-order discrete Hamiltonian system
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Yongkun Li
2010-12-01
Full Text Available By means of a three critical points theorem proposed by Brezis and Nirenberg and a general version of Mountain Pass Theorem, we obtain some multiplicity results for periodic solutions of a fourth-order discrete Hamiltonian system Δ4u(t-2+∇ F(t,u(t=0 for all t∈ Z.
International Nuclear Information System (INIS)
Fiedler, B.; Schimming, R.
1983-01-01
The fourth order field equations proposed by TREDER with a linear combination of BACH's tensor and EINSTEIN's tensor on the left-hand side admit static centrally symmetric solutions which are analytical and non-flat in some neighborhood of the centre of symmetry. (author)
Three symmetric positive solutions of fourth-order singular nonlocal boundary value problems
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Fuyi Xu
2011-12-01
Full Text Available In this paper, we study the existence of three positive solutions of fourth-order singular nonlocal boundary value problems. We show that there exist triple symmetric positive solutions by using Leggett-Williams fixed-point theorem. The conclusions in this paper essentially extend and improve some known results.
Sanderse, B.; Verstappen, R.W.C.P.; Koren, B.
2014-01-01
A discretization method for the incompressible Navier–Stokes equations conserving the secondary quantities kinetic energy and vorticity was introduced, besides the primary quantities mass and momentum. This method was extended to fourth order accuracy. In this paper we propose a new consistent
Ramírez Suárez, O. L.; Sparenberg, J.-M.
2017-09-01
We introduce a simplified effective-range function for charged nuclei, related to the modified K matrix but differing from it in several respects. Negative-energy zeros of this function correspond to bound states. Positive-energy zeros correspond to resonances and "echo poles" appearing in elastic-scattering phase-shifts, while its poles correspond to multiple-of-π phase shifts. Padé expansions of this function allow one to parametrize phase shifts on large energy ranges and to calculate resonance and bound-state properties in a very simple way, independently of any potential model. The method is first tested on a d -wave 12C+α potential model. It is shown to lead to a correct estimate of the subthreshold-bound-state asymptotic normalization constant (ANC) starting from the elastic-scattering phase shifts only. Next, the 12C+α experimental p -wave and d -wave phase shifts are analyzed. For the d wave, the relatively large error bars on the phase shifts do not allow one to improve the ANC estimate with respect to existing methods. For the p wave, a value agreeing with the 12C(6Li,d )16O transfer-reaction measurement and with the recent remeasurement of the 16Nβ -delayed α decay is obtained, with improved accuracy. However, the method displays two difficulties: the results are sensitive to the Padé-expansion order and the simplest fits correspond to an imaginary ANC, i.e., to a negative-energy "echo pole," the physical meaning of which is still debatable.
Effect of elastic constants of liquid crystals in their electro-optical properties
Parang, Z.; Ghaffary, T.; Gharahbeigi, M. M.
Recently following the success of the density functional theory (DFT) in obtaining the structure and thermodynamics of homogeneous and inhomogeneous classical systems such as simple fluids, dipolar fluid and binary hard spheres, this theory was also applied to obtain the density profile of a molecular fluid in between hard planar walls by Kalpaxis and Rickayzen. In the theory of molecular fluids, the direct correlation function (DCF) can be used to calculate the equation of state, free energy, phase transition, elastic constants, etc. It is well known that the hard core molecular models play an important role in understanding complex liquids such as liquid crystals. In this paper, a classical fluid of nonspherical molecules is studied. The required homogeneous (DCF) is obtained by solving Orenstein-Zernike (OZ) integral equation numerically. Some of the molecules in the liquid crystals have a sphere shape and this kind of molecular fluid is considered here. The DCF sphere of the molecular fluid is calculated and it will be shown that the results are in good agreement with the pervious works and the results of computer simulation. Finally the electro-optical properties of ellipsoid liquid crystal using DCF of these molecules are calculated.
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Le Riche R.
2010-06-01
Full Text Available A major challenge in the identification of material properties is handling different sources of uncertainty in the experiment and the modelling of the experiment for estimating the resulting uncertainty in the identified properties. Numerous improvements in identification methods have provided increasingly accurate estimates of various material properties. However, characterizing the uncertainty in the identified properties is still relatively crude. Different material properties obtained from a single test are not obtained with the same confidence. Typically the highest uncertainty is associated with respect to properties to which the experiment is the most insensitive. In addition, the uncertainty in different properties can be strongly correlated, so that obtaining only variance estimates may be misleading. A possible approach for handling the different sources of uncertainty and estimating the uncertainty in the identified properties is the Bayesian method. This method was introduced in the late 1970s in the context of identification [1] and has been applied since to different problems, notably identification of elastic constants from plate vibration experiments [2]-[4]. The applications of the method to these classical pointwise tests involved only a small number of measurements (typically ten natural frequencies in the previously cited vibration test which facilitated the application of the Bayesian approach. For identifying elastic constants, full field strain or displacement measurements provide a high number of measured quantities (one measurement per image pixel and hence a promise of smaller uncertainties in the properties. However, the high number of measurements represents also a major computational challenge in applying the Bayesian approach to full field measurements. To address this challenge we propose an approach based on the proper orthogonal decomposition (POD of the full fields in order to drastically reduce their
Gogu, C.; Yin, W.; Haftka, R.; Ifju, P.; Molimard, J.; Le Riche, R.; Vautrin, A.
2010-06-01
A major challenge in the identification of material properties is handling different sources of uncertainty in the experiment and the modelling of the experiment for estimating the resulting uncertainty in the identified properties. Numerous improvements in identification methods have provided increasingly accurate estimates of various material properties. However, characterizing the uncertainty in the identified properties is still relatively crude. Different material properties obtained from a single test are not obtained with the same confidence. Typically the highest uncertainty is associated with respect to properties to which the experiment is the most insensitive. In addition, the uncertainty in different properties can be strongly correlated, so that obtaining only variance estimates may be misleading. A possible approach for handling the different sources of uncertainty and estimating the uncertainty in the identified properties is the Bayesian method. This method was introduced in the late 1970s in the context of identification [1] and has been applied since to different problems, notably identification of elastic constants from plate vibration experiments [2]-[4]. The applications of the method to these classical pointwise tests involved only a small number of measurements (typically ten natural frequencies in the previously cited vibration test) which facilitated the application of the Bayesian approach. For identifying elastic constants, full field strain or displacement measurements provide a high number of measured quantities (one measurement per image pixel) and hence a promise of smaller uncertainties in the properties. However, the high number of measurements represents also a major computational challenge in applying the Bayesian approach to full field measurements. To address this challenge we propose an approach based on the proper orthogonal decomposition (POD) of the full fields in order to drastically reduce their dimensionality. POD is
Line-focus acoustic microscopy of Ti-6242 α/β single colony: determination of elastic constants
International Nuclear Information System (INIS)
Kim, J.-Y.; Yakovlev, V.; Rokhlin, S.I.
2002-01-01
Time-resolved line-focus acoustic microscopy is performed for determining elastic constants of Ti-6242 α/β-single colony and Ti-6 α-phase single crystal. Surface acoustic wave (SAW) velocities are obtained as a function of the propagation angle from measured time-delays of SAW signals. The propagation of surface waves in a semi-infinite half space formed by anisotropic layers inclined arbitrarily to the sample surface is studied to model a quasi-random lamellar structure of the Ti-6242 α/β-single colony. Effective elastic constants of the multilayered structure are derived and verified through the comparison with exact ones, based on which SAW velocities in non-principal planes are calculated. Effective and constituent elastic constants of the α/β-single colony and the α-phase single crystal are inversely determined from the measured and calculated SAW velocities. The α- and β-phase elastic constants from the α/β-single colony so determined are compared with those from the α-single crystal and data in the literature
Lattice Boltzmann method for bosons and fermions and the fourth-order Hermite polynomial expansion.
Coelho, Rodrigo C V; Ilha, Anderson; Doria, Mauro M; Pereira, R M; Aibe, Valter Yoshihiko
2014-04-01
The Boltzmann equation with the Bhatnagar-Gross-Krook collision operator is considered for the Bose-Einstein and Fermi-Dirac equilibrium distribution functions. We show that the expansion of the microscopic velocity in terms of Hermite polynomials must be carried to the fourth order to correctly describe the energy equation. The viscosity and thermal coefficients, previously obtained by Yang et al. [Shi and Yang, J. Comput. Phys. 227, 9389 (2008); Yang and Hung, Phys. Rev. E 79, 056708 (2009)] through the Uehling-Uhlenbeck approach, are also derived here. Thus the construction of a lattice Boltzmann method for the quantum fluid is possible provided that the Bose-Einstein and Fermi-Dirac equilibrium distribution functions are expanded to fourth order in the Hermite polynomials.
Seeley-Gilkey coefficients for fourth-order operators on Riemannian manifold
International Nuclear Information System (INIS)
Gusynin, V.P.
1990-01-01
The covariant pseudodifferential-operator method of Widom is developed for computing the coefficients in the heat kernel expansion. It allows one to calculate Seeley-Gilkey coefficients for both minimal and nonminimal differential operators acting on a vector bundle over a riemannian manifold. The coefficients for the fourth-order minimal operators in arbitrary dimensions of space are calculated. In contrast to the second-order operators the coefficients for the fourth-order (and higher) operators turn out to be essentially dependent on the space dimension. The algorithmic character of the method allows one to calculate the coefficients by computer using an analytical calculation system. The method also permits a simple generalization to manifolds with torsion and supermanifolds. (orig.)
Fourth-order poisson solver for the simulation of bounded plasmas
International Nuclear Information System (INIS)
Knorr, G.; Joyce, G.; Marcus, A.J.
1980-01-01
The solution of the two-dimensional Poisson equation in a rectangle with periodic boundaries in one direction and Dirichlet or Neumann boundaries in the other can be handled by a Fast Fourier Transform in one dimension and a fast nonperiodic procedure such as splines in the other. Such a solution is necessary for the simulation of semiperiodic plasma systems. A method is presented which is direct and of fourth order in both the electric potential and the electric fields
Inflation from M-theory with fourth-order corrections and large extra dimensions
International Nuclear Information System (INIS)
Maeda, Kei-ichi; Ohta, Nobuyoshi
2004-01-01
We study inflationary solutions in the M-theory. Including the fourth-order curvature correction terms, we find three generalized de Sitter solutions, in which our 3-space expands exponentially. Taking one of the solutions, we propose an inflationary scenario of the early universe. This provides us a natural explanation for large extra dimensions in a brane world, and suggests some connection between the 60 e-folding expansion of inflation and TeV gravity based on the large extra dimensions
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Qiong Liu
2012-01-01
Full Text Available We study the following fourth-order elliptic equations: Δ2+Δ=(,,∈Ω,=Δ=0,∈Ω, where Ω⊂ℝ is a bounded domain with smooth boundary Ω and (, is asymptotically linear with respect to at infinity. Using an equivalent version of Cerami's condition and the symmetric mountain pass lemma, we obtain the existence of multiple solutions for the equations.
On one two-point BVP for the fourth order linear ordinary differential equation
Czech Academy of Sciences Publication Activity Database
Mukhigulashvili, Sulkhan; Manjikashvili, M.
2017-01-01
Roč. 24, č. 2 (2017), s. 265-275 ISSN 1072-947X Institutional support: RVO:67985840 Keywords : fourth order linear ordinary differential equations * two-point boundary value problems Subject RIV: BA - General Mathematics OBOR OECD: Applied mathematics Impact factor: 0.290, year: 2016 https://www.degruyter.com/view/j/gmj.2017.24.issue-2/gmj-2016-0077/gmj-2016-0077.xml
Special polynomials associated with the fourth order analogue to the Painleve equations
International Nuclear Information System (INIS)
Kudryashov, Nikolai A.; Demina, Maria V.
2007-01-01
Rational solutions of the fourth order analogue to the Painleve equations are classified. Special polynomials associated with the rational solutions are introduced. The structure of the polynomials is found. Formulae for their coefficients and degrees are derived. It is shown that special solutions of the Fordy-Gibbons, the Caudrey-Dodd-Gibbon and the Kaup-Kupershmidt equations can be expressed through solutions of the equation studied
On one two-point BVP for the fourth order linear ordinary differential equation
Czech Academy of Sciences Publication Activity Database
Mukhigulashvili, Sulkhan; Manjikashvili, M.
2017-01-01
Roč. 24, č. 2 (2017), s. 265-275 ISSN 1072-947X Institutional support: RVO:67985840 Keywords : fourth order linear ordinary differential equations * two-point boundary value problems Subject RIV: BA - General Mathematics OBOR OECD: Applied mathematics Impact factor: 0.290, year: 2016 https://www.degruyter.com/view/j/gmj.2017.24.issue-2/gmj-2016-0077/gmj-2016-0077. xml
Infinitely many solutions for a fourth-order boundary-value problem
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Seyyed Mohsen Khalkhali
2012-09-01
Full Text Available In this article we consider the existence of infinitely many solutions to the fourth-order boundary-value problem $$displaylines{ u^{iv}+alpha u''+eta(x u=lambda f(x,u+h(u,quad xin]0,1[cr u(0=u(1=0,cr u''(0=u''(1=0,. }$$ Our approach is based on variational methods and critical point theory.
Energy Technology Data Exchange (ETDEWEB)
Brown, Judith Alice [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Steck, Daniel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Brown, Judith Alice [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Long, Kevin Nicholas [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2017-08-01
Previous numerical studies of Sylgard filled with glass microballoons (GMB) have relied on various microstructure idealizations to achieve a large range of volume fractions with high mesh quality. This study investigates how different microstructure idealizations and constraints affect the apparent homogenized elastic constants in the virgin state of the material, in which all GMBs are intact and perfectly bonded to the Sylgard matrix, and in the fully damaged state of the material in which all GMBs are destroyed. In the latter state, the material behaves as an elastomeric foam. Four microstructure idealizations are considered relating to how GMBs are packed into a representative volume element (RVE): (1) no boundary penetration nor GMB-GMB overlap, (2) GMB-GMB overlap, (3) boundary penetration, and (4) boundary penetration and GMB-GMB overlap. First order computational homogenization with kinematically uniform displacement boundary conditions (KUBCs) was employed to determine the homogenized (apparent) bulk and shear moduli for the four microstructure idealizations in the intact and fully broken GMB material states. It was found that boundary penetration has a significant effect on the shear modulus for microstructures with intact GMBs, but that neither boundary penetration nor GMB overlap have a significant effect on homogenized properties for microstructures with fully broken GMBs. The primary conclusion of the study is that future investigations into Sylgard/GMB micromechanics should either force GMBs to stay within the RVE fully and/or use periodic BCs (PBCs) to eliminate the boundary penetration issues. The implementation of PBCs requires the improvement of existing tools in Sandia’s Sierra/SM code.
Thermal expansion and temperature variation of elastic constants of Li(H,D) and Na(H,D) systems
International Nuclear Information System (INIS)
Islam, A.K.M.A.; Hoque, M.T.
1994-11-01
An analysis of thermal expansion of Li(H,D) systems up to melting temperature has been performed using the theory of anharmonic lattice. The study has for the first time been extended to Na(H,D) systems where very little or no data are available. The calculated lattice constants of Li(H,D) systems show quite good agreement with experiment. The success of the present calculation with Li(H,D) and room temperature lattice constant data for Na(H,D) given an indication of the reliability of the computed lattice constants and thermal expansion coefficients for Na(H,D) systems. The study also allows us to predict the hitherto unknown lattice constants of Na(H,D) crystal at 0K. The temperature dependence of elastic constants for Li(H,D) systems has also been evaluated. Comparison with measurements shows the reliability of the present calculations. (author). 45 refs, 4 figs
International Nuclear Information System (INIS)
Iadicola, Mark A.; Gnäupel-Herold, Thomas H.
2012-01-01
Accurate measurement of stresses by X-ray diffraction requires accurate X-ray elastic constants. Calibration experiments are one method to determine these for a specific material in a specific condition. In this paper, uniaxial tension experiments are used to investigate the variation of these constants after uniaxial and equal-biaxial plastic deformation for an aluminum alloy (AA5754-O) of interest to the automotive industry. These data are critical for accurate measurement of the biaxial mechanical properties of the material using a recent experimental method combining specialized sheet metal forming equipment with portable X-ray diffraction equipment. The measured effective X-ray elastic constants show some minor variation with increased plastic deformation, and this behavior was found to be consistent for both uniaxially and equal-biaxially strained samples. The use of two average values for effective X-ray elastic constants, one in the rolling direction and one transverse to the rolling direction of the sheet material, is shown to be of sufficient accuracy for the combined tests of interest. Comparison of uniaxial data measured using X-ray diffraction and standard methods show good agreement, and biaxial stress–strain results show good repeatability. Additionally, the calibration data show some non-linear behavior, which is analyzed in regards to crystallographic texture and intergranular stress effects. The non-linear behavior is found to be the result of intergranular stresses based on comparison with additional measurements using other X-ray diffraction equipment and neutron diffraction.
Barkaoui, Abdelwahed; Chamekh, Abdessalem; Merzouki, Tarek; Hambli, Ridha; Mkaddem, Ali
2014-03-01
The complexity and heterogeneity of bone tissue require a multiscale modeling to understand its mechanical behavior and its remodeling mechanisms. In this paper, a novel multiscale hierarchical approach including microfibril scale based on hybrid neural network (NN) computation and homogenization equations was developed to link nanoscopic and macroscopic scales to estimate the elastic properties of human cortical bone. The multiscale model is divided into three main phases: (i) in step 0, the elastic constants of collagen-water and mineral-water composites are calculated by averaging the upper and lower Hill bounds; (ii) in step 1, the elastic properties of the collagen microfibril are computed using a trained NN simulation. Finite element calculation is performed at nanoscopic levels to provide a database to train an in-house NN program; and (iii) in steps 2-10 from fibril to continuum cortical bone tissue, homogenization equations are used to perform the computation at the higher scales. The NN outputs (elastic properties of the microfibril) are used as inputs for the homogenization computation to determine the properties of mineralized collagen fibril. The mechanical and geometrical properties of bone constituents (mineral, collagen, and cross-links) as well as the porosity were taken in consideration. This paper aims to predict analytically the effective elastic constants of cortical bone by modeling its elastic response at these different scales, ranging from the nanostructural to mesostructural levels. Our findings of the lowest scale's output were well integrated with the other higher levels and serve as inputs for the next higher scale modeling. Good agreement was obtained between our predicted results and literature data. Copyright © 2013 John Wiley & Sons, Ltd.
The fourth-order non-linear sigma models and asymptotic freedom in four dimensions
International Nuclear Information System (INIS)
Buchbinder, I.L.; Ketov, S.V.
1991-01-01
Starting with the most general Lagrangian of the fourth-order non-linear sigma model in four space-time dimensions, we calculate the one-loop, on-shell ultra-violet-divergent part of the effective action. The formalism is based on the background field method and the generalised Schwinger-De Witt technique. The multiplicatively renormalisable case is investigated in some detail. The renormalisation group equations are obtained, and the conditions for a realisation of asymptotic freedom are considered. (orig.)
Calatroni, Luca
2013-08-01
We present directional operator splitting schemes for the numerical solution of a fourth-order, nonlinear partial differential evolution equation which arises in image processing. This equation constitutes the H -1-gradient flow of the total variation and represents a prototype of higher-order equations of similar type which are popular in imaging for denoising, deblurring and inpainting problems. The efficient numerical solution of this equation is very challenging due to the stiffness of most numerical schemes. We show that the combination of directional splitting schemes with implicit time-stepping provides a stable and computationally cheap numerical realisation of the equation.
Lie symmetry analysis and conservation laws for the time fractional fourth-order evolution equation
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Wang Li
2017-06-01
Full Text Available In this paper, we study Lie symmetry analysis and conservation laws for the time fractional nonlinear fourth-order evolution equation. Using the method of Lie point symmetry, we provide the associated vector fields, and derive the similarity reductions of the equation, respectively. The method can be applied wisely and efficiently to get the reduced fractional ordinary differential equations based on the similarity reductions. Finally, by using the nonlinear self-adjointness method and Riemann-Liouville time-fractional derivative operator as well as Euler-Lagrange operator, the conservation laws of the equation are obtained.
Nuclear axial current operators to fourth order in chiral effective field theory
Energy Technology Data Exchange (ETDEWEB)
Krebs, H., E-mail: hermann.krebs@rub.de [Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Epelbaum, E., E-mail: evgeny.epelbaum@rub.de [Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93016 (United States); Meißner, U.-G., E-mail: meissner@hiskp.uni-bonn.de [Helmholtz-Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Universität Bonn, D-53115 Bonn (Germany); Institut für Kernphysik, Institute for Advanced Simulation, and Jülich Center for Hadron Physics, Forschungszentrum Jülich, D-52425 Jülich (Germany); JARA - High Performance Computing, Forschungszentrum Jülich, D-52425 Jülich (Germany)
2017-03-15
We present the complete derivation of the nuclear axial charge and current operators as well as the pseudoscalar operators to fourth order in the chiral expansion relative to the dominant one-body contribution using the method of unitary transformation. We demonstrate that the unitary ambiguity in the resulting operators can be eliminated by the requirement of renormalizability and by matching of the pion-pole contributions to the nuclear forces. We give expressions for the renormalized single-, two- and three-nucleon contributions to the charge and current operators and pseudoscalar operators including the relevant relativistic corrections. We also verify explicitly the validity of the continuity equation.
Some existence results for a fourth order equation involving critical exponent
Ben-Ayed, M; Hammami, M
2003-01-01
In this paper a fourth order equation involving critical growth is considered under the Navier boundary condition: DELTA sup 2 u = Ku sup p , u > 0 in OMEGA, u = DELTA u = 0 on partial deriv OMEGA, where K is a positive function, OMEGA is a bounded smooth domain in R sup n , n >= 5 and p + 1 2n/(n - 4) is the critical Sobolev exponent. We give some topological conditions on K to ensure the existence of solutions. Our methods involve the study of the critical points at infinity and their contribution to the topology of the level sets of the associated Euler Lagrange functional.
Calatroni, Luca; Dü ring, Bertram; Schö nlieb, Carola-Bibiane
2013-01-01
We present directional operator splitting schemes for the numerical solution of a fourth-order, nonlinear partial differential evolution equation which arises in image processing. This equation constitutes the H -1-gradient flow of the total variation and represents a prototype of higher-order equations of similar type which are popular in imaging for denoising, deblurring and inpainting problems. The efficient numerical solution of this equation is very challenging due to the stiffness of most numerical schemes. We show that the combination of directional splitting schemes with implicit time-stepping provides a stable and computationally cheap numerical realisation of the equation.
Positive solutions with changing sign energy to a nonhomogeneous elliptic problem of fourth order
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M.Talbi
2011-01-01
Full Text Available In this paper, we study the existence for two positive solutions toa nonhomogeneous elliptic equation of fourth order with a parameter lambda such tha 0 < lambda < lambda^. The first solution has a negative energy while the energy of the second one is positive for 0 < lambda < lambda_0 and negative for lambda_0 < lambda < lambda^. The values lambda_0 and lambda^ are given under variational form and we show that every corresponding critical point is solution of the nonlinear elliptic problem (with a suitable multiplicative term.
Asymptotically stable fourth-order accurate schemes for the diffusion equation on complex shapes
International Nuclear Information System (INIS)
Abarbanel, S.; Ditkowski, A.
1997-01-01
An algorithm which solves the multidimensional diffusion equation on complex shapes to fourth-order accuracy and is asymptotically stable in time is presented. This bounded-error result is achieved by constructing, on a rectangular grid, a differentiation matrix whose symmetric part is negative definite. The differentiation matrix accounts for the Dirichlet boundary condition by imposing penalty-like terms. Numerical examples in 2-D show that the method is effective even where standard schemes, stable by traditional definitions, fail. The ability of the paradigm to be applied to arbitrary geometric domains is an important feature of the algorithm. 5 refs., 14 figs
Symmetry Reduction and Cauchy Problems for a Class of Fourth-Order Evolution Equations
International Nuclear Information System (INIS)
Li Jina; Zhang Shunli
2008-01-01
We exploit higher-order conditional symmetry to reduce initial-value problems for evolution equations to Cauchy problems for systems of ordinary differential equations (ODEs). We classify a class of fourth-order evolution equations which admit certain higher-order generalized conditional symmetries (GCSs) and give some examples to show the main reduction procedure. These reductions cannot be derived within the framework of the standard Lie approach, which hints that the technique presented here is something essential for the dimensional reduction of evolution equations
Crisis induced intermittency in a fourth-order autonomous electric circuit
International Nuclear Information System (INIS)
Stouboulos, I.N.; Miliou, A.N.; Valaristos, A.P.; Kyprianidis, I.M.; Anagnostopoulos, A.N.
2007-01-01
The chaotic dynamics of a fourth-order autonomous nonlinear electric circuit has been studied. The circuit consists of two active elements, one linear negative conductance and one nonlinear resistor exhibiting a symmetrical piecewise-linear v-i characteristic and two capacitances C 1 and C 2 , which serve as the control parameters of the system. Experimental time series and the corresponding phase portraits were used to register the intermittent behaviour of the corresponding dynamical system between two interacting subattractors. The distribution of the times τ, between successive transitions from the one subattractor to the other indicates that a crisis induced intermittency occurs in the studied circuit
Elastic constants of the hard disc system in the self-consistent free volume approximation
International Nuclear Information System (INIS)
Wojciechowski, K.W.
1990-09-01
Elastic moduli of the two dimensional hard disc crystal are determined exactly within the Kirkwood self-consistent free volume approximation and compared with the Monte Carlo simulation results. (author). 22 refs, 1 fig., 1 tab
The elastic constants and anisotropy of superconducting MgCNi3 and CdCNi3 under different pressure
Feng, Huifang
2013-11-23
The second-order elastic constants (SOECs) and third-order elastic constants (TOECs) of MgCNi3 and CdCNi3 are presented by using first-principles methods combined with homogeneous deformation theory. The Voigt-Reuss-Hill (VRH) approximation are used to calculate the bulk modulus B, shear modulus G, averaged Young\\'s modulus E and Poisson\\'s ratio ν for polycrystals and these effective modulus are consistent with the experiments. The SOECs under different pressure of MgCNi3 and CdCNi3 are also obtained based on the TOECs. Furthermore, the Zener anisotropy factor, Chung-Buessem anisotropy index, and the universal anisotropy index are used to describe the anisotropy of MgCNi3 and CdCNi3. The anisotropy of Young\\'s modulus of single-crystal under different pressure is also presented. © 2013 Springer Science+Business Media New York.
Hao, Wenfeng; Liu, Ye; Huang, Xinrong; Liu, Yinghua; Zhu, Jianguo
2018-06-01
In this work, the elastic constants of 3D four directional cylindrical braided composite shafts were predicted using analytical and numerical methods. First, the motion rule of yarn carrier of 3D four directional cylindrical braided composite shafts was analyzed, and the horizontal projection of yarn motion trajectory was obtained. Then, the geometry models of unit-cells with different braiding angles and fiber volume contents were built up, and the meso-scale models of 3D cylindrical braided composite shafts were obtained. Finally, the effects of braiding angles and fiber volume contents on the elastic constants of 3D braided composite shafts were analyzed theoretically and numerically. These results play a crucial role in investigating the mechanical properties of 3D 4-directional braided composites shafts.
Motsepa, Tanki; Aziz, Taha; Fatima, Aeeman; Khalique, Chaudry Masood
2018-03-01
The optimal investment-consumption problem under the constant elasticity of variance (CEV) model is investigated from the perspective of Lie group analysis. The Lie symmetry group of the evolution partial differential equation describing the CEV model is derived. The Lie point symmetries are then used to obtain an exact solution of the governing model satisfying a standard terminal condition. Finally, we construct conservation laws of the underlying equation using the general theorem on conservation laws.
Fourth-order Perturbed Eigenvalue Equation for Stepwise Damage Detection of Aeroplane Wing
Directory of Open Access Journals (Sweden)
Wong Chun Nam
2016-01-01
Full Text Available Perturbed eigenvalue equations up to fourth-order are established to detect structural damage in aeroplane wing. Complete set of perturbation terms including orthogonal and non-orthogonal coefficients are computed using perturbed eigenvalue and orthonormal equations. Then the perturbed eigenparameters are optimized using BFGS approach. Finite element model with small to large stepwise damage is used to represent actual aeroplane wing. In small damaged level, termination number is the same for both approaches, while rms errors and termination d-norms are very close. For medium damaged level, termination number is larger for third-order perturbation with lower d-norm and smaller rms error. In large damaged level, termination number is much larger for third-order perturbation with same d-norm and larger rms error. These trends are more significant as the damaged level increases. As the stepwise damage effect increases with damage level, the increase in stepwise effect leads to the increase in model order. Hence, fourth-order perturbation is more accurate to estimate the model solution.
Sparse Method for Direction of Arrival Estimation Using Denoised Fourth-Order Cumulants Vector.
Fan, Yangyu; Wang, Jianshu; Du, Rui; Lv, Guoyun
2018-06-04
Fourth-order cumulants (FOCs) vector-based direction of arrival (DOA) estimation methods of non-Gaussian sources may suffer from poor performance for limited snapshots or difficulty in setting parameters. In this paper, a novel FOCs vector-based sparse DOA estimation method is proposed. Firstly, by utilizing the concept of a fourth-order difference co-array (FODCA), an advanced FOCs vector denoising or dimension reduction procedure is presented for arbitrary array geometries. Then, a novel single measurement vector (SMV) model is established by the denoised FOCs vector, and efficiently solved by an off-grid sparse Bayesian inference (OGSBI) method. The estimation errors of FOCs are integrated in the SMV model, and are approximately estimated in a simple way. A necessary condition regarding the number of identifiable sources of our method is presented that, in order to uniquely identify all sources, the number of sources K must fulfill K ≤ ( M 4 - 2 M 3 + 7 M 2 - 6 M ) / 8 . The proposed method suits any geometry, does not need prior knowledge of the number of sources, is insensitive to associated parameters, and has maximum identifiability O ( M 4 ) , where M is the number of sensors in the array. Numerical simulations illustrate the superior performance of the proposed method.
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Rui Wang
2017-10-01
Full Text Available We establish a relation between the equation of state of nuclear matter and the fourth-order symmetry energy asym,4(A of finite nuclei in a semi-empirical nuclear mass formula by self-consistently considering the bulk, surface and Coulomb contributions to the nuclear mass. Such a relation allows us to extract information on nuclear matter fourth-order symmetry energy Esym,4(ρ0 at normal nuclear density ρ0 from analyzing nuclear mass data. Based on the recent precise extraction of asym,4(A via the double difference of the “experimental” symmetry energy extracted from nuclear masses, for the first time, we estimate a value of Esym,4(ρ0=20.0±4.6 MeV. Such a value of Esym,4(ρ0 is significantly larger than the predictions from mean-field models and thus suggests the importance of considering the effects of beyond the mean-field approximation in nuclear matter calculations.
Directory of Open Access Journals (Sweden)
Yunjiao Bai
2015-01-01
Full Text Available The traditional fourth-order nonlinear diffusion denoising model suffers the isolated speckles and the loss of fine details in the processed image. For this reason, a new fourth-order partial differential equation based on the patch similarity modulus and the difference curvature is proposed for image denoising. First, based on the intensity similarity of neighbor pixels, this paper presents a new edge indicator called patch similarity modulus, which is strongly robust to noise. Furthermore, the difference curvature which can effectively distinguish between edges and noise is incorporated into the denoising algorithm to determine the diffusion process by adaptively adjusting the size of the diffusion coefficient. The experimental results show that the proposed algorithm can not only preserve edges and texture details, but also avoid isolated speckles and staircase effect while filtering out noise. And the proposed algorithm has a better performance for the images with abundant details. Additionally, the subjective visual quality and objective evaluation index of the denoised image obtained by the proposed algorithm are higher than the ones from the related methods.
International Nuclear Information System (INIS)
Liu, Rong-Xiang; Tian, Bo; Liu, Li-Cai; Qin, Bo; Lü, Xing
2013-01-01
In this paper we investigate a fourth-order dispersive nonlinear Schrödinger equation, which governs the dynamics of a one-dimensional anisotropic Heisenberg ferromagnetic spin chain with the octuple–dipole interaction in condensed-matter physics as well as the alpha helical proteins with higher-order excitations and interactions in biophysics. Beyond the existing constraint, upon the introduction of an auxiliary function, bilinear forms and N-soliton solutions are constructed with the Hirota method. Asymptotic analysis on the two-soliton solutions indicates that the soliton interactions are elastic. Soliton velocity varies linearly with the coefficient of discreteness and higher-order magnetic interactions. Bound-state solitons can also exist under certain conditions. Period of a bound-state soliton is inversely correlated to the coefficient of discreteness and higher-order magnetic interactions. Interactions among the three solitons are all pairwise elastic
National Research Council Canada - National Science Library
Gibou, Frederic; Fedkiw, Ronald
2004-01-01
In this paper, the authors first describe a fourth order accurate finite difference discretization for both the Laplace equation and the heat equation with Dirichlet boundary conditions on irregular domains...
International Nuclear Information System (INIS)
Giri, Dilip Kumar; Gupta, P S
2003-01-01
The concept of fourth-order squeezing of the electromagnetic field is investigated in the fundamental mode in spontaneous and stimulated four- and six-wave mixing processes under the short-time approximation based on a fully quantum mechanical approach. The coupled Heisenberg equations of motion involving real and imaginary parts of the quadrature operators are established. The possibility of obtaining fourth-order squeezing is studied. The dependence of fourth-order squeezing on the number of photons is also investigated. It is shown that fourth-order squeezing, which is a higher-order squeezing, allows a much larger fractional noise reduction than lower-order squeezing. It is shown that squeezing is greater in a stimulated process than the corresponding squeezing in spontaneous interaction. The conditions for obtaining maximum and minimum squeezing are obtained. We have also established the non-classical nature of squeezed radiation using the Glauber-Sudarshan representation
Directory of Open Access Journals (Sweden)
Mabrouk Briki
2016-05-01
Full Text Available In this paper, a fourth-order boundary value problem on the half-line is considered and existence of solutions is proved using a minimization principle and the mountain pass theorem.
International Nuclear Information System (INIS)
Wilson, S.; Silver, D.M.
1979-01-01
Third-order diagrammatic perturbation theory provides a simple and accurate description of the electronic structure of atoms and molecules beyond that afforded by independent electron models. The largest corrections to such treatments, the fourth-order terms, are presented and discussed. All of the diagrams, which arise when the closed-shell Hartree--Fock function is utilized as a reference function, are given through fourth order. 18 references
Pure perceptual-based learning of second-, third-, and fourth-order sequential probabilities.
Remillard, Gilbert
2011-07-01
There is evidence that sequence learning in the traditional serial reaction time task (SRTT), where target location is the response dimension, and sequence learning in the perceptual SRTT, where target location is not the response dimension, are handled by different mechanisms. The ability of the latter mechanism to learn sequential contingencies that can be learned by the former mechanism was examined. Prior research has established that people can learn second-, third-, and fourth-order probabilities in the traditional SRTT. The present study reveals that people can learn such probabilities in the perceptual SRTT. This suggests that the two mechanisms may have similar architectures. A possible neural basis of the two mechanisms is discussed.
The de Sitter spacetime as an attractor solution in fourth-order gravity
International Nuclear Information System (INIS)
Schmidt, H.-J.
1988-01-01
We investigate the general vacuum solution of fourth-order gravity, and include the Bach tensor. For L 2 = 1.3μR 2 + 1/2αC 2 the expanding de Sitter spacetime is an attractor in the set of axially symmetric Bianchi type-I models if and only if αμ ≤ 0 or α > 4μ holds. It will be argued that this result holds true for a large class of inhomogeneous models. As a byproduct, a new closed-form cosmological solution, is obtained. It is also shown that the de Sitter spacetime is an attractor for the Bach-Einstein gravity with a minimally coupled scalar field φ. Specialised to Einstein gravity (i.e. α = 0 above) this conformal equivalence remains a non-trivial one. (author)
International Nuclear Information System (INIS)
Cullen, D.E.; Perkins, S.T.
1977-01-01
Multi-group averaged reaction rates and transfer matrices were calculated for charged particle induced elastic nuclear (plus interference) scattering. Results are presented using a ten group structure for all twenty-five permutations of projectile and target for the following charged particles: p, d, t, 3 He and alpha. Transfer matrices are presented in a simplified form for both incident projectile and the knock-ons; these matrices explicitly conserve energy
Bhatia, K. G.; Vyas, S. M.; Patel, A. B.; Bhatt, N. K.; Vyas, P. R.; Gohel, V. B.
2018-05-01
Using parameter-free (first principles local) pseudopotential, in the present communication we have calculated dynamical elastic constants (C11, C12 and C44), bulk modulus (B), shear modulus (µp), Young's modulus (Y) and Poisson's ratio (σ) in long wavelength limit. Our computed results are well agreed for C44 and B with experiment and with other theoretical results obtained within framework of second order perturbation pseudopotential theory. From the present study we conclude that pseudopotential used contain s-p hybridization and no extra term is required to account core-core repulsion.
Sherrit, Stewart; Masys, Tony J; Wiederick, Harvey D; Mukherjee, Binu K
2011-09-01
We present a procedure for determining the reduced piezoelectric, dielectric, and elastic coefficients for a C(∞) material, including losses, from a single disk sample. Measurements have been made on a Navy III lead zirconate titanate (PZT) ceramic sample and the reduced matrix of coefficients for this material is presented. In addition, we present the transform equations, in reduced matrix form, to other consistent material constant sets. We discuss the propagation of errors in going from one material data set to another and look at the limitations inherent in direct calculations of other useful coefficients from the data.
Ultrasonic measurement of elastic constants at temperatures from 20 to 11000C
International Nuclear Information System (INIS)
Moyer, M.W.; Hammond, J.P.
1976-09-01
Measurements of the elastic moduli at temperatures from 20 to 1100 0 C of a number of materials of interest in the Liquid Metal Fast Breeder Reactor and the High Temperature Gas Reactor were accomplished using acoustic techniques. A two-step process was required to complete the measurements. First, the acoustic velocities were measured accurately on bulk samples at room temperature, then a wire sample was used to make elevated-temperature measurements. A computer was used to calculate the moduli and plot the data. A detailed summary has been made of the sources of error and a calculation of the precision of the measurements is given
Elastic constants and the structural phase transition in La2-xSrxCuO4
International Nuclear Information System (INIS)
Sarrao, J.L.; Lei, Ming; Stekel, A.; Bell, T.M.; Leisure, R.G.; Sham, L.J.; Visscher, W.M.; Migliori, A.; Bussmann-Holder, A.; Tanaka, I.; Kojima, H.
1991-01-01
Resonant ultrasound spectroscopy is used to measure the temperature dependence of all six elastic moduli of La 2-x Sr x CuO 4 . A giant softening (> 50% reduction) in the in-plane shear modulus, c 66 , is observed and is attributed to the tetragonal-orthorhombic structural phase transition in this material. This phase transition and the corresponding softening is examined with a simple anharmonic mechanical model and a macroscopic Ginsburg-Landau formalism exploiting the full symmetry of the crystal. 16 refs., 5 figs
Lucchetti, Liana; Fraccia, Tommaso P; Ciciulla, Fabrizio; Bellini, Tommaso
2017-07-10
Throughout the whole history of liquid crystals science, the balancing of intrinsic elasticity with coupling to external forces has been the key strategy for most application and investigation. While the coupling of the optical field to the nematic director is at the base of a wealth of thoroughly described optical effects, a significant variety of geometries and materials have not been considered yet. Here we show that by adopting a simple cell geometry and measuring the optically induced birefringence, we can readily extract the twist elastic coefficient K 22 of thermotropic and lyotropic chiral nematics (N*). The value of K 22 we obtain for chiral doped 5CB thermotropic N* well matches those reported in the literature. With this same strategy, we could determine for the first time K 22 of the N* phase of concentrated aqueous solutions of DNA oligomers, bypassing the limitations that so far prevented measuring the elastic constants of this class of liquid crystalline materials. The present study also enlightens the significant nonlinear optical response of DNA liquid crystals.
Berryman, James G
2011-04-01
Methods for computing Hashin-Shtrikman bounds and related self-consistent estimates of elastic constants for polycrystals composed of crystals having orthorhombic symmetry have been known for about three decades. However, these methods are underutilized, perhaps because of some perceived difficulties with implementing the necessary computational procedures. Several simplifications of these techniques are introduced, thereby reducing the overall computational burden, as well as the complications inherent in mapping out the Hashin-Shtrikman bounding curves. The self-consistent estimates of the effective elastic constants are very robust, involving a quickly converging iteration procedure. Once these self-consistent values are known, they may then be used to speed up the computations of the Hashin-Shtrikman bounds themselves. It is shown furthermore that the resulting orthorhombic polycrystal code can be used as well to compute both bounds and self-consistent estimates for polycrystals of higher-symmetry tetragonal, hexagonal, and cubic (but not trigonal) materials. The self-consistent results found this way are shown to be the same as those obtained using the earlier methods, specifically those methods designed specially for each individual symmetry type. But the Hashin-Shtrikman bounds found using the orthorhombic code are either the same or (more typically) tighter than those found previously for these special cases (i.e., tetragonal, hexagonal, and cubic). The improvement in the Hashin-Shtrikman bounds is presumably due to the additional degrees of freedom introduced into the available search space.
Energy Technology Data Exchange (ETDEWEB)
Berryman, J. G.
2011-02-01
Methods for computing Hashin-Shtrikman bounds and related self-consistent estimates of elastic constants for polycrystals composed of crystals having orthorhombic symmetry have been known for about three decades. However, these methods are underutilized, perhaps because of some perceived difficulties with implementing the necessary computational procedures. Several simplifications of these techniques are introduced, thereby reducing the overall computational burden, as well as the complications inherent in mapping out the Hashin-Shtrikman bounding curves. The self-consistent estimates of the effective elastic constants are very robust, involving a quickly converging iteration procedure. Once these self-consistent values are known, they may then be used to speed up the computations of the Hashin-Shtrikman bounds themselves. It is shown furthermore that the resulting orthorhombic polycrystal code can be used as well to compute both bounds and self-consistent estimates for polycrystals of higher-symmetry tetragonal, hexagonal, and cubic (but not trigonal) materials. The self-consistent results found this way are shown to be the same as those obtained using the earlier methods, specifically those methods designed specially for each individual symmetry type. But the Hashin-Shtrikman bounds found using the orthorhombic code are either the same or (more typically) tighter than those found previously for these special cases (i.e., tetragonal, hexagonal, and cubic). The improvement in the Hashin-Shtrikman bounds is presumably due to the additional degrees of freedom introduced into the available search space.
Elastic constants of non-modulated Ni-Mn-Ga martensite
Czech Academy of Sciences Publication Activity Database
Sedlák, Petr; Seiner, Hanuš; Bodnárová, Lucie; Heczko, Oleg; Landa, Michal
2017-01-01
Roč. 136, July (2017), s. 20-23 ISSN 1359-6462 R&D Projects: GA ČR GA17-00062S Institutional support: RVO:61388998 ; RVO:68378271 Keywords : acoustic methods * elastic behavior * ferromagnetic shape memory alloys * martensitic phase transformation Subject RIV: BM - Solid Matter Physics ; Magnetism; BM - Solid Matter Physics ; Magnetism (FZU-D) OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.); Condensed matter physics (including formerly solid state physics, supercond.) (FZU-D) Impact factor: 3.747, year: 2016 http://ac.els-cdn.com/S1359646217301768/1-s2.0-S1359646217301768-main.pdf?_tid=9b99b306-4a83-11e7-8ec6-00000aacb35e&acdnat=1496731657_35d3b5f3132e926d5bc8c6043961bb6d
Garca Fernández, P.; Colet, P.; Toral, R.; San Miguel, M.; Bermejo, F. J.
1991-05-01
The squeezing properties of a model of a degenerate parametric amplifier with absorption losses and an added fourth-order nonlinearity have been analyzed. The approach used consists of obtaining the Langevin equation for the optical field from the Heisenberg equation provided that a linearization procedure is valid. The steady states of the deterministic equations have been obtained and their local stability has been analyzed. The stationary covariance matrix has been calculated below and above threshold. Below threshold, a squeezed vacuum state is obtained and the nonlinear effects in the fluctuations have been taken into account by a Gaussian decoupling. In the case above threshold, a phase-squeezed coherent state is obtained and numerical simulations allowed to compute the time interval, depending on the loss parameter, on which the system jumps from one stable state to the other. Finally, the variances numerically determined have been compared with those obtained from the linearized theory and the limits of validity of the linear theory have been analyzed. It has become clear that the nonlinear contribution may perhaps be profitably used for the construction of above-threshold squeezing devices.
Genetic algorithm-based improved DOA estimation using fourth-order cumulants
Ahmed, Ammar; Tufail, Muhammad
2017-05-01
Genetic algorithm (GA)-based direction of arrival (DOA) estimation is proposed using fourth-order cumulants (FOC) and ESPRIT principle which results in Multiple Invariance Cumulant ESPRIT algorithm. In the existing FOC ESPRIT formulations, only one invariance is utilised to estimate DOAs. The unused multiple invariances (MIs) must be exploited simultaneously in order to improve the estimation accuracy. In this paper, a fitness function based on a carefully designed cumulant matrix is developed which incorporates MIs present in the sensor array. Better DOA estimation can be achieved by minimising this fitness function. Moreover, the effectiveness of Newton's method as well as GA for this optimisation problem has been illustrated. Simulation results show that the proposed algorithm provides improved estimation accuracy compared to existing algorithms, especially in the case of low SNR, less number of snapshots, closely spaced sources and high signal and noise correlation. Moreover, it is observed that the optimisation using Newton's method is more likely to converge to false local optima resulting in erroneous results. However, GA-based optimisation has been found attractive due to its global optimisation capability.
Analysis of a fourth-order compact scheme for convection-diffusion
International Nuclear Information System (INIS)
Yavneh, I.
1997-01-01
In, 1984 Gupta et al. introduced a compact fourth-order finite-difference convection-diffusion operator with some very favorable properties. In particular, this scheme does not seem to suffer excessively from spurious oscillatory behavior, and it converges with standard methods such as Gauss Seidel or SOR (hence, multigrid) regardless of the diffusion. This scheme has been rederived, developed (including some variations), and applied in both convection-diffusion and Navier-Stokes equations by several authors. Accurate solutions to high Reynolds-number flow problems at relatively coarse resolutions have been reported. These solutions were often compared to those obtained by lower order discretizations, such as second-order central differences and first-order upstream discretizations. The latter, it was stated, achieved far less accurate results due to the artificial viscosity, which the compact scheme did not include. We show here that, while the compact scheme indeed does not suffer from a cross-stream artificial viscosity (as does the first-order upstream scheme when the characteristic direction is not aligned with the grid), it does include a streamwise artificial viscosity that is inversely proportional to the natural viscosity. This term is not always benign. 7 refs., 1 fig., 1 tab
Vogman, Genia
Plasmas are made up of charged particles whose short-range and long-range interactions give rise to complex behavior that can be difficult to fully characterize experimentally. One of the most complete theoretical descriptions of a plasma is that of kinetic theory, which treats each particle species as a probability distribution function in a six-dimensional position-velocity phase space. Drawing on statistical mechanics, these distribution functions mathematically represent a system of interacting particles without tracking individual ions and electrons. The evolution of the distribution function(s) is governed by the Boltzmann equation coupled to Maxwell's equations, which together describe the dynamics of the plasma and the associated electromagnetic fields. When collisions can be neglected, the Boltzmann equation is reduced to the Vlasov equation. High-fidelity simulation of the rich physics in even a subset of the full six-dimensional phase space calls for low-noise high-accuracy numerical methods. To that end, this dissertation investigates a fourth-order finite-volume discretization of the Vlasov-Maxwell equation system, and addresses some of the fundamental challenges associated with applying these types of computationally intensive enhanced-accuracy numerical methods to phase space simulations. The governing equations of kinetic theory are described in detail, and their conservation-law weak form is derived for Cartesian and cylindrical phase space coordinates. This formulation is well known when it comes to Cartesian geometries, as it is used in finite-volume and finite-element discretizations to guarantee local conservation for numerical solutions. By contrast, the conservation-law weak form of the Vlasov equation in cylindrical phase space coordinates is largely unexplored, and to the author's knowledge has never previously been solved numerically. Thereby the methods described in this dissertation for simulating plasmas in cylindrical phase space
Muhiddin, F. A.; Sulaiman, J.
2017-09-01
The aim of this paper is to investigate the effectiveness of the Successive Over-Relaxation (SOR) iterative method by using the fourth-order Crank-Nicolson (CN) discretization scheme to derive a five-point Crank-Nicolson approximation equation in order to solve diffusion equation. From this approximation equation, clearly, it can be shown that corresponding system of five-point approximation equations can be generated and then solved iteratively. In order to access the performance results of the proposed iterative method with the fourth-order CN scheme, another point iterative method which is Gauss-Seidel (GS), also presented as a reference method. Finally the numerical results obtained from the use of the fourth-order CN discretization scheme, it can be pointed out that the SOR iterative method is superior in terms of number of iterations, execution time, and maximum absolute error.
Sarangapani, Radhakrishnan; Reddy, Sreekantha T; Sikder, Arun K
2015-04-01
Molecular dynamics simulations studies are carried out on hydroxyl terminated polyethers that are useful in energetic polymeric binder applications. Energetic polymers derived from oxetanes with heterocyclic side chains with different energetic substituents are designed and simulated under the ensembles of constant particle number, pressure, temperature (NPT) and constant particle number, volume, temperature (NVT). Specific volume of different amorphous polymeric models is predicted using NPT-MD simulations as a function of temperature. Plots of specific volume versus temperature exhibited a characteristic change in slope when amorphous systems change from glassy to rubbery state. Several material properties such as Young's, shear, and bulk modulus, Poisson's ratio, etc. are predicted from equilibrated structures and established the structure-property relations among designed polymers. Energetic performance parameters of these polymers are calculated and results reveal that the performance of the designed polymers is comparable to the benchmark energetic polymers like polyNIMMO, polyAMMO and polyBAMO. Overall, it is worthy remark that this molecular simulations study on novel energetic polyethers provides a good guidance on mastering the design principles and allows us to design novel polymers of tailored properties. Copyright © 2015 Elsevier Inc. All rights reserved.
Constantin, Lucian A; Fabiano, Eduardo; Della Sala, Fabio
2017-09-12
Using the semiclassical neutral atom theory, we developed a modified fourth-order kinetic energy (KE) gradient expansion (GE4m) that keeps unchanged all the linear-response terms of the uniform electron gas and gives a significant improvement with respect to the known semilocal functionals for both large atoms and jellium surfaces. On the other hand, GE4m is not accurate for light atoms; thus, we modified the GE4m coefficients making them dependent on a novel ingredient, the reduced Hartree potential, recently introduced in the Journal of Chemical Physics 2016, 145, 084110, in the context of exchange functionals. The resulting KE gradient expansion functional, named uGE4m, belongs to the novel class of u-meta-generalized-gradient-approximations (uMGGA) whose members depend on the conventional ingredients (i.e., the reduced gradient and Laplacian of the density) as well as on the reduced Hartree potential. To test uGE4m, we defined an appropriate benchmark (including total KE and KE differences for atoms, molecules and jellium clusters) for gradient expansion functionals, that is, including only those systems which are mainly described by a slowly varying density regime. While most of the GGA and meta-GGA KE functionals (we tested 18 of them) are accurate for some properties and inaccurate for others, uGE4m shows a consistently good performance for all the properties considered. This represents a qualitative boost in the KE functional development and highlights the importance of the reduced Hartree potential for the construction of next-generation KE functionals.
Shimada, Kazuhiro
2018-03-01
We perform first-principles calculations to investigate the crystal structure, elastic and piezoelectric properties, and spontaneous polarization of orthorhombic M2O3 (M = Al, Ga, In, Sc, Y) with Pna21 space group based on density functional theory. The lattice parameters, full elastic stiffness constants, piezoelectric stress and strain constants, and spontaneous polarization are successfully predicted. Comparison with available experimental and computational results indicates the validity of our computational results. Detailed analysis of the results clarifies the difference in the bonding character and the origin of the strong piezoelectric response and large spontaneous polarization.
International Nuclear Information System (INIS)
Lepkowski, S.P.; Majewski, J.A.
2004-01-01
We studied the nonlinear elasticity effects for the case of III-N compounds. Particularly, we determined the pressure dependences of elastic constants, in zinc-blende InN, GaN, and AlN by performing ab initio calculations in the framework of plane-wave pseudopotential implementation of the density-functional theory. We found significant and almost linear increase in C 11 , C 12 with pressure for considered nitrides compounds. Much weaker dependences on pressure was observed for C 44 . We also discussed pressure dependences of two-dimensional Poisson's ratio and elastic anisotropy coefficient. Finally, we showed that the pressure dependence of elastic constants results in significant reduction of the pressure coefficient of the energy emission in cubic InGaN/GaN quantum well and essentially improves the agreement between experimental and theoretical values. (author)
Energy Technology Data Exchange (ETDEWEB)
Nyawere, P.W.O., E-mail: otienop98@yahoo.ca [Computational Materials Science Group, Department of Physics, University of Eldoret, P.O. Box 1125-30100 Eldoret (Kenya); Department of Computing, Kabarak University, P.O. - Private Bag - 20157 Kabarak (Kenya); The Abdus Salam International Centre for Theoretical Physics, Trieste (Italy); Makau, N.W., E-mail: wanimak@yahoo.com [Computational Materials Science Group, Department of Physics, University of Eldoret, P.O. Box 1125-30100 Eldoret (Kenya); Amolo, G.O., E-mail: georgeamolo862@gmail.com [Computational Materials Science Group, Department of Physics, University of Eldoret, P.O. Box 1125-30100 Eldoret (Kenya)
2014-02-01
All the elastic constants of cubic, orthorhombic and hexagonal phases of BaF{sub 2} have been calculated using first principles methods. We have employed density-functional theory within generalized gradient approximation (GGA) using a plane-wave pseudopotentials method and a plane-wave basis set. The calculated elastic constant values for a cubic phase compare well with recent theoretical and experimental calculations. The bulk modulus derived from the elastic constant calculations of orthorhombic phase of BaF{sub 2} is 94.5 GPa and those of hexagonal phase is 161 GPa. These values are in good agreement with experimental data available. Stability of these phases of BaF{sub 2} is also estimated in different crystallographic directions.
Directory of Open Access Journals (Sweden)
Shahid Hasnain
2017-07-01
Full Text Available This research paper represents a numerical approximation to non-linear three dimension reaction diffusion equation with non-linear source term from population genetics. Since various initial and boundary value problems exist in three dimension reaction diffusion phenomena, which are studied numerically by different numerical methods, here we use finite difference schemes (Alternating Direction Implicit and Fourth Order Douglas Implicit to approximate the solution. Accuracy is studied in term of L2, L∞ and relative error norms by random selected grids along time levels for comparison with analytical results. The test example demonstrates the accuracy, efficiency and versatility of the proposed schemes. Numerical results showed that Fourth Order Douglas Implicit scheme is very efficient and reliable for solving 3-D non-linear reaction diffusion equation.
Hasnain, Shahid; Saqib, Muhammad; Mashat, Daoud Suleiman
2017-07-01
This research paper represents a numerical approximation to non-linear three dimension reaction diffusion equation with non-linear source term from population genetics. Since various initial and boundary value problems exist in three dimension reaction diffusion phenomena, which are studied numerically by different numerical methods, here we use finite difference schemes (Alternating Direction Implicit and Fourth Order Douglas Implicit) to approximate the solution. Accuracy is studied in term of L2, L∞ and relative error norms by random selected grids along time levels for comparison with analytical results. The test example demonstrates the accuracy, efficiency and versatility of the proposed schemes. Numerical results showed that Fourth Order Douglas Implicit scheme is very efficient and reliable for solving 3-D non-linear reaction diffusion equation.
Hale, Lucas M.; Trautt, Zachary T.; Becker, Chandler A.
2018-07-01
Atomistic simulations using classical interatomic potentials are powerful investigative tools linking atomic structures to dynamic properties and behaviors. It is well known that different interatomic potentials produce different results, thus making it necessary to characterize potentials based on how they predict basic properties. Doing so makes it possible to compare existing interatomic models in order to select those best suited for specific use cases, and to identify any limitations of the models that may lead to unrealistic responses. While the methods for obtaining many of these properties are often thought of as simple calculations, there are many underlying aspects that can lead to variability in the reported property values. For instance, multiple methods may exist for computing the same property and values may be sensitive to certain simulation parameters. Here, we introduce a new high-throughput computational framework that encodes various simulation methodologies as Python calculation scripts. Three distinct methods for evaluating the lattice and elastic constants of bulk crystal structures are implemented and used to evaluate the properties across 120 interatomic potentials, 18 crystal prototypes, and all possible combinations of unique lattice site and elemental model pairings. Analysis of the results reveals which potentials and crystal prototypes are sensitive to the calculation methods and parameters, and it assists with the verification of potentials, methods, and molecular dynamics software. The results, calculation scripts, and computational infrastructure are self-contained and openly available to support researchers in performing meaningful simulations.
International Nuclear Information System (INIS)
Tomar, Monika; Gupta, Vinay; Sreenivas, K
2003-01-01
The influence of sputtered SiO 2 over-layer on the SAW propagation characteristics of a 128 deg. rotated Y-cut X-propagating lithium niobate SAW filter has been studied. Experimentally measured SAW phase velocity and temperature coefficient of delay (TCD), with varying SiO 2 over-layer thickness, show a significant deviation from the theoretically calculated values using the bulk material parameters of SiO 2 . The observed deviation is attributed to the differences in the material parameters (density, elastic and dielectric constants and their temperature coefficient) of the deposited SiO 2 over-layer. The density and the dielectric constant of the deposited SiO 2 layer were determined separately, and the elastic constants and their temperature coefficients were estimated by fitting the experimental velocity and TCD data, respectively. The deviation in the dielectric constant and the density in comparison to the bulk was insignificant, and the estimated values of the elastic constants (C 11 = 0.75x10 11 N m -2 and C 44 0.225x10 11 N m -2 ) were found to be lower, and the respective temperature coefficients (5.0x10 -4 deg C -1 and 2.0x10 -4 deg C -1 ) were high in comparison to the bulk material parameters
Energy Technology Data Exchange (ETDEWEB)
Tomar, Monika; Gupta, Vinay; Sreenivas, K [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)
2003-08-07
The influence of sputtered SiO{sub 2} over-layer on the SAW propagation characteristics of a 128 deg. rotated Y-cut X-propagating lithium niobate SAW filter has been studied. Experimentally measured SAW phase velocity and temperature coefficient of delay (TCD), with varying SiO{sub 2} over-layer thickness, show a significant deviation from the theoretically calculated values using the bulk material parameters of SiO{sub 2}. The observed deviation is attributed to the differences in the material parameters (density, elastic and dielectric constants and their temperature coefficient) of the deposited SiO{sub 2} over-layer. The density and the dielectric constant of the deposited SiO{sub 2} layer were determined separately, and the elastic constants and their temperature coefficients were estimated by fitting the experimental velocity and TCD data, respectively. The deviation in the dielectric constant and the density in comparison to the bulk was insignificant, and the estimated values of the elastic constants (C{sub 11} = 0.75x10{sup 11} N m{sup -2} and C{sub 44} 0.225x10{sup 11} N m{sup -2}) were found to be lower, and the respective temperature coefficients (5.0x10{sup -4} deg C{sup -1} and 2.0x10{sup -4} deg C{sup -1}) were high in comparison to the bulk material parameters.
Wu, Shaohua; Wu, Xiaozhi; Wang, Rui; Liu, Qing; Gan, Liyong
2014-01-01
Effects of Ni vacancy, Ni antisite in Al sublattice, Cr in Al sublattice, Pt in Ni sublattice on the second-order elastic constants (SOECs) and third-order elastic constants (TOECs) of the B2 NiAl have been investigated using the first-principles methods. Lattice constant and the SOECs of NiAl are in good agreement with the previous results. The brittle/ductile transition map based on Pugh ratio G/B and Cauchy pressure Pc shows that Ni antisite, Cr, Pt and pressure can improve the ductility of NiAl, respectively. Ni vacancy and lower pressure can enhance the Vickers hardness Hv of NiAl. The density of states (DOS) and the charge density difference are also used to analysis the effects of vacancy, Ni antisite, Cr and Pt on the mechanical properties of NiAl, and the results are in consistent with the transition map. © 2014 Elsevier Ltd. All rights reserved.
Wu, Shaohua
2014-12-01
Effects of Ni vacancy, Ni antisite in Al sublattice, Cr in Al sublattice, Pt in Ni sublattice on the second-order elastic constants (SOECs) and third-order elastic constants (TOECs) of the B2 NiAl have been investigated using the first-principles methods. Lattice constant and the SOECs of NiAl are in good agreement with the previous results. The brittle/ductile transition map based on Pugh ratio G/B and Cauchy pressure Pc shows that Ni antisite, Cr, Pt and pressure can improve the ductility of NiAl, respectively. Ni vacancy and lower pressure can enhance the Vickers hardness Hv of NiAl. The density of states (DOS) and the charge density difference are also used to analysis the effects of vacancy, Ni antisite, Cr and Pt on the mechanical properties of NiAl, and the results are in consistent with the transition map. © 2014 Elsevier Ltd. All rights reserved.
Nonexistence of bounded energy solutions for a fourth order equation on thin annuli
International Nuclear Information System (INIS)
Ben Ayed, Mohamed; Hammami, Mokhless; El Mehdi, Khalil
2004-01-01
In this paper we study the problem P ε : Δ 2 u ε u ε (n+4)/(n-4) , u ε > in 0 in A ε ; u ε = Δu ε = 0 on ∂A ε , where {A ε is contained in R n , ε > 0} is a family of bounded annulus shaped domains such that A ε becomes 'thin' as ε → 0. Our main result is the following: Assume n ≥ 6 and let C > 0 be a constant. Then there exists ε 0 > 0 such that for any ε 0 , the problem P ε has no solution u ε , whose energy, ∫ A ε vertical barΔu ε vertical bar 2 is less than C. Our proof involves a rather delicate analysis of asymptotic profiles of solutions u ε when ε → 0. (author)
Astrophysical Tests of Kinematical Conformal Cosmology in Fourth-Order Conformal Weyl Gravity
Directory of Open Access Journals (Sweden)
Gabriele U. Varieschi
2014-12-01
Full Text Available In this work we analyze kinematical conformal cosmology (KCC, an alternative cosmological model based on conformal Weyl gravity (CG, and test it against current type Ia supernova (SNIa luminosity data and other astrophysical observations. Expanding upon previous work on the subject, we revise the analysis of SNIa data, confirming that KCC can explain the evidence for an accelerating expansion of the Universe without using dark energy or other exotic components. We obtain an independent evaluation of the Hubble constant, H0 = 67:53 kms-1 Mpc-1, very close to the current best estimates. The main KCC and CG parameters are re-evaluated and their revised values are found to be close to previous estimates. We also show that available data for the Hubble parameter as a function of redshift can be fitted using KCC and that this model does not suffer from any apparent age problem. Overall,
Energy Technology Data Exchange (ETDEWEB)
Kotane, L M; Comins, J D; Every, A G [Materials Physics Research Institute, School of Physics, University of the Witwatersrand, Johannesburg, Wits 2050 (South Africa); Botha, J R, E-mail: Lesias.Kotane@wits.ac.z [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)
2011-01-01
Surface Brillouin scattering of light has been used to measure the angular dependence of the Rayleigh surface acoustic wave (SAW), pseudo surface acoustic wave (PSAW) and longitudinal lateral wave (LLW) speeds in a (100)-oriented single crystal of the ternary semiconductor alloy InAs{sub 0.91}Sb{sub 0.09}. The wave speed measurements have been used to determine the room temperature values of the elastic constants C{sub 11}, C{sub 12} and C{sub 44} of the alloy. A simple and robust fitting procedure has been implemented for recovering the elastic constants, in which the merit function is constructed from explicit secular functions that determine the surface and lateral wave speeds in the [001] and [011] crystallographic directions. In the fitting, relatively larger weighting factors have been assigned to the SAW and PSAW data because of the greater precision with which the surface modes can be measured as compared with the lateral wave.
Surface Brillouin scattering measurement of the elastic constants of single crystal InAs0.91Sb0.09
International Nuclear Information System (INIS)
Kotane, L M; Comins, J D; Every, A G; Botha, J R
2011-01-01
Surface Brillouin scattering of light has been used to measure the angular dependence of the Rayleigh surface acoustic wave (SAW), pseudo surface acoustic wave (PSAW) and longitudinal lateral wave (LLW) speeds in a (100)-oriented single crystal of the ternary semiconductor alloy InAs 0.91 Sb 0.09 . The wave speed measurements have been used to determine the room temperature values of the elastic constants C 11 , C 12 and C 44 of the alloy. A simple and robust fitting procedure has been implemented for recovering the elastic constants, in which the merit function is constructed from explicit secular functions that determine the surface and lateral wave speeds in the [001] and [011] crystallographic directions. In the fitting, relatively larger weighting factors have been assigned to the SAW and PSAW data because of the greater precision with which the surface modes can be measured as compared with the lateral wave.
Li, Yingmin; Wang, Jiaxi; Clark, Melissa L.; Kubiak, Clifford P.; Xiong, Wei
2016-04-01
We report the first fourth-order 3D SFG spectroscopy of a monolayer of the catalyst Re(diCN-bpy)(CO)3Cl on a gold surface. Besides measuring the vibrational coherences of single vibrational modes, the fourth-order 3D SFG spectrum also measures the dynamics of interstate coherences and vibrational coherences states between two vibrational modes. By comparing the 3D SFG to the corresponding 2D and third-order 3D IR spectroscopy of the same molecules in solution, we found that the interstate coherences exist in both liquid and surface systems, suggesting that the interstate coherence is not disrupted by surface interactions. However, by analyzing the 3D spectral lineshape, we found that the interstate coherences also experience non-negligible homogenous dephasing dynamics that originate from surface interactions. This unique ability of determining interstate vibrational coherence dynamics of the molecular monolayer can help in understanding of how energy flows within surface catalysts and other molecular monolayers.
International Nuclear Information System (INIS)
Andrushchak, A. S.; Laba, H. P.; Yurkevych, O. V.; Mytsyk, B. G.; Solskii, I. M.; Kityk, A. V.; Sahraoui, B.
2009-01-01
This paper presents the results of ultrasonic measurements of LiNbO 3 and LiNbO 3 :MgO crystals. The tensors of piezoelectric coefficients, elastic stiffness constants, and elastic compliances are determined for both crystals at room temperature. Combining these data with the results of piezo-optical measurements, a complete set of photoelastic tensor coefficients is also calculated. Doping of LiNbO 3 crystals by MgO does not lead to a considerable modification of their elastic and photoelastic properties. However, LiNbO 3 :MgO is characterized by a considerably higher resistance with respect to powerful light radiation, making it promising for future application in acousto-optic devices that deal with superpowerful laser radiation. Presented here are the complete tensor sets of elastic constants and photoelastic coefficients of LiNbO 3 and LiNbO 3 :MgO crystals that may be used for a geometry optimization of acousto-optical interaction providing the best diffraction efficiency of acousto-optical cells made of these materials.
International Nuclear Information System (INIS)
Landa, Michal; Sedlak, Petr; Sittner, Petr; Seiner, Hanus; Heller, Ludek
2008-01-01
Elastic constants of austenite and martensite phases in shape memory alloys reflect fundamental thermodynamic properties of these materials-i.e. important physical information can be deduced not just from the values of the constants but, mainly from their temperature and stress dependencies. As regards to the parent austenite phase, such information is available in the literature for most of the known shape memory alloys. For the martensitic phases, however, only few reliable experimental data exist, due to the experimental difficulties with the preparation of martensite single crystals as well as due to the difficulties with the ultrasonic measurement of elastic properties of strongly anisotropic media with low symmetry. In this work, the temperature dependence of all elastic constants of cubic austenite and orthorhombic 2H martensite phases in Cu-Al-Ni alloy determined by resonance ultrasound spectroscopy (RUS) is reported. Experimental and theoretical improvements of the RUS method which had to be made to perform the successful measurements on strongly anisotropic and martensitic phases are discussed
International Nuclear Information System (INIS)
Ledbetter, H.M.
1983-01-01
This chapter investigates the following five aspects of engineering-material solid-state elastic constants: general properties, interrelationships, relationships to other physical properties, changes during cooling from ambient to near-zero temperature, and near-zero-temperature behavior. Topics considered include compressibility, bulk modulus, Young's modulus, shear modulus, Poisson's ratio, Hooke's law, elastic-constant measuring methods, thermodynamic potentials, higher-order energy terms, specific heat, thermal expansivity, magnetic materials, structural phase transitions, polymers, composites, textured aggregates, and other-phenomena correlations. Some of the conclusions concerning polycrystalline elastic properties and their temperature dependence are: elastic constants are physical, not mechanical, properties which relate thermodynamically to other physical properties such as specific heat and thermal expansivity; elastic constants at low temperatures are nearly temperature independent, as required by the third law of thermodynamics; and elastic constants can be used to study directional properties of materials, such as textured aggregates and composites
Akbar, M Ali; Hj Mohd Ali, Norhashidah
2014-01-01
The exp(-Ф(η))-expansion method is an ascending method for obtaining exact and solitary wave solutions for nonlinear evolution equations. In this article, we implement the exp(-Ф(η))-expansion method to build solitary wave solutions to the fourth order Boussinesq equation. The procedure is simple, direct and useful with the help of computer algebra. By using this method, we obtain solitary wave solutions in terms of the hyperbolic functions, the trigonometric functions and elementary functions. The results show that the exp(-Ф(η))-expansion method is straightforward and effective mathematical tool for the treatment of nonlinear evolution equations in mathematical physics and engineering. 35C07; 35C08; 35P99.
Capmany, J; Pastor, D; Sales, S; Ortega, B
2002-06-01
We present a closed-form expression for computation of the output pulse's rms time width in an optical fiber link with up to fourth-order dispersion (FOD) by use of an optical source with arbitrary linewidth and chirp parameters. We then specialize the expression to analyze the effect of FOD on the transmission of very high-speed linear optical time-division multiplexing systems. By suitable source chirping, FOD can be compensated for to an upper link-length limit above which other techniques must be employed. Finally, a design formula to estimate the maximum attainable bit rate limited by FOD as a function of the link length is also presented.
Lucchetti, Liana; Fraccia, Tommaso P.; Ciciulla, Fabrizio; Bellini, Tommaso
2017-01-01
Throughout the whole history of liquid crystals science, the balancing of intrinsic elasticity with coupling to external forces has been the key strategy for most application and investigation. While the coupling of the optical field to the nematic director is at the base of a wealth of thoroughly described optical effects, a significant variety of geometries and materials have not been considered yet. Here we show that by adopting a simple cell geometry and measuring the optically induced bi...
Rodgers, Michael J.; Wen, Shengmin; Keer, Leon M.
2000-08-01
A three-dimensional quasi-static model of faulting in an elastic half-space with a horizontal change of material properties (i.e., joined elastic quarter spaces) is considered. A boundary element method is used with a stress drop slip zone approach so that the fault surface relative displacements as well as the free surface displacements are approximated in elements over their respective domains. Stress intensity factors and free surface displacements are calculated for a variety of cases to show the phenomenological behavior of faulting in such a medium. These calculations showed that the behavior could be distinguished from a uniform half-space. Slip in a stiffer material increases, while slip in a softer material decreases the energy release rate and the free surface displacements. Also, the 1989 Kalapana earthquake was located on the basis of a series of forward searches using this method and leveling data. The located depth is 8 km, which is the closer to the seismically inferred depth than that determined from other models. Finally, the energy release rate, which can be used as a fracture criterion for fracture at this depth, is calculated to be 11.1×106 J m-2.
The elastic constants of MgSiO3 perovskite at pressures and temperatures of the Earth's mantle.
Oganov, A R; Brodholt, J P; Price, G D
2001-06-21
The temperature anomalies in the Earth's mantle associated with thermal convection can be inferred from seismic tomography, provided that the elastic properties of mantle minerals are known as a function of temperature at mantle pressures. At present, however, such information is difficult to obtain directly through laboratory experiments. We have therefore taken advantage of recent advances in computer technology, and have performed finite-temperature ab initio molecular dynamics simulations of the elastic properties of MgSiO3 perovskite, the major mineral of the lower mantle, at relevant thermodynamic conditions. When combined with the results from tomographic images of the mantle, our results indicate that the lower mantle is either significantly anelastic or compositionally heterogeneous on large scales. We found the temperature contrast between the coldest and hottest regions of the mantle, at a given depth, to be about 800 K at 1,000 km, 1,500 K at 2,000 km, and possibly over 2,000 K at the core-mantle boundary.
A new fourth-order Fourier-Bessel split-step method for the extended nonlinear Schroedinger equation
International Nuclear Information System (INIS)
Nash, Patrick L.
2008-01-01
Fourier split-step techniques are often used to compute soliton-like numerical solutions of the nonlinear Schroedinger equation. Here, a new fourth-order implementation of the Fourier split-step algorithm is described for problems possessing azimuthal symmetry in 3 + 1-dimensions. This implementation is based, in part, on a finite difference approximation Δ perpendicular FDA of 1/r (∂)/(∂r) r(∂)/(∂r) that possesses an associated exact unitary representation of e i/2λΔ perpendicular FDA . The matrix elements of this unitary matrix are given by special functions known as the associated Bessel functions. Hence the attribute Fourier-Bessel for the method. The Fourier-Bessel algorithm is shown to be unitary and unconditionally stable. The Fourier-Bessel algorithm is employed to simulate the propagation of a periodic series of short laser pulses through a nonlinear medium. This numerical simulation calculates waveform intensity profiles in a sequence of planes that are transverse to the general propagation direction, and labeled by the cylindrical coordinate z. These profiles exhibit a series of isolated pulses that are offset from the time origin by characteristic times, and provide evidence for a physical effect that may be loosely termed normal mode condensation. Normal mode condensation is consistent with experimentally observed pulse filamentation into a packet of short bursts, which may occur as a result of short, intense irradiation of a medium
Galaktionov, Victor A.
2009-02-01
As a basic higher-order model, the fourth-order Boussinesq-type quasilinear wave equation (the QWE-4) \\[ \\begin{equation*}\\fl u_{tt} = -(|u|^n u)_{xxxx} \\tqs in\\ \\mathbb{R} \\times \\mathbb{R}_+, \\quad with\\ exponent\\ n > 0,\\end{equation*} \\] is considered. Self-similar blow-up solutions \\[ \\begin{eqnarray*}\\tqs\\tqs u_-(x,t)=g(z), \\quad\\, z=\\frac x{\\sqrt{T-t}},\\\\ where\\ g\\ solved\\ the\\ ODE\\ \\frac 14 g'' z^2 + \\frac 34 g'z = -(|g|^n g)^{(4)},\\end{eqnarray*} \\] are shown to exist that generate as t → T- discontinuous shock waves. The QWE-4 is also shown to admit a smooth (for t > 0) global 'fundamental solution' \\[ \\begin{eqnarray*}\\fl b_n(x,t)= t^{\\frac{2}{n+4}} F_n(y),\\ y = x/t^{\\frac{n+2}{n+4}},\\ such\\ that\\ b_{n}(x,0)= 0,\\ b_{nt}(x,0)= {\\delta}(x),\\end{eqnarray*} \\] i.e. having a measure as initial data. A 'homotopic' limit n → 0 is used to get b_0(x,t)= \\sqrt t \\, F_0(x/\\sqrt t) being the classic fundamental solution of the 1D linear beam equation \\[ \\begin{equation*}u_{tt} = -u_{xxxx} \\tqs in\\ \\mathbb{R} \\times \\mathbb{R}_+.\\end{equation*} \\
On Higgs-exchange DIS, physical evolution kernels and fourth-order splitting functions at large x
International Nuclear Information System (INIS)
Soar, G.; Vogt, A.; Vermaseren, J.A.M.
2009-12-01
We present the coefficient functions for deep-inelastic scattering (DIS) via the exchange of a scalar φ directly coupling only to gluons, such as the Higgs boson in the limit of a very heavy top quark and n f effectively massless light flavours, to the third order in perturbative QCD. The two-loop results are employed to construct the next-to-next-to-leading order physical evolution kernels for the system (F 2 ,F φ ) of flavour-singlet structure functions. The practical relevance of these kernels as an alternative to MS factorization is bedevilled by artificial double logarithms at small values of the scaling variable x, where the large top-mass limit ceases to be appropriate. However, they show an only single-logarithmic enhancement at large x. Conjecturing that this feature persists to the next order also in the present singlet case, the three-loop coefficient functions facilitate exact predictions (backed up by their particular colour structure) of the double-logarithmic contributions to the fourth-order singlet splitting functions, i.e., of the terms (1-x) a ln k (1-x) with k=4,5,6 and k=3,4,5, respectively, for the off-diagonal and diagonal quantities to all powers a in (1-x). (orig.)
Energy Technology Data Exchange (ETDEWEB)
Contreras Lopez, Enrique [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)
1995-12-31
Departing from the analysis of a data base on the velocities of the compression waves (V{sub p}) and the transverse waves (V{sub s}) in a group of 97 specimens of sedimentary, igneous and metamorphic rocks, the existence of four types of empirical correlation very well entailed between the dynamic elastic constants and the velocities V{sub p} and V{sub s}. These correlation allow the estimation with a very close approximation the elastic dynamic constants without the need of having available of the complete set of data (V{sub p}, V{sub s} and total density) that is normally required for its determination. The identified correlation is mathematically expressed by means of adjustment equations that reproduce in all of the cases the experimental values with a standard error of estimation within 10%, for the universe of rocks studied and with much less error for different specific lithological groups. The application methodologies of the correlation found for different cases of practical interest, are described. [Espanol] A partir del analisis de una base de datos experimentales sobre la velocidad de las ondas compresionales (V{sub p}) y de las ondas transversales (V{sub s}) de un conjunto de 97 especimenes de rocas sedimentarias, igneas y metamorficas, se identifica la existencia de cuatro tipos de correlaciones empiricas muy bien comportadas entre las constantes elasticas dinamicas y las velocidades V{sub p} y V{sub s}. Estas correlaciones permiten estimar con muy buena aproximacion las constantes elasticas dinamicas de las rocas sin tener que disponer del conjunto completo de datos (V{sub p}, V{sub s} y densidad total) que normalmente se requieren para su determinacion. Las correlaciones identificadas se expresan matematicamente mediante ecuaciones de ajuste que reproducen en todos los casos los valores experimentales con un error estandar de estimacion dentro de 10% para el universo de las rocas estudiadas, y con mucho menor error para diferentes grupos litologicos
Energy Technology Data Exchange (ETDEWEB)
Contreras Lopez, Enrique [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)
1996-12-31
Departing from the analysis of a data base on the velocities of the compression waves (V{sub p}) and the transverse waves (V{sub s}) in a group of 97 specimens of sedimentary, igneous and metamorphic rocks, the existence of four types of empirical correlation very well entailed between the dynamic elastic constants and the velocities V{sub p} and V{sub s}. These correlation allow the estimation with a very close approximation the elastic dynamic constants without the need of having available of the complete set of data (V{sub p}, V{sub s} and total density) that is normally required for its determination. The identified correlation is mathematically expressed by means of adjustment equations that reproduce in all of the cases the experimental values with a standard error of estimation within 10%, for the universe of rocks studied and with much less error for different specific lithological groups. The application methodologies of the correlation found for different cases of practical interest, are described. [Espanol] A partir del analisis de una base de datos experimentales sobre la velocidad de las ondas compresionales (V{sub p}) y de las ondas transversales (V{sub s}) de un conjunto de 97 especimenes de rocas sedimentarias, igneas y metamorficas, se identifica la existencia de cuatro tipos de correlaciones empiricas muy bien comportadas entre las constantes elasticas dinamicas y las velocidades V{sub p} y V{sub s}. Estas correlaciones permiten estimar con muy buena aproximacion las constantes elasticas dinamicas de las rocas sin tener que disponer del conjunto completo de datos (V{sub p}, V{sub s} y densidad total) que normalmente se requieren para su determinacion. Las correlaciones identificadas se expresan matematicamente mediante ecuaciones de ajuste que reproducen en todos los casos los valores experimentales con un error estandar de estimacion dentro de 10% para el universo de las rocas estudiadas, y con mucho menor error para diferentes grupos litologicos
Elastic Constants of Plane Orthotropic Elasticity
DEFF Research Database (Denmark)
Krenk, Steen
1979-01-01
The four independent material parameters of plane orthotropic elasti city are introduced as the effective stiffness, the effective Poisson ratio, the stiffness ratio and the shear parameter. It is proved that stress boundary value problems with zero resulting force on internal contours lead...
Energy Technology Data Exchange (ETDEWEB)
Tiriolo, Raffaele [Department of Medical and Surgical Sciences, University Magna Graecia of Catanzaro, Viale Europa 88100 Catanzaro Italy; Rangnekar, Neel [Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave SE Minneapolis MN 55455 USA; Zhang, Han [Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave SE Minneapolis MN 55455 USA; Shete, Meera [Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave SE Minneapolis MN 55455 USA; Bai, Peng [Department of Chemistry and Chemistry Theory Center, University of Minnesota, 207 Pleasant St SE Minneapolis MN 55455 USA; Nelson, John [Characterization Facility, University of Minnesota, 12 Shepherd Labs, 100 Union St. S.E. Minneapolis MN 55455 USA; Karapetrova, Evguenia [Surface Scattering and Microdiffraction, X-ray Science Division, Argonne National Laboratory, 9700 S. Cass Ave, Building 438-D002 Argonne IL 60439 USA; Macosko, Christopher W. [Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave SE Minneapolis MN 55455 USA; Siepmann, Joern Ilja [Department of Chemistry and Chemistry Theory Center, University of Minnesota, 207 Pleasant St SE Minneapolis MN 55455 USA; Lamanna, Ernesto [Department of Health Sciences, University Magna Graecia of Catanzaro, Viale Europa 88100 Catanzaro Italy; Lavano, Angelo [Department of Medical and Surgical Sciences, University Magna Graecia of Catanzaro, Viale Europa 88100 Catanzaro Italy; Tsapatsis, Michael [Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave SE Minneapolis MN 55455 USA
2017-05-08
A low-temperature synthesis coupled with mild activation produces zeolite films exhibiting low dielectric constant (low-k) matching the theoretically predicted and experimentally measured values for single crystals. This synthesis and activation method allows for the fabrication of a device consisting of a b-oriented film of the pure-silica zeolite MFI (silicalite-1) supported on a gold-coated silicon wafer. The zeolite seeds are assembled by a manual assembly process and subjected to optimized secondary growth conditions that do not cause corrosion of the gold underlayer, while strongly promoting in-plane growth. The traditional calcination process is replaced with a non-thermal photochemical activation to ensure preservation of an intact gold layer. The dielectric constant (k), obtained through measurement of electrical capacitance in a metal-insulator-metal configuration, highlights the ultralow k approximate to 1.7 of the synthetized films, which is among the lowest values reported for an MFI film. There is large improvement in elastic modulus of the film (E approximate to 54 GPa) over previous reports, potentially allowing for integration into silicon wafer processing technology.
Field Dependence of Elastic Constants in the Bilayer Manganite: (La1-z Prz )1.2Sr1.8Mn2O7 for z=0.6
International Nuclear Information System (INIS)
Nakanishi, Y.; Shimomura, K.; Matasukawa, M.; Yoshizawa, M.; Apost, M.; Suryanarayanan, R.; Revcolevischi, A.
2003-01-01
Elastic properties of the Pr-doped bilayer manganite: (La 1-z Pr z ) 1.2 Sr 1.8 Mn 2 O 7 for z=0.6 was investigated by means of the ultrasonic measurement. No remarkable anomaly was observed around the transition temperature in the temperature dependence of C 33 in zero field. A pronounced elastic anomaly, however, has been observed around the magnetic phase transition field Ht in the longitudinal elastic constants C 11 , indicating the phase can be induced in magnetic fields. The transition accompanies a large hysteresis, implying the ordered state to be so-called ''orbital-glass state''. The origin of observed elastic anomalies are discussed in terms of the coupling between elastic strains and magnetic moments of Mn ions, and a change of carrier numbers. (author)
Boukheddaden, Kamel
2013-10-01
We present theoretical investigations on surface elastic energy in spin-crossover (SC) solids studied in the frame of a microscopic elastic model, coupling spin, and lattice deformations. Although surface energy plays a crucial role in driving the SC transition, specific quantitative investigations on its effect have been neglected in most of the recent theoretical works based on atomistic descriptions of the SC transitions, resolved by Monte Carlo or by molecular dynamics simulations. Here, we perform a quantitative study of the surface energy resulting from an inserted high-spin (HS) domain in a low-spin (LS) lattice. This situation may be produced experimentally in SC solids, at low temperature, through a photoexcitation by a single pulse laser shot. We demonstrate that the surface energy depends on the ratio between the local molecular volume misfit (between the LS and HS sites) δυ and the lattice volume V, such as Esurf˜δυ2/V for the HS atom at the center of lattice, while it is Esurf˜δυ2/L (L is the length of the lattice) in the case of the HS atom located on the edge of the lattice. We then derived the image pressure (negative in the case of embedded dilatation centers) through the work of the free surface atoms and evaluated the Eshelby constant, which was found equal to γ˜1.90, in very good agreement with the available data of literature. Energetic configuration diagrams in the homogeneous (HS and LS) and heterogeneous (coexistence of HS and LS) are calculated, from which estimations of the macroscopic bulk modulus were deduced.
Yan, Yangqian; Blume, D
2016-06-10
The unitary equal-mass Fermi gas with zero-range interactions constitutes a paradigmatic model system that is relevant to atomic, condensed matter, nuclear, particle, and astrophysics. This work determines the fourth-order virial coefficient b_{4} of such a strongly interacting Fermi gas using a customized ab initio path-integral Monte Carlo (PIMC) algorithm. In contrast to earlier theoretical results, which disagreed on the sign and magnitude of b_{4}, our b_{4} agrees within error bars with the experimentally determined value, thereby resolving an ongoing literature debate. Utilizing a trap regulator, our PIMC approach determines the fourth-order virial coefficient by directly sampling the partition function. An on-the-fly antisymmetrization avoids the Thomas collapse and, combined with the use of the exact two-body zero-range propagator, establishes an efficient general means to treat small Fermi systems with zero-range interactions.
Directory of Open Access Journals (Sweden)
Manfred Möller
2013-01-01
Full Text Available Considered is a regular fourth order ordinary differential equation which depends quadratically on the eigenvalue parameter λ and which has separable boundary conditions depending linearly on λ. It is shown that the eigenvalues lie in the closed upper half plane or on the imaginary axis and are symmetric with respect to the imaginary axis. The first four terms in the asymptotic expansion of the eigenvalues are provided.
Cao, Quankun; Xie, Huimin
2017-12-01
Fused deposition modelling (FDM), a widely used rapid prototyping process, is a promising technique in manufacturing engineering. In this work, a method for characterizing elastic constants of FDM-fabricated materials is proposed. First of all, according to the manufacturing process of FDM, orthotropic constitutive model is used to describe the mechanical behavior. Then the virtual fields method (VFM) is applied to characterize all the mechanical parameters (Q_{11}, Q_{22}, Q_{12}, Q_{66}) using the full-field strain, which is measured by digital image correlation (DIC). Since the principal axis of the FDM-fabricated structure is sometimes unknown due to the complexity of the manufacturing process, a disk in diametrical compression is used as the load configuration so that the loading angle can be changed conveniently. To verify the feasibility of the proposed method, finite element method (FEM) simulation is conducted to obtain the strain field of the disk. The simulation results show that higher accuracy can be achieved when the loading angle is close to 30°. Finally, a disk fabricated by FDM was used for the experiment. By rotating the disk, several tests with different loading angles were conducted. To determine the position of the principal axis in each test, two groups of parameters (Q_{11}, Q_{22}, Q_{12}, Q_{66}) are calculated by two different groups of virtual fields. Then the corresponding loading angle can be determined by minimizing the deviation between two groups of the parameters. After that, the four constants (Q_{11}, Q_{22}, Q_{12}, Q_{66}) were determined from the test with an angle of 27°.
Yang, X X; Li, J W; Zhou, Z F; Wang, Y; Yang, L W; Zheng, W T; Sun, Chang Q
2012-01-21
From the perspective of bond relaxation and bond vibration, we have formulated the Raman phonon relaxation of graphene, under the stimuli of the number-of-layers, the uni-axial strain, the pressure, and the temperature, in terms of the response of the length and strength of the representative bond of the entire specimen to the applied stimuli. Theoretical unification of the measurements clarifies that: (i) the opposite trends of the Raman shifts, which are due to the number-of-layers reduction, of the G-peak shift and arises from the vibration of a pair of atoms, while the D- and the 2D-peak shifts involve the z-neighbor of a specific atom; (ii) the tensile strain-induced phonon softening and phonon-band splitting arise from the asymmetric response of the C(3v) bond geometry to the C(2v) uni-axial bond elongation; (iii) the thermal softening of the phonons originates from bond expansion and weakening; and (iv) the pressure stiffening of the phonons results from bond compression and work hardening. Reproduction of the measurements has led to quantitative information about the referential frequencies from which the Raman frequencies shift as well as the length, energy, force constant, Debye temperature, compressibility and elastic modulus of the C-C bond in graphene, which is of instrumental importance in the understanding of the unusual behavior of graphene.
International Nuclear Information System (INIS)
Baruah, D; Choudhury, S; Singh, K M; Ghatak, K P
2007-01-01
In this paper we study the carrier contribution to elastic constants in quantum confined heavily doped non-linear optical compounds on the basis of a newly formulated electron dispersion law taking into account the anisotropies of the effective electron masses and spin orbit splitting constants together with the proper inclusion of the crystal field splitting in the Hamiltonian within the framework of k.p formalism. All the results of heavily doped three, and two models of Kane for heavily doped III-V materials form special cases of our generalized analysis. It has been found, taking different heavily doped quantum confined materials that, the carrier contribution to the elastic constants increases with increase in electron statistics and decrease in film thickness in ladder like manners for all types of quantum confinements with different numerical values which are totally dependent on the energy band constants. The said contribution is greatest in quantum dots and least in quantum wells together with the fact the heavy doping enhances the said contributions for all types of quantum confined materials. We have suggested an experimental method of determining the carrier contribution to the elastic constants in nanostructured materials having arbitrary band structures
Pan, Liang; Xu, Kun; Li, Qibing; Li, Jiequan
2016-12-01
For computational fluid dynamics (CFD), the generalized Riemann problem (GRP) solver and the second-order gas-kinetic scheme (GKS) provide a time-accurate flux function starting from a discontinuous piecewise linear flow distributions around a cell interface. With the adoption of time derivative of the flux function, a two-stage Lax-Wendroff-type (L-W for short) time stepping method has been recently proposed in the design of a fourth-order time accurate method for inviscid flow [21]. In this paper, based on the same time-stepping method and the second-order GKS flux function [42], a fourth-order gas-kinetic scheme is constructed for the Euler and Navier-Stokes (NS) equations. In comparison with the formal one-stage time-stepping third-order gas-kinetic solver [24], the current fourth-order method not only reduces the complexity of the flux function, but also improves the accuracy of the scheme. In terms of the computational cost, a two-dimensional third-order GKS flux function takes about six times of the computational time of a second-order GKS flux function. However, a fifth-order WENO reconstruction may take more than ten times of the computational cost of a second-order GKS flux function. Therefore, it is fully legitimate to develop a two-stage fourth order time accurate method (two reconstruction) instead of standard four stage fourth-order Runge-Kutta method (four reconstruction). Most importantly, the robustness of the fourth-order GKS is as good as the second-order one. In the current computational fluid dynamics (CFD) research, it is still a difficult problem to extend the higher-order Euler solver to the NS one due to the change of governing equations from hyperbolic to parabolic type and the initial interface discontinuity. This problem remains distinctively for the hypersonic viscous and heat conducting flow. The GKS is based on the kinetic equation with the hyperbolic transport and the relaxation source term. The time-dependent GKS flux function
International Nuclear Information System (INIS)
Buryi, E V; Kosygin, A A
2004-01-01
It is shown that, when the angular resolution of a receiving optical system is insufficient, the angular dimensions of a located object can be estimated and its shape can be reconstructed by estimating the parameters of the fourth-order correlation function (CF) of scattered coherent radiation. The reliability of the estimates of CF counts obtained by the method of a discrete spatial convolution of the intensity-field counts, the possibility of estimating the CF profile counts by the method of one-dimensional convolution of intensity counts, and the applicability of the method for reconstructing the object shape are confirmed experimentally. (laser applications and other topics in quantum electronics)
International Nuclear Information System (INIS)
Sasaki, Toshihiko; Kuramoto, Makoto; Yoshioka, Yasuo.
1990-01-01
This paper describes the method and the experiment for the determination of the x-ray elastic constants of Zn-Ni-alloy electroplate. For this material, the sin 2 ψ method is not adequate to use because this material shows severely curved sin 2 ψ diagrams. Therefore, a new method developed by the authors was explained first. This new method is effective for materials showing nonlinear sin 2 ψ diagrams. Secondly, the experiment was made on the application of this method to the Zn-Ni-alloy electroplate. And it was found out that the experimental data agreed well to the theory of this method. As a result, the following values were obtained as the x-ray elastic constants of the sample measured: (1+ν)/E=8.44 TPa -1 ν/E=2.02 TPa -1 (author)
Directory of Open Access Journals (Sweden)
Ruili Wen
2016-08-01
Full Text Available We consider an open-loop system of a fourth order Schrodinger equation with variable coefficients and Neumann boundary control and collocated observation. Using the multiplier method on Riemannian manifold we show that that the system is well-posed in the sense of Salamon. This implies that the exponential stability of the closed-loop system under the direct proportional output feedback control and the exact controllability of open-loop system are equivalent. So in order to conclude feedback stabilization from well-posedness, we study the exact controllability under a uniqueness assumption by presenting the observability inequality for the dual system. In addition, we show that the system is regular in the sense of Weiss, and that the feedthrough operator is zero.
Czech Academy of Sciences Publication Activity Database
Landa, Michal; Sedlák, Petr; Šittner, Petr; Seiner, Hanuš; Heller, Luděk
481-482, - (2008), s. 567-573 ISSN 0921-5093 R&D Projects: GA ČR GA101/06/0768 Institutional research plan: CEZ:AV0Z20760514; CEZ:AV0Z10100520 Keywords : modal resonant ultrasound spectroscopy * elastic properties * shape memory alloy s Subject RIV: BI - Acoustics Impact factor: 1.806, year: 2008
Stock, C.; Gehring, P. M.; Hiraka, H.; Swainson, I.; Xu, Guangyong; Ye, Z.-G.; Luo, H.; Li, J.-F.; Viehland, D.
2012-09-01
We use neutron inelastic scattering to characterize the acoustic phonons in the relaxor Pb(Mg1/3Nb2/3)O3 (PMN) and demonstrate the presence of a highly anisotropic damping mechanism that is directly related to short-range polar correlations. For a large range of temperatures above Tc˜210 K, where dynamic, short-range polar correlations are present, acoustic phonons propagating along [11¯0] and polarized along [110] (TA2 phonons) are overdamped and softened across most of the Brillouin zone. By contrast, acoustic phonons propagating along [100] and polarized along [001] (TA1 phonons) are overdamped and softened for a more limited range of wave vectors q. The anisotropy and temperature dependence of the acoustic phonon energy linewidth Γ are directly correlated with neutron diffuse scattering cross section, indicating that polar nanoregions are the cause of the anomalous behavior. The damping and softening vanish for q→0, i.e., for long-wavelength acoustic phonons near the zone center, which supports the notion that the anomalous damping is a result of the coupling between the relaxational component of the diffuse scattering and the harmonic TA phonons. Therefore, these effects are not due to large changes in the elastic constants with temperature because the elastic constants correspond to the long-wavelength limit. We compare the elastic constants we measure to those from Brillouin scattering experiments and to values reported for pure PbTiO3. We show that while the values of C44 are quite similar, those for C11 and C12 are significantly less in PMN and result in a softening of (C11-C12) over PbTiO3. The elastic constants also show an increased elastic anisotropy [2C44/(C11-C12)] in PMN versus that in PbTiO3. These results are suggestive of an instability to TA2 acoustic fluctuations in PMN and other relaxor ferroelectrics. We discuss our results in the context of the current debate over the “waterfall” effect and show that they are inconsistent with
Poroseva, Svetlana V.
2013-11-01
Simulations of turbulent boundary-layer flows are usually conducted using a set of the simplified Reynolds-Averaged Navier-Stokes (RANS) equations obtained by order-of-magnitude analysis (OMA) of the original RANS equations. The resultant equations for the mean-velocity components are closed using the Boussinesq approximation for the Reynolds stresses. In this study OMA is applied to the fourth-order RANS (FORANS) set of equations. The FORANS equations are chosen as they can be closed on the level of the 5th-order correlations without using unknown model coefficients, i.e. no turbulent diffusion modeling is required. New models for the 2nd-, 3rd- and 4th-order velocity-pressure gradient correlations are derived for the current FORANS equations. This set of FORANS equations and models are analyzed for the case of two-dimensional mean flow. The equations include familiar transport terms for the mean-velocity components along with algebraic expressions for velocity correlations of different orders specific to the FORANS approach. Flat plate DNS data (Spalart, 1988) are used to verify these expressions and the areas of the OMA applicability within the boundary layer. The material is based upon work supported by NASA under award NNX12AJ61A.
International Nuclear Information System (INIS)
Wang, Pan; Tian, Bo; Jiang, Yan; Wang, Yu-Feng
2013-01-01
For describing the dynamics of alpha helical proteins with internal molecular excitations, nonlinear couplings between lattice vibrations and molecular excitations, and spin excitations in one-dimensional isotropic biquadratic Heisenberg ferromagnetic spin with the octupole–dipole interactions, we consider an inhomogeneous generalized fourth-order nonlinear Schrödinger equation. Based on the Ablowitz–Kaup–Newell–Segur system, infinitely many conservation laws for the equation are derived. Through the auxiliary function, bilinear forms and N-soliton solutions for the equation are obtained. Interactions of solitons are discussed by means of the asymptotic analysis. Effects of linear inhomogeneity on the interactions of solitons are also investigated graphically and analytically. Since the inhomogeneous coefficient of the equation h=α x+β, the soliton takes on the parabolic profile during the evolution. Soliton velocity is related to the parameter α, distance scale coefficient and biquadratic exchange coefficient, but has no relation with the parameter β. Soliton amplitude and width are only related to α. Soliton position is related to β
Chudnovsky, A.; Dolgopolsky, A.; Kachanov, M.
1987-01-01
The elastic interactions of a two-dimensional configuration consisting of a crack with an array of microcracks located near the tip are studied. The general form of the solution is based on the potential representations and approximations of tractions on the microcracks by polynomials. In the second part, the technique is applied to two simple two-dimensional configurations involving one and two microcracks. The problems of stress shielding and stress amplification (the reduction or increase of the effective stress intensity factor due to the presence of microcracks) are discussed, and the refinements introduced by higher order polynomial approximations are illustrated.
Energy Technology Data Exchange (ETDEWEB)
Wu Yurong [College of Electromechanical Engineering, Hunan University of Science and Technology, Xiantang 411201 (China); Hu Wangyu [Department of Applied Physics, Hunan University, Changsha 410082 (China)], E-mail: wangyuhu2001cn@yahoo.com.cn; Han Shaochang [Department of Applied Physics, Hunan University, Changsha 410082 (China)
2008-10-01
First-principles calculations have been used to study the elastic and electronic properties of ductility rare-earth alloy YM (M=Ag, Cu, Rh) systems. The ductility mechanism for these alloys is studied from microscopic aspect, via electronic density of states (DOS). The Fermi energy lies near a local minimum, and the hybridization is stronger than that of the common NiAl alloy, demonstrating that the ductility of these alloys is much better than that of NiAl alloy. Elastic modulus, namely, shear modulus C'=(C{sub 11}-C{sub 12})/2, bulk modulus B and C{sub 44} are calculated by volume-conserving orthorhombic, hydrostatic pressure and tri-axial shear strain, respectively. Moreover, lattice parameters, antiphase boundary (APB) energies and unstable stacking fault energies of these alloys are also studied. The APB energies are greater than the unstable stacking fault energies for these alloy systems, and this is a characteristic of the ductility rare-earth alloy. The APB energies of YRh are the highest ones in these three YM alloys, which make dislocation dissociation difficult. The DOS and APB energy results show that the ductility of YRh may be worst in these three YM systems.
International Nuclear Information System (INIS)
Wu Yurong; Hu Wangyu; Han Shaochang
2008-01-01
First-principles calculations have been used to study the elastic and electronic properties of ductility rare-earth alloy YM (M=Ag, Cu, Rh) systems. The ductility mechanism for these alloys is studied from microscopic aspect, via electronic density of states (DOS). The Fermi energy lies near a local minimum, and the hybridization is stronger than that of the common NiAl alloy, demonstrating that the ductility of these alloys is much better than that of NiAl alloy. Elastic modulus, namely, shear modulus C'=(C 11 -C 12 )/2, bulk modulus B and C 44 are calculated by volume-conserving orthorhombic, hydrostatic pressure and tri-axial shear strain, respectively. Moreover, lattice parameters, antiphase boundary (APB) energies and unstable stacking fault energies of these alloys are also studied. The APB energies are greater than the unstable stacking fault energies for these alloy systems, and this is a characteristic of the ductility rare-earth alloy. The APB energies of YRh are the highest ones in these three YM alloys, which make dislocation dissociation difficult. The DOS and APB energy results show that the ductility of YRh may be worst in these three YM systems
Kumar, Rajesh; Srivastava, Subodh; Srivastava, Rajeev
2017-07-01
For cancer detection from microscopic biopsy images, image segmentation step used for segmentation of cells and nuclei play an important role. Accuracy of segmentation approach dominate the final results. Also the microscopic biopsy images have intrinsic Poisson noise and if it is present in the image the segmentation results may not be accurate. The objective is to propose an efficient fuzzy c-means based segmentation approach which can also handle the noise present in the image during the segmentation process itself i.e. noise removal and segmentation is combined in one step. To address the above issues, in this paper a fourth order partial differential equation (FPDE) based nonlinear filter adapted to Poisson noise with fuzzy c-means segmentation method is proposed. This approach is capable of effectively handling the segmentation problem of blocky artifacts while achieving good tradeoff between Poisson noise removals and edge preservation of the microscopic biopsy images during segmentation process for cancer detection from cells. The proposed approach is tested on breast cancer microscopic biopsy data set with region of interest (ROI) segmented ground truth images. The microscopic biopsy data set contains 31 benign and 27 malignant images of size 896 × 768. The region of interest selected ground truth of all 58 images are also available for this data set. Finally, the result obtained from proposed approach is compared with the results of popular segmentation algorithms; fuzzy c-means, color k-means, texture based segmentation, and total variation fuzzy c-means approaches. The experimental results shows that proposed approach is providing better results in terms of various performance measures such as Jaccard coefficient, dice index, Tanimoto coefficient, area under curve, accuracy, true positive rate, true negative rate, false positive rate, false negative rate, random index, global consistency error, and variance of information as compared to other
Elastic and plastic characteristics of a model Cu–Zr amorphous alloy
International Nuclear Information System (INIS)
Nakamura, Akiho; Kamimura, Yasushi; Edagawa, Keiichi; Takeuchi, Shin
2014-01-01
Athermal quasistatic simulation of shear deformation has been conducted for a realistic model Cu–Zr amorphous alloy to investigate characteristic features of elasticity and plasticity of the material. Significant reduction of the shear modulus by nonaffine atomic displacements and appreciable nonlinearity of elasticity have been observed. The fourth-order elastic constant in shear deformation and the ideal shear strength have been evaluated. Plastic deformation has been observed to start with isolated local shear transformations (LSTs) followed by collective LSTs leading to the formation of a shear band. Participation-ratio analysis (PRA) has demonstrated how the nonaffine displacement field converges as the system approaches the critical point of losing structural stability. PRA has also evaluated quantitatively the numbers of atoms participating in LSTs – the average number is about 30. Spatially anisotropic development of nascent shear band on a plane has been shown, attributable to anisotropic internal stress field induced by an LST. The evaluated stresses for the shear-band nucleation and for its propagation have indicated that the yielding in real materials is controlled by the shear-band propagation, as previously pointed out
International Nuclear Information System (INIS)
Kumazawa, Mineo; Kunitomo, Takahiro; Nakajima, Takahiro; Fujii, Naoyuki; Shigeta, Naotaka; Tsuruga, Kayoko; Hasada, Yoko; Nagao, Hiromichi; Matsumoto, Hiroshi; Kasahara, Junzo
2007-03-01
The developmental study made at Tono Geoscience Center under the Earthquake Frontier Research Project since 1996 is reported for a brand new technology system called ACROSS (Accurately Controlled, Routinely Operated, Signal System invented at Kagoya University in 1994). Various technology elements have been combined together under a specific theoretical framework for the underground exploration and monitoring of structures and physical states. The ACROSS is essentially a spectroscopy of the underground space consisted of complex media subjected to environmental noise. The robustness against noise is devised by utilizing coherent elastic and electromagnetic waves with phase controlled very accurately. Demanded hardware technology has been developed successfully and know how has been accumulated for practical applications. Accurate synchronization of transmission and observation systems has provided us with reliable data on the tensor transfer function between the source and receiver, which is equivalent to Green function within a limited frequency range. Several examples of the field application are demonstrated by the test experiments at Tono Mine site. After the developmental works of 10 years, the ACROSS is brought to be a practical method applied to the remote monitoring of temporal variation of underground states at the Horonobe Underground Research Laboratory and also it is being applied to the expected focal region of the coming Tokai earthquake near Hamaoka in Shizuoka prefecture. Whereas ACROSS technology is not mature enough yet, it is shown to be a potential and versatile methodology applied even for the health monitoring of the construction such as building strongly coupled with the ground in addition to the underground study. (author)
Bounds and self-consistent estimates for elastic constants of polycrystals of hcp solid He {}^{4}
Energy Technology Data Exchange (ETDEWEB)
Berryman, James G.
2012-03-01
Recent advances in methods for computing both Hashin-Shtrikman bounds and related selfconsistent (or CPA) estimates of elastic constants for polycrystals composed of randomly oriented crystals can be applied successfully to hexagonal close packed solid He{sup 4}. In particular, since the shear modulus C{sub 44} of hexagonal close-packed solid He is known to undergo large temperature variations when 20 mK {<=} T {<=} 200 mK, bounds and estimates computed with this class of effective medium methods, while using C{sub 44} {r_arrow} 0 as a proxy for melting, are found to be both qualitatively and quantitatively very similar to prior results obtained using Monte Carlo methods. Hashin- Shtrikman bounds provide significantly tighter constraints on the polycrystal behavior than do the traditional Voigt and Reuss bounds.
Temperature dependence of elastic properties of paratellurite
International Nuclear Information System (INIS)
Silvestrova, I.M.; Pisarevskii, Y.V.; Senyushenkov, P.A.; Krupny, A.I.
1987-01-01
New data are presented on the temperature dependence of the elastic wave velocities, elastic stiffness constants, and thermal expansion of paratellurite. It is shown that the external pressure appreciably influences the elastic properties of TeO 2 , especially the temperature dependence of the elastic modulus connected with the crystal soft mode. (author)
Collusion and the elasticity of demand
David Collie
2004-01-01
The analysis of collusion in infinitely repeated Cournot oligopoly games has generally assumed that demand is linear, but this note uses constant-elasticity demand functions to investigate how the elasticity of demand affects the sustainability of collusion.
International Nuclear Information System (INIS)
Foos, J.
1999-01-01
This paper is written in two tables. The first one describes the different particles (bosons and fermions). The second one gives the isotopes nuclear constants of the different elements, for Z = 1 to 56. (A.L.B.)
International Nuclear Information System (INIS)
Foos, J.
2000-01-01
This paper is written in two tables. The first one describes the different particles (bosons and fermions). The second one gives the isotopes nuclear constants of the different elements, for Z = 56 to 68. (A.L.B.)
International Nuclear Information System (INIS)
Foos, J.
1998-01-01
This paper is made of two tables. The first table describes the different particles (bosons and fermions) while the second one gives the nuclear constants of isotopes from the different elements with Z = 1 to 25. (J.S.)
International Nuclear Information System (INIS)
Foos, J.
1999-01-01
This paper is written in two tables. The first one describes the different particles (bosons and fermions). The second one gives the isotopes nuclear constants of the different elements, for Z = 56 to 68. (A.L.B.)
Are fundamental constants really constant
International Nuclear Information System (INIS)
Norman, E.B.
1986-01-01
Reasons for suspecting that fundamental constants might change with time are reviewed. Possible consequences of such variations are examined. The present status of experimental tests of these ideas is discussed
Visualising elastic anisotropy: theoretical background and computational implementation
Nordmann, J.; Aßmus, M.; Altenbach, H.
2018-02-01
In this article, we present the technical realisation for visualisations of characteristic parameters of the fourth-order elasticity tensor, which is classified by three-dimensional symmetry groups. Hereby, expressions for spatial representations of uc(Young)'s modulus and bulk modulus as well as plane representations of shear modulus and uc(Poisson)'s ratio are derived and transferred into a comprehensible form to computer algebra systems. Additionally, we present approaches for spatial representations of both latter parameters. These three- and two-dimensional representations are implemented into the software MATrix LABoratory. Exemplary representations of characteristic materials complete the present treatise.
Jiang, Yi; Li, Guoyang; Qian, Lin-Xue; Liang, Si; Destrade, Michel; Cao, Yanping
2015-10-01
We use supersonic shear wave imaging (SSI) technique to measure not only the linear but also the nonlinear elastic properties of brain matter. Here, we tested six porcine brains ex vivo and measured the velocities of the plane shear waves induced by acoustic radiation force at different states of pre-deformation when the ultrasonic probe is pushed into the soft tissue. We relied on an inverse method based on the theory governing the propagation of small-amplitude acoustic waves in deformed solids to interpret the experimental data. We found that, depending on the subjects, the resulting initial shear modulus [Formula: see text] varies from 1.8 to 3.2 kPa, the stiffening parameter [Formula: see text] of the hyperelastic Demiray-Fung model from 0.13 to 0.73, and the third- [Formula: see text] and fourth-order [Formula: see text] constants of weakly nonlinear elasticity from [Formula: see text]1.3 to [Formula: see text]20.6 kPa and from 3.1 to 8.7 kPa, respectively. Paired [Formula: see text] test performed on the experimental results of the left and right lobes of the brain shows no significant difference. These values are in line with those reported in the literature on brain tissue, indicating that the SSI method, combined to the inverse analysis, is an efficient and powerful tool for the mechanical characterization of brain tissue, which is of great importance for computer simulation of traumatic brain injury and virtual neurosurgery.
Energy Technology Data Exchange (ETDEWEB)
Yang, Jin-Wei; Gao, Yi-Tian, E-mail: gaoyt163@163.com; Wang, Qi-Min; Su, Chuan-Qi; Feng, Yu-Jie; Yu, Xin
2016-01-15
In this paper, a fourth-order variable-coefficient nonlinear Schrödinger equation is studied, which might describe a one-dimensional continuum anisotropic Heisenberg ferromagnetic spin chain with the octuple–dipole interaction or an alpha helical protein with higher-order excitations and interactions under continuum approximation. With the aid of auxiliary function, we derive the bilinear forms and corresponding constraints on the variable coefficients. Via the symbolic computation, we obtain the Lax pair, infinitely many conservation laws, one-, two- and three-soliton solutions. We discuss the influence of the variable coefficients on the solitons. With different choices of the variable coefficients, we obtain the parabolic, cubic, and periodic solitons, respectively. We analyse the head-on and overtaking interactions between/among the two and three solitons. Interactions between a bound state and a single soliton are displayed with different choices of variable coefficients. We also derive the quasi-periodic formulae for the three cases of the bound states.
Elastic properties of icosahedral and decagonal quasicrystals
International Nuclear Information System (INIS)
Chernikov, Mikhail A
2005-01-01
Problems associated with determining the symmetry properties of the elastic constant tensor of icosahedral and decagonal quasicrystals are reviewed. Notions of elastic isotropy and anisotropy are considered, and their relation to the components of the elastic constant tensor is discussed. The question is addressed of how to determine experimentally whether a system under study is elastically isotropic. Experimental results produced by resonant ultrasound spectroscopy of icosahedral Al-Li-Cu and decagonal Al-Ni-Co single quasicrystals are discussed in detail. (methodological notes)
Teaching nonlinear dynamics through elastic cords
International Nuclear Information System (INIS)
Chacon, R; Galan, C A; Sanchez-Bajo, F
2011-01-01
We experimentally studied the restoring force of a length of stretched elastic cord. A simple analytical expression for the restoring force was found to fit all the experimental results for different elastic materials. Remarkably, this analytical expression depends upon an elastic-cord characteristic parameter which exhibits two limiting values corresponding to two nonlinear springs with different Hooke's elastic constants. Additionally, the simplest model of elastic cord dynamics is capable of exhibiting a great diversity of nonlinear phenomena, including bifurcations and chaos, thus providing a suitable alternative model system for discussing the basic essentials of nonlinear dynamics in the context of intermediate physics courses at university level.
Vliet, Jurg; Wel, Steven; Dowd, Dara
2011-01-01
While it's always been possible to run Java applications on Amazon EC2, Amazon's Elastic Beanstalk makes the process easier-especially if you understand how it works beneath the surface. This concise, hands-on book not only walks you through Beanstalk for deploying and managing web applications in the cloud, you'll also learn how to use this AWS tool in other phases of development. Ideal if you're a developer familiar with Java applications or AWS, Elastic Beanstalk provides step-by-step instructions and numerous code samples for building cloud applications on Beanstalk that can handle lots
Elasticity theory of ultrathin nanofilms
International Nuclear Information System (INIS)
Li, Jiangang; Yun, Guohong; Narsu, B; Yao, Haiyan
2015-01-01
A self-consistent theoretical scheme for describing the elastic behavior of ultrathin nanofilms (UTNFs) was proposed. Taking into account the lower symmetry of an UTNF compared to its bulk counterpart, additional elastic and magnetoelastic parameters were introduced to model the elasticity rigorously. The applications of current theory to several elastic and magnetoelastic systems gave excellent agreement with experiments. More importantly, the surface elastic and magnetoelastic parameters used to fit the experimental results are physically reasonable and in close agreement with those obtained from experiment and simulation. This fact suggests that the additional elastic (magnetoelastic) constants due to symmetry breaking are of great importance in theoretical description of the mechanical properties of UTNFs. And we proved that the elasticity of UTNFs should be described by a three-dimensional model just including the intrinsic surface and bulk parameters, but not the effective surface parameters. It is believed that the theory reported here is a universal strategy for elasticity and magnetoelasticity of ultrathin films. (paper)
Liu, Lili
2014-07-31
The elastic properties and generalized stacking fault energy curves of antiperovskite-type Ni-rich nitrides MNNi3 (M = Zn, Cd) under different pressure have been obtained from the first-principles calculations. By using the variational method, the core width and Peierls stresses of (Formula presented.) edge dislocation and screw dislocation in ZnNNi3 and CdNNi3 within the improved Peierls-Nabarro (P-N) model in which the lattice discrete effect is taken into account have been investigated. Whatever the material or the pressure range, the Peierls stress of edge dislocation is smaller than that of screw dislocation. This also demonstrates that the edge dislocation is considered to be the dominant factor in determining the plastic behavior of MNNi3 (M = Zn, Cd) in the pressure range of 0–30 GPa.
Wang Li; Sun, L L; Wang, W H; Wang, W K
2003-01-01
The pressure dependence of the acoustic velocities of a Pd sub 3 sub 9 Ni sub 1 sub 0 Cu sub 3 sub 0 P sub 2 sub 1 bulk metallic glass have been investigated up to 0.5 GPa at room temperature with the pulse echo overlap method. Two independent second-order elastic coefficients C sub 1 sub 1 and C sub 4 sub 4 and their pressure derivatives are yielded. The vibrational anharmonicity is shown by calculating both the acoustic mode Grueneisen parameters in the long-wavelength limit and the thermal Grueneisen parameter, and this result is compared with that for the Pd sub 4 sub 0 Ni sub 4 sub 0 P sub 2 sub 0 bulk glass.
Strain gradient elasticity within the symmetric BEM formulation
Directory of Open Access Journals (Sweden)
S. Terravecchia,
2014-07-01
Full Text Available The symmetric Galerkin Boundary Element Method is used to address a class of strain gradient elastic materials featured by a free energy function of the (classical strain and of its (first gradient. With respect to the classical elasticity, additional response variables intervene, such as the normal derivative of the displacements on the boundary, and the work-coniugate double tractions. The fundamental solutions - featuring a fourth order partial differential equations (PDEs system - exhibit singularities which in 2D may be of the order 1/ r 4 . New techniques are developed, which allow the elimination of most of the latter singularities. The present paper has to be intended as a research communication wherein some results, being elaborated within a more general paper [1], are reported.
Effective elastic properties of damaged isotropic solids
International Nuclear Information System (INIS)
Lee, U Sik
1998-01-01
In continuum damage mechanics, damaged solids have been represented by the effective elastic stiffness into which local damage is smoothly smeared. Similarly, damaged solids may be represented in terms of effective elastic compliances. By virtue of the effective elastic compliance representation, it may become easier to derive the effective engineering constants of damaged solids from the effective elastic compliances, all in closed form. Thus, in this paper, by using a continuum modeling approach based on both the principle of strain energy equivalence and the equivalent elliptical micro-crack representation of local damage, the effective elastic compliance and effective engineering constants are derived in terms of the undamaged (virgin) elastic properties and a scalar damage variable for both damaged two-and three-dimensional isotropic solids
Elastic properties of graphite and interstitial defects
International Nuclear Information System (INIS)
Ayasse, J.-B.
1977-01-01
The graphite elastic constants C 33 and C 44 , reflecting the interaction of the graphitic planes, were experimentally measured as a function of irradiation and temperature. A model of non-central strength atomic interaction was established to explain the experimental results obtained. This model is valid at zero temperature. The temperature dependence of the elastic properties was analyzed. The influence of the elastic property variations on the specific heat of the lattice at very low temperature was investigated [fr
International Nuclear Information System (INIS)
Leader, Elliot
1991-01-01
With very few unexplained results to challenge conventional ideas, physicists have to look hard to search for gaps in understanding. An area of physics which offers a lot more than meets the eye is elastic and diffractive scattering where particles either 'bounce' off each other, emerging unscathed, or just graze past, emerging relatively unscathed. The 'Blois' workshops provide a regular focus for this unspectacular, but compelling physics, attracting highly motivated devotees
Adaptation of generalized Hill inequalities to anisotropic elastic ...
African Journals Online (AJOL)
user
Thallium manganese chloride(TIMnCl 3 ). 101.4. 16.5. 32.2. 5.2 For Isotropic Media. For some materials, it is possible to make approaches from cubic symmetry to isotropic symmetry. With cubic symmetry, three independent elastic constants are needed. If the medium is elastically isotropic, the elastic properties are ...
Fu, Y. B.; Ogden, R. W.
2001-05-01
This collection of papers by leading researchers in the field of finite, nonlinear elasticity concerns itself with the behavior of objects that deform when external forces or temperature gradients are applied. This process is extremely important in many industrial settings, such as aerospace and rubber industries. This book covers the various aspects of the subject comprehensively with careful explanations of the basic theories and individual chapters each covering a different research direction. The authors discuss the use of symbolic manipulation software as well as computer algorithm issues. The emphasis is placed firmly on covering modern, recent developments, rather than the very theoretical approach often found. The book will be an excellent reference for both beginners and specialists in engineering, applied mathematics and physics.
Appraisal of elastic follow up
International Nuclear Information System (INIS)
Roche, R.L.
1981-08-01
The aim of this paper is to provide indications to choose what fraction of a self limiting stress can be considered as secondary. At first, considerations are given to a simple structure which could be called ''creep relaxation tensile test''. A bar (with constant cross section) is loaded by an elastic spring in order to obtain a given elongation of the assembly. The stress evolution is studied. Then the creep damage is computed, and compared to the damage corresponding to the elastic computed stress. This comparison gives the fraction of the self limiting stress which must be considered as primary. This involve the structural parameter 0 which is the initial value of the ratio of elastic energy to dissipating power. Extension of the rule is made with the help of KACHANOV approximation. As a conclusion a procedure is described which determines what fraction of a self limiting stress must be considered as primary
Zhao, Xin
2013-01-01
Elastic rods have been studied intensively since the 18th century. Even now the theory of elastic rods is still developing and enjoying popularity in computer graphics and physical-based simulation. Elastic rods also draw attention from architects
The poverty elasticity of growth
Heltberg, Rasmus
2002-01-01
How much does economic growth contribute to poverty reduction? I discuss analytical and empirical approches to assess the poverty elasticity of growth, and emphasize that the relationship between growth and poverty change is non-constant. For a given poverty measure, it depends on initial inequality and on the location of the poverty line relative to mean income. In most cases, growth is more important for poverty reduction than changes in inequality, but this does not tender inequality unimp...
Constant physics and characteristics of fundamental constant
International Nuclear Information System (INIS)
Tarrach, R.
1998-01-01
We present some evidence which supports a surprising physical interpretation of the fundamental constants. First, we relate two of them through the renormalization group. This leaves as many fundamental constants as base units. Second, we introduce and a dimensional system of units without fundamental constants. Third, and most important, we find, while interpreting the units of the a dimensional system, that is all cases accessible to experimentation the fundamental constants indicate either discretization at small values or boundedness at large values of the corresponding physical quantity. (Author) 12 refs
Elastic constants of nanoporous III-V semiconductors
Czech Academy of Sciences Publication Activity Database
Janovská, Michaela; Sedlák, Petr; Kruisová, Alena; Seiner, Hanuš; Landa, Michal; Grym, Jan
2015-01-01
Roč. 48, č. 24 (2015) ISSN 0022-3727 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61388998 ; RVO:67985882 Keywords : nanoporous semiconductors * resonant ultrasound spectroscopy * finite elements modelling Subject RIV: BM - Solid Matter Physics ; Magnetism; BM - Solid Matter Physics ; Magnetism (URE-Y) Impact factor: 2.772, year: 2015 http://iopscience.iop.org/0022-3727/48/24/245102/article
Superconducting transition temperatures of the elements related to elastic constants
Angilella, G. G. N.; March, N. H.; Pucci, R.
2004-01-01
For a given crystal structure, say body-centred-cubic, the many-body Hamiltonian in which nuclear and electron motions are to be treated from the outset on the same footing, has parameters, for the elements, which can be classified as (i) atomic mass M, (ii) atomic number Z, characterizing the external potential in which electrons move, and (iii) bcc lattice spacing, or equivalently one can utilize atomic volume, Omega. Since the thermodynamic quantities can be determined from H, we conclude ...
A Comparative Analysis of the Effective Elastic Constants of ...
African Journals Online (AJOL)
Results of various finite element and closed form models developed in the attempt to evaluate and establish accurate values of the Young's modulus, E; the shear modulus G; and the Poisson's ratio,< for laminated composite plates having soft matrix and high fibre volume fraction are discussed in this paper. Their merits and ...
Zhao, Xin
2013-05-01
Elastic rods have been studied intensively since the 18th century. Even now the theory of elastic rods is still developing and enjoying popularity in computer graphics and physical-based simulation. Elastic rods also draw attention from architects. Architectural structures, NODUS, were constructed by elastic rods as a new method of form-finding. We study discrete models of elastic rods and NODUS structures. We also develop computational tools to find the equilibria of elastic rods and the shape of NODUS. Applications of elastic rods in forming torus knot and closing Bishop frame are included in this thesis.
Three-dimensional inverse modelling of damped elastic wave propagation in the Fourier domain
Petrov, Petr V.; Newman, Gregory A.
2014-09-01
3-D full waveform inversion (FWI) of seismic wavefields is routinely implemented with explicit time-stepping simulators. A clear advantage of explicit time stepping is the avoidance of solving large-scale implicit linear systems that arise with frequency domain formulations. However, FWI using explicit time stepping may require a very fine time step and (as a consequence) significant computational resources and run times. If the computational challenges of wavefield simulation can be effectively handled, an FWI scheme implemented within the frequency domain utilizing only a few frequencies, offers a cost effective alternative to FWI in the time domain. We have therefore implemented a 3-D FWI scheme for elastic wave propagation in the Fourier domain. To overcome the computational bottleneck in wavefield simulation, we have exploited an efficient Krylov iterative solver for the elastic wave equations approximated with second and fourth order finite differences. The solver does not exploit multilevel preconditioning for wavefield simulation, but is coupled efficiently to the inversion iteration workflow to reduce computational cost. The workflow is best described as a series of sequential inversion experiments, where in the case of seismic reflection acquisition geometries, the data has been laddered such that we first image highly damped data, followed by data where damping is systemically reduced. The key to our modelling approach is its ability to take advantage of solver efficiency when the elastic wavefields are damped. As the inversion experiment progresses, damping is significantly reduced, effectively simulating non-damped wavefields in the Fourier domain. While the cost of the forward simulation increases as damping is reduced, this is counterbalanced by the cost of the outer inversion iteration, which is reduced because of a better starting model obtained from the larger damped wavefield used in the previous inversion experiment. For cross-well data, it is
Elastic and optical behaviour of some europium monochalcogenides
International Nuclear Information System (INIS)
Islam, A.K.M.A.; Shahdatullah, M.S.
1994-11-01
A study of the elastic and optical properties of some Eu-monochalcogenides with NaCl structure has been carried out in this paper. Various anharmonic properties e.g. thermal expansion, third order elastic constants, Grueneisen parameter, and the pressure and temperature derivatives of second order elastic constants of EuS and EuO are also studied. A comparison of the calculated elastic and dielectric properties with the available experimental results and other theoretical estimates gives an indication of the applicability of the methods applied. (author). 49 refs, 3 figs, 3 tabs
Marangoni elasticity of flowing soap films
Kim, Ildoo; Mandre, Shreyas
2016-01-01
We measure the Marangoni elasticity of a flowing soap film to be 22 dyne/cm irrespective of its width, thickness, flow speed, or the bulk soap concentration. We perform this measurement by generating an oblique shock in the soap film and measuring the shock angle, flow speed and thickness. We postulate that the elasticity is constant because the film surface is crowded with soap molecules. Our method allows non-destructive measurement of flowing soap film elasticity, and the value 22 dyne/cm ...
Marangoni elasticity of flowing soap films
Kim, Ildoo; Mandre, Shreyas
2017-08-01
We measure the Marangoni elasticity of a flowing soap film to be 22 mN/m irrespective of its width, thickness, flow speed, or the bulk soap concentration. We perform this measurement by generating an oblique shock in the soap film and measuring the shock angle, flow speed, and thickness. We postulate that the elasticity is constant because the film surface is crowded with soap molecules. Our method allows nondestructive measurement of flowing soap film elasticity and the value 22 mN/m is likely applicable to other similarly constructed flowing soap films.
Cosmological Hubble constant and nuclear Hubble constant
International Nuclear Information System (INIS)
Horbuniev, Amelia; Besliu, Calin; Jipa, Alexandru
2005-01-01
The evolution of the Universe after the Big Bang and the evolution of the dense and highly excited nuclear matter formed by relativistic nuclear collisions are investigated and compared. Values of the Hubble constants for cosmological and nuclear processes are obtained. For nucleus-nucleus collisions at high energies the nuclear Hubble constant is obtained in the frame of different models involving the hydrodynamic flow of the nuclear matter. Significant difference in the values of the two Hubble constant - cosmological and nuclear - is observed
Elastic properties of uniaxial-fiber reinforced composites - General features
Datta, Subhendu; Ledbetter, Hassel; Lei, Ming
The salient features of the elastic properties of uniaxial-fiber-reinforced composites are examined by considering the complete set of elastic constants of composites comprising isotropic uniaxial fibers in an isotropic matrix. Such materials exhibit transverse-isotropic symmetry and five independent elastic constants in Voigt notation: C(11), C(33), C(44), C(66), and C(13). These C(ij) constants are calculated over the entire fiber-volume-fraction range 0.0-1.0, using a scattered-plane-wave ensemple-average model. Some practical elastic constants such as the principal Young moduli and the principal Poisson ratios are considered, and the behavior of these constants is discussed. Also presented are the results for the four principal sound velocities used to study uniaxial-fiber-reinforced composites: v(11), v(33), v(12), and v(13).
FORMATION CONSTANTS AND THERMODYNAMIC ...
African Journals Online (AJOL)
KEY WORDS: Metal complexes, Schiff base ligand, Formation constant, DFT calculation ... best values for the formation constants of the proposed equilibrium model by .... to its positive charge distribution and the ligand deformation geometry.
Coupling constant metamorphosis and Nth-order symmetries in classical and quantum mechanics
Energy Technology Data Exchange (ETDEWEB)
Kalnins, E G [Department of Mathematics and Statistics, University of Waikato, Hamilton (New Zealand); Miller, W Jr; Post, S [School of Mathematics, University of Minnesota, Minneapolis, MN 55455 (United States)], E-mail: miller@ima.umn.edu
2010-01-22
We review the fundamentals of coupling constant metamorphosis (CCM) and the Staeckel transform, and apply them to map integrable and superintegrable systems of all orders into other such systems on different manifolds. In general, CCM does not preserve the order of constants of the motion or even take polynomials in the momenta to polynomials in the momenta. We study specializations of these actions which preserve polynomials and also the structure of the symmetry algebras in both the classical and quantum cases. We give several examples of non-constant curvature third- and fourth-order superintegrable systems in two space dimensions obtained via CCM, with some details on the structure of the symmetry algebras preserved by the transform action.
Coupling constant metamorphosis and Nth-order symmetries in classical and quantum mechanics
International Nuclear Information System (INIS)
Kalnins, E G; Miller, W Jr; Post, S
2010-01-01
We review the fundamentals of coupling constant metamorphosis (CCM) and the Staeckel transform, and apply them to map integrable and superintegrable systems of all orders into other such systems on different manifolds. In general, CCM does not preserve the order of constants of the motion or even take polynomials in the momenta to polynomials in the momenta. We study specializations of these actions which preserve polynomials and also the structure of the symmetry algebras in both the classical and quantum cases. We give several examples of non-constant curvature third- and fourth-order superintegrable systems in two space dimensions obtained via CCM, with some details on the structure of the symmetry algebras preserved by the transform action.
Ion exchange equilibrium constants
Marcus, Y
2013-01-01
Ion Exchange Equilibrium Constants focuses on the test-compilation of equilibrium constants for ion exchange reactions. The book first underscores the scope of the compilation, equilibrium constants, symbols used, and arrangement of the table. The manuscript then presents the table of equilibrium constants, including polystyrene sulfonate cation exchanger, polyacrylate cation exchanger, polymethacrylate cation exchanger, polysterene phosphate cation exchanger, and zirconium phosphate cation exchanger. The text highlights zirconium oxide anion exchanger, zeolite type 13Y cation exchanger, and
Pricing perpetual American options under multiscale stochastic elasticity of variance
International Nuclear Information System (INIS)
Yoon, Ji-Hun
2015-01-01
Highlights: • We study the effects of the stochastic elasticity of variance on perpetual American option. • Our SEV model consists of a fast mean-reverting factor and a slow mean-revering factor. • A slow scale factor has a very significant impact on the option price. • We analyze option price structures through the market prices of elasticity risk. - Abstract: This paper studies pricing the perpetual American options under a constant elasticity of variance type of underlying asset price model where the constant elasticity is replaced by a fast mean-reverting Ornstein–Ulenbeck process and a slowly varying diffusion process. By using a multiscale asymptotic analysis, we find the impact of the stochastic elasticity of variance on the option prices and the optimal exercise prices with respect to model parameters. Our results enhance the existing option price structures in view of flexibility and applicability through the market prices of elasticity risk
Goods-Time Elasticity of Substitution in Health Production.
Du, Juan; Yagihashi, Takeshi
2017-11-01
We examine how inputs for health production, in particular, medical care and health-enhancing time, are combined to improve health. The estimated elasticity of substitution from a constant elasticity of substitution production function is significantly less than one for the working-age population, rejecting the unit elasticity of substitution used in previous studies. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
Influence of temperature on elastic properties of caesium cyanide
International Nuclear Information System (INIS)
Singh, Preeti; Gaur, N.K.; Singh, R.K.
2007-01-01
An extended three body force shell model (ETSM), which incorporates the effects of translational-rotational (TR) coupling, three body interactions (TBI) and anharmonicity, has been applied to investigate the temperature dependence of the second order elastic constants (c ij , i,j=1,2) of CsCN. The elastic constant c 44 obtained by us shows an anomalous behaviour with the variation of temperature. The variations of elastic constants (c 11 , c 12 , c 44 ) with temperature are almost in excellent agreement with Brillouin scattering measured data. We have also evaluated the temperature variations of the third order elastic constants (c ijk ) and the pressure derivatives of the c ij in the CsCN material. However, their values could not be compared due to lack of experimental data. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Size effect of the elastic modulus of rectangular nanobeams: Surface elasticity effect
International Nuclear Information System (INIS)
Yao Hai-Yan; Fan Wen-Liang; Yun Guo-Hong
2013-01-01
The size-dependent elastic property of rectangular nanobeams (nanowires or nanoplates) induced by the surface elasticity effect is investigated by using a developed modified core-shell model. The effect of surface elasticity on the elastic modulus of nanobeams can be characterized by two surface related parameters, i.e., inhomogeneous degree constant and surface layer thickness. The analytical results show that the elastic modulus of the rectangular nanobeam exhibits a distinct size effect when its characteristic size reduces below 100 nm. It is also found that the theoretical results calculated by a modified core-shell model have more obvious advantages than those by other models (core-shell model and core-surface model) by comparing them with relevant experimental measurements and computational results, especially when the dimensions of nanostructures reduce to a few tens of nanometers. (condensed matter: structural, mechanical, and thermal properties)
Boron nitride elastic and thermal properties. Irradiation effects
International Nuclear Information System (INIS)
Jager, Bernard.
1977-01-01
The anisotropy of boron nitride (BN) and especially thermal and elastic properties were studied. Specific heat and thermal conductivity between 1.2 and 300K, thermal conductivity between 4 and 350K and elastic constants C 33 and C 44 were measured. BN was irradiated with electrons at 77K and with neutrons at 27K to determine properties after irradiation [fr
ELASTIC CHARACTERIZATION OF Eucalyptus citriodora WOOD
Directory of Open Access Journals (Sweden)
Adriano Wagner Ballarin
2003-01-01
Full Text Available This paper contributed to the elastic characterization of Eucalyptus citriodora grown inBrazil, considering an orthotropic model and evaluating its most important elastic constants.Considering this as a reference work to establish basic elastic ratios — several important elasticconstants of Brazilian woods were not determined yet - the experimental set-up utilized one tree of 65years old from plantations of “Horto Florestal Navarro de Andrade”, at Rio Claro-SP, Brazil. All theexperimental procedures attended NBR 7190/97 – Brazilian Code for wooden structures –withconventional tension and compression tests. Results showed statistical identity between compressionand tension modulus of elasticity. The relation observed between longitudinal and radial modulus ofelasticity was 10 (EL/ER ≈ 10 and same relation, considering shear modulus (modulus of rigidity was20 (EL/GLR ≈ 20. These results, associated with Poisson’s ratios herein determined, allow theoreticalmodeling of wood mechanical behavior in structures.
Elastic softness of hybrid lead halide perovskites
Ferreira, A. C.; Lé toublon, A.; Paofai, S.; Raymond, S.; Ecolivet, C.; Rufflé , B.; Cordier, S.; Katan, C.; Saidaminov, Makhsud I.; Zhumekenov, A. A.; Bakr, Osman; Even, J.; Bourges, Ph.
2018-01-01
scattering, low frequency acoustic phonons in four different hybrid perovskite single crystals: MAPbBr3, FAPbBr3, MAPbI3 and α-FAPbI3 (MA: methylammonium, FA: formamidinium). We report a complete set of elastic constants caracterized by a very soft shear
In Silico Measurement of Elastic Moduli of Nematic Liquid Crystals
Sidky, Hythem; de Pablo, Juan J.; Whitmer, Jonathan K.
2018-03-01
Experiments on confined droplets of the nematic liquid crystal 5CB have questioned long-established bounds imposed on the elastic free energy of nematic systems. This elasticity, which derives from molecular alignment within nematic systems, is quantified through a set of moduli which can be difficult to measure experimentally and, in some cases, can only be probed indirectly. This is particularly true of the surfacelike saddle-splay elastic term, for which the available experimental data indicate values on the cusp of stability, often with large uncertainties. Here, we demonstrate that all nematic elastic moduli, including the saddle-splay elastic constant k24, may be calculated directly from atomistic molecular simulations. Importantly, results obtained through in silico measurements of the 5CB elastic properties demonstrate unambiguously that saddle-splay elasticity alone is unable to describe the observed confined morphologies.
Microstructural evolution in inhomogeneous elastic media
International Nuclear Information System (INIS)
Jou, H.J.; Leo, P.H.; Lowengrub, J.S.
1997-01-01
We simulate the diffusional evolution of microstructures produced by solid state diffusional transformations in elastically stressed binary alloys in two dimensions. The microstructure consists of arbitrarily shaped precipitates embedded coherently in an infinite matrix. The precipitate and matrix are taken to be elastically isotropic, although they may have different elastic constants (elastically inhomogeneous). Both far-field applied strains and mismatch strains between the phases are considered. The diffusion and elastic fields are calculated using the boundary integral method, together with a small scale preconditioner to remove ill-conditioning. The precipitate-matrix interfaces are tracked using a nonstiff time updating method. The numerical method is spectrally accurate and efficient. Simulations of a single precipitate indicate that precipitate shapes depend strongly on the mass flux into the system as well as on the elastic fields. Growing shapes (positive mass flux) are dendritic while equilibrium shapes (zero mass flux) are squarish. Simulations of multiparticle systems show complicated interactions between precipitate morphology and the overall development of microstructure (i.e., precipitate alignment, translation, merging, and coarsening). In both single and multiple particle simulations, the details of the microstructural evolution depend strongly o the elastic inhomogeneity, misfit strain, and applied fields. 57 refs., 24 figs
Elastic scattering and quasi-elastic transfers
International Nuclear Information System (INIS)
Mermaz, M.C.
1978-01-01
Experiments are presented which it will be possible to carry out at GANIL on the elastic scattering of heavy ions: diffraction phenomena if the absorption is great, refraction phenomena if absorption is low. The determination of the optical parameters can be performed. The study of the quasi-elastic transfer reactions will make it possible to know the dynamics of the nuclear reactions, form exotic nuclei and study their energy excitation spectrum, and analyse the scattering and reaction cross sections [fr
Nonlinear Elasticity of Borocarbide Superconductor YNi2B2C: A First-Principles Study
Directory of Open Access Journals (Sweden)
Lili Liu
2017-01-01
Full Text Available First-principles calculations combined with homogeneous deformation methods are used to investigate the second- and third-order elastic constants of YNi2B2C with tetragonal structure. The predicted lattice constants and second-order elastic constants of YNi2B2C agree well with the available data. The effective second-order elastic constants are obtained from the second- and third-order elastic constants for YNi2B2C. Based on the effective second-order elastic constants, Pugh’s modulus ratio, Poisson’s ratio, and Vickers hardness of YNi2B2C under high pressure are further investigated. It is shown that the ductility of YNi2B2C increases with increasing pressure.
Kaspar, Jan; Deile, M
The seemingly simple elastic scattering of protons still presents a challenge for the theory. In this thesis we discuss the elastic scattering from theoretical as well as experimental point of view. In the theory part, we present several models and their predictions for the LHC. We also discuss the Coulomb-hadronic interference, where we present a new eikonal calculation to all orders of alpha, the fine-structure constant. In the experimental part we introduce the TOTEM experiment which is dedicated, among other subjects, to the measurement of the elastic scattering at the LHC. This measurement is performed primarily with the Roman Pot (RP) detectors - movable beam-pipe insertions hundreds of meters from the interaction point, that can detect protons scattered to very small angles. We discuss some aspects of the RP simulation and reconstruction software. A central point is devoted to the techniques of RP alignment - determining the RP sensor positions relative to each other and to the beam. At the end we pres...
Indian Academy of Sciences (India)
IAS Admin
The article discusses the importance of the fine structure constant in quantum mechanics, along with the brief history of how it emerged. Al- though Sommerfelds idea of elliptical orbits has been replaced by wave mechanics, the fine struc- ture constant he introduced has remained as an important parameter in the field of ...
Generalized monotonicity from global minimization in fourth-order ODEs
M.A. Peletier (Mark)
2000-01-01
textabstractWe consider solutions of the stationary Extended Fisher-Kolmogorov equation with general potential that are global minimizers of an associated variational problem. We present results that relate the global minimization property to a generalized concept of monotonicity of the solutions.
Positive solutions for a fourth order boundary value problem
Directory of Open Access Journals (Sweden)
Bo Yang
2005-02-01
Full Text Available We consider a boundary value problem for the beam equation, in which the boundary conditions mean that the beam is embedded at one end and free at the other end. Some new estimates to the positive solutions to the boundary value problem are obtained. Some sufficient conditions for the existence of at least one positive solution for the boundary value problem are established. An example is given at the end of the paper to illustrate the main results.
Ghost-free, finite, fourth-order D = 3 gravity.
Deser, S
2009-09-04
Canonical analysis of a recently proposed linear + quadratic curvature gravity model in D = 3 establishes its pure, irreducibly fourth derivative, quadratic curvature limit as both ghost-free and power-counting UV finite, thereby maximally violating standard folklore. This limit is representative of a generic class whose kinetic terms are conformally invariant in any dimension, but it is unique in simultaneously avoiding the transverse-traceless graviton ghosts plaguing D > 3 quadratic actions as well as double pole propagators in its other variables. While the two-term model is also unitary, its additional mode's second-derivative nature forfeits finiteness.
Fourth-order structural steganalysis and analysis of cover assumptions
Ker, Andrew D.
2006-02-01
We extend our previous work on structural steganalysis of LSB replacement in digital images, building detectors which analyse the effect of LSB operations on pixel groups as large as four. Some of the method previously applied to triplets of pixels carries over straightforwardly. However we discover new complexities in the specification of a cover image model, a key component of the detector. There are many reasonable symmetry assumptions which we can make about parity and structure in natural images, only some of which provide detection of steganography, and the challenge is to identify the symmetries a) completely, and b) concisely. We give a list of possible symmetries and then reduce them to a complete, non-redundant, and approximately independent set. Some experimental results suggest that all useful symmetries are thus described. A weighting is proposed and its approximate variance stabilisation verified empirically. Finally, we apply symmetries to create a novel quadruples detector for LSB replacement steganography. Experimental results show some improvement, in most cases, over other detectors. However the gain in performance is moderate compared with the increased complexity in the detection algorithm, and we suggest that, without new insight, further extension of structural steganalysis may provide diminishing returns.
Becker, K.; Shapiro, S.; Stanchits, S.; Dresen, G.; Kaselow, A.; Vinciguerra, S.
2005-12-01
Elastic properties of rocks are sensitive to changes of the in-situ stress and damage state. In particular, seismic velocities are strongly affected by stress-induced formation and deformation of cracks or shear-enhanced pore collapse. The effect of stress on seismic velocities as a result of pore space deformation in isotropic rock at isostatic compression may be expressed by the equation: A+K*P-B*exp (-D*P) (1), where P=Pc-Pp is the effective pressure, the pure difference between confining pressure and pore pressure. The parameter A, K, B and D describe material constants determined using experimental data. The physical meaning of the parameters is given by Shapiro (2003, in Geophysics Vol.68(Nr.2)). Parameter D is related to the stress sensitivity of the rock. A similar relation was derived by Shapiro and Kaselow (2005, in Geophysics in press) for weak anisotropic rocks under arbitrary load. They describe the stress dependent anisotropy in terms of Thomson's (1986, in Geophysics, Vol. 51(Nr.10)) anisotropy parameters ɛ and γ as a function of stress in the case of an initially isotropic rock: ɛ ∝ E2-E3, γ ∝ E3-E2 (2) with Ei=exp (D*Pi). The exponential terms Ei are controlled by the effective stress components Pi. To test this relation, we have conducted a series of triaxial compression tests on dry samples of initially isotropic Etnean Basalt in a servo-controlled MTS loading frame equipped with a pressure cell. Confining pressure was 60, 40 and 20 MPa. Samples were 5 cm in diameter and 10 cm in length. Elastic anisotropy was induced by axial compression of the samples through opening and growth of microcracks predominantly oriented parallel to the sample axis. Ultrasonic P- and S- wave velocities were monitored parallel and normal to the sample axis by an array of 20 piezoceramic transducers glued to the surface. Preamplified full waveform signals were stored in two 12 channel transient recorders. According to equation 2 the anisotropy parameters are
Membrane elastic properties and cell function.
Directory of Open Access Journals (Sweden)
Bruno Pontes
Full Text Available Recent studies indicate that the cell membrane, interacting with its attached cytoskeleton, is an important regulator of cell function, exerting and responding to forces. We investigate this relationship by looking for connections between cell membrane elastic properties, especially surface tension and bending modulus, and cell function. Those properties are measured by pulling tethers from the cell membrane with optical tweezers. Their values are determined for all major cell types of the central nervous system, as well as for macrophage. Astrocytes and glioblastoma cells, which are considerably more dynamic than neurons, have substantially larger surface tensions. Resting microglia, which continually scan their environment through motility and protrusions, have the highest elastic constants, with values similar to those for resting macrophage. For both microglia and macrophage, we find a sharp softening of bending modulus between their resting and activated forms, which is very advantageous for their acquisition of phagocytic functions upon activation. We also determine the elastic constants of pure cell membrane, with no attached cytoskeleton. For all cell types, the presence of F-actin within tethers, contrary to conventional wisdom, is confirmed. Our findings suggest the existence of a close connection between membrane elastic constants and cell function.
First-principles calculations for elastic properties of OsB{sub 2} under pressure
Energy Technology Data Exchange (ETDEWEB)
Yang Junwei [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Chen Xiangrong, E-mail: x.r.chen@tom.co [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); International Centre for Materials Physics, Chinese Academy of Sciences, Shenyang 110016 (China); Luo Fen [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Ji Guangfu [Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, Chinese Academy of Engineering Physics, Mianyang 621900 (China)
2009-11-01
The structure, elastic properties and elastic anisotropy of orthorhombic OsB{sub 2} are investigated by density functional theory method with the ultrasoft pseudopotential scheme in the frame of the generalized gradient approximation (GGA) as well as local density approximation (LDA). The obtained structural parameters, elastic constants, elastic anisotropy and Debye temperature for OsB{sub 2} under pressure are consistent with the available experimental data and other theoretical results. It is found that the elastic constants, bulk modulus and Debye temperature of OsB{sub 2} tend to increase with increasing pressure. It is predicted that OsB{sub 2} is not a superhard material from our calculations.
First-principles calculations for elastic properties of OsB2 under pressure
International Nuclear Information System (INIS)
Yang Junwei; Chen Xiangrong; Luo Fen; Ji Guangfu
2009-01-01
The structure, elastic properties and elastic anisotropy of orthorhombic OsB 2 are investigated by density functional theory method with the ultrasoft pseudopotential scheme in the frame of the generalized gradient approximation (GGA) as well as local density approximation (LDA). The obtained structural parameters, elastic constants, elastic anisotropy and Debye temperature for OsB 2 under pressure are consistent with the available experimental data and other theoretical results. It is found that the elastic constants, bulk modulus and Debye temperature of OsB 2 tend to increase with increasing pressure. It is predicted that OsB 2 is not a superhard material from our calculations.
First-principles calculations for elastic properties of OsB 2 under pressure
Yang, Jun-Wei; Chen, Xiang-Rong; Luo, Fen; Ji, Guang-Fu
2009-11-01
The structure, elastic properties and elastic anisotropy of orthorhombic OsB 2 are investigated by density functional theory method with the ultrasoft pseudopotential scheme in the frame of the generalized gradient approximation (GGA) as well as local density approximation (LDA). The obtained structural parameters, elastic constants, elastic anisotropy and Debye temperature for OsB 2 under pressure are consistent with the available experimental data and other theoretical results. It is found that the elastic constants, bulk modulus and Debye temperature of OsB 2 tend to increase with increasing pressure. It is predicted that OsB 2 is not a superhard material from our calculations.
Paro, Alberto
2013-01-01
Written in an engaging, easy-to-follow style, the recipes will help you to extend the capabilities of ElasticSearch to manage your data effectively.If you are a developer who implements ElasticSearch in your web applications, manage data, or have decided to start using ElasticSearch, this book is ideal for you. This book assumes that you've got working knowledge of JSON and Java
Cosmological constants and variations
International Nuclear Information System (INIS)
Barrow, John D
2005-01-01
We review properties of theories for the variation of the gravitation and fine structure 'constants'. We highlight some general features of the cosmological models that exist in these theories with reference to recent quasar data that is consistent with time-variation in the fine structure 'constant' since a redshift of 3.5. The behaviour of a simple class of varying alpha cosmologies is outlined in the light of all the observational constraints. We also discuss some of the consequences of varying 'constants' for oscillating universes and show by means of exact solutions that they appear to evolve monotonically in time even though the scale factor of the universe oscillates
The cosmological constant problem
International Nuclear Information System (INIS)
Dolgov, A.D.
1989-05-01
A review of the cosmological term problem is presented. Baby universe model and the compensating field model are discussed. The importance of more accurate data on the Hubble constant and the Universe age is stressed. 18 refs
Density functional calculations of elastic properties of portlandite, Ca(OH)(2)
DEFF Research Database (Denmark)
Laugesen, Jakob Lund
2005-01-01
The elastic constants of portlandite, Ca(OH)(2), are calculated by use of density functional theory. A lattice optimization of an infinite (periodic boundary conditions) lattice is performed on which strains are applied. The elastic constants are extracted by minimizing Hooke's law of linear...
Elastic anisotropy and low-temperature thermal expansion in the shape memory alloy Cu-Al-Zn.
Kuruvilla, Santhosh Potharay; Menon, C S
2008-04-01
Cu-based shape memory alloys are known for their technologically important pseudo-elastic and shapememory properties, which are intimately associated with the martensitic transformation. A combination of deformation theory and finite-strain elasticity theory has been employed to arrive at the expressions for higher order elastic constants of Cu-Al-Zn based on Keating's approach. The second- and third-order elastic constants are in good agreement with the measurements. The aggregate elastic properties like bulk modulus, pressure derivatives, mode Grüneisen parameters of the elastic waves, low temperature limit of thermal expansion, and the Anderson-Grüneisen parameter are also presented.
Temperature effect on elastic properties of yttrium ferrite garnet Y3Fe5O12
International Nuclear Information System (INIS)
Burenkov, Yu.A.; Nikanorov, S.P.
2002-01-01
One studied temperature dependence of all independent elastic constants describing comprehensively elastic anisotropy of yttrium ferrite garnet within temperature wide range covering T c . One measured the Young modules for [100] and [110] crystallographic directions and the module of shift for [100] direction of specially pure single crystal of yttrium ferrite garnet within 20-600 deg C temperature range. One analyzed behavior of elastic modules and of elastic anisotropy factor near the critical temperature of magnetic phase transition [ru
Paro, Alberto
2015-01-01
If you are a developer who implements ElasticSearch in your web applications and want to sharpen your understanding of the core elements and applications, this is the book for you. It is assumed that you've got working knowledge of JSON and, if you want to extend ElasticSearch, of Java and related technologies.
Elasticity theory and applications
Saada, Adel S; Hartnett, James P; Hughes, William F
2013-01-01
Elasticity: Theory and Applications reviews the theory and applications of elasticity. The book is divided into three parts. The first part is concerned with the kinematics of continuous media; the second part focuses on the analysis of stress; and the third part considers the theory of elasticity and its applications to engineering problems. This book consists of 18 chapters; the first of which deals with the kinematics of continuous media. The basic definitions and the operations of matrix algebra are presented in the next chapter, followed by a discussion on the linear transformation of points. The study of finite and linear strains gradually introduces the reader to the tensor concept. Orthogonal curvilinear coordinates are examined in detail, along with the similarities between stress and strain. The chapters that follow cover torsion; the three-dimensional theory of linear elasticity and the requirements for the solution of elasticity problems; the method of potentials; and topics related to cylinders, ...
Measuring global gasoline and diesel price and income elasticities
International Nuclear Information System (INIS)
Dahl, Carol A.
2012-01-01
Price and income elasticities of transport fuel demand have numerous applications. They help forecast increases in fuel consumption as countries get richer, they help develop appropriate tax policies to curtail consumption, help determine how the transport fuel mix might evolve, and show the price response to a fuel disruption. Given their usefulness, it is understandable why hundreds of studies have focused on measuring such elasticities for gasoline and diesel fuel consumption. In this paper, I focus my attention on price and income elasticities in the existing studies to see what can be learned from them. I summarize the elasticities from these historical studies. I use statistical analysis to investigate whether income and price elasticities seem to be constant across countries with different incomes and prices. Although income and price elasticities for gasoline and diesel fuel are not found to be the same at high and low incomes and at high and low prices, patterns emerge that allow me to develop suggested price and income elasticities for gasoline and diesel demand for over one hundred countries. I adjust these elasticities for recent fuel mix policies, and suggest an agenda of future research topics. - Research highlights: ► Surveyed econometric studies of transport fuel demand. ► Developed price elasticities of demand for gasoline and diesel fuel for 120 countries. ► Developed income elasticities of demand for gasoline and diesel fuel for 120 countries. ► Suggested a research agenda for future work.
Elastic properties of some transition metal arsenides
Nayak, Vikas; Verma, U. P.; Bisht, P. S.
2018-05-01
The elastic properties of transition metal arsenides (TMAs) have been studied by employing Wien2K package based on density functional theory in the zinc blende (ZB) and rock salt (RS) phase treating valance electron scalar relativistically. Further, we have also treated them non-relativistically to find out the relativistic effect. We have calculated the elastic properties by computing the volume conservative stress tensor for small strains, using the method developed by Charpin. The obtained results are discussed in paper. From the obtained results, it is clear that the values of C11 > C12 and C44 for all the compounds. The values of shear moduli of these compounds are also calculated. The internal parameter for these compounds shows that ZB structures of these compounds have high resistance against bond order. We find that the estimated elastic constants are in good agreement with the available data.
Radiographic constant exposure technique
DEFF Research Database (Denmark)
Domanus, Joseph Czeslaw
1985-01-01
The constant exposure technique has been applied to assess various industrial radiographic systems. Different X-ray films and radiographic papers of two producers were compared. Special attention was given to fast film and paper used with fluorometallic screens. Radiographic image quality...... was tested by the use of ISO wire IQI's and ASTM penetrameters used on Al and Fe test plates. Relative speed and reduction of kilovoltage obtained with the constant exposure technique were calculated. The advantages of fast radiographic systems are pointed out...
Elasticity of Tantalum to 105 Gpa using a stress and angle-resolved x-ray diffraction
International Nuclear Information System (INIS)
Cynn, H; Yoo, C S
1999-01-01
Determining the mechanical properties such as elastic constants of metals at Mbar pressures has been a difficult task in experiment. Following the development of anisotropic elastic theory by Singh et al.[l], Mao et a1.[2] have recently developed a novel experimental technique to determine the elastic constants of Fe by using the stress and energy-dispersive x-ray diffraction (SEX). In this paper, we present an improved complementary technique, stress and angle-resolved x-ray diffraction (SAX), which we have applied to determine the elastic constants of tantalum to 105 GPa. The extrapolation of the tantalum elastic data shows an excellent agreement with the low-pressure ultrasonic data[3]. We also discuss the improvement of this SAX method over the previous SEX.[elastic constant, anisotropic elastic theory, angle-dispersive synchrotron x-ray diffraction, mechanical properties
International Nuclear Information System (INIS)
Chandra, R.
1977-01-01
On the grounds of the two correspondence limits, the Newtonian limit and the special theory limit of Einstein field equations, a modification of the cosmical constant has been proposed which gives realistic results in the case of a homogeneous universe. Also, according to this modification an explanation for the negative pressure in the steady-state model of the universe has been given. (author)
International Nuclear Information System (INIS)
Weinberg, S.
1989-01-01
Cosmological constant problem is discussed. History of the problem is briefly considered. Five different approaches to solution of the problem are described: supersymmetry, supergravity, superstring; anthropic approach; mechamism of lagrangian alignment; modification of gravitation theory and quantum cosmology. It is noted that approach, based on quantum cosmology is the most promising one
International Nuclear Information System (INIS)
O Murchadha, N.
1991-01-01
The set of riemannian three-metrics with positive Yamabe constant defines the space of independent data for the gravitational field. The boundary of this set is investigated, and it is shown that metrics close to the boundary satisfy the positive-energy theorem. (Author) 18 refs
Rao, Ch. K.; Rao, L. B.
2017-07-01
The problem of stability of fluid-conveying carbon nanotubes embedded in an elastic medium is investigated in this paper. A nonlocal continuum mechanics formulation, which takes the small length scale effects into consideration, is utilized to derive the governing fourth-order partial differential equations. The Fourier series method is used for the case of the pinned-pinned boundary condition of the tube. The Galerkin technique is utilized to find a solution of the governing equation for the case of the clamped-clamped boundary. Closed-form expressions for the critical flow velocity are obtained for different values of the Winkler and Pasternak foundation stiffness parameters. Moreover, new and interesting results are also reported for varying values of the nonlocal length parameter. It is observed that the nonlocal length parameter along with the Winkler and Pasternak foundation stiffness parameters exert considerable effects on the critical velocities of the fluid flow in nanotubes.
Elastic fiber-mediated enthesis in the human middle ear.
Kawase, Tetsuaki; Shibata, Shunichi; Katori, Yukio; Ohtsuka, Aiji; Murakami, Gen; Fujimiya, Mineko
2012-10-01
Adaptation to constant vibration (acoustic oscillation) is likely to confer a specific morphology at the bone-tendon and bone-ligament interfaces at the ear ossicles, which therefore represent an exciting target of enthesis research. We histologically examined (i) the bone attachments of the tensor tympani and stapedius muscles and (ii) the annular ligament of the incudostapedial joint obtained from seven elderly donated cadavers. Notably, both aldehyde-fuchsin and elastic-Masson staining demonstrated that the major fibrous component of the entheses was not collagen fibers but mature elastic fibers. The positive controls for elastic fiber staining were the arterial wall elastic laminae included in the temporal bone materials. The elastic fibers were inserted deeply into the type II collagen-poor fibrocartilage covering the ear ossicles. The muscle tendons were composed of an outer thin layer of collagen fibers and an inner thick core of elastic fibers near the malleus or stapes. In the unique elastic fiber-mediated entheses, hyaluronan, versican and fibronectin were expressed strongly along the elastic fibers. The hyaluronan seemed to act as a friction-reducing lubricant for the elastic fibers. Aggrecan was labeled strongly in a disk- or plica-like fibrous mass on the inner side of the elastic fiber-rich ligament, possibly due to compression stress from the ligament. Tenascin-c was not evident in the entheses. The elastic fiber-mediated entheses appeared resistant to tissue destruction in an environment exposed to constant vibration. The morphology was unlikely to be the result of age-related degeneration. © 2012 The Authors Journal of Anatomy © 2012 Anatomical Society.
Super-Grid Modeling of the Elastic Wave Equation in Semi-Bounded Domains
Energy Technology Data Exchange (ETDEWEB)
Petersson, N. Anders; Sjögreen, Björn
2014-10-01
We develop a super-grid modeling technique for solving the elastic wave equation in semi-bounded two- and three-dimensional spatial domains. In this method, waves are slowed down and dissipated in sponge layers near the far-field boundaries. Mathematically, this is equivalent to a coordinate mapping that transforms a very large physical domain to a significantly smaller computational domain, where the elastic wave equation is solved numerically on a regular grid. To damp out waves that become poorly resolved because of the coordinate mapping, a high order artificial dissipation operator is added in layers near the boundaries of the computational domain. We prove by energy estimates that the super-grid modeling leads to a stable numerical method with decreasing energy, which is valid for heterogeneous material properties and a free surface boundary condition on one side of the domain. Our spatial discretization is based on a fourth order accurate finite difference method, which satisfies the principle of summation by parts. We show that the discrete energy estimate holds also when a centered finite difference stencil is combined with homogeneous Dirichlet conditions at several ghost points outside of the far-field boundaries. Therefore, the coefficients in the finite difference stencils need only be boundary modified near the free surface. This allows for improved computational efficiency and significant simplifications of the implementation of the proposed method in multi-dimensional domains. Numerical experiments in three space dimensions show that the modeling error from truncating the domain can be made very small by choosing a sufficiently wide super-grid damping layer. The numerical accuracy is first evaluated against analytical solutions of Lamb’s problem, where fourth order accuracy is observed with a sixth order artificial dissipation. We then use successive grid refinements to study the numerical accuracy in the more
Statistical mechanics of elasticity
Weiner, JH
2012-01-01
Advanced, self-contained treatment illustrates general principles and elastic behavior of solids. Topics include thermoelastic behavior of crystalline and polymeric solids, interatomic force laws, behavior of solids, and thermally activated processes. 1983 edition.
Elasticity of energy consumption
International Nuclear Information System (INIS)
Stam, M.
2004-01-01
Insight is given into the price elasticities of several energy carriers. Next, attention is paid to the impact of the discussion on changes of the Regulating Energy Levy (REB, abbreviated in Dutch) in the Netherlands [nl
Kuc, Rafal
2013-01-01
A practical tutorial that covers the difficult design, implementation, and management of search solutions.Mastering ElasticSearch is aimed at to intermediate users who want to extend their knowledge about ElasticSearch. The topics that are described in the book are detailed, but we assume that you already know the basics, like the query DSL or data indexing. Advanced users will also find this book useful, as the examples are getting deep into the internals where it is needed.
Production in constant evolution
International Nuclear Information System (INIS)
Lozano, T.
2009-01-01
The Cofrentes Nuclear Power Plant now has 25 years of operation behind it: a quarter century adding value and demonstrating the reasons why it is one of the most important energy producing facilities in the Spanish power market. Particularly noteworthy is the enterprising spirit of the plant, which has strived to continuously improve with the large number of modernization projects that it has undertaken over the past 25 years. The plant has constantly evolved thanks to the amount of investments made to improve safety and reliability and the perseverance to stay technologically up to date. Efficiency, training and teamwork have been key to the success of the plant over these 25 years of constant change and progress. (Author)
International Nuclear Information System (INIS)
Blake, J.B.; Dearborn, D.S.P.
1979-01-01
Small fluctuations in the solar constant can occur on timescales much shorter than the Kelvin time. Changes in the ability of convection to transmit energy through the superadiabatic and transition regions of the convection zone cause structure adjustments which can occur on a time scale of days. The bulk of the convection zone reacts to maintain hydrostatic equilibrium (though not thermal equilibrium) and causes a luminosity change. While small radius variations will occur, most of the change will be seen in temperature
Stabilized power constant alimentation
International Nuclear Information System (INIS)
Roussel, L.
1968-06-01
The study and realization of a stabilized power alimentation variable from 5 to 100 watts are described. In order to realize a constant power drift of Lithium compensated diodes, we have searched a 1 per cent precision of regulation and a response time minus than 1 sec. Recent components like Hall multiplicator and integrated amplifiers give this possibility and it is easy to use permutable circuits. (author) [fr
Yongquan, Han
2016-10-01
The ideal gas state equation is not applicable to ordinary gas, it should be applied to the Electromagnetic ``gas'' that is applied to the radiation, the radiation should be the ultimate state of matter changes or initial state, the universe is filled with radiation. That is, the ideal gas equation of state is suitable for the Singular point and the universe. Maybe someone consider that, there is no vessel can accommodate radiation, it is because the Ordinary container is too small to accommodate, if the radius of your container is the distance that Light through an hour, would you still think it can't accommodates radiation? Modern scientific determinate that the radius of the universe now is about 1027 m, assuming that the universe is a sphere whose volume is approximately: V = 4.19 × 1081 cubic meters, the temperature radiation of the universe (cosmic microwave background radiation temperature of the universe, should be the closest the average temperature of the universe) T = 3.15k, radiation pressure P = 5 × 10-6 N / m 2, according to the law of ideal gas state equation, PV / T = constant = 6 × 1075, the value of this constant is the universe, The singular point should also equal to the constant Author: hanyongquan
Connecting Fundamental Constants
International Nuclear Information System (INIS)
Di Mario, D.
2008-01-01
A model for a black hole electron is built from three basic constants only: h, c and G. The result is a description of the electron with its mass and charge. The nature of this black hole seems to fit the properties of the Planck particle and new relationships among basic constants are possible. The time dilation factor in a black hole associated with a variable gravitational field would appear to us as a charge; on the other hand the Planck time is acting as a time gap drastically limiting what we are able to measure and its dimension will appear in some quantities. This is why the Planck time is numerically very close to the gravitational/electric force ratio in an electron: its difference, disregarding a π√(2) factor, is only 0.2%. This is not a coincidence, it is always the same particle and the small difference is between a rotating and a non-rotating particle. The determination of its rotational speed yields accurate numbers for many quantities, including the fine structure constant and the electron magnetic moment
Stressed-deformed state of mountain rocks in elastic stage and between elasticity
Directory of Open Access Journals (Sweden)
Samedov A.M.
2017-12-01
Full Text Available The problems of the stress-strain state of rocks in the elastic stage and beyond the elastic limits, and the ways of schematizing the tension and compression diagrams were reviewed in the article. To simplify calculations outside the elastic range, the tension (compression diagrams are usually schematized, i.e. are replaced by curved smooth lines having a fairly simple mathematical expression and at the same time well coinciding with the experimentally obtained diagrams. When diagram is to be schematized, it is necessary to take a constant temperature of superheated water steam if a rock test is planned in a relaxed form. Note that when the diagram is schematizing, the difference between the limits of proportionality and fluidity is erased. This allows the limit of proportionality to be considered the limit of fluidity. Schematicization can be carried out in the area where the tensile strength (compression is planned to be destroyed with the established weakening of rocks by exposure to water steam or chemical reagents. Samples of rocks in natural form were tested and weakened by means of superheated water steam (220 °C and more and chemical reagents for tension and compression. The data are obtained, the diagrams of deformation are constructed and schematized in the elastic stage and beyond the elastic limit. Based on the schematic diagrams of deformation, the components of stress and strain were composed in the elastic stage and beyond the elastic limit. It is established in the publication that rocks under compression and stretching deform, both within the elastic stage, and beyond the limits of elasticity. This could be seen when the samples, both in natural and in weakened state, with superheated water steam (more than 220 °C or chemical reagents were tested. In their natural form, they are mainly deformed within the elastic stage and are destroyed as a brittle material, and in a weakened form they can deform beyond the elastic stage and
Elasticity of methane hydrate phases at high pressure
Energy Technology Data Exchange (ETDEWEB)
Beam, Jennifer; Yang, Jing; Liu, Jin [Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78712 (United States); Liu, Chujie [Laboratory of Seismology and Physics of Earth’s Interior, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026 (China); Lin, Jung-Fu, E-mail: afu@jsg.utexas.edu [Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78712 (United States); Center for High Pressure Science and Advanced Technology Research (HPSTAR), Shanghai 201203 (China)
2016-04-21
Determination of the full elastic constants (c{sub ij}) of methane hydrates (MHs) at extreme pressure-temperature environments is essential to our understanding of the elastic, thermodynamic, and mechanical properties of methane in MH reservoirs on Earth and icy satellites in the solar system. Here, we have investigated the elastic properties of singe-crystal cubic MH-sI, hexagonal MH-II, and orthorhombic MH-III phases at high pressures in a diamond anvil cell. Brillouin light scattering measurements, together with complimentary equation of state (pressure-density) results from X-ray diffraction and methane site occupancies in MH from Raman spectroscopy, were used to derive elastic constants of MH-sI, MH-II, and MH-III phases at high pressures. Analysis of the elastic constants for MH-sI and MH-II showed intriguing similarities and differences between the phases′ compressional wave velocity anisotropy and shear wave velocity anisotropy. Our results show that these high-pressure MH phases can exhibit distinct elastic, thermodynamic, and mechanical properties at relevant environments of their respective natural reservoirs. These results provide new insight into the determination of how much methane exists in MH reservoirs on Earth and on icy satellites elsewhere in the solar system and put constraints on the pressure and temperature conditions of their environment.
Piezoelectric excitation of elastic waves in centrosymmetrical potassium tantalate crystal
International Nuclear Information System (INIS)
Smolenskij, G.A.; Lemanov, V.V.; Sotnikov, A.V.; Syrnikov, P.P.; Yushin, N.K.
1981-01-01
Experiment results on excitation of elastic oscillations in potassium tantalate crystals are considered. The experiment has been conducted by usual for supersonic measurements technique: an impulse of the variable electric field has been applied to one of plane-parallel sample end-faces, at the same end-face signals corresponding to elastic pulses propagating in the crystal have been detected. Basic radiopulses parameters: basic frequency 30 MHz, duration 1-2 μs, pulse recurrence frequency 500 Hz, power 10 W. The investigation carried out has shown that the application to the sample at T=80 K temperature of constant external electrical field parallel to direction of elastic wave propagation leads to hysteresis dependence of elastic waves amplitude on the external voltage value. With temperature increase the hysteresis loop is deformed. It has been found when investigating temperature dependence of elastic wave amplitude that in the absence of external constant electrical field in short-circuited by constant current samples the oxillation excitation effect disappears at T approximately equal to 200 K. An essential influence on the elastic wave amplitude value is exerted by illumination of the crystal surface by light with 360-630 nm wave length. At T 130 K bacaee of photovoltaic effect in illuminated samples [ru
How Credible Are Shrinking Wage Elasticities of Married Women Labour Supply?
Directory of Open Access Journals (Sweden)
Duo Qin
2015-12-01
Full Text Available This paper delves into the well-known phenomenon of shrinking wage elasticities for married women in the US over recent decades. The results of a novel model experimental approach via sample data ordering unveil considerable heterogeneity across different wage groups. Yet, surprisingly constant wage elasticity estimates are maintained within certain wage groups over time. In addition to those constant wage elasticity estimates, we find that the composition of working women into different wage groups has changed considerably, resulting in shrinking wage elasticity estimates at the aggregate level. These findings would be impossible to obtain had we not dismantled and discarded the instrumental variable estimation route.
Nonlinear elastic waves in materials
Rushchitsky, Jeremiah J
2014-01-01
The main goal of the book is a coherent treatment of the theory of propagation in materials of nonlinearly elastic waves of displacements, which corresponds to one modern line of development of the nonlinear theory of elastic waves. The book is divided on five basic parts: the necessary information on waves and materials; the necessary information on nonlinear theory of elasticity and elastic materials; analysis of one-dimensional nonlinear elastic waves of displacement – longitudinal, vertically and horizontally polarized transverse plane nonlinear elastic waves of displacement; analysis of one-dimensional nonlinear elastic waves of displacement – cylindrical and torsional nonlinear elastic waves of displacement; analysis of two-dimensional nonlinear elastic waves of displacement – Rayleigh and Love nonlinear elastic surface waves. The book is addressed first of all to people working in solid mechanics – from the students at an advanced undergraduate and graduate level to the scientists, professional...
Directory of Open Access Journals (Sweden)
Neal Jackson
2015-09-01
Full Text Available I review the current state of determinations of the Hubble constant, which gives the length scale of the Universe by relating the expansion velocity of objects to their distance. There are two broad categories of measurements. The first uses individual astrophysical objects which have some property that allows their intrinsic luminosity or size to be determined, or allows the determination of their distance by geometric means. The second category comprises the use of all-sky cosmic microwave background, or correlations between large samples of galaxies, to determine information about the geometry of the Universe and hence the Hubble constant, typically in a combination with other cosmological parameters. Many, but not all, object-based measurements give H_0 values of around 72–74 km s^–1 Mpc^–1, with typical errors of 2–3 km s^–1 Mpc^–1. This is in mild discrepancy with CMB-based measurements, in particular those from the Planck satellite, which give values of 67–68 km s^–1 Mpc^–1 and typical errors of 1–2 km s^–1 Mpc^–1. The size of the remaining systematics indicate that accuracy rather than precision is the remaining problem in a good determination of the Hubble constant. Whether a discrepancy exists, and whether new physics is needed to resolve it, depends on details of the systematics of the object-based methods, and also on the assumptions about other cosmological parameters and which datasets are combined in the case of the all-sky methods.
International Nuclear Information System (INIS)
Willson, R.C.; Hudson, H.
1984-01-01
The Active Cavity Radiometer Irradiance Monitor (ACRIM) of the Solar Maximum Mission satellite measures the radiant power emitted by the sun in the direction of the earth and has worked flawlessly since 1980. The main motivation for ACRIM's use to measure the solar constant is the determination of the extent to which this quantity's variations affect earth weather and climate. Data from the solar minimum of 1986-1987 is eagerly anticipated, with a view to the possible presence of a solar cycle variation in addition to that caused directly by sunspots
Elasticity of Hard-Spheres-And-Tether Systems
International Nuclear Information System (INIS)
Farago, O.; Kantor, Y.
1999-01-01
Physical properties of a large class of systems ranging from noble gases to polymers and rubber are primarily determined by entropy, while the internal energy plays a minor role. Such systems can be conveniently modeled and numerically studied using ''hard' (i.e., ''infinity-or-zero'') potentials, such as hard sphere repulsive interactions, or inextensible (''tether'') bonds which limit the distance between the bonded monomers, but have zero energy at all permitted distances. The knowledge of elastic constants is very important for understanding the behavior of entropy-dominated systems. Computational methods for determination of the elastic constants in such systems are broadly classified into ''strain'' methods and (fluctuation methods. In the former, the elastic constants are extracted from stress-strain relations, while in the latter they are determined from measurements of stress fluctuations. The fluctuation technique usually enables more accurate and well-controlled determination of the elastic constants since in this method the elastic constants are computed directly from simulations of the un strained system with no need to deform the simulation cell and perform numerical differentiations. For central forces systems, the original ''fluctuation'' formalism can be applied provided the pair potential is twice differentiable. We have extended this formalism to apply to hard-spheres-and-tether models in which this requirement is not fulfilled. We found that for such models the components of the tensor of elastic constants can be related to (two-, three- and four-point) probability densities of contacts between hard spheres and stretched bonds. We have tested our formalism on simple (phantom networks and three-dimensional hard spheres systems
Electromyographic Comparison of Squats Using Constant or Variable Resistance.
Andersen, Vidar; Steiro Fimland, Marius; Knutson Kolnes, Maria; Jensen, Susanne; Laume, Martine; Hole Saeterbakken, Atle
2016-12-01
Andersen, V, Fimland, MS, Kolnes, MK, Jensen, S, Laume, M and Saeterbakken, AH. Electromyographic comparison of squats using constant or variable resistance. J Strength Cond Res 30(12): 3456-3463, 2016-The aim of the study was to compare the electromyographic (EMG) activity of vastus lateralis, vastus medialis, rectus femoris, and biceps femoris when performing the squat with constant resistance or variable resistance with 2 or 4 elastic bands, respectively, contributing with a mean of 39 and 73% of the total loads. Nineteen resistance-trained women performed 6 repetition maximum using 3 different experimental conditions: free weights (FW), free weights + 2 elastic bands (FW + 2EB), and free weights + 4 elastic bands (FW + 4EB). During analyses, each repetition was divided into 6 phases: upper (more extended knee), middle, and lower phase of the descending and ascending movements. Increased activation in the upper parts of the movement was observed for both variable resistance conditions compared with constant resistance (9-51%, p squat using free weights in combination with elastic bands seems to be preferable compared with free weights alone and more so with a high contribution from variable resistance to the total load.
Effective constants for wave propagation through partially saturated porous media
International Nuclear Information System (INIS)
Berryman, J.G.; Thigpen, L.
1985-01-01
The multipole scattering coefficients for elastic wave scattering from a spherical inhomogeneity in a fluid-saturated porous medium have been calculated. These coefficients may be used to obtain estimates of the effective macroscopic constants for long-wavelength propagation of elastic waves through partially saturated media. If the volume average of the single scattering from spherical bubbles of gas and liquid is required to vanish, the resulting equations determine the effective bulk modulus, density, and viscosity of the multiphase fluid filling the pores. The formula for the effective viscosity during compressional wave excitation is apparently new
Elastic anisotropy of crystals
Directory of Open Access Journals (Sweden)
Christopher M. Kube
2016-09-01
Full Text Available An anisotropy index seeks to quantify how directionally dependent the properties of a system are. In this article, the focus is on quantifying the elastic anisotropy of crystalline materials. Previous elastic anisotropy indices are reviewed and their shortcomings discussed. A new scalar log-Euclidean anisotropy measure AL is proposed, which overcomes these deficiencies. It is based on a distance measure in a log-Euclidean space applied to fourth-rank elastic tensors. AL is an absolute measure of anisotropy where the limiting case of perfect isotropy yields zero. It is a universal measure of anisotropy applicable to all crystalline materials. Specific examples of strong anisotropy are highlighted. A supplementary material provides an anisotropy table giving the values of AL for 2,176 crystallite compounds.
International Nuclear Information System (INIS)
Das, Y.C.; Kedia, K.K.
1977-01-01
No realistic analytical work in the area of Shells on Elastic Foundations has been reported in the literature. Various foundation models have been proposed by several authors. These models involve one or more than one parameters to characterise the foundation medium. Some of these models cannot be used to derive the basic equations governing the behaviour of shells on elastic foundations. In the present work, starting from an elastic continuum hypothesis, a mathematical model for foundation has been derived in curvilinear orthogonal coordinates by the help of principle of virtual displacements, treating one of the virtual displacements as known to satisfy certain given conditions at its edge surfaces. In this model, several foundation parameters can be considered and it can also be used for layered medium of both finite and infinite thickness. (Auth.)
Effective stress law for anisotropic elastic deformation
International Nuclear Information System (INIS)
Carroll, M.M.
1979-01-01
An effective stress law is derived analytically to describe the effect of pore fluid pressure on the linearly elastic response of saturated porous rocks which exhibit anisotropy. For general anisotropy the difference between the effective stress and the applied stress is not hydrostatic. The effective stress law involves two constants for transversely isotropic response and three constants for orthotropic response; these constants can be expressed in terms of the moduli of the porous material and of the solid material. These expressions simplify considerably when the anisotropy is structural rather than intrinsic, i.e., in the case of an isotropic solid material with an anisotropic pore structure. In this case the effective stress law involves the solid or grain bulk modulus and two or three moduli of the porous material, for transverse isotropy and orthotropy, respectively. The law reduces, in the case of isotropic response, to that suggested by Geertsma (1957) and by Skempton (1961) and derived analytically by Nur and Byerlee
Hwu, Chyanbin
2010-01-01
As structural elements, anisotropic elastic plates find wide applications in modern technology. The plates here are considered to be subjected to not only in plane load but also transverse load. In other words, both plane and plate bending problems as well as the stretching-bending coupling problems are all explained in this book. In addition to the introduction of the theory of anisotropic elasticity, several important subjects have are discussed in this book such as interfaces, cracks, holes, inclusions, contact problems, piezoelectric materials, thermoelastic problems and boundary element a
Lai, Yun
2011-06-26
Metamaterials can exhibit electromagnetic and elastic characteristics beyond those found in nature. In this work, we present a design of elastic metamaterial that exhibits multiple resonances in its building blocks. Band structure calculations show two negative dispersion bands, of which one supports only compressional waves and thereby blurs the distinction between a fluid and a solid over a finite frequency regime, whereas the other displays super anisotropy-in which compressional waves and shear waves can propagate only along different directions. Such unusual characteristics, well explained by the effective medium theory, have no comparable analogue in conventional solids and may lead to novel applications. © 2011 Macmillan Publishers Limited. All rights reserved.
Lai, Yun; Wu, Ying; Sheng, Ping; Zhang, Zhaoqing
2011-01-01
Metamaterials can exhibit electromagnetic and elastic characteristics beyond those found in nature. In this work, we present a design of elastic metamaterial that exhibits multiple resonances in its building blocks. Band structure calculations show two negative dispersion bands, of which one supports only compressional waves and thereby blurs the distinction between a fluid and a solid over a finite frequency regime, whereas the other displays super anisotropy-in which compressional waves and shear waves can propagate only along different directions. Such unusual characteristics, well explained by the effective medium theory, have no comparable analogue in conventional solids and may lead to novel applications. © 2011 Macmillan Publishers Limited. All rights reserved.
Directory of Open Access Journals (Sweden)
Sergio Cesare Masin
2010-01-01
Full Text Available Participants estimated the imagined elongation of a spring while they were imagining that a load was stretching the spring. This elongation turned out to be a multiplicative function of spring length and load weight-a cognitive law analogous to Hooke¿s law of elasticity. Participants also estimated the total imagined elongation of springs joined either in series or in parallel. This total elongation was longer for serial than for parallel springs, and increased proportionally to the number of serial springs and inversely proportionally to the number of parallel springs. The results suggest that participants integrated load weight with imagined elasticity rather than with spring length.
Rogozinski, Marek
2014-01-01
This book is a detailed, practical, hands-on guide packed with real-life scenarios and examples which will show you how to implement an ElasticSearch search engine on your own websites.If you are a web developer or a user who wants to learn more about ElasticSearch, then this is the book for you. You do not need to know anything about ElastiSeach, Java, or Apache Lucene in order to use this book, though basic knowledge about databases and queries is required.
Elastic plastic fracture mechanics
International Nuclear Information System (INIS)
Simpson, L.A.
1978-07-01
The application of linear elastic fracture mechanics (LEFM) to crack stability in brittle structures is now well understood and widely applied. However, in many structural materials, crack propagation is accompanied by considerable crack-tip plasticity which invalidates the use of LEFM. Thus, present day research in fracture mechanics is aimed at developing parameters for predicting crack propagation under elastic-plastic conditions. These include critical crack-opening-displacement methods, the J integral and R-curve techniques. This report provides an introduction to these concepts and gives some examples of their applications. (author)
Identification of elastic properties of composite plate
International Nuclear Information System (INIS)
Kovalovs, A; Rucevskis, S
2011-01-01
Composite laminates are used extensively in the aerospace industry, especially for the fabrication of high-performance structures. The determination of stiffness parameters for complex materials, such as fibre-reinforced composites, is much more complicated than for isotropic materials. A conventional way is testing the coupon specimens, which are manufactured by technology similar to that used for the real, large structures. When such a method is used, the question arises of whether the material properties obtained from the coupon tests are the same as those in the large structure. Therefore, the determination of actual material properties for composite laminates using non-destructive evaluation techniques has been widely investigated. A number of various non-destructive evaluation techniques have been proposed for determining the material properties of composite laminates. In the present study, attention is focused on the identification of the elastic properties of laminated plate using vibration test data. The problem associated with vibration testing is converting the measured modal frequencies to elastic constants. A standard method for solving this problem is the use of a numerical-experimental model and optimization techniques. The identification functional represents the gap between the numerical model response and the experimental one. This gap should be minimized, taking into account the side constraints on the design variables (elastic constants). The minimization problem is solved by using non-linear mathematical programming techniques and sensitivity analysis. The results obtained were verified by comparing the experimentally measured eigenfrequencies with the numerical ones obtained by FEM at the point of optima
Pretko, Michael; Radzihovsky, Leo
2018-05-01
Motivated by recent studies of fractons, we demonstrate that elasticity theory of a two-dimensional quantum crystal is dual to a fracton tensor gauge theory, providing a concrete manifestation of the fracton phenomenon in an ordinary solid. The topological defects of elasticity theory map onto charges of the tensor gauge theory, with disclinations and dislocations corresponding to fractons and dipoles, respectively. The transverse and longitudinal phonons of crystals map onto the two gapless gauge modes of the gauge theory. The restricted dynamics of fractons matches with constraints on the mobility of lattice defects. The duality leads to numerous predictions for phases and phase transitions of the fracton system, such as the existence of gauge theory counterparts to the (commensurate) crystal, supersolid, hexatic, and isotropic fluid phases of elasticity theory. Extensions of this duality to generalized elasticity theories provide a route to the discovery of new fracton models. As a further consequence, the duality implies that fracton phases are relevant to the study of interacting topological crystalline insulators.
Cocco, Alberto; Masin, Sergio Cesare
2010-01-01
Participants estimated the imagined elongation of a spring while they were imagining that a load was stretching the spring. This elongation turned out to be a multiplicative function of spring length and load weight--a cognitive law analogous to Hooke's law of elasticity. Participants also estimated the total imagined elongation of springs joined…
Modeling Pseudo-elastic Behavior of Springback
International Nuclear Information System (INIS)
Xia, Z. Cedric
2005-01-01
constant. In the context of this investigation we refer psuedoelastic behavior in the most general sense as any deviation from linearity in the unloading curve. The non-linearity leads to a hysteresis loop upon reloading. The approach is based on the non-conventional theory with a vanishing elastic region as advanced by Dafalias and Popov. The treatment is purely phenomenological where we don't distinguish between macroscopic plasticity and micro-plasticity. The macroscopic uniaxial stress-strain curve is used to define effective plastic response in the same manner as classical plasticity theory except that the nonlinearity during unloading and reloading are incorporated into plasticity. It is shown that such models can be easily formulated within the context of elastoplasticity without violating any physical mechanisms of deformation. Springback for a plane strain bending model is used to demonstrate the potential effect if such a model is applied
Autonomic Vertical Elasticity of Docker Containers with ElasticDocker
Al-Dhuraibi , Yahya; Paraiso , Fawaz; Djarallah , Nabil; Merle , Philippe
2017-01-01
International audience; Elasticity is the key feature of cloud computing to scale computing resources according to application workloads timely. In the literature as well as in industrial products, much attention was given to the elasticity of virtual machines, but much less to the elasticity of containers. However, containers are the new trend for packaging and deploying microservices-based applications. Moreover, most of approaches focus on horizontal elasticity, fewer works address vertica...
Potential constants and centrifugal distortion constants of octahedral hexafluoride molecules
Energy Technology Data Exchange (ETDEWEB)
Manivannan, G [Government Thirumagal Mill' s Coll., Gudiyattam, Tamil Nadu (India)
1981-04-01
The kinetic constants method outlined by Thirugnanasambandham (1964) based on Wilson's (1955) group theory has been adapted in evaluating the potential constants for SF/sub 6/, SeF/sub 6/, WF/sub 6/, IrF/sub 6/, UF/sub 6/, NpF/sub 6/, and PuF/sub 6/ using the experimentally observed vibrational frequency data. These constants are used to calculate the centrifugal distortion constants for the first time.
Elastic softness of hybrid lead halide perovskites
Ferreira, A. C.
2018-01-26
Much recent attention has been devoted towards unravelling the microscopic optoelectronic properties of hybrid organic-inorganic perovskites (HOP). Here we investigate by coherent inelastic neutron scattering spectroscopy and Brillouin light scattering, low frequency acoustic phonons in four different hybrid perovskite single crystals: MAPbBr3, FAPbBr3, MAPbI3 and α-FAPbI3 (MA: methylammonium, FA: formamidinium). We report a complete set of elastic constants caracterized by a very soft shear modulus C44. Further, a tendency towards an incipient ferroelastic transition is observed in FAPbBr3. We observe a systematic lower sound group velocity in the technologically important iodide-based compounds compared to the bromide-based ones. The findings suggest that low thermal conductivity and hot phonon bottleneck phenomena are expected to be enhanced by low elastic stiffness, particularly in the case of the ultrasoft α-FAPbI3.
Data-Driven Problems in Elasticity
Conti, S.; Müller, S.; Ortiz, M.
2018-01-01
We consider a new class of problems in elasticity, referred to as Data-Driven problems, defined on the space of strain-stress field pairs, or phase space. The problem consists of minimizing the distance between a given material data set and the subspace of compatible strain fields and stress fields in equilibrium. We find that the classical solutions are recovered in the case of linear elasticity. We identify conditions for convergence of Data-Driven solutions corresponding to sequences of approximating material data sets. Specialization to constant material data set sequences in turn establishes an appropriate notion of relaxation. We find that relaxation within this Data-Driven framework is fundamentally different from the classical relaxation of energy functions. For instance, we show that in the Data-Driven framework the relaxation of a bistable material leads to material data sets that are not graphs.
Non-linear elastic deformations
Ogden, R W
1997-01-01
Classic in the field covers application of theory of finite elasticity to solution of boundary-value problems, analysis of mechanical properties of solid materials capable of large elastic deformations. Problems. References.
Correlations between elastic moduli and properties in bulk metallic glasses
International Nuclear Information System (INIS)
Wang Weihua
2006-01-01
A survey of the elastic, mechanical, fragility, and thermodynamic properties of bulk metallic glasses (BMGs) and glass-forming liquids is presented. It is found that the elastic moduli of BMGs have correlations with the glass transition temperature, melting temperature, mechanical properties, and even liquid fragility. On the other hand, the elastic constants of available BMGs show a rough correlation with a weighted average of the elastic constants for the constituent elements. Although the theoretical and physical reasons for the correlations are to be clarified, these correlations could assist in understanding the long-standing issues of glass formation and the nature of glass and simulate the work of theorists. Based on the correlation, we show that the elastic moduli can assist in selecting alloying components for controlling the elastic properties and glass-forming ability of the BMGs and thus can guide BMG design. As case study, we report the formation of the families of rare-earth-based BMGs with controllable properties
Designing interactively with elastic splines
DEFF Research Database (Denmark)
Brander, David; Bærentzen, Jakob Andreas; Fisker, Ann-Sofie
2018-01-01
We present an algorithm for designing interactively with C1 elastic splines. The idea is to design the elastic spline using a C1 cubic polynomial spline where each polynomial segment is so close to satisfying the Euler-Lagrange equation for elastic curves that the visual difference becomes neglig...... negligible. Using a database of cubic Bézier curves we are able to interactively modify the cubic spline such that it remains visually close to an elastic spline....
Approximation by planar elastic curves
DEFF Research Database (Denmark)
Brander, David; Gravesen, Jens; Nørbjerg, Toke Bjerge
2016-01-01
We give an algorithm for approximating a given plane curve segment by a planar elastic curve. The method depends on an analytic representation of the space of elastic curve segments, together with a geometric method for obtaining a good initial guess for the approximating curve. A gradient......-driven optimization is then used to find the approximating elastic curve....
1995-08-01
about the distances to galaxies and thereby about the expansion rate of the Universe. A simple way to determine the distance to a remote galaxy is by measuring its redshift, calculate its velocity from the redshift and divide this by the Hubble constant, H0. For instance, the measured redshift of the parent galaxy of SN 1995K (0.478) yields a velocity of 116,000 km/sec, somewhat more than one-third of the speed of light (300,000 km/sec). From the universal expansion rate, described by the Hubble constant (H0 = 20 km/sec per million lightyears as found by some studies), this velocity would indicate a distance to the supernova and its parent galaxy of about 5,800 million lightyears. The explosion of the supernova would thus have taken place 5,800 million years ago, i.e. about 1,000 million years before the solar system was formed. However, such a simple calculation works only for relatively ``nearby'' objects, perhaps out to some hundred million lightyears. When we look much further into space, we also look far back in time and it is not excluded that the universal expansion rate, i.e. the Hubble constant, may have been different at earlier epochs. This means that unless we know the change of the Hubble constant with time, we cannot determine reliable distances of distant galaxies from their measured redshifts and velocities. At the same time, knowledge about such change or lack of the same will provide unique information about the time elapsed since the Universe began to expand (the ``Big Bang''), that is, the age of the Universe and also its ultimate fate. The Deceleration Parameter q0 Cosmologists are therefore eager to determine not only the current expansion rate (i.e., the Hubble constant, H0) but also its possible change with time (known as the deceleration parameter, q0). Although a highly accurate value of H0 has still not become available, increasing attention is now given to the observational determination of the second parameter, cf. also the Appendix at the
Elastic Properties of Hard Films Multi-Layer Protective Coatings by Light Scattering
National Research Council Canada - National Science Library
Sooryakumar, R
2000-01-01
... (silicon oxynitride and ZnSe) and free-standing membranes (SiN). These harmonics provide a direct means to investigate the longitudinal and transverse sound velocities and thereby to determine the C11 and C44 elastic constants...
Elastic properties of surfactant monolayers at liquid-liquid interfaces: A molecular dynamics study
DEFF Research Database (Denmark)
Laradji, Mohamed; Mouritsen, Ole G.
2000-01-01
Using a simple molecular model based on the Lennard-Jones potential, we systematically study the elastic properties of liquid-liquid interfaces containing surfactant molecules by means of extensive and large-scale molecular dynamics simulations. The main elastic constants of the interface, corres...
Analytic approximations for the elastic moduli of two-phase materials
DEFF Research Database (Denmark)
Zhang, Z. J.; Zhu, Y. K.; Zhang, P.
2017-01-01
Based on the models of series and parallel connections of the two phases in a composite, analytic approximations are derived for the elastic constants (Young's modulus, shear modulus, and Poisson's ratio) of elastically isotropic two-phase composites containing second phases of various volume...
On the multiplicity of option prices under CEV with positive elasticity of variance
Veestraeten, D.
2017-01-01
The discounted stock price under the Constant Elasticity of Variance model is not a martingale when the elasticity of variance is positive. Two expressions for the European call price then arise, namely the price for which put-call parity holds and the price that represents the lowest cost of
On the multiplicity of option prices under CEV with positive elasticity of variance
Veestraeten, D.
2014-01-01
The discounted stock price under the Constant Elasticity of Variance (CEV) model is a strict local martingale when the elasticity of variance is positive. Two expressions for the European call price then arise, namely the risk-neutral call price and an alternative price that is linked to the unique
Development of elastic properties of Cu-based shape memory alloys during martensitic transformation
Czech Academy of Sciences Publication Activity Database
Novák, Václav; Landa, Michal; Šittner, Petr
2004-01-01
Roč. 115, - (2004), s. 363 ISSN 1155-4339 Institutional research plan: CEZ:AV0Z1010914 Keywords : Cu-based shape memory alloy s * elastic properties * elastic constants * modelling Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.294, year: 2004
Direct mechanics assessment of elastic symmetries and properties of trabecular bone architecture
Rietbergen, van B.; Odgaard, A.; Kabel, J.; Huiskes, H.W.J.
1996-01-01
A method is presented to find orthotropic elastic symmetries and constants directly from the elastic coefficients in the overall stiffness matrix of trabecular bone test specimens. Contrary to earlier developed techniques, this method does not require pure orthotropic behavior or additional fabric
To optimal elasticity of adhesives mimicking gecko foot-hairs
International Nuclear Information System (INIS)
Filippov, A.E.; Popov, V.
2006-01-01
Artificial structure of a plate with elastic fibers interacting with rough fractal surface by Van der Waals forces is simulated numerically to find an optimal relation between the system parameters. The force balance equations are solved numerically for different values of elastic constant and variable surface roughness. An optimal elasticity is found to provide maximum cohesion force between the plate and surface. It is shown that high flexibility of the fibers is not always good to efficiency of the system, artificial adhesives must be made from stiff enough polymers. If the ellasticity is close to an optimum, the force is almost constant at a wide interval of the surface roughness. It is desirable to make system adaptive to wide spectrum of applications
Association constants of telluronium salts
International Nuclear Information System (INIS)
Kovach, N.A.; Rivkin, B.B.; Sadekov, T.D.; Shvajka, O.P.
1996-01-01
Association constants in acetonitrile of triphenyl telluronium salts, which are dilute electrolytes, are determined through the conductometry method. Satisfactory correlation dependence of constants of interion association and threshold molar electroconductivity on the Litvinenko-Popov constants for depositing groups is identified. 6 refs
Anisotropic constant-roll inflation
Energy Technology Data Exchange (ETDEWEB)
Ito, Asuka; Soda, Jiro [Kobe University, Department of Physics, Kobe (Japan)
2018-01-15
We study constant-roll inflation in the presence of a gauge field coupled to an inflaton. By imposing the constant anisotropy condition, we find new exact anisotropic constant-roll inflationary solutions which include anisotropic power-law inflation as a special case. We also numerically show that the new anisotropic solutions are attractors in the phase space. (orig.)
Quintessence and the cosmological constant
International Nuclear Information System (INIS)
Doran, M.; Wetterich, C.
2003-01-01
Quintessence -- the energy density of a slowly evolving scalar field -- may constitute a dynamical form of the homogeneous dark energy in the universe. We review the basic idea in the light of the cosmological constant problem. Cosmological observations or a time variation of fundamental 'constants' can distinguish quintessence from a cosmological constant
Elasticity in Elastics-An in-vitro study.
Kamisetty, Supradeep Kumar; Nimagadda, Chakrapani; Begam, Madhoom Ponnachi; Nalamotu, Raghuveer; Srivastav, Trilok; Gs, Shwetha
2014-04-01
Orthodontic tooth movement results from application of forces to teeth. Elastics in orthodontics have been used both intra-orally and extra- orally to a great effect. Their use, combined with good patient co-operation provides the clinician with the ability to correct both anteroposterior and vertical discrepancies. Force decay over a period of time is a major problem in the clinical usage of latex elastics and synthetic elastomers. This loss of force makes it difficult for the clinician to determine the actual force transmitted to the dentition. It's the intent of the clinician to maintain optimal force values over desired period of time. The majority of the orthodontic elastics on the market are latex elastics. Since the early 1990s, synthetic products have been offered in the market for latex-sensitive patients and are sold as nonlatex elastics. There is limited information on the risk that latex elastics may pose to patients. Some have estimated that 0.12-6% of the general population and 6.2% of dental professionals have hypersensitivity to latex protein. There are some reported cases of adverse reactions to latex in the orthodontic population but these are very limited to date. Although the risk is not yet clear, it would still be inadvisable to prescribe latex elastics to a patient with a known latex allergy. To compare the in-vitro performance of latex and non latex elastics. Samples of 0.25 inch, latex and non latex elastics (light, medium, heavy elastics) were obtained from three manufacturers (Forestadent, GAC, Glenroe) and a sample size of ten elastics per group was tested. The properties tested included cross sectional area, internal diameter, initial force generated by the elastics, breaking force and the force relaxation for the different types of elastics. Force relaxation testing involved stretching the elastics to three times marketed internal diameter (19.05 mm) and measuring force level at intervals over a period of 48 hours. The data were
Emergence of linear elasticity from the atomistic description of matter
Energy Technology Data Exchange (ETDEWEB)
Cakir, Abdullah, E-mail: acakir@ntu.edu.sg [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University (Singapore); Pica Ciamarra, Massimo [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University (Singapore); Dipartimento di Scienze Fisiche, CNR–SPIN, Università di Napoli Federico II, I-80126 Napoli (Italy)
2016-08-07
We investigate the emergence of the continuum elastic limit from the atomistic description of matter at zero temperature considering how locally defined elastic quantities depend on the coarse graining length scale. Results obtained numerically investigating different model systems are rationalized in a unifying picture according to which the continuum elastic limit emerges through a process determined by two system properties, the degree of disorder, and a length scale associated to the transverse low-frequency vibrational modes. The degree of disorder controls the emergence of long-range local shear stress and shear strain correlations, while the length scale influences the amplitude of the fluctuations of the local elastic constants close to the jamming transition.
Emergence of linear elasticity from the atomistic description of matter
International Nuclear Information System (INIS)
Cakir, Abdullah; Pica Ciamarra, Massimo
2016-01-01
We investigate the emergence of the continuum elastic limit from the atomistic description of matter at zero temperature considering how locally defined elastic quantities depend on the coarse graining length scale. Results obtained numerically investigating different model systems are rationalized in a unifying picture according to which the continuum elastic limit emerges through a process determined by two system properties, the degree of disorder, and a length scale associated to the transverse low-frequency vibrational modes. The degree of disorder controls the emergence of long-range local shear stress and shear strain correlations, while the length scale influences the amplitude of the fluctuations of the local elastic constants close to the jamming transition.
Elastic wave excitation in centrosymmetric strontium titanate crystals
International Nuclear Information System (INIS)
Yushin, N.K.; Sotnikov, A.V.
1980-01-01
The main experimental dependencies are measured and the excitation mechanism of elastic waves in centrosymmetric crystals is established. The surface generation of three-dimensional elastic waves of the 30 MHz frequency in strontium titanate crystals is observed and studied. Elastic wave excitation is observed in the 4 350 K temperature range. The efficiency of hysteresis excitation depends on the external electric field. The effect of light irradiation on the amplitude of excited elastic waves is observed. It is shown that escitation is connected with linearization of electrostriction by the constant electric field appearing in a near-surface crystal layer due to phenomena in the Schottky barrier and appearance of electretic near-electrode layers
Structural, elastic, electronic and optical properties of bi-alkali ...
Indian Academy of Sciences (India)
The structural parameters, elastic constants, electronic and optical properties of the bi-alkali ... and efficient method for the calculation of the ground-state ... Figure 2. Optimization curve (E–V) of the bi-alkali antimonides: (a) Na2KSb, (b) Na2RbSb, (c) Na2CsSb, .... ical shape of the charge distributions in the contour plots.
Anomalous structural changes and elastic properties of bismuth oxide superconductors
International Nuclear Information System (INIS)
He, Y.S.; Xiang, J.; Chang, F.G.; Zhang, J.C.; He, A.S.; Wang, H.; Gu, B.L.
1989-01-01
Ultrasonic measurement revealed that there are anomalous structural changes near 200 K in single 2212 or 2223 phase samples of Bi(Pb)-Sr-Ca-Cu-O. Detailed study showed such anomalous changes are isothermal-like processes and have a characteristics of second order phase transition, accompanying with increases in lattice constants. The elastic properties of these ceramics and related systems are discussed
Third-order elastic moduli for alkali-halide crystals possessing the sodium chloride structure
International Nuclear Information System (INIS)
Ray, U.
2010-01-01
The values of third-order elastic moduli for alkali halides, having NaCl-type crystal structure are calculated according to the Born-Mayer potential model, considering the repulsive interactions up to the second nearest neighbours and calculating the values of the potential parameters for each crystal, independently, from the compressibility data. This work presents the first published account of the calculation of the third-order elastic moduli taking the actual value of the potential parameter unlike the earlier works. Third-order elastic constants have been computed for alkali halides at 0 and 300 K. The results of the third-order elastic constants are compared with the available experimental and theoretical data. Very good agreement between experimental and theoretical third-order elastic constant data (except C 123 ) is found. We have also computed the values of the pressure derivatives of second-order elastic constants and Anderson-Grueneisen parameter for alkali halides, which agree reasonably well with the experimental values, indicating the satisfactory nature of our computed data for third-order elastic constants.
Introduction to linear elasticity
Gould, Phillip L
2013-01-01
Introduction to Linear Elasticity, 3rd Edition, provides an applications-oriented grounding in the tensor-based theory of elasticity for students in mechanical, civil, aeronautical, and biomedical engineering, as well as materials and earth science. The book is distinct from the traditional text aimed at graduate students in solid mechanics by introducing the subject at a level appropriate for advanced undergraduate and beginning graduate students. The author's presentation allows students to apply the basic notions of stress analysis and move on to advanced work in continuum mechanics, plasticity, plate and shell theory, composite materials, viscoelasticity and finite method analysis. This book also: Emphasizes tensor-based approach while still distilling down to explicit notation Provides introduction to theory of plates, theory of shells, wave propagation, viscoelasticity and plasticity accessible to advanced undergraduate students Appropriate for courses following emerging trend of teaching solid mechan...
Effective cosmological constant within the expanding axion universe
Energy Technology Data Exchange (ETDEWEB)
Pierpoint, M.P., E-mail: M.Pierpoint@lboro.ac.uk; Kusmartsev, F.V., E-mail: F.Kusmartsev@lboro.ac.uk
2014-09-12
We show that the value of an effective cosmological constant, Λ{sub eff}, is influenced by the dimensionality of the space. Results were obtained in the framework of the axion model describing expansion of the inhomogeneous universe. Λ{sub eff} determines the tension of the space (i.e. elasticity), and is relaxed when extra dimensions are accessible. We demonstrate that the effective value of the cosmological constant may be tuned to be consistent with experimental observation. Inhomogeneities considered are representative of temperature fluctuations observed within the cosmic microwave background radiation.
Elastic Resistance Effectiveness on Increasing Strength of Shoulders and Hips.
Picha, Kelsey J; Almaddah, Muataz R; Barker, Jordan; Ciochetty, Tavis; Black, W Scott; Uhl, Tim L
2017-09-12
Elastic resistance is a common training method used to gain strength. Currently, progression with elastic resistance is based on the perceived exertion of the exercise or completion of targeted repetitions; exact resistance is typically unknown. This study's objective is to determine if knowledge of load during elastic resistance exercise will increase strength gains during exercises. Participants were randomized into two strength training groups, elastic resistance only and elastic resistance using a load cell (LC) that displays force during exercise. The LC group used a Smart Handle (Patterson Medical Supply, Chicago, IL) to complete all exercises. Each participant completed the same exercises three times weekly for 8 weeks. The LC group was provided with a set load for exercises whereas the elastic resistance only group was not. Participant's strength was tested at baseline and program completion, measuring isometric strength for shoulder abduction (SAb), shoulder external rotation (SER), hip abduction (HAb), and hip extension (HEx). Independent t-tests were used to compare the normalized torques between groups. No significant differences were found between groups. Shoulder strength gains did not differ between groups (SAb p>0.05; SER p>0.05). Hip strength gains did not differ between groups (HAb p>0.05; HEx p>0.05). Both groups increased strength due to individual supervision, constantly evaluating degree of difficulty associated with exercise and providing feedback while using elastic resistance. Using a LC is as effective as supervised training and could provide value in a clinic setting when patients are working unsupervised.
International Nuclear Information System (INIS)
Magomedov, A.M.
1986-01-01
Rates of propagation of longitudinal and transverse acoustic waves in samples as well as density of Tl, Pb, Sn, Bi, Cd, Zn and their binary alloys with indium are determined. The results obtained are used for calculation of elasticity constants of these materials. It is stated that concentration dependences of elasticity constants for indium alloys have non-linear character; negative deflection from the additive line is observed
Elasticity of semiflexible polymers in two dimensions
Prasad, Ashok; Hori, Yuko; Kondev, Jané
2005-10-01
We study theoretically the entropic elasticity of a semiflexible polymer, such as DNA, confined to two dimensions. Using the worm-like-chain model we obtain an exact analytical expression for the partition function of the polymer pulled at one end with a constant force. The force-extension relation for the polymer is computed in the long chain limit in terms of Mathieu characteristic functions. We also present applications to the interaction between a semiflexible polymer and a nematic field, and derive the nematic order parameter and average extension of the polymer in a strong field.
Elastic energy for reflection-symmetric topologies
International Nuclear Information System (INIS)
Majumdar, A; Robbins, J M; Zyskin, M
2006-01-01
Nematic liquid crystals in a polyhedral domain, a prototype for bistable displays, may be described by a unit-vector field subject to tangent boundary conditions. Here we consider the case of a rectangular prism. For configurations with reflection-symmetric topologies, we derive a new lower bound for the one-constant elastic energy. For certain topologies, called conformal and anticonformal, the lower bound agrees with a previous result. For the remaining topologies, called nonconformal, the new bound is an improvement. For nonconformal topologies we derive an upper bound, which differs from the lower bound by a factor depending only on the aspect ratios of the prism
International Nuclear Information System (INIS)
Vavra, G.
1978-01-01
Considered are the limit and the intermediate values of the Young modulus E, modulus of shear G and of linear modulus of compression K obtainable at various temperatures (4.2 to 1133 K) for single crystals of α-zirconium. Determined and presented are the corrected isotropic elasticity characteristics of E, G, K over the above range of temperatures of textured and non-textured α-Zr
Energy Technology Data Exchange (ETDEWEB)
Aprile, E; Cantale, G; Degli-Agosti, S; Hausammann, R; Heer, E; Hess, R; Lechanoine-LeLuc, C; Leo, W; Morenzoni, S; Onel, Y [Geneva Univ. (Switzerland). Dept. de Physique Nucleaire et Corpusculaire
1983-01-01
The aim of the elastic pp experimental program at SIN was to measure enough spin dependent parameters in order to do a direct experimental reconstruction of the elastic scattering amplitudes at a few energies between 400 and 600 MeV and at several angles between 38/sup 0/ cm and 90/sup 0/ cm. This reconstruction was not possible until recently due to lack of experimental data. Information instead has come mainly from phase shift analysis (PSA). The only way to extract the elastic scattering amplitudes without any hypotheses except those of basic symmetries, is to measure a sufficient set of spin dependent parameters at a given angle and energy. With this in view, the authors have measured at 448, 494, 515, 536 and 579 MeV, the polarization, the spin correlation parameters Asub(00nn), Asub(00ss), Asub(00kk), Asub(00ks), the 2-spin parameters Dsub(n0n0), Ksub(n00n), Dsub(s'0s0), Dsub(s'0k0) and the 3-spin parameters Msub(s'0sn), Msub(s'0kn) between 34/sup 0/ cm and 118/sup 0/ cm. A few of these parameters have also been measured at 560 and 470 MeV and at a few energies below 448 MeV. The indices refer to the polarization orientation of the scattered, recoil, beam and target particle respectively.
International Nuclear Information System (INIS)
Zharikov, E.V.; Zagumennyj, A.I.; Kitaeva, V.F.; Lutts, G.B.; Terskov, D.B.
1991-01-01
The Gd-Sc-Al garnet (GSAG) crystals grown from the melt with composition Gd 2.88 Sc 1.89 Al 3.23 O 12 , were investigated. The GSAG doped with chromium was also studied. The Mandelstam-Brillouin (MB) light scattering in the GSAG crystals was observed. The garnet elastic components were determined using the data on the MB component shifts, the products of the elastic constants by molar volume were calculated as well. The GSAG is elastically anisotropic. The doping addition introduction do not cause noticeable change in the elastic properties. The obtained values of elastic constants and their combinations for GSAG were compared with the data for aluminium and gallium garnets. The comparison has shown that the values of elastic constants for GSAG is closer to those for Gd-Sc-Ga garnet than to the corresponding values for the Y-Al one
Elastic properties of Gum Metal
International Nuclear Information System (INIS)
Kuramoto, Shigeru; Furuta, Tadahiko; Hwang, Junghwan; Nishino, Kazuaki; Saito, Takashi
2006-01-01
In situ X-ray diffraction measurements under tensile loading and dynamic mechanical analysis were performed to investigate the mechanisms of elastic deformation in Gum Metal. Tensile stress-strain curves for Gum Metal indicate that cold working substantially decreases the elastic modulus while increasing the yield strength, thereby confirming nonlinearity in the elastic range. The gradient of each curve decreased continuously to about one-third its original value near the elastic limit. As a result of this decrease in elastic modulus and nonlinearity, elastic deformability reaches 2.5% after cold working. Superelasticity is attributed to stress-induced martensitic transformations, although the large elastic deformation in Gum Metal is not accompanied by a phase transformation
Prediction study of structural, elastic and electronic properties of FeMP (M = Ti, Zr, Hf) compounds
Tanto, A.; Chihi, T.; Ghebouli, M. A.; Reffas, M.; Fatmi, M.; Ghebouli, B.
2018-06-01
First principles calculations are applied in the study of FeMP (M = Ti, Zr, Hf) compounds. We investigate the structural, elastic, mechanical and electronic properties by combining first-principles calculations with the CASTEP approach. For ideal polycrystalline FeMP (M = Ti, Zr, Hf) the shear modulus, Young's modulus, Poisson's ratio, elastic anisotropy indexes, Pugh's criterion, elastic wave velocities and Debye temperature are also calculated from the single crystal elastic constants. The shear anisotropic factors and anisotropy are obtained from the single crystal elastic constants. The Debye temperature is calculated from the average elastic wave velocity obtained from shear and bulk modulus as well as the integration of elastic wave velocities in different directions of the single crystal.
International Nuclear Information System (INIS)
Ullemeyer, K; Keppler, R; Lokajíček, T; Vasin, R N; Behrmann, J H
2015-01-01
The elastic anisotropy of bulk rock depends on the mineral textures, the crack fabric and external parameters like, e.g., confining pressure. The texture-related contribution to elastic anisotropy can be predicted from the mineral textures, the largely sample-dependent contribution of the other parameters must be determined experimentally. Laboratory measurements of the elastic wave velocities are mostly limited to pressures of the intermediate crust. We describe a method, how the elastic wave velocity trends and, by this means, the elastic constants can be extrapolated to the pressure conditions of the lower crust. The extrapolated elastic constants are compared to the texture-derived ones. Pronounced elastic anisotropy is evident for phyllosilicate minerals, hence, the approach is demonstrated for two phyllosilicate-rich gneisses with approximately identical volume fractions of the phyllosilicates but different texture types. (paper)
3D Orthorhombic Elastic Wave Propagation Pre-Test Simulation of SPE DAG-1 Test
Jensen, R. P.; Preston, L. A.
2017-12-01
A more realistic representation of many geologic media can be characterized as a dense system of vertically-aligned microfractures superimposed on a finely-layered horizontal geology found in shallow crustal rocks. This seismic anisotropy representation lends itself to being modeled as an orthorhombic elastic medium comprising three mutually orthogonal symmetry planes containing nine independent moduli. These moduli can be determined by observing (or prescribing) nine independent P-wave and S-wave phase speeds along different propagation directions. We have developed an explicit time-domain finite-difference (FD) algorithm for simulating 3D elastic wave propagation in a heterogeneous orthorhombic medium. The components of the particle velocity vector and the stress tensor are governed by a set of nine, coupled, first-order, linear, partial differential equations (PDEs) called the velocity-stress system. All time and space derivatives are discretized with centered and staggered FD operators possessing second- and fourth-order numerical accuracy, respectively. Additionally, we have implemented novel perfectly matched layer (PML) absorbing boundary conditions, specifically designed for orthorhombic media, to effectively suppress grid boundary reflections. In support of the Source Physics Experiment (SPE) Phase II, a series of underground chemical explosions at the Nevada National Security Site, the code has been used to perform pre-test estimates of the Dry Alluvium Geology - Experiment 1 (DAG-1). Based on literature searches, realistic geologic structure and values for orthorhombic P-wave and S-wave speeds have been estimated. Results and predictions from the simulations are presented.
Impact loads on beams on elastic foundations
International Nuclear Information System (INIS)
Kameswara Rao, N.S.V.; Prasad, B.B.
1975-01-01
Quite often, complex structural components are idealised as beams in engineering analysis and design. Also, equations governing the responses of shallow shells are mathematically equivalent to the equations governing the responses of beams on elastic foundations. Hence with possible applications in several technical disciplines, the behaviour of beams on elastic foundations subjected to impact loads is studied in detail in the present investigation both analytically and experimentally. The analytical methods include analysis and energy method. The effect of foundation parameters (stiffness, and damping constants) on the dynamic responses of the beam-foundation system has been analysed. In modal analysis, the free-vibration equation has been solved by replacing the applied impulse by suitable initial conditions and the solution has been obtained as the linear combination of an infinite sequence of discrete eigen-vectors. In the energy method, the beam-foundation system is treated to be under forced vibrations and the forcing function has been obtained using the Hertz's law of impact. In the case of free-free end conditions of the beam, the rigid body modes and the elastic modes have been superposed to obtain the total response. The responses predicted using modal analysis are higher than those obtained using energy method. From the present study it is observed that model analysis is preferable to energy method. (Auth.)
Form finding in elastic gridshells
Baek, Changyeob; Sageman-Furnas, Andrew O.; Jawed, Mohammad K.; Reis, Pedro M.
2018-01-01
Elastic gridshells comprise an initially planar network of elastic rods that are actuated into a shell-like structure by loading their extremities. The resulting actuated form derives from the elastic buckling of the rods subjected to inextensibility. We study elastic gridshells with a focus on the rational design of the final shapes. Our precision desktop experiments exhibit complex geometries, even from seemingly simple initial configurations and actuation processes. The numerical simulations capture this nonintuitive behavior with excellent quantitative agreement, allowing for an exploration of parameter space that reveals multistable states. We then turn to the theory of smooth Chebyshev nets to address the inverse design of hemispherical elastic gridshells. The results suggest that rod inextensibility, not elastic response, dictates the zeroth-order shape of an actuated elastic gridshell. As it turns out, this is the shape of a common household strainer. Therefore, the geometry of Chebyshev nets can be further used to understand elastic gridshells. In particular, we introduce a way to quantify the intrinsic shape of the empty, but enclosed regions, which we then use to rationalize the nonlocal deformation of elastic gridshells to point loading. This justifies the observed difficulty in form finding. Nevertheless, we close with an exploration of concatenating multiple elastic gridshell building blocks.
Mathematical foundations of elasticity
Marsden, Jerrold E
1994-01-01
This advanced-level study approaches mathematical foundations of three-dimensional elasticity using modern differential geometry and functional analysis. It is directed to mathematicians, engineers and physicists who wish to see this classical subject in a modern setting with examples of newer mathematical contributions. Prerequisites include a solid background in advanced calculus and the basics of geometry and functional analysis.The first two chapters cover the background geometry ― developed as needed ― and use this discussion to obtain the basic results on kinematics and dynamics of con
Elastic and viscoplastic properties
International Nuclear Information System (INIS)
Lebensohn, R.A.
2015-01-01
In this chapter, we review crystal elasticity and plasticity-based self-consistent theories and apply them to the determination of the effective response of polycrystalline aggregates. These mean-field formulations, which enable the prediction of the mechanical behaviour of polycrystalline aggregates based on the heterogeneous and/or directional properties of their constituent single crystal grains and phases, are ideal tools to establish relationships between microstructure and properties of these materials, ubiquitous among fuels and structural materials for nuclear systems. (author)
Elongational flow of polymer melts at constant strain rate, constant stress and constant force
Wagner, Manfred H.; Rolón-Garrido, Víctor H.
2013-04-01
Characterization of polymer melts in elongational flow is typically performed at constant elongational rate or rarely at constant tensile stress conditions. One of the disadvantages of these deformation modes is that they are hampered by the onset of "necking" instabilities according to the Considère criterion. Experiments at constant tensile force have been performed even more rarely, in spite of the fact that this deformation mode is free from necking instabilities and is of considerable industrial relevance as it is the correct analogue of steady fiber spinning. It is the objective of the present contribution to present for the first time a full experimental characterization of a long-chain branched polyethylene melt in elongational flow. Experiments were performed at constant elongation rate, constant tensile stress and constant tensile force by use of a Sentmanat Extensional Rheometer (SER) in combination with an Anton Paar MCR301 rotational rheometer. The accessible experimental window and experimental limitations are discussed. The experimental data are modelled by using the Wagner I model. Predictions of the steady-start elongational viscosity in constant strain rate and creep experiments are found to be identical, albeit only by extrapolation of the experimental data to Hencky strains of the order of 6. For constant stress experiments, a minimum in the strain rate and a corresponding maximum in the elongational viscosity is found at a Hencky strain of the order of 3, which, although larger than the steady-state value, follows roughly the general trend of the steady-state elongational viscosity. The constitutive analysis also reveals that constant tensile force experiments indicate a larger strain hardening potential than seen in constant elongation rate or constant tensile stress experiments. This may be indicative of the effect of necking under constant elongation rate or constant tensile stress conditions according to the Considère criterion.
Mathematical methods in elasticity imaging
Ammari, Habib; Garnier, Josselin; Kang, Hyeonbae; Lee, Hyundae; Wahab, Abdul
2015-01-01
This book is the first to comprehensively explore elasticity imaging and examines recent, important developments in asymptotic imaging, modeling, and analysis of deterministic and stochastic elastic wave propagation phenomena. It derives the best possible functional images for small inclusions and cracks within the context of stability and resolution, and introduces a topological derivative-based imaging framework for detecting elastic inclusions in the time-harmonic regime. For imaging extended elastic inclusions, accurate optimal control methodologies are designed and the effects of uncertainties of the geometric or physical parameters on stability and resolution properties are evaluated. In particular, the book shows how localized damage to a mechanical structure affects its dynamic characteristics, and how measured eigenparameters are linked to elastic inclusion or crack location, orientation, and size. Demonstrating a novel method for identifying, locating, and estimating inclusions and cracks in elastic...
Graphene nanoribbon as an elastic damper
Evazzade, Iman; Lobzenko, Ivan P.; Saadatmand, Danial; Korznikova, Elena A.; Zhou, Kun; Liu, Bo; Dmitriev, Sergey V.
2018-05-01
Heterostructures composed of dissimilar two-dimensional nanomaterials can have nontrivial physical and mechanical properties which are potentially useful in many applications. Interestingly, in some cases, it is possible to create heterostructures composed of weakly and strongly stretched domains with the same chemical composition, as has been demonstrated for some polymer chains, DNA, and intermetallic nanowires supporting this effect of two-phase stretching. These materials, at relatively strong tension forces, split into domains with smaller and larger tensile strains. Within this region, average strain increases at constant tensile force due to the growth of the domain with the larger strain, at the expense of the domain with smaller strain. Here, the two-phase stretching phenomenon is described for graphene nanoribbons with the help of molecular dynamics simulations. This unprecedented feature of graphene that is revealed in our study is related to the peculiarities of nucleation and the motion of the domain walls separating the domains of different elastic strain. It turns out that the loading–unloading curves exhibit a hysteresis-like behavior due to the energy dissipation during the domain wall nucleation and motion. Here, we put forward the idea of implementing graphene nanoribbons as elastic dampers, efficiently converting mechanical strain energy into heat during cyclic loading–unloading through elastic extension where domains with larger and smaller strains coexist. Furthermore, in the regime of two-phase stretching, graphene nanoribbon is a heterostructure for which the fraction of domains with larger and smaller strain, and consequently its physical and mechanical properties, can be tuned in a controllable manner by applying elastic strain and/or heat.
Energy Technology Data Exchange (ETDEWEB)
Loewenthal, M.; Loseke, K.; Dow, T.A.; Scattergood, R.O.
1988-12-01
Elastic emission polishing, also called elastic emission machining (EEM), is a process where a stream of abrasive slurry is used to remove material from a substrate and produce damage free surfaces with controlled surface form. It is a noncontacting method utilizing a thick elasto-hydrodynamic film formed between a soft rotating ball and the workpiece to control the flow of the abrasive. An apparatus was built in the Center, which consists of a stationary spindle, a two-axis table for the workpiece, and a pump to circulate the working fluid. The process is controlled by a programmable computer numerical controller (CNC), which presently can operate the spindle speed and movement of the workpiece in one axis only. This apparatus has been used to determine material removal rates on different material samples as a function of time, utilizing zirconium oxide (ZrO{sub 2}) particles suspended in distilled water as the working fluid. By continuing a study of removal rates the process should become predictable, and thus create a new, effective, yet simple tool for ultra-precision mechanical machining of surfaces.
International Nuclear Information System (INIS)
Mermaz, M.C.
1984-01-01
Diffraction and refraction play an important role in particle elastic scattering. The optical model treats correctly and simultaneously both phenomena but without disentangling them. Semi-classical discussions in terms of trajectories emphasize the refractive aspect due to the real part of the optical potential. The separation due to to R.C. Fuller of the quantal cross section into two components coming from opposite side of the target nucleus allows to understand better the refractive phenomenon and the origin of the observed oscillations in the elastic scattering angular distributions. We shall see that the real part of the potential is responsible of a Coulomb and a nuclear rainbow which allows to determine better the nuclear potential in the interior region near the nuclear surface since the volume absorption eliminates any effect of the real part of the potential for the internal partial scattering waves. Resonance phenomena seen in heavy ion scattering will be discussed in terms of optical model potential and Regge pole analysis. Compound nucleus resonances or quasi-molecular states can be indeed the more correct and fundamental alternative
Design guidance for elastic followup
International Nuclear Information System (INIS)
Naugle, F.V.
1983-01-01
The basic mechanism of elastic followup is discussed in relation to piping design. It is shown how mechanistic insight gained from solutions for a two-bar problem can be used to identify dominant design parameters and to determine appropriate modifications where elastic followup is a potential problem. It is generally recognized that quantitative criteria are needed for elastic followup in the creep range where badly unbalanced lines can pose potential problems. Approaches for criteria development are discussed
Income Elasticity of Environmental Amenities
Daniel Miles; Andrés Pereyra; Máximo Rossi
2000-01-01
In this paper we are concerned with the estimation of income elasticities of environmental amenities. The novelty is the application of econometric methods that take into account the problem of measurement errors when estimating these elasticities, which are common in microeconomic data and are not usually considered in the applied literature related with this issue. Our aim is to discuss whether the measurement error has signi…cant e¤ects on the elasticities. Data from the Expenditure Budget...
Spectrophotometric determination of association constant
DEFF Research Database (Denmark)
2016-01-01
Least-squares 'Systematic Trial-and-Error Procedure' (STEP) for spectrophotometric evaluation of association constant (equilibrium constant) K and molar absorption coefficient E for a 1:1 molecular complex, A + B = C, with error analysis according to Conrow et al. (1964). An analysis of the Charge...
Elastic properties of silicon nitride ceramics reinforced with graphene nanofillers
Czech Academy of Sciences Publication Activity Database
Seiner, Hanuš; Ramírez, C.; Koller, M.; Sedlák, Petr; Landa, Michal; Miranzo, P.; Belmonte, M.; Osendí, M. I.
2015-01-01
Roč. 87, December (2015), s. 675-680 ISSN 0264-1275 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61388998 Keywords : multilayer graphene * graphene oxide (GO) * silicon nitride * elastic constants * elastic modulus * shear modulus Subject RIV: JI - Composite Materials Impact factor: 3.997, year: 2015 http://www.sciencedirect.com/science/article/pii/S0264127515302938/pdfft?md5=571e00fd7f976e9b66ed789ae2a868b2&pid=1-s2.0-S0264127515302938-main.pdf
Resonant Column Tests and Nonlinear Elasticity in Simulated Rocks
Sebastian, Resmi; Sitharam, T. G.
2018-01-01
Rocks are generally regarded as linearly elastic even though the manifestations of nonlinearity are prominent. The variations of elastic constants with varying strain levels and stress conditions, disagreement between static and dynamic moduli, etc., are some of the examples of nonlinear elasticity in rocks. The grain-to-grain contact, presence of pores and joints along with other compliant features induce the nonlinear behavior in rocks. The nonlinear elastic behavior of rocks is demonstrated through resonant column tests and numerical simulations in this paper. Resonant column tests on intact and jointed gypsum samples across varying strain levels have been performed in laboratory and using numerical simulations. The paper shows the application of resonant column apparatus to obtain the wave velocities of stiff samples at various strain levels under long wavelength condition, after performing checks and incorporating corrections to the obtained resonant frequencies. The numerical simulation and validation of the resonant column tests using distinct element method are presented. The stiffness reductions of testing samples under torsional and flexural vibrations with increasing strain levels have been analyzed. The nonlinear elastic behavior of rocks is reflected in the results, which is enhanced by the presence of joints. The significance of joint orientation and influence of joint spacing during wave propagation have also been assessed and presented using the numerical simulations. It has been found that rock joints also exhibit nonlinear behavior within the elastic limit.
Synthetic Strategies for High Dielectric Constant Silicone Elastomers
DEFF Research Database (Denmark)
Madsen, Frederikke Bahrt
synthetic strategies were developed in this Ph.D. thesis, in order to create silicone elastomers with high dielectric constants and thereby higher energy densities. The work focused on maintaining important properties such as dielectric loss, electrical breakdown strength and elastic modulus....... The methodology therefore involved chemically grafting high dielectric constant chemical groups onto the elastomer network, as this would potentially provide a stable elastomer system upon continued activation of the material. The first synthetic strategy involved the synthesis of a new type of cross...... extender’ that allowed for chemical modifications such as Cu- AAC. This route was promising for one-pot elastomer preparation and as a high dielectric constant additive to commercial silicone systems. The second approach used the borane-catalysed Piers-Rubinsztajn reaction to form spatially well...
Effect of van der Waals interactions on the structural and elastic properties of black phosphorus
DEFF Research Database (Denmark)
Appalakondaiah, S.; Vaitheeswaran, G.; Lebègue, S.
2012-01-01
constant is significantly larger than the C11 and C33 parameters, implying that black phosphorus is stiffer against strain along the a axis than along the b and c axes. From the calculated elastic constants, the mechanical properties, such as bulk modulus, shear modulus, Young's modulus, and Poisson...
Engelbrecht, Jüri
2015-01-01
This book addresses the modelling of mechanical waves by asking the right questions about them and trying to find suitable answers. The questions follow the analytical sequence from elementary understandings to complicated cases, following a step-by-step path towards increased knowledge. The focus is on waves in elastic solids, although some examples also concern non-conservative cases for the sake of completeness. Special attention is paid to the understanding of the influence of microstructure, nonlinearity and internal variables in continua. With the help of many mathematical models for describing waves, physical phenomena concerning wave dispersion, nonlinear effects, emergence of solitary waves, scales and hierarchies of waves as well as the governing physical parameters are analysed. Also, the energy balance in waves and non-conservative models with energy influx are discussed. Finally, all answers are interwoven into the canvas of complexity.
International Nuclear Information System (INIS)
Milosevic, M.
1979-01-01
One-dimensional variational method for cylindrical configuration was applied for calculating group constants, together with effects of elastic slowing down, anisotropic elastic scattering, inelastic scattering, heterogeneous resonance absorption with the aim to include the presence of a number of different isotopes and effects of neutron leakage from the reactor core. Neutron flux shape P 3 and adjoint function are proposed in order to enable calculation of smaller size reactors and inclusion of heterogeneity effects by cell calculations. Microscopic multigroup constants were prepared based on the UKNDL data library. Analytical-numerical approach was applied for solving the equations of the P 3 approximation to obtain neutron flux moments and adjoint functions
Nonlinear Elasticity of Doped Semiconductors
2017-02-01
AFRL-RY-WP-TR-2016-0206 NONLINEAR ELASTICITY OF DOPED SEMICONDUCTORS Mark Dykman and Kirill Moskovtsev Michigan State University...2016 4. TITLE AND SUBTITLE NONLINEAR ELASTICITY OF DOPED SEMICONDUCTORS 5a. CONTRACT NUMBER FA8650-16-1-7600 5b. GRANT NUMBER 5c. PROGRAM...vibration amplitude. 15. SUBJECT TERMS semiconductors , microresonators, microelectromechanical 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF
Cell Elasticity Determines Macrophage Function
Patel, Naimish R.; Bole, Medhavi; Chen, Cheng; Hardin, Charles C.; Kho, Alvin T.; Mih, Justin; Deng, Linhong; Butler, James; Tschumperlin, Daniel; Fredberg, Jeffrey J.; Krishnan, Ramaswamy; Koziel, Henry
2012-01-01
Macrophages serve to maintain organ homeostasis in response to challenges from injury, inflammation, malignancy, particulate exposure, or infection. Until now, receptor ligation has been understood as being the central mechanism that regulates macrophage function. Using macrophages of different origins and species, we report that macrophage elasticity is a major determinant of innate macrophage function. Macrophage elasticity is modulated not only by classical biologic activators such as LPS and IFN-γ, but to an equal extent by substrate rigidity and substrate stretch. Macrophage elasticity is dependent upon actin polymerization and small rhoGTPase activation, but functional effects of elasticity are not predicted by examination of gene expression profiles alone. Taken together, these data demonstrate an unanticipated role for cell elasticity as a common pathway by which mechanical and biologic factors determine macrophage function. PMID:23028423
Cell elasticity determines macrophage function.
Directory of Open Access Journals (Sweden)
Naimish R Patel
Full Text Available Macrophages serve to maintain organ homeostasis in response to challenges from injury, inflammation, malignancy, particulate exposure, or infection. Until now, receptor ligation has been understood as being the central mechanism that regulates macrophage function. Using macrophages of different origins and species, we report that macrophage elasticity is a major determinant of innate macrophage function. Macrophage elasticity is modulated not only by classical biologic activators such as LPS and IFN-γ, but to an equal extent by substrate rigidity and substrate stretch. Macrophage elasticity is dependent upon actin polymerization and small rhoGTPase activation, but functional effects of elasticity are not predicted by examination of gene expression profiles alone. Taken together, these data demonstrate an unanticipated role for cell elasticity as a common pathway by which mechanical and biologic factors determine macrophage function.
Multipurpose hooks for elastic attachment
Directory of Open Access Journals (Sweden)
Siddharth Shashidhar Revankar
2014-01-01
Full Text Available As certain bracket systems do not include hooks on premolar brackets for elastic attachment, Kobayashi or custom made ligature hooks have proven as an alternative. However, these hooks tend to bend labially when used with heavy elastics and these elastics can even pop loose from the hooks on mouth opening. The following article describes an innovative multipurpose hook which is simple, stiff and inexpensive and can be used for engagement of class II elastics on premolars in case of missing molars as well as engagement of intermaxillary elastics for settling of occlusion in finishing stages. As the hooks can be prefabricated, this saves a lot of chair side time and is more practical for use in day-to-day orthodontic practice.
Reply to Comment on 'On the importance of the free energy for elasticity under pressure'
International Nuclear Information System (INIS)
Marcus, P M; Qiu, S L
2004-01-01
All criticisms by Steinle-Neumann and Cohen of the correctness of our calculations of equilibrium structure and elastic constants under pressure from the Gibbs free energy are answered and the criticisms are rejected. The difference between the free energy and the internal energy as functions of structure is described to clarify the use of the free energy. The meaning of elastic constants in a system under pressure is discussed in order to derive the basic quadratic expansion of the free energy in the strains. The coefficients in the expansion are the elastic constants under pressure and are in agreement with well-known work. We give reasons why calculations based on the Gibbs free energy are simpler and more accurate than the usual calculations based on minima of the energy at constant volume. (reply)
Blocky inversion of multichannel elastic impedance for elastic parameters
Mozayan, Davoud Karami; Gholami, Ali; Siahkoohi, Hamid Reza
2018-04-01
Petrophysical description of reservoirs requires proper knowledge of elastic parameters like P- and S-wave velocities (Vp and Vs) and density (ρ), which can be retrieved from pre-stack seismic data using the concept of elastic impedance (EI). We propose an inversion algorithm which recovers elastic parameters from pre-stack seismic data in two sequential steps. In the first step, using the multichannel blind seismic inversion method (exploited recently for recovering acoustic impedance from post-stack seismic data), high-resolution blocky EI models are obtained directly from partial angle-stacks. Using an efficient total-variation (TV) regularization, each angle-stack is inverted independently in a multichannel form without prior knowledge of the corresponding wavelet. The second step involves inversion of the resulting EI models for elastic parameters. Mathematically, under some assumptions, the EI's are linearly described by the elastic parameters in the logarithm domain. Thus a linear weighted least squares inversion is employed to perform this step. Accuracy of the concept of elastic impedance in predicting reflection coefficients at low and high angles of incidence is compared with that of exact Zoeppritz elastic impedance and the role of low frequency content in the problem is discussed. The performance of the proposed inversion method is tested using synthetic 2D data sets obtained from the Marmousi model and also 2D field data sets. The results confirm the efficiency and accuracy of the proposed method for inversion of pre-stack seismic data.
Varying Constants, Gravitation and Cosmology
Directory of Open Access Journals (Sweden)
Jean-Philippe Uzan
2011-03-01
Full Text Available Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. Thus, it is of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, solar system observations, meteorite dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.
Atomistic calculations of interface elastic properties in noncoherent metallic bilayers
International Nuclear Information System (INIS)
Mi Changwen; Jun, Sukky; Kouris, Demitris A.; Kim, Sung Youb
2008-01-01
The paper describes theoretical and computational studies associated with the interface elastic properties of noncoherent metallic bicrystals. Analytical forms of interface energy, interface stresses, and interface elastic constants are derived in terms of interatomic potential functions. Embedded-atom method potentials are then incorporated into the model to compute these excess thermodynamics variables, using energy minimization in a parallel computing environment. The proposed model is validated by calculating surface thermodynamic variables and comparing them with preexisting data. Next, the interface elastic properties of several fcc-fcc bicrystals are computed. The excess energies and stresses of interfaces are smaller than those on free surfaces of the same crystal orientations. In addition, no negative values of interface stresses are observed. Current results can be applied to various heterogeneous materials where interfaces assume a prominent role in the systems' mechanical behavior
Elastic gauge fields and Hall viscosity of Dirac magnons
Ferreiros, Yago; Vozmediano, María A. H.
2018-02-01
We analyze the coupling of elastic lattice deformations to the magnon degrees of freedom of magnon Dirac materials. For a honeycomb ferromagnet we find that, as happens in the case of graphene, elastic gauge fields appear coupled to the magnon pseudospinors. For deformations that induce constant pseudomagnetic fields, the spectrum around the Dirac nodes splits into pseudo-Landau levels. We show that when a Dzyaloshinskii-Moriya interaction is considered, a topological gap opens in the system and a Chern-Simons effective action for the elastic degrees of freedom is generated. Such a term encodes a phonon Hall viscosity response, entirely generated by quantum fluctuations of magnons living in the vicinity of the Dirac points. The magnon Hall viscosity vanishes at zero temperature, and grows as temperature is raised and the states around the Dirac points are increasingly populated.
Energy Technology Data Exchange (ETDEWEB)
Tamer, M., E-mail: mehmet.tamer@zirve.edu.tr [Zirve University Faculty of Education, 27260, Gaziantep (Turkey)
2016-06-15
Structural, optical and electronic properties and elastic constants of Cd1{sub -x-y}Zn{sub x} Hg{sub y}Te alloys have been studied by employing the commercial code Castep based on density functional theory. The generalized gradient approximation and local density approximation were utilized as exchange correlation. Using elastic constants for compounds, bulk modulus, band gap, Fermi energy and Kramers–Kronig relations, dielectric constants and the refractive index have been found through calculations. Apart from these, X-ray measurements revealed elastic constants and Vegard’s law. It is seen that results obtained from theory and experiments are all in agreement.
Stabilized power constant alimentation; Alimentation regulee a puissance constante
Energy Technology Data Exchange (ETDEWEB)
Roussel, L [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1968-06-01
The study and realization of a stabilized power alimentation variable from 5 to 100 watts are described. In order to realize a constant power drift of Lithium compensated diodes, we have searched a 1 per cent precision of regulation and a response time minus than 1 sec. Recent components like Hall multiplicator and integrated amplifiers give this possibility and it is easy to use permutable circuits. (author) [French] On decrit l'etude et la realisation d'une alimentation a puissance constante reglable dans une gamme de 5 a 100 watts. Prevue pour le drift a puissance constante des diodes compensees au lithium, l'etude a ete menee en vue d'obtenir une precision de regulation de 1 pour cent et un temps de reponse inferieur a la seconde. Des systemes recents tels que multiplicateurs a effet Hall et circuits integres ont permis d'atteindre ce but tout en facilitant l'emploi de modules interchangeables. (auteur)
From the Rydberg constant to the fundamental constants metrology
International Nuclear Information System (INIS)
Nez, F.
2005-06-01
This document reviews the theoretical and experimental achievements of the author since the beginning of his scientific career. This document is dedicated to the spectroscopy of hydrogen, deuterium and helium atoms. The first part is divided into 6 sub-sections: 1) the principles of hydrogen spectroscopy, 2) the measurement of the 2S-nS/nD transitions, 3) other optical frequency measurements, 4) our contribution to the determination of the Rydberg constant, 5) our current experiment on the 1S-3S transition, 6) the spectroscopy of the muonic hydrogen. Our experiments have improved the accuracy of the Rydberg Constant by a factor 25 in 15 years and we have achieved the first absolute optical frequency measurement of a transition in hydrogen. The second part is dedicated to the measurement of the fine structure constant and the last part deals with helium spectroscopy and the search for optical references in the near infrared range. (A.C.)
Magnetic and elastic properties of the antiferromagnet uranium mononitride
International Nuclear Information System (INIS)
Van Doorn, C.F.
1976-10-01
The magnetic and elastic properties of antiferromagnetic uranium mononitride single crystals are studied in the thesis from the measurements of the temperature dependences of the magnetic susceptibility, electrical resistivity and elastic constants. The elastic constants C 11 , C 12 and C 44 were determined in the temperature interval 4 to 300 K by ultrasonic measurements of the five possible wave velocities in the [100] and [110] directions. A test for internal consistency was also made. A dip of about 9 percent occurs in C 11 at a temperature of 5 to 6 K lower than the Neel temperature T(N) (equals about 53 K). Starting at T(N), a renormalization in C 44 is proportional to the square of the sublattice magnetization also occurs. Both these results agree with model calculations which include spin-phonon interactions. The investigation of this anomaly was extended by measuring the electrical resistivity of a sample cut from the same crystal as that on which the elasticity was measured. No anomalous behavior was observed at the temperature where C 11 displays its anomaly. However, a discontinuity in the temperature derivative of the resistance was found at T(N). The possible effect of a magnetic field on the resistivity, as well as on the elasticity, was investigated without any measurable effect. The magnetic susceptibility was measured with a Foner magnetometer between 4 and 1 000 K. It was found that above the Neel temperature the paramagnetic susceptibility followed a revised Curie-Weiss law. In an attempt to ascertain the ionic state of the 5f-uranium ion in UN, use was made of the experimentally determined Weiss constant, spin disorder resistivity and Knight shift. A calculation was made that gave a good representation of the ratio of the experimental susceptibilities along the [100] and [110] directions in the ordered region [af
Theoretical studies of the pressure-induced phase transition and elastic properties of BeS
Energy Technology Data Exchange (ETDEWEB)
Ji, Xu [College of Polymer Science and Engineering, Sichuan University, Chengdu 610065 (China); College of Chemical Engineering, Sichuan University, Chengdu 610065 (China); Yu, Yang, E-mail: yuyang@scu.edu.cn [Department of Logistics Management, Sichuan University, Chengdu 610065 (China); Ji, Junyi [College of Chemical Engineering, Sichuan University, Chengdu 610065 (China); Long, Jianping [College of Materials and Chemistry and Chemical Engineering, Chengdu University of Technology, Chengdu 610059 (China); Chen, Jianjun; Liu, Daijun [College of Chemical Engineering, Sichuan University, Chengdu 610065 (China)
2015-02-25
Highlights: • Transition pressure from B3 to B8 of BeS is 58.86 GPa. • Elastic properties of BeS under pressure are predicted for the first time. • Elastic moduli of BeS increase monotonically with increasing pressure. • Elastic anisotropy of BeS has been investigated. - Abstract: First-principles calculations were performed to investigate the structural, electronic and elastic properties of BeS in both B3 and B8 structures. The structural phase transition from B3 to B8 occurs at 58.86 GPa with a volume decrease of 10.74%. The results of the electronic band structure show that the energy gap is indirect for B3 and B8 phases. The pressure dependence of the direct and indirect band gaps for BeS has been investigated. Especially, the elastic constants of B8 BeS under high pressure have been studied for the first time. The mechanical stability of the two phases has been discussed based on the pressure dependence of the elastic constants. In addition, the pressure dependence of bulk modulus, shear modulus, Young’s modulus, elastic wave velocities and brittle–ductile behavior of BeS are all successfully obtained. Finally, the elastic anisotropy has been investigated by using two different methods.
Learning Read-constant Polynomials of Constant Degree modulo Composites
DEFF Research Database (Denmark)
Chattopadhyay, Arkadev; Gavaldá, Richard; Hansen, Kristoffer Arnsfelt
2011-01-01
Boolean functions that have constant degree polynomial representation over a fixed finite ring form a natural and strict subclass of the complexity class \\textACC0ACC0. They are also precisely the functions computable efficiently by programs over fixed and finite nilpotent groups. This class...... is not known to be learnable in any reasonable learning model. In this paper, we provide a deterministic polynomial time algorithm for learning Boolean functions represented by polynomials of constant degree over arbitrary finite rings from membership queries, with the additional constraint that each variable...
bessel functions for axisymmetric elasticity problems of the elastic
African Journals Online (AJOL)
HOD
2, 3DEPARTMENT OF CIVIL ENGINEERING, UNIVERSITY OF NIGERIA, NSUKKA. ENUGU STATE. ... theory of elasticity and in the case of vertical applied loads, was first ... partial differential equations in bodies having cylindrical symmetry.
Elastic properties of Ti-24Nb-4Zr-8Sn single crystals with bcc crystal structure
International Nuclear Information System (INIS)
Zhang, Y.W.; Li, S.J.; Obbard, E.G.; Wang, H.; Wang, S.C.; Hao, Y.L.; Yang, R.
2011-01-01
Research highlights: → The single crystals of Ti2448 alloy with the bcc crystal structure were prepared. → The elastic moduli and constants were measured by several resonant methods. → The crystal shows significant elastic asymmetry in tension and compression. → The crystal exhibits weak nonlinear elasticity with large elastic strain ∼2.5%. → The crystal has weak atomic interactions against crystal distortion to low symmetry. - Abstract: Single crystals of Ti2448 alloy (Ti-24Nb-4Zr-8Sn in wt.%) were grown successfully using an optical floating-zone furnace. Several kinds of resonant methods gave consistent Young's moduli of 27.1, 56.3 and 88.1 GPa and shear moduli of 34.8, 11.0 and 14.6 GPa for the , and oriented single crystals, and C 11 , C 12 and C 44 of 57.2, 36.1 and 35.9 GPa respectively. Uniaxial testing revealed asymmetrical elastic behaviors of the crystals: tension caused elastic softening with a large reversible strain of ∼4% and a stress plateau of ∼250 MPa, whereas compression resulted in gradual elastic stiffening with much smaller reversible strain. The crystals exhibited weak nonlinear elasticity with a large elastic strain of ∼2.5% and a high strength, approaching ∼20% and ∼30% of its ideal shear and ideal tensile strength respectively. The crystals showed linear elasticity with a small elastic strain of ∼1%. These elastic deformation characteristics have been interpreted in terms of weakened atomic interactions against crystal distortion to low crystal symmetry under external applied stresses. These results are consistent with the properties of polycrystalline Ti2448, including high strength, low elastic modulus, large recoverable strain and weak strengthening effect due to grain refinement.
High energy elastic hadron scattering
International Nuclear Information System (INIS)
Fearnly, T.A.
1986-04-01
The paper deals with the WA7 experiment at the CERN super proton synchrotron (SPS). The elastic differential cross sections of pion-proton, kaon-proton, antiproton-proton, and proton-proton at lower SPS energies over a wide range of momentum transfer were measured. Some theoretical models in the light of the experimental results are reviewed, and a comprehensive impact parameter analysis of antiproton-proton elastic scattering over a wide energy range is presented. A nucleon valence core model for high energy proton-proton and antiproton-proton elastic scattering is described
CONCERNING THE ELASTIC ORTHOTROPIC MODEL APPLIED TO WOOD ELASTIC PROPERTIES
Tadeu Mascia,Nilson
2003-01-01
Among the construction materials, wood reveals an orthotropic pattern, because of unique characteristics in its internal structure with three axes of wood biological directions (longitudinal, tangential and radial). elastic symmetry: longitudinal, tangential and radial, reveals an orthotropic pattern. The effect of grain angle orientation onin the elastic modulus constitutes the fundamental cause forof wood anisotropy. It is responsible for the greatest changes in the values of the constituti...
Spectral dimension of elastic Sierpinski gaskets with general elastic forces
International Nuclear Information System (INIS)
Liu, S.H.; Liu, A.J.
1985-01-01
The spectral dimension is calculated for a Sierpinski gasket with the most general elastic restoring forces allowed by symmetry. The elastic forces consist of bond-stretching and angle-bending components. The spectral dimension is the same as that for the bond-stretching-force (central-force) model. This demonstrates that on the Sierpinski gasket the two types of forces belong to the same universality class
The first-principles calculations for the elastic properties of Zr2Al under compression
International Nuclear Information System (INIS)
Yuan Xiaoli; Wei Dongqing; Chen Xiangrong; Zhang Qingming; Gong Zizheng
2011-01-01
Graphical abstract: The calculated elastic constants C ij as a function of pressure P. Display Omitted Research highlights: → It is found that the five independent elastic constants increase monotonically with pressure. C 11 and C 33 vary rapidly as pressure increases, C 13 and C 12 becomes moderate. However, C 44 increases comparatively slowly with pressure. Figure shows excellent satisfaction of the calculated elastic constants of Zr 2 Al to these equations and hence in our calculation, the Zr 2 Al is mechanically stable at pressure up to 100 GPa. - Abstract: The first-principles calculations were applied to investigate the structural, elastic constants of Zr 2 Al alloy with increasing pressure. These properties are based on the plane wave pseudopotential density functional theory (DFT) method within the generalized gradient approximation (GGA) for exchange and correlation. The result of the heat of formation of Zr 2 Al crystal investigated is in excellent consistent with results from other study. The anisotropy, the shear modulus, and Young's modulus for the ideal polycrystalline Zr 2 Al are also studied. It is found that (higher) pressure can significantly improve the ductility of Zr 2 Al. Moreover, the elastic constants of Zr 2 Al increase monotonically and the anisotropies decrease with the increasing pressure. Finally, it is observed that Zr d electrons are mainly contributed to the density of states at the Fermi level.
Energy Technology Data Exchange (ETDEWEB)
Nez, F
2005-06-15
This document reviews the theoretical and experimental achievements of the author since the beginning of his scientific career. This document is dedicated to the spectroscopy of hydrogen, deuterium and helium atoms. The first part is divided into 6 sub-sections: 1) the principles of hydrogen spectroscopy, 2) the measurement of the 2S-nS/nD transitions, 3) other optical frequency measurements, 4) our contribution to the determination of the Rydberg constant, 5) our current experiment on the 1S-3S transition, 6) the spectroscopy of the muonic hydrogen. Our experiments have improved the accuracy of the Rydberg Constant by a factor 25 in 15 years and we have achieved the first absolute optical frequency measurement of a transition in hydrogen. The second part is dedicated to the measurement of the fine structure constant and the last part deals with helium spectroscopy and the search for optical references in the near infrared range. (A.C.)
Systematics of constant roll inflation
Anguelova, Lilia; Suranyi, Peter; Wijewardhana, L. C. R.
2018-02-01
We study constant roll inflation systematically. This is a regime, in which the slow roll approximation can be violated. It has long been thought that this approximation is necessary for agreement with observations. However, recently it was understood that there can be inflationary models with a constant, and not necessarily small, rate of roll that are both stable and compatible with the observational constraint ns ≈ 1. We investigate systematically the condition for such a constant-roll regime. In the process, we find a whole new class of inflationary models, in addition to the known solutions. We show that the new models are stable under scalar perturbations. Finally, we find a part of their parameter space, in which they produce a nearly scale-invariant scalar power spectrum, as needed for observational viability.
Elastic properties of magnetostrictive rare-earth-iron alloys
International Nuclear Information System (INIS)
Cullen, J.R.; Blessing, G.; Rinaldi, S.
1978-01-01
The elastic properties of certain magnetostrictive rare-earth-iron alloys, namely polycrystalline Tbsub(0.3)Dysub(0.7)Fesub(2), Smsub(0.88)Dysub(0.12)Fesub(2)and amorphous TbFesub(2), were investigated ultrasonically. In all cases two shear waves were observed propagating simultaneously when a magnetic field was applied perpendicular to the direction of propagation. A model to explain this behaviour, based on magnetic-elastic coupling within local regions of these disordered materials, is developed and discussed in two limiting cases: (i) strongly coupled regions for which an effective isotropic magneto-elastic coupling is appropriate, and (ii) materials for which the elastic properties of the conglomerate are determined by averaging over those of independent regions. Experimental results up to fields of 25 kOe on the alloys mentioned above are exhibited and compared with the limiting cases (i) and (ii). In the case of polycrystalline Tbsub(0.3)Dysub(0.7)Fesub(2) further comparison is made between the determination of the magneto-elastic coupling constants using this model and the determination by using the results of a previous single-crystal study. (author)
Inverse problemfor an inhomogeneous elastic beam at a combined strength
Directory of Open Access Journals (Sweden)
Andreev Vladimir Igorevich
2014-01-01
Full Text Available In the article the authors describe a method of optimizing the stress state of an elastic beam, subject to the simultaneous action of the central concentrated force and bending moment. The optimization method is based on solving the inverse problem of the strength of materials, consisting in defining the law of changing in elasticity modulus with beam cross-section altitude. With this changing the stress state will be preset. Most problems of the elasticity theory of inhomogeneous bodies are solved in direct formulation, the essence of which is to determine the stress-strain state of a body at the known dependences of the material elastic characteristics from the coordinates. There are also some solutions of the inverse problems of the elasticity theory, in which the dependences of the mechanical characteristics from the coordinates, at which the stress state of a body is preset, are determined. In the paper the authors solve the problem of finding a dependence modulus of elasticity, where the stresses will be constant over the beam’s cross section. We will solve the problem of combined strength (in the case of the central stretching and bending. We will use an iterative method. As the initial solution, we take the solution for a homogeneous material. As the first approximation, we consider the stress state of a beam, when the modulus of elasticity varies linearly. According to the results, it can be stated that three approximations are sufficient in the considered problem. The obtained results allow us to use them in assessing the strength of a beam and its optimization.
A Membrane Model from Implicit Elasticity Theory
Freed, A. D.; Liao, J.; Einstein, D. R.
2014-01-01
A Fungean solid is derived for membranous materials as a body defined by isotropic response functions whose mathematical structure is that of a Hookean solid where the elastic constants are replaced by functions of state derived from an implicit, thermodynamic, internal-energy function. The theory utilizes Biot’s (1939) definitions for stress and strain that, in 1-dimension, are the stress/strain measures adopted by Fung (1967) when he postulated what is now known as Fung’s law. Our Fungean membrane model is parameterized against a biaxial data set acquired from a porcine pleural membrane subjected to three, sequential, proportional, planar extensions. These data support an isotropic/deviatoric split in the stress and strain-rate hypothesized by our theory. These data also demonstrate that the material response is highly non-linear but, otherwise, mechanically isotropic. These data are described reasonably well by our otherwise simple, four-parameter, material model. PMID:24282079
Surface phonons and elastic surface waves
Büscher, H.; Klein-Heßling, W.; Ludwig, W.
Theoretical investigations on the dynamics of the (001), (110) and (111) surfaces of some cubic metals (Ag, Cu, Ni) will be reviewed. Both, lattice dynamical and continuum theoretical results are obtained via a Green's function formalism. The main attitude of this paper is the comparison of our results with experiments and with results obtained via slab-calculations. The calculation of elastic surface waves has been performed using a modified surface-green-function-matching method. We have used two different approaches of calculation the bulk Green's function (a) using the spectral representation and (b) a method, what works on residues. The investigations are carried out using shortrange phenomenological potentials. The atomic force constants in the first surface layers are modified to describe surface phonon anomalies, observed by experiments. In the case of Ag (100) and Ag(110) we conclude that the detection of odd symmetry shear modes by Erskine et al. [1 a, b] was not very accurate.
Ultrabroadband elastic cloaking in thin plates.
Farhat, Mohamed; Guenneau, Sebastien; Enoch, Stefan
2009-07-10
Control of waves with metamaterials is of great topical interest, and is fueled by rapid progress in broadband acoustic and electromagnetic cloaks. We propose a design for a cloak to control bending waves propagating in isotropic heterogeneous thin plates. This is achieved through homogenization of a multilayered concentric coating filled with piecewise constant isotropic elastic material. Significantly, our cloak displays no phase shift for both backward and forward scattering. To foster experimental efforts, we provide a simplified design of the cloak which is shown to work in a more than two-octave frequency range (30 Hz to 150 Hz) when it consists of 10 layers using only 6 different materials overall. This metamaterial should be easy to manufacture, with potential applications ranging from car industry to anti-earthquake passive systems for smart buildings, depending upon the plate dimensions and wavelengths.
Surface phonons and elastic surface waves
International Nuclear Information System (INIS)
Buescher, H.; Klein-Hessling, W.; Ludwig, W.
1993-01-01
Theoretical investigations on the dynamics of the (001), (110) and (111) surfaces of some cubic metals (Ag, Cu, Ni) will be reviewed. Both, lattice dynamical and continuum theoretical results are obtained via a Green's function formalism. The main attitude of this paper is the comparison of our results with experiments and with results obtained via slab-calculations. The calculation of elastic surface waves has been performed using a modified surface-green-function-matching method. We have used two different approaches of calculation the bulk Green's function (a) using the spectral representation and (b) a method, what works on residues. The investigations are carried out using shortrange phenomenological potentials. The atomic force constants in the first surface layers are modified to describe surface phonon anomalies, observed by experiments. In the case of Ag(100) and Ag(110) we conclude that the detection of odd symmetry shear modes by Erskine et al. was not very accurate. (orig.)
Astronomical optics and elasticity theory
Lemaitre, Gerard Rene
2008-01-01
Astronomical Optics and Elasticity Theory provides a very thorough and comprehensive account of what is known in this field. After an extensive introduction to optics and elasticity, the book discusses variable curvature and multimode deformable mirrors, as well as, in depth, active optics, its theory and applications. Further, optical design utilizing the Schmidt concept and various types of Schmidt correctors, as well as the elasticity theory of thin plates and shells are elaborated upon. Several active optics methods are developed for obtaining aberration corrected diffraction gratings. Further, a weakly conical shell theory of elasticity is elaborated for the aspherization of grazing incidence telescope mirrors. The very didactic and fairly easy-to-read presentation of the topic will enable PhD students and young researchers to actively participate in challenging astronomical optics and instrumentation projects.
Uniqueness theorems in linear elasticity
Knops, Robin John
1971-01-01
The classical result for uniqueness in elasticity theory is due to Kirchhoff. It states that the standard mixed boundary value problem for a homogeneous isotropic linear elastic material in equilibrium and occupying a bounded three-dimensional region of space possesses at most one solution in the classical sense, provided the Lame and shear moduli, A and J1 respectively, obey the inequalities (3 A + 2 J1) > 0 and J1>O. In linear elastodynamics the analogous result, due to Neumann, is that the initial-mixed boundary value problem possesses at most one solution provided the elastic moduli satisfy the same set of inequalities as in Kirchhoffs theorem. Most standard textbooks on the linear theory of elasticity mention only these two classical criteria for uniqueness and neglect altogether the abundant literature which has appeared since the original publications of Kirchhoff. To remedy this deficiency it seems appropriate to attempt a coherent description ofthe various contributions made to the study of uniquenes...
Wrinkling of Pressurized Elastic Shells
Vella, Dominic; Ajdari, Amin; Vaziri, Ashkan; Boudaoud, Arezki
2011-01-01
We study the formation of localized structures formed by the point loading of an internally pressurized elastic shell. While unpressurized shells (such as a ping-pong ball) buckle into polygonal structures, we show that pressurized shells
Chirality-dependent anisotropic elastic properties of a monolayer graphene nanosheet.
Guo, Jian-Gang; Zhou, Li-Jun; Kang, Yi-Lan
2012-04-01
An analytical approach is presented to predict the elastic properties of a monolayer graphene nanosheet based on interatomic potential energy and continuum mechanics. The elastic extension and torsional springs are utilized to simulate the stretching and angle variation of carbon-carbon bond, respectively. The constitutive equation of the graphene nanosheet is derived by using the strain energy density, and the analytical formulations for nonzero elastic constants are obtained. The in-plane elastic properties of the monolayer graphene nanosheet are proved to be anisotropic. In addition, Young's moduli, Poisson's ratios and shear modulus of the monolayer graphene nanosheet are calculated according to the force constants derived from Morse potential and AMBER force field, respectively, and they were proved to be chirality-dependent. The comparison with experimental results shows a very agreement.
International Nuclear Information System (INIS)
Medkour, Y.; Roumili, A.; Maouche, D.; Saoudi, A.; Louail, L.
2012-01-01
Highlights: ► Single crystal elastic constants C 11 , C 12 and C 44 were calculated. ► Elastic moduli for polycrystalline aggregate were obtained. ► Increasing the atomic number of A element reduces B, G′, Y and v. ► Mn 3 AlC has a high melting point and light weight. - Abstract: First principle calculations were made to investigate the elastic properties of Mn 3 AC antiperovskites, A = Zn, Al, Ga, In, Tl, Ge and Sn. The estimated equilibrium lattice parameters are in agreement with the experimental ones. From the single crystal elastic constants we have calculated the polycrystalline elastic moduli: the bulk modulus B, shear modulus G, tetragonal shear modulus G′, Young’s modulus Y, Cauchy’s pressure CP, Poisson’s ratio v, elastic anisotropy factor and Pugh’s criterion G/B. Using Debye’s approximation we have deduced the elastic wave velocities and Debye’s temperature.
CONFERENCE: Elastic and diffractive scattering
Energy Technology Data Exchange (ETDEWEB)
White, Alan
1989-09-15
Elastic scattering, when particles appear to 'bounce' off each other, and the related phenomena of diffractive scattering are currently less fashionable than the study of hard scattering processes. However this could change rapidly if unexpected results from the UA4 experiment at the CERN Collider are confirmed and their implications tested. These questions were highlighted at the third 'Blois Workshop' on Elastic and Diffractive Scattering, held early in May on the Evanston campus of Northwestern University, near Chicago.
A Labor Supply Elasticity Accord?
Lars Ljungqvist; Thomas J. Sargent
2011-01-01
A dispute about the size of the aggregate labor supply elasticity has been fortified by a contentious aggregation theory used by real business cycle theorists. The replacement of that aggregation theory with one more congenial to microeconomic observations opens possibilities for an accord about the aggregate labor supply elasticity. The new aggregation theory drops features to which empirical microeconomists objected and replaces them with life-cycle choices. Whether the new aggregation theo...
Integrodifferential relations in linear elasticity
Kostin, Georgy V
2012-01-01
This work treats the elasticity of deformed bodies, including the resulting interior stresses and displacements.It also takes into account that some of constitutive relations can be considered in a weak form. To discuss this problem properly, the method of integrodifferential relations is used, and an advanced numerical technique for stress-strain analysis is presented and evaluated using various discretization techniques. The methods presented in this book are of importance for almost all elasticity problems in materials science and mechanical engineering.
International Nuclear Information System (INIS)
Leont'ev, K.L.
1981-01-01
Known theoretical and empirical formulae are considered for the difference in specific heats at constant pressure and volume. On the basis of the Grunaiser law on the ratio of specific heat to thermal expansion and on the basis of the correlation proposed by the author, between this ratio and average velocity of elastic waves obtained in a new expression for the difference in specific heats and determined are conditions at which empiric Nernst-Lindeman equation can be considered to be strict. Results of calculations for metals with fcc lattice are presented
Universal relation between spectroscopic constants
Indian Academy of Sciences (India)
(3) The author has used eq. (6) of his paper to calculate De. This relation leads to a large deviation from the correct value depending upon the extent to which experimental values are known. Guided by this fact, in our work, we used experimentally observed De values to derive the relation between spectroscopic constants.
Tachyon constant-roll inflation
Mohammadi, A.; Saaidi, Kh.; Golanbari, T.
2018-04-01
The constant-roll inflation is studied where the inflaton is taken as a tachyon field. Based on this approach, the second slow-roll parameter is taken as a constant which leads to a differential equation for the Hubble parameter. Finding an exact solution for the Hubble parameter is difficult and leads us to a numerical solution for the Hubble parameter. On the other hand, since in this formalism the slow-roll parameter η is constant and could not be assumed to be necessarily small, the perturbation parameters should be reconsidered again which, in turn, results in new terms appearing in the amplitude of scalar perturbations and the scalar spectral index. Utilizing the numerical solution for the Hubble parameter, we estimate the perturbation parameter at the horizon exit time and compare it with observational data. The results show that, for specific values of the constant parameter η , we could have an almost scale-invariant amplitude of scalar perturbations. Finally, the attractor behavior for the solution of the model is presented, and we determine that the feature could be properly satisfied.
In Situ elastic property sensors
International Nuclear Information System (INIS)
Olness, D.; Hirschfeld, T.; Kishiyama, K.; Steinhaus, R.
1987-01-01
Elasticity is an important property of many materials. Loss of elasticity can have serious consequences, such as when a gasket deteriorates and permits leakage of an expensive or hazardous material, or when a damping system begins to go awry. Loss of elasticity can also provide information related to an ancillary activity such as degradation of electrical insulation, loss of plasticizer in a plastic, or changes in permeability of a thin film. In fact, the mechanical properties of most organic compounds are altered when the compound degrades. Thus, a sensor for the mechanical properties can be used to monitor associated characteristics as well. A piezoelectric material in contact with an elastomer forms an oscillating system that can provide real-time elasticity monitoring. This combination constitutes a forced harmonic oscillator with damping provided by the elastomer. A ceramic oscillator with a total volume of a few mm 3 was used as an elasticity sensor. It was placed in intimate contact with an elastomer and then monitored remotely with a simple oscillator circuit and standard frequency counting electronics. Resonant frequency shifts and changes in Q value were observed corresponding to changes in ambient temperature and/or changes in pressure applied to the sample. Elastomer samples pretreated with ozone (to simulate aging) showed changes in Q value and frequency response, even though there were no visible changes in the elastic samples
The πHe3H3 coupling constant estimation using the Chew-Low equation
International Nuclear Information System (INIS)
Mach, R.; Nichitiu, F.
1976-01-01
A semi-phenomenological analysis of the π +- He 3 elastic scattering at 98, 120, 135 and 156 Mev is presented. An information of the πHe 3 H 3 coupling constant using the Chew-Low plot for the P 33 partial wave is obtained. (author)
The πHe3H3 coupling constant estimation using the Chew-Low equation
International Nuclear Information System (INIS)
Mach, R.; Nichitiu, F.
1975-01-01
In this paper it is presented an estimation of the πHe 3 H 3 coupling constant using the Chew-Low equation and a semi-phenomenological analysis of the π -+ He 3 elastic differential cross sections at 98, 120, 135 and 156 MeV
De Basabe, Jonás D.
2010-04-01
We investigate the stability of some high-order finite element methods, namely the spectral element method and the interior-penalty discontinuous Galerkin method (IP-DGM), for acoustic or elastic wave propagation that have become increasingly popular in the recent past. We consider the Lax-Wendroff method (LWM) for time stepping and show that it allows for a larger time step than the classical leap-frog finite difference method, with higher-order accuracy. In particular the fourth-order LWM allows for a time step 73 per cent larger than that of the leap-frog method; the computational cost is approximately double per time step, but the larger time step partially compensates for this additional cost. Necessary, but not sufficient, stability conditions are given for the mentioned methods for orders up to 10 in space and time. The stability conditions for IP-DGM are approximately 20 and 60 per cent more restrictive than those for SEM in the acoustic and elastic cases, respectively. © 2010 The Authors Journal compilation © 2010 RAS.
Stabilized power constant alimentation; Alimentation regulee a puissance constante
Energy Technology Data Exchange (ETDEWEB)
Roussel, L. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1968-06-01
The study and realization of a stabilized power alimentation variable from 5 to 100 watts are described. In order to realize a constant power drift of Lithium compensated diodes, we have searched a 1 per cent precision of regulation and a response time minus than 1 sec. Recent components like Hall multiplicator and integrated amplifiers give this possibility and it is easy to use permutable circuits. (author) [French] On decrit l'etude et la realisation d'une alimentation a puissance constante reglable dans une gamme de 5 a 100 watts. Prevue pour le drift a puissance constante des diodes compensees au lithium, l'etude a ete menee en vue d'obtenir une precision de regulation de 1 pour cent et un temps de reponse inferieur a la seconde. Des systemes recents tels que multiplicateurs a effet Hall et circuits integres ont permis d'atteindre ce but tout en facilitant l'emploi de modules interchangeables. (auteur)
Effect of price elasticity of demand in monopolies with gradient adjustment
International Nuclear Information System (INIS)
Cavalli, Fausto; Naimzada, Ahmad
2015-01-01
Highlights: •A monopoly with isoelastic demand function is studied. •Reduced rationality monopolist uses gradient adjustment. •If marginal cost is small, increasing elasticity leads to stable dynamics. •For large marginal cost, dynamic can be unstable for both small and large elasticity. -- Abstract: We study a monopolistic market characterized by a constant elasticity demand function, in which the firm technology is described by a linear total cost function. The firm is assumed to be boundedly rational and to follow a gradient rule to adjust the production level in order to optimize its profit. We focus on what happens on varying the price elasticity of demand, studying the effect on the equilibrium stability. We prove that, depending on the relation between the market size and the marginal cost, two different scenarios are possible, in which elasticity has either a stabilizing or a mixed stabilizing/destabilizing effect
Elasticity and hardness of nano-polycrystalline boron nitrides: The apparent Hall-Petch effect
International Nuclear Information System (INIS)
Nagakubo, A.; Ogi, H.; Hirao, M.; Sumiya, H.
2014-01-01
Nano-polycrystalline boron nitride (BN) is expected to replace diamond as a superhard and superstiff material. Although its hardening was reported, its elasticity remains unclear and the as-measured hardness could be significantly different from the true value due to the elastic recovery. In this study, we measured the longitudinal-wave elastic constant of nano-polycrystalline BNs using picosecond ultrasound spectroscopy and confirmed the elastic softening for small-grain BNs. We also measured Vickers and Knoop hardness for the same specimens and clarified the relationship between hardness and stiffness. The Vickers hardness significantly increased as the grain size decreased, while the Knoop hardness remained nearly unchanged. We attribute the apparent increase in Vickers hardness to the elastic recovery and propose a model to support this insight.
First-Principle Calculations for Elastic and Thermodynamic Properties of Diamond
International Nuclear Information System (INIS)
Fu Zhijian; Chen Xiangrong; Gou Qingquan; Ji Guangfu
2009-01-01
The elastic constants and thermodynamic properties of diamond are investigated by using the CRYSTAL03 program. The lattice parameters, the bulk modulus, the heat capacity, the Grueneisen parameter, and the Debye temperature are obtained. The results are in good agreement with the available experimental and theoretical data. Moreover, the relationship between V/V 0 and pressure, the elastic constants under high pressure are successfully obtained. Especially, the elastic constants of diamond under high pressure are firstly obtained theoretically. At the same time, the variations of the thermal expansion α with pressure P and temperature Tare obtained systematically in the ranges of 0-870 GPa and 0-1600 K. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
Elasticity of Pargasite Amphibole: A Hydrous Phase at Mid Lithospheric Discontinuity
Peng, Y.; Mookherjee, M.
2017-12-01
Mid Lithospheric Discontinuity (MLD) is characterized by a low shear wave velocity ( 3 to 10 %). In cratons, the depth of MLD varies between 80 and 100 km. The reduction of the shear wave velocity at MLD is similar to what is observed in the lithosphere-asthenosphere boundary (LAB). Such low velocity at MLD could be caused by partial melting, temperature induced grain boundary sliding, changes in the elastic anisotropy, and/or metasomatism which may lead to the formation of hydrous phases including mica and amphibole. Thus, it is clear that in order to assess the role of metasomatism at MLD, we need better constraints on the elasticity of hydrous phases. However, such elasticity data are scarce. In this study, we explore elasticity of pargasite amphibole [NaCa2(Mg4Al)(Si6Al2)O22(OH)2] using density functional theory (DFT) with local density approximation (LDA) and generalized gradient approximation (GGA). We find that the pressure-volume results can be adequately described by a finite strain equation with the bulk modulus, K0 being 102 and 85 GPa for LDA and GGA respectively. We also determined the full elastic constant tensor (Cij) using the finite difference method. The bulk modulus, K0 determined from the full elastic constant tensor is 104 GPa for LDA and 87 GPa for GGA. The shear modulus, G0 determined from the full elastic constant tensor is 64 GPa for LDA and 58 GPa for GGA. The bulk and shear moduli predicted with LDA are 5 and 1 % stiffer than the recent results [1]. In contrast, the bulk and shear moduli predicted with GGA are 12 and 10 % softer compared to the recent results [1]. The full elastic constant tensor for pargasite shows significant anisotropy. For instance, LDA predicts compressional (AVP) and shear (AVS) wave anisotropy of 22 and 20 % respectively. At higher pressure, elastic moduli stiffen. However, temperature is likely to have an opposite effect on the elasticity and this remains largely unknown for pargasite. Compared to the major mantle
Directory of Open Access Journals (Sweden)
K. A. Pestka II
2011-09-01
Full Text Available The complete elastic tensors of SmScO3 and NdScO3 were measured using resonant ultrasound spectroscopy (RUS in combination with ab-initio calculations. Measurement of the elastic tensor of these recently synthesized single crystal RE scandates is essential for understanding dynamic lattice applications including phonon confinement, strain induced thin film growth and superlattice construction. On average, the experimental elastic constants differed by less than 5% of the theoretical values, further validating the accuracy of modern ab-initio calculations as a means of estimating the initial elastic constants used in RUS measurements.
Exploring the Local Elastic Properties of Bilayer Membranes Using Molecular Dynamics Simulations
DEFF Research Database (Denmark)
Pieffet, Gilles; Botero, Alonso; Peters, Günther H.J.
2014-01-01
Membrane mechanical elastic properties regulate a variety of cellular processes involving local membrane deformation, such as ion channel function and vesicle fusion. In this work, we used molecular dynamics simulations to estimate the local elastic properties of a membrane. For this, we calculated...... the stretching process in molecular detail, allowing us to fit this profile to a previously proposed continuum elastic model. Through this approach, we calculated an effective membrane spring constant of 42 kJ-2.mol-1, which is in good agreement with the PMF calculation. Furthermore, the solvation energy we...
Elastic models for the non-Arrhenius relaxation time of glass-forming liquids
DEFF Research Database (Denmark)
Dyre, Jeppe
We first review the phenomenology of viscous liquids and the standard models used for explaining the non-Arrhenius average relaxation time. Then the focus is turned to the so-called elastic models, arguing that these models are all equivalent in the Einstein approximation (where the short-time...... elastic properties are all determined by just one effective, temperature-dependent force constant). We finally discuss the connection between the elastic models and two well-established research fields of condensed-matter physics: point defects in crystals and solid-state diffusion....
Elastic models for the Non-Arrhenius Relaxation Time of Glass-Forming Liquids
DEFF Research Database (Denmark)
Dyre, J. C.
2006-01-01
We first review the phenomenology of viscous liquids and the standard models used for explaining the non-Arrhenius average relaxation time. Then the focus is turned to the so-called elastic models, arguing that these models are all equivalent in the Einstein approximation (where the short-time...... elastic properties are all determined by just one effective, temperature-dependent force constant). We finally discuss the connection between the elastic models and two well-established research fields of condensed-matter physics: point defects in crystals and solid-state diffusion....
The Measurement of the Quasi-Elastic Neutrino-Nucleon Scattering Cross Section at the Tevatron
Energy Technology Data Exchange (ETDEWEB)
Suwonjandee, Narumon [Cincinnati U.
2004-01-01
The quasi-elastic neutrino nucleon cross section measurement has been measured in the low energy region less than 100 Ge V. The data agree well with the model proposed by C. H. Llewellyn Smith. This model predicts that the quasi-elastic cross section should be constant in the high enery region. The NuTeV experiment at Fermilab provides data which allows us to measure the quasi-elastic cross section for both neutrinos and anti-neutrinos at high energy. We find that $\\sigma^{Neucleon}_{qe}(v) = 0.94 \\pm 0.03(stat.) \\pm 0.07(syst.)$, and $\\sigma^{Neucleon}_{qe}(\\bar\
Structural phase transition and elastic properties of mercury chalcogenides
Energy Technology Data Exchange (ETDEWEB)
Varshney, Dinesh, E-mail: vdinesh33@rediffmail.com [School of Physics, Vigyan Bhavan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India); Shriya, S. [School of Physics, Vigyan Bhavan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India); Khenata, R. [Laboratoire de Physique Quantique et de Modelisation Mathematique (LPQ3M), Departement de Technologie, Universite de Mascara, 29000 Mascara (Algeria)
2012-08-15
Pressure induced structural transition and elastic properties of ZnS-type (B3) to NaCl-type (B1) structure in mercury chalcogenides (HgX; X = S, Se and Te) are presented. An effective interionic interaction potential (EIOP) with long-range Coulomb, as well charge transfer interactions, Hafemeister and Flygare type short-range overlap repulsion extended up to the second neighbor ions and van der Waals interactions are considered. Emphasis is on the evaluation of the pressure dependent Poisson's ratio {nu}, the ratio R{sub BT/G} of B (bulk modulus) over G (shear modulus), anisotropy parameter, Shear and Young's modulus, Lame constant, Kleinman parameter, elastic wave velocity and thermodynamical property as Debye temperature. The Poisson's ratio behavior infers that Mercury chalcogenides are brittle in nature. To our knowledge this is the first quantitative theoretical prediction of the pressure dependence of elastic and thermodynamical properties explicitly the ductile (brittle) nature of HgX and still awaits experimental confirmations. Highlights: Black-Right-Pointing-Pointer Vast volume discontinuity in phase diagram infers transition from ZnS to NaCl structure. Black-Right-Pointing-Pointer The shear elastic constant C{sub 44} is nonzero confirms the mechanical stability. Black-Right-Pointing-Pointer Pressure dependence of {theta}{sub D} infers the softening of lattice with increasing pressure. Black-Right-Pointing-Pointer Estimated bulk, shear and tetragonal moduli satisfied elastic stability criteria. Black-Right-Pointing-Pointer In both B3 and B1 phases, C{sub 11} and C{sub 12} increase linearly with pressure.
The elastic properties of zirconium alloy fuel cladding and pressure tubing materials
International Nuclear Information System (INIS)
Rosinger, H.E.; Northwood, D.O.
1979-01-01
A knowledge of the elastic properties of zirconium alloys is required in the mathematical modelling of cladding and pressure tubing performance. Until recently, little of this type of data was available, particularly at elevated temperatures. The dynamic elastic moduli of zircaloy-2, zircaloy-4, the alloys Zr-1.0 wt%Nb, Zr-2.5 wt%Nb and Marz grade zirconium have therefore been determined over the temperature range 275 to 1000 K. Young's modulus and shear modulus for all the zirconium alloys decrease with temperature and are expressed by empirical relations fitted to the data. The elastic properties are texture dependent and a detailed study has been conducted on the effect of texture on the elastic properties of Zr-1.0 wt% Nb over the temperature range 275 to 775 K. The results are compared with polycrystalline elastic constants computed from single crystal elastic constants, and the effect of texture on the dynamic elastic moduli is discussed in detail. (Auth.)
Evolution of the solar constant
International Nuclear Information System (INIS)
Newman, M.J.
1978-01-01
The ultimate source of the energy utilized by life on Earth is the Sun, and the behavior of the Sun determines to a large extent the conditions under which life originated and continues to thrive. What can be said about the history of the Sun. Has the solar constant, the rate at which energy is received by the Earth from the Sun per unit area per unit time, been constant at its present level since Archean times. Three mechanisms by which it has been suggested that the solar energy output can vary with time are discussed, characterized by long (approx. 10 9 years), intermediate (approx. 10 8 years), and short (approx. years to decades) time scales
Calculation of magnetic hyperfine constants
International Nuclear Information System (INIS)
Bufaical, R.F.; Maffeo, B.; Brandi, H.S.
1975-01-01
The magnetic hyperfine constants of the V sub(K) center in CaF 2 , SrF 2 and BaF 2 have been calculated assuming a phenomenological model, based on the F 2 - 'central molucule', to describe the wavefunction of the defect. Calculations have shown that introduction of a small degree of covalence, between this central molecule and neighboring ions, is necessary to improve the electronic structure description of the defect. It was also shown that the results for the hyperfine constants are strongly dependent on the relaxations of the ions neighboring the central molecule; these relaxations have been determined by fitting the experimental data. The present results are compared with other previous calculations where similar and different theoretical methods have been used
The Morishima Gross elasticity of substitution
Blackorby, Charles; Primont, Daniel; Russell, R. Robert
2007-01-01
We show that the Hotelling-Lau elasticity of substitution, an extension of the Allen-Uzawa elasticity to allow for optimal output-quantity (or utility) responses to changes in factor prices, inherits all of the failings of the Allen-Uzawa elasticity identified by Blackorby and Russell [1989 AER]. An analogous extension of the Morishima elasticity of substitution to allow for output quantity changes preserves the salient properties of the original Hicksian notion of elasticity of substitution.
On the gravitational constant change
International Nuclear Information System (INIS)
Milyukov, V.K.
1986-01-01
The nowadays viewpoint on the problem of G gravitational constant invariability is presented in brief. The methods and results of checking of the G dependence on the nature of substance (checking of the equivalence principle), G dependepce on distance (checking of Newton gravity law) and time (cosmological experiments) are presented. It is pointed out that all performed experiments don't give any reasons to have doubts in G constancy in space and time and G independence on the nature of the substance
Photodissociation constant of NO2
International Nuclear Information System (INIS)
Nootebos, M.A.; Bange, P.
1992-01-01
The velocity of the dissociation of NO 2 into ozone and NO mainly depends on the ultraviolet sunlight quantity, and with that the cloudiness. A correct value for this reaction constant is important for the accurate modelling of O 3 - and NO 2 -concentrations in plumes of electric power plants, in particular in the case of determination of the amount of photochemical summer smog. An advanced signal processing method (deconvolution, correlation) was applied on the measurements. The measurements were carried out from aeroplanes
Effects of hydrogen on the single crystalline elastic constants of niobium
Energy Technology Data Exchange (ETDEWEB)
Schlader, Daniel Michael [Iowa State Univ., Ames, IA (United States)
1977-06-01
A special hydriding system was designed and constructed to satisfy conditions for hydriding niobium. This system controlled the temperature and hydrogen atmosphere surrounding the niobium while ultrasonic measurements were recorded. Ultrasonic wave velocities were determined by measurement of the times for ultrasonic pulses to transit and then echo through known dimensions of test specimens. The method which was employed is commonly known as the pulse-echo-overlap method. This study confirmed the general trends of earlier investigations. In this study C' continued to decrease and C_{44} continued to increase up to 4.69 atomic percent hydrogen which is the maximum concentration which has yet been examined. In the case of the niobium-hydrogen system the Snoek effect may well be a contributory factor to the decrease of C' with increasing hydrogen concentration. However, crystallographic considerations preclude this effect from contributing a concentration dependence to C_{44} or B. The observation of the present work implies that other factors must also be contributing to the overall behavior.
Effects of hydrogen on the single crystalline elastic constants of niobium
International Nuclear Information System (INIS)
Schlader, D.M.
1977-06-01
A special hydriding system was designed and constructed to satisfy conditions for hydriding niobium. This system controlled the temperature and hydrogen atmosphere surrounding the niobium while ultrasonic measurements were recorded. Ultrasonic wave velocities were determined by measurement of the times for ultrasonic pulses to transit and then echo through known dimensions of test specimens. The method which was employed is commonly known as the pulse-echo-overlap method. This study confirmed the general trends of earlier investigations. In this study C' continued to decrease and C 44 continued to increase up to 4.69 atomic percent hydrogen which is the maximum concentration which has yet been examined. In the case of the niobium-hydrogen system the Snoek effect may well be a contributory factor to the decrease of C' with increasing hydrogen concentration. However, crystallographic considerations preclude this effect from contributing a concentration dependence to C 44 or B. The observation of the present work implies that other factors must also be contributing to the overall behavior
Effective medium approximation for elastic constants of porous solids with microscopic heterogeneity
International Nuclear Information System (INIS)
Berryman, J.G.
1986-01-01
Formulas for the scattering from an inhomogeneous sphere in a fluid-saturated porous medium are used to construct a self-consistent effective medium approximation for the coefficients in Biot's equations of poroelasticity [J. Acoust. Soc. Am. 28, 168 (1956)] when the material constituting the porous solid frame is not homogeneous on the microscopic scale. The discussion is restricted to porous materials exhibiting both macroscopic and microscopic isotropy. Brown and Korringa [Geophysics 40, 608 (1975)] have previously found the general form of these coefficients. The present results give explicit estimates of all the coefficients in terms of the moduli of the solid constituents. The results are also shown to be completely consistent with the well-known results of Gassmann and of Biot and Willis, as well as those of Brown and Korringa
Econometric estimation of the “Constant Elasticity of Substitution" function in R
DEFF Research Database (Denmark)
Henningsen, Arne; Henningsen, Geraldine
for estimating the traditional CES function with two inputs as well as nested CES functions with three and four inputs. Furthermore, we demonstrate how these approaches can be applied in R using the add-on package micEconCES and we describe how the various estimation approaches are implemented in the mic......EconCES package. Finally, we illustrate the usage of this package by replicating some estimations of CES functions that are reported in the literature....
Pawlik, Marzena; Lu, Yiling
2018-05-01
Computational micromechanics is a useful tool to predict properties of carbon fibre reinforced polymers. In this paper, a representative volume element (RVE) is used to investigate a fuzzy fibre reinforced polymer. The fuzzy fibre results from the introduction of nanofillers in the fibre surface. The composite being studied contains three phases, namely: the T650 carbon fibre, the carbon nanotubes (CNTs) reinforced interphase and the epoxy resin EPIKOTE 862. CNTs are radially grown on the surface of the carbon fibre, and thus resultant interphase composed of nanotubes and matrix is transversely isotropic. Transversely isotropic properties of the interphase are numerically implemented in the ANSYS FEM software using element orientation command. Obtained numerical predictions are compared with the available analytical models. It is found that the CNTs interphase significantly increased the transverse mechanical properties of the fuzzy fibre reinforced polymer. This extent of enhancement changes monotonically with the carbon fibre volume fraction. This RVE model enables to investigate different orientation of CNTs in the fuzzy fibre model.
International Nuclear Information System (INIS)
Stelzer, J.; Trebin, H.R.; Longa, L.
1994-08-01
We report NVT and NPT molecular dynamics simulations of a Gay-Berne nematic liquid crystal using generalization of recently proposed algorithm by Toxvaerd [Phys. Rev. E47, 343, 1993]. On the basis of these simulations the Oseen-Zoher-Frank elastic constants K 11 , K 22 and K 33 as well as the surface constants K 13 and K 24 have been calculated within the framework of the direct correlation function approach of Lipkin et al. [J. Chem. Phys. 82, 472 (1985)]. The angular coefficients of the direct pair correlation function, which enter the final formulas, have been determined from the computer simulation data for the pair correlation function of the nematic by combining the Ornstein-Zernike relation and the Wienier-Hopf factorization scheme. The unoriented nematic approximation has been assumed when constructing the reference, isotropic state of Lipkin et al. By an extensive study of the model over a wide range of temperatures, densities and pressures a very detailed information has been provided about elastic behaviour of the Gay-Berne nematic. Interestingly, it is found that the results for the surface elastic constants are qualitatively different than those obtained with the help of analytical approximations for the isotropic, direct pair correlation function. For example, the values of the surface elastic constants are negative and an order of magnitude smaller than the bulk elasticity. (author). 30 refs, 9 figs
Energy Technology Data Exchange (ETDEWEB)
Erba, A., E-mail: alessandro.erba@unito.it; Mahmoud, A.; Dovesi, R. [Dipartimento di Chimica and Centre of Excellence NIS (Nanostructured Interfaces and Surfaces), Università di Torino, via Giuria 5, IT-10125 Torino (Italy); Belmonte, D. [DISTAV, Università di Genova, Corso Europa 26, 16132 Genoa (Italy)
2014-03-28
A computational strategy is devised for the accurate ab initio simulation of elastic properties of crystalline materials under pressure. The proposed scheme, based on the evaluation of the analytical stress tensor and on the automated computation of pressure-dependent elastic stiffness constants, is implemented in the CRYSTAL solid state quantum-chemical program. Elastic constants and related properties (bulk, shear and Young moduli, directional seismic wave velocities, elastic anisotropy index, Poisson's ratio, etc.) can be computed for crystals of any space group of symmetry. We apply such a technique to the study of high-pressure elastic properties of three silicate garnet end-members (namely, pyrope, grossular, and andradite) which are of great geophysical interest, being among the most important rock-forming minerals. The reliability of this theoretical approach is proved by comparing with available experimental measurements. The description of high-pressure properties provided by several equations of state is also critically discussed.
International Nuclear Information System (INIS)
Erba, A.; Mahmoud, A.; Dovesi, R.; Belmonte, D.
2014-01-01
A computational strategy is devised for the accurate ab initio simulation of elastic properties of crystalline materials under pressure. The proposed scheme, based on the evaluation of the analytical stress tensor and on the automated computation of pressure-dependent elastic stiffness constants, is implemented in the CRYSTAL solid state quantum-chemical program. Elastic constants and related properties (bulk, shear and Young moduli, directional seismic wave velocities, elastic anisotropy index, Poisson's ratio, etc.) can be computed for crystals of any space group of symmetry. We apply such a technique to the study of high-pressure elastic properties of three silicate garnet end-members (namely, pyrope, grossular, and andradite) which are of great geophysical interest, being among the most important rock-forming minerals. The reliability of this theoretical approach is proved by comparing with available experimental measurements. The description of high-pressure properties provided by several equations of state is also critically discussed
Energy Technology Data Exchange (ETDEWEB)
Duru, Kenneth, E-mail: kduru@stanford.edu [Department of Geophysics, Stanford University, Stanford, CA (United States); Dunham, Eric M. [Department of Geophysics, Stanford University, Stanford, CA (United States); Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA (United States)
2016-01-15
Dynamic propagation of shear ruptures on a frictional interface in an elastic solid is a useful idealization of natural earthquakes. The conditions relating discontinuities in particle velocities across fault zones and tractions acting on the fault are often expressed as nonlinear friction laws. The corresponding initial boundary value problems are both numerically and computationally challenging. In addition, seismic waves generated by earthquake ruptures must be propagated for many wavelengths away from the fault. Therefore, reliable and efficient numerical simulations require both provably stable and high order accurate numerical methods. We present a high order accurate finite difference method for: a) enforcing nonlinear friction laws, in a consistent and provably stable manner, suitable for efficient explicit time integration; b) dynamic propagation of earthquake ruptures along nonplanar faults; and c) accurate propagation of seismic waves in heterogeneous media with free surface topography. We solve the first order form of the 3D elastic wave equation on a boundary-conforming curvilinear mesh, in terms of particle velocities and stresses that are collocated in space and time, using summation-by-parts (SBP) finite difference operators in space. Boundary and interface conditions are imposed weakly using penalties. By deriving semi-discrete energy estimates analogous to the continuous energy estimates we prove numerical stability. The finite difference stencils used in this paper are sixth order accurate in the interior and third order accurate close to the boundaries. However, the method is applicable to any spatial operator with a diagonal norm satisfying the SBP property. Time stepping is performed with a 4th order accurate explicit low storage Runge–Kutta scheme, thus yielding a globally fourth order accurate method in both space and time. We show numerical simulations on band limited self-similar fractal faults revealing the complexity of rupture
Directory of Open Access Journals (Sweden)
Boudia Keltouma
2015-12-01
Full Text Available Structural, elastic, electronic and thermodynamic properties of ternary cubic filled skutterudite compound were calculated. We have computed the elastic modulus and its pressure dependence. From the elastic parameter behavior, it is inferred that this compound is elastically stable and ductile in nature. Through the quasi-harmonic Debye model, in which phononic effects are considered, the effect of pressure P (0 to 50 GPa and temperature T (0 to 3000 °C on the lattice constant, elastic parameters, bulk modulus B, heat capacity, thermal expansion coefficient α, internal energy U, entropy S, Debye temperature θD, Helmholtz free energy A, and Gibbs free energy G are investigated.
Elastic properties of cubic perovskite BaRuO{sub 3} from first-principles calculations
Energy Technology Data Exchange (ETDEWEB)
Han Deming; Liu Xiaojuan; Lv Shuhui; Li Hongping [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Meng Jian, E-mail: jmeng@ciac.jl.c [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)
2010-08-01
We present first-principles investigations on the structural and elastic properties of the cubic perovskite BaRuO{sub 3} using density-functional theory within both local density approximation (LDA) and generalized gradient approximation (GGA). Basic physical properties, such as lattice constant, shear modulus, elastic constants (C{sub ij}) are calculated. The calculated energy band structures show that the cubic perovskite BaRuO{sub 3} is metallic. We have also predicted the Young's modulus (Y), Poisson's ratio ({upsilon}), and Anisotropy factor (A).
Temperature-dependent elastic properties of Ti{sub 1−x}Al{sub x}N alloys
Energy Technology Data Exchange (ETDEWEB)
Shulumba, Nina [Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Functional Materials, Saarland University, D-66123 Saarbrücken (Germany); Hellman, Olle [Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California 91125 (United States); Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Rogström, Lina; Raza, Zamaan; Tasnádi, Ferenc; Odén, Magnus [Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Abrikosov, Igor A. [Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Materials Modeling and Development Laboratory, NUST “MISIS,” 119049 Moscow (Russian Federation); LACOMAS Laboratory, Tomsk State University, 634050 Tomsk (Russian Federation)
2015-12-07
Ti{sub 1−x}Al{sub x}N is a technologically important alloy that undergoes a process of high temperature age-hardening that is strongly influenced by its elastic properties. We have performed first principles calculations of the elastic constants and anisotropy using the symmetry imposed force constant temperature dependent effective potential method, which include lattice vibrations and therefore the effects of temperature, including thermal expansion and intrinsic anharmonicity. These are compared with in situ high temperature x-ray diffraction measurements of the lattice parameter. We show that anharmonic effects are crucial to the recovery of finite temperature elasticity. The effects of thermal expansion and intrinsic anharmonicity on the elastic constants are of the same order, and cannot be considered separately. Furthermore, the effect of thermal expansion on elastic constants is such that the volume change induced by zero point motion has a significant effect. For TiAlN, the elastic constants soften non-uniformly with temperature: C{sub 11} decreases substantially when the temperature increases for all compositions, resulting in an increased anisotropy. These findings suggest that an increased Al content and annealing at higher temperatures will result in a harder alloy.
Fine-structure constant: Is it really a constant
International Nuclear Information System (INIS)
Bekenstein, J.D.
1982-01-01
It is often claimed that the fine-structure ''constant'' α is shown to be strictly constant in time by a variety of astronomical and geophysical results. These constrain its fractional rate of change alpha-dot/α to at least some orders of magnitude below the Hubble rate H 0 . We argue that the conclusion is not as straightforward as claimed since there are good physical reasons to expect alpha-dot/α 0 . We propose to decide the issue by constructing a framework for a variability based on very general assumptions: covariance, gauge invariance, causality, and time-reversal invariance of electromagnetism, as well as the idea that the Planck-Wheeler length (10 -33 cm) is the shortest scale allowable in any theory. The framework endows α with well-defined dynamics, and entails a modification of Maxwell electrodynamics. It proves very difficult to rule it out with purely electromagnetic experiments. In a cosmological setting, the framework predicts an alpha-dot/α which can be compatible with the astronomical constraints; hence, these are too insensitive to rule out α variability. There is marginal conflict with the geophysical constraints: however, no firm decision is possible because of uncertainty about various cosmological parameters. By contrast the framework's predictions for spatial gradients of α are in fatal conflict with the results of the Eoetvoes-Dicke-Braginsky experiments. Hence these tests of the equivalence principle rule out with confidence spacetime variability of α at any level
International Nuclear Information System (INIS)
Ravindran, P.; Fast, L.; Korzhavyi, P.A.; Johansson, B.; Wills, J.; Eriksson, O.
1998-01-01
A theoretical formalism to calculate the single crystal elastic constants for orthorhombic crystals from first principle calculations is described. This is applied for TiSi 2 and we calculate the elastic constants using a full potential linear muffin-tin orbital method using the local density approximation (LDA) and generalized gradient approximation (GGA). The calculated values compare favorably with recent experimental results. An expression to calculate the bulk modulus along crystallographic axes of single crystals, using elastic constants, has been derived. From this the calculated linear bulk moduli are found to be in good agreement with the experiments. The shear modulus, Young's modulus, and Poisson's ratio for ideal polycrystalline TiSi 2 are also calculated and compared with corresponding experimental values. The directional bulk modulus and the Young's modulus for single crystal TiSi 2 are estimated from the elastic constants obtained from LDA as well as GGA calculations and are compared with the experimental results. The shear anisotropic factors and anisotropy in the linear bulk modulus are obtained from the single crystal elastic constants. From the site and angular momentum decomposed density of states combined with a charge density analysis and the elastic anisotropies, the chemical bonding nature between the constituents in TiSi 2 is analyzed. The Debye temperature is calculated from the average elastic wave velocity obtained from shear and bulk modulus as well as the integration of elastic wave velocities in different directions of the single crystal. The calculated elastic properties are found to be in good agreement with experimental values when the generalized gradient approximation is used for the exchange and correlation potential. copyright 1998 American Institute of Physics
Phason elasticity and surface roughening
International Nuclear Information System (INIS)
Tang Leihan; Jaric, M.V.
1990-01-01
The phason elasticity of two-dimensional (2D) equilibrium quasicrystals is discussed in analogy with surface roughening phenomena. Taking a Penrose tiling model as an example, we show that the phason elastic energy is linear in the phason strain at zero temperature (T = 0), but becomes quadratic at any T > 0 and sufficiently small strain. Heuristic and real-space renormalization group arguments are given for the thermal roughening of the hyper-surface which represents quasicrystal tiling. Monte Carlo method is applied to illustrate the logarithmically diverging phason fluctuations and power-law diffraction intensities at T > 0. For three-dimensional systems, we present arguments which suggest a finite temperature transition between two quasicrystal phases, characterized by linear and quadratic phason elastic energy, respectively. (author). 17 refs, 12 figs
Investor response to consumer elasticity
International Nuclear Information System (INIS)
Grenaa Jensen, Stine; Meibom, Peter; Ravn, H.F.; Straarup, Sarah
2004-01-01
In the Nordic electricity system there is considerable uncertainty with respect to the long-term development in production capacity. The process towards liberalisation of the electricity sector started in a situation with a large reserve margin, but this margin is gradually vanishing. Since the potential investors in new production capacity are unaccustomed with investments under the new regime it is unknown if and when investments will take place. The electricity price is the key market signal to potential investors. The price is settled as a balance between supply and demand, and it is generally assumed that the demand side has an important role in this, and increasingly so. However, since consumers have not earlier had the incentive to respond to electricity prices, no reliable estimate of demand elasticity is known. The purpose of the present study is to analyse the role of electricity demand elasticity for investments in new electricity production capacity. Electricity price scenarios generated with a partial equilibrium model (Balmorel) are combined with a model of investment decisions. In this, various scenarios concerning the development in the demand elasticity are used. The simulated investment decisions are taken in a stochastic, dynamic setting, where a key point is the timing of the investment decision in relation to the gathering of new information relative to the stochastic elements. Based on this, the consequences of the development in consumer price elasticity for investments in a base load and a peak load plant are investigated. The main result of the analysis is that peak load investments can be made unprofitable by the development in consumer price elasticity, such that an investor will tend to wait with his peak load investment, until the development in consumer price elasticity has been revealed. (au)
Chandra Independently Determines Hubble Constant
2006-08-01
A critically important number that specifies the expansion rate of the Universe, the so-called Hubble constant, has been independently determined using NASA's Chandra X-ray Observatory. This new value matches recent measurements using other methods and extends their validity to greater distances, thus allowing astronomers to probe earlier epochs in the evolution of the Universe. "The reason this result is so significant is that we need the Hubble constant to tell us the size of the Universe, its age, and how much matter it contains," said Max Bonamente from the University of Alabama in Huntsville and NASA's Marshall Space Flight Center (MSFC) in Huntsville, Ala., lead author on the paper describing the results. "Astronomers absolutely need to trust this number because we use it for countless calculations." Illustration of Sunyaev-Zeldovich Effect Illustration of Sunyaev-Zeldovich Effect The Hubble constant is calculated by measuring the speed at which objects are moving away from us and dividing by their distance. Most of the previous attempts to determine the Hubble constant have involved using a multi-step, or distance ladder, approach in which the distance to nearby galaxies is used as the basis for determining greater distances. The most common approach has been to use a well-studied type of pulsating star known as a Cepheid variable, in conjunction with more distant supernovae to trace distances across the Universe. Scientists using this method and observations from the Hubble Space Telescope were able to measure the Hubble constant to within 10%. However, only independent checks would give them the confidence they desired, considering that much of our understanding of the Universe hangs in the balance. Chandra X-ray Image of MACS J1149.5+223 Chandra X-ray Image of MACS J1149.5+223 By combining X-ray data from Chandra with radio observations of galaxy clusters, the team determined the distances to 38 galaxy clusters ranging from 1.4 billion to 9.3 billion
Cryptography in constant parallel time
Applebaum, Benny
2013-01-01
Locally computable (NC0) functions are 'simple' functions for which every bit of the output can be computed by reading a small number of bits of their input. The study of locally computable cryptography attempts to construct cryptographic functions that achieve this strong notion of simplicity and simultaneously provide a high level of security. Such constructions are highly parallelizable and they can be realized by Boolean circuits of constant depth.This book establishes, for the first time, the possibility of local implementations for many basic cryptographic primitives such as one-way func
Low power constant fraction discriminator
International Nuclear Information System (INIS)
Krishnan, Shanti; Raut, S.M.; Mukhopadhyay, P.K.
2001-01-01
This paper describes the design of a low power ultrafast constant fraction discriminator, which significantly reduces the power consumption. A conventional fast discriminator consumes about 1250 MW of power whereas this low power version consumes about 440 MW. In a multi detector system, where the number of discriminators is very large, reduction of power is of utmost importance. This low power discriminator is being designed for GRACE (Gamma Ray Atmospheric Cerenkov Experiments) telescope where 1000 channels of discriminators are required. A novel method of decreasing power consumption has been described. (author)
Can coupling constants be related
International Nuclear Information System (INIS)
Nandi, Satyanarayan; Ng, Wing-Chiu.
1978-06-01
We analyze the conditions under which several coupling constants in field theory can be related to each other. When the relation is independent of the renormalization point, the relation between any g and g' must satisfy a differential equation as follows from the renormalization group equations. Using this differential equation, we investigate the criteria for the feasibility of a power-series relation for various theories, especially the Weinberg-Salam type (including Higgs bosons) with an arbitrary number of quark and lepton flavors. (orig./WL) [de
Exact constants in approximation theory
Korneichuk, N
1991-01-01
This book is intended as a self-contained introduction for non-specialists, or as a reference work for experts, to the particular area of approximation theory that is concerned with exact constants. The results apply mainly to extremal problems in approximation theory, which in turn are closely related to numerical analysis and optimization. The book encompasses a wide range of questions and problems: best approximation by polynomials and splines; linear approximation methods, such as spline-approximation; optimal reconstruction of functions and linear functionals. Many of the results are base
Hydrodynamic constants from cosmic censorship
International Nuclear Information System (INIS)
Nakamura, Shin
2008-01-01
We study a gravity dual of Bjorken flow of N=4 SYM-theory plasma. We point out that the cosmic censorship hypothesis may explain why the regularity of the dual geometry constrains the hydrodynamic constants. We also investigate the apparent horizon of the dual geometry. We find that the dual geometry constructed on Fefferman-Graham (FG) coordinates is not appropriate for examination of the apparent horizon since the coordinates do not cover the trapped region. However, the preliminary analysis on FG coordinates suggests that the location of the apparent horizon is very sensitive to the hydrodynamic parameters. (author)
CONFERENCE: Elastic and diffractive scattering
International Nuclear Information System (INIS)
White, Alan
1989-01-01
Elastic scattering, when particles appear to 'bounce' off each other, and the related phenomena of diffractive scattering are currently less fashionable than the study of hard scattering processes. However this could change rapidly if unexpected results from the UA4 experiment at the CERN Collider are confirmed and their implications tested. These questions were highlighted at the third 'Blois Workshop' on Elastic and Diffractive Scattering, held early in May on the Evanston campus of Northwestern University, near Chicago
International Nuclear Information System (INIS)
Gale, J.; Tiselj, I.
2002-01-01
One dimensional two-fluid six-equation model of two-phase flow, that can be found in computer codes like RELAP5, TRAC, and CATHARE, was upgraded with additional terms, which enable modelling of the pressure waves in elastic pipes. It is known that pipe elasticity reduces the propagation velocity of the shock and other pressure waves in the piping systems. Equations that include the pipe elasticty terms are used in WAHA code, which is being developed within the WAHALoads project of 5't'h EU research program.(author)
DEFF Research Database (Denmark)
Kanchana, V.; Vaitheeswaran, G.; Ma, Yanming
2009-01-01
agree well with the experimental values. The elastic constants of Fe2VAl and Fe2VGa are predicted. From the elastic constants the shear modulus, Young's modulus, Poisson's ratio, sound velocities, and Debye temperatures are obtained. By analyzing the ratio between the bulk and shear moduli, we conclude...
Theoretical study of elastic, mechanical and thermodynamic properties of MgRh intermetallic compound
Directory of Open Access Journals (Sweden)
S. Boucetta
2014-03-01
Full Text Available In the last years, Magnesium alloys are known to be of great technological importance and high scientific interest. In this work, density functional theory plane-wave pseudo potential method, with local density approximation (LDA and generalized gradient approximation (GGA are used to perform first-principles quantum mechanics calculations in order to investigate the structural, elastic and mechanical properties of the intermetallic compound MgRh with a CsCl-type structure. Comparison of the calculated equilibrium lattice constant and experimental data shows good agreement. The elastic constants were determined from a linear fit of the calculated stress–strain function according to Hooke's law. From the elastic constants, the bulk modulus B, shear modulus G, Young's modulus E, Poisson's ratio σ, anisotropy factor A and the ratio B/G for MgRh compound are obtained. The sound velocities and Debye temperature are also predicted from elastic constants. Finally, the linear response method has been used to calculate the thermodynamic properties. The temperature dependence of the enthalpy H, free energy F, entropy S, and heat capacity at constant volume Cv of MgRh crystal in a quasi-harmonic approximation have been obtained from phonon density of states and discussed for the first report. This is the first quantitative theoretical prediction of these properties.
Does maltose influence on the elasticity of SOPC membrane?
Energy Technology Data Exchange (ETDEWEB)
Genova, J; Zheliaskova, A; Mitov, M D, E-mail: ulia@issp.bas.b [Institute of Solid State Physics, Bulgarian Academy of Sciences, 72, Tzarigradsko Chaussee Blvd., 1784 Sofia (Bulgaria)
2010-11-01
Thermally induced shape fluctuations of giant quasi-spherical lipid vesicles are used to study the influence of the disaccharide maltose, dissolved in the aqueous solution, on the curvature elasticity k{sub c} of a lipid membrane. The influence of the carbohydrate solute is investigated throughout a considerably wide interval of concentrations. The values of the bending elastic modulus for 200 mM and 400 mM of maltose in the water solution are obtained. The data for k{sub c} in presence of maltose is compared with previously obtained results for this constant for the most popular hydrocarbons: monosaccharides glucose and fructose and disaccharides sucrose and trehalose. It is shown that the presence of maltose, dissolved in the aqueous phase surrounding the membrane does not influence on the bending elasticity with the increase of its concentration in the aqueous solution. Up to our knowledge this is the first sugar that does not show decrease of the bending elastic modulus of the lipid membrane, when present in the water surrounding it in concentration up to 400 mM.
Numerical simulation of ultrasonic wave propagation in elastically anisotropic media
International Nuclear Information System (INIS)
Jacob, Victoria Cristina Cheade; Jospin, Reinaldo Jacques; Bittencourt, Marcelo de Siqueira Queiroz
2013-01-01
The ultrasonic non-destructive testing of components may encounter considerable difficulties to interpret some inspections results mainly in anisotropic crystalline structures. A numerical method for the simulation of elastic wave propagation in homogeneous elastically anisotropic media, based on the general finite element approach, is used to help this interpretation. The successful modeling of elastic field associated with NDE is based on the generation of a realistic pulsed ultrasonic wave, which is launched from a piezoelectric transducer into the material under inspection. The values of elastic constants are great interest information that provide the application of equations analytical models, until small and medium complexity problems through programs of numerical analysis as finite elements and/or boundary elements. The aim of this work is the comparison between the results of numerical solution of an ultrasonic wave, which is obtained from transient excitation pulse that can be specified by either force or displacement variation across the aperture of the transducer, and the results obtained from a experiment that was realized in an aluminum block in the IEN Ultrasonic Laboratory. The wave propagation can be simulated using all the characteristics of the material used in the experiment valuation associated to boundary conditions and from these results, the comparison can be made. (author)
A micromechanics model of the elastic properties of human dentine
Energy Technology Data Exchange (ETDEWEB)
Kinney, J. H. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Balooch, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Marshall, G. W. [Univ. of California, San Francisco, CA (United States). Dept. of Restorative Dentistry; Marshall, S. J. [Univ. of California, San Francisco, CA (United States). Dept. of Restorative Dentistry
1999-10-01
A generalized self-consistent model of cylindrical inclusions in a homogeneous and isotropic matrix phase was used to study the effects of tubule orientation on the elastic properties of dentin. Closed form expressions for the five independent elastic constants of dentin were derived in terms of tubule concentration, and the Young's moduli and Poisson ratios of peri- and intertubular dentin. An atomic force microscope (AFM) indentation technique determined the Young's moduli of the peri- and intertubular dentin as approximately 30 GPa and 15 GPa, respectively. Over the natural variation in tubule density found in dentin, there was only a slight variation in the axial and transverse shear moduli with position in the tooth, and there was no measurable effect of tubule orientation. We conclude that tubule orientation has no appreciable effect on the elastic behavior of normal dentin, and that the elastic properties of healthy dentin can be modeled as an isotropic continuum with a Young's modulus of approximately 16 GPa and a shear modulus of 6.2 GPa.
Relaxing a large cosmological constant
International Nuclear Information System (INIS)
Bauer, Florian; Sola, Joan; Stefancic, Hrvoje
2009-01-01
The cosmological constant (CC) problem is the biggest enigma of theoretical physics ever. In recent times, it has been rephrased as the dark energy (DE) problem in order to encompass a wider spectrum of possibilities. It is, in any case, a polyhedric puzzle with many faces, including the cosmic coincidence problem, i.e. why the density of matter ρ m is presently so close to the CC density ρ Λ . However, the oldest, toughest and most intriguing face of this polyhedron is the big CC problem, namely why the measured value of ρ Λ at present is so small as compared to any typical density scale existing in high energy physics, especially taking into account the many phase transitions that our Universe has undergone since the early times, including inflation. In this Letter, we propose to extend the field equations of General Relativity by including a class of invariant terms that automatically relax the value of the CC irrespective of the initial size of the vacuum energy in the early epochs. We show that, at late times, the Universe enters an eternal de Sitter stage mimicking a tiny positive cosmological constant. Thus, these models could be able to solve the big CC problem without fine-tuning and have also a bearing on the cosmic coincidence problem. Remarkably, they mimic the ΛCDM model to a large extent, but they still leave some characteristic imprints that should be testable in the next generation of experiments.