Showing papers on "Elasticity (economics) published in 1989"

A Probabilistic Choice Model for Market Segmentation and Elasticity Structure

Abstract: Marketing scholars commonly characterize market structure by studying the patterns of substitution implied by brand switching. Though the approach is useful, it typically ignores the destabilizing ...

Bending elasticity and thermal fluctuations of lipid membranes. Theoretical and experimental requirements

Abstract: Thermal fluctuations of giant lipid vesicles have been investigated both theoretically and experimentally. At the theoretical level, the model developed here takes explicitly into account the conservation of vesicle volume and membrane area. Under these conditions, the amplitude of thermal fluctuations depends critically not only on the bending elasticity of the bilayer, but also on the membrane tension and/or hydrostatic pressure difference between the interior and exterior of the vesicle. At the experimental level, the determination of the bending modulus kc first requires the analysis of a large number (several hundred) of vesicle contours to obtain a significant statistics. Secondly, the contribution of the experimental error on the contour coordinates, which results in a white noise on the Fourier amplitudes, must be eliminated, and this can be done by using the angular autocorrelation function of the fluctuations. Finally, the amplitudes of harmonics having short correlation times must be corrected from the effect of the integration time (40 ms) of the video camera, which otherwise leads to an overestimation of kc. All these theoretical and experimental requirements have been considered in the analysis of the thermal fluctuations of 42 giant vesicles composed of egg phosphatidylcholine. The behaviour of this population of vesicles can be accounted for with a bending modulus kc equal to 0.4 - 0.5 x 10-19 J, and extremely low membrane tensions, ranging below 15 × 10-5 mN/m.

In Quest of the Slutsky Diamond

Abstract: The Slutsky equation can be constructed as a parallelogram (a diamond), the area of which is proportional to the elasticity of substitution. This construction permits to show immediately that demand functions become concave on an interval if the elasticity of substitution increases sufficiently. Also, the diamond sheds light on the fact that the production level increases with the elasticity of substitution. As an application, the author shows that the elasticity of substitution has a direct bearing not only on the rate of growth of an economy, but also on the very existence of sustained growth. Copyright 1989 by American Economic Association.

Contribution of the electric double layer to the curvature elasticity of charged amphiphilic monolayers

Abstract: The electrostatic contribution to the bending moduli of an amphiphilic monolayer is calculated on the basis of the Poisson-Boltzmann equation. The electrical free energy for a spherical and cylindrical surface is expanded in inverse powers of the radius of curvature a. The coefficient (1/a)2 in the electrical free energy gives the bending elastic moduli.

Calculations of steady-state viscoelastic flow in an undulating tube

Abstract: The flow of a viscoelastic fluid in an undulating tube is of importance both for modeling the flow of polymeric fluids through porous media and for testing numerical techniques for the simulation of viscoelastic flows. This geometry represents one of the simplest pore models for the consideration of the converging-diverging nature of the flow field in applications ranging from enhanced oil recovery to manufacturing of advanced composites using resin transfer molding. For an upper convected Maxwell fluid, a mixed pseudospectral/finite difference method (PSFD) is developed, employing the coordinate system provided by the streamlines and the lines orthogonal to them. For an Oldroyd-B fluid, a modification of the PSFD method is used, implemented in a stretched cylindrical coordinate system (PCFD method). For both the Maxwell and the Oldroyd-B fluid, solutions converged with mesh refinement are obtained up to high Deborah numbers. The results obtained using the Maxwell fluid show no increase in the flow resistance with increasing flow elasticity, in reference to the purely viscous flow. The results for the Oldroyd-B fluid show a very small increase in the flow resistance. These findings are in disagreement with experimental data reported in the literature, which have been obtained with Boger fluids. For the Maxwell fluid, a perturbation analysis valid for small amplitudes of undulation shows that extremely steep boundary layers are developed with increasing elasticity in the flow. The boundary layers are developed both near the wall and the centerline of the tube and their resolution becomes a key element for any potentially successful numerical method. In addition, their presence explains, at least partially, the failure of previous attempts by other investigators to obtain converged solutions at high values of elasticity.

Fundamental Principles of Fiber Reinforced Composites

Abstract: Specific Strength and Specific Modulus - Materials and Processing - Anisotropy of Stress - Anisotropy of Elasticity - Elasticity of Orthotropic Laminates - Anisotropy of Thermal Expansion - Stresses in a Plate Arising from the Presence of a Hole - Fracture and Fracture Mechanics - Anisotropy of Strength - Environmental Degradation - Joining and Repair - Non-Destructive Evaluation

Capillary Waves and Bending Elasticity of Monolayers on Water Studied by X-Ray Reflectivity as a Function of Surface Pressure

Abstract: Thermally induced capillary waves on a monolayer of behenic acid on water have been investigated by x-ray reflectivity. The corresponding roughness is measured as a function of the surface pressure. The experimental data are discussed using a theory of thermal fluctuations. A strong decrease in the roughness is observed at the transition to the solid state. This striking feature is attributed to the rigidity of the monolayer in the solid phase whose value has been determined.

Experiments on the elasticity of dry and swollen networks: implications for the Frenkel-Flory-Rehner hypothesis

Abstract: Mesure de l'elasticite d'echantillons cylindriques de caoutchouc naturel reticule par le peroxyde de dicumyle secs ou gonfles a l'equilibre par un solvant, afin de verifier l'hypothese de Frenkel, Flory et Rehner, a savoir que l'elasticite n'est pas modifiee significativement par la presence du solvant. Les resultats obtenues sont en accord avec cette hypothese

Elastically deformable fluid actuator

Abstract: An actuator for use in an arm or hand of an industrial robot comprises a tubular elastic body of which interior is separated into a plurality of pressure chambers by an axially extending partition, and means for adjusting respective pressures of the pressure chambers to render the tubular elastic body to take a motion at a multi-degree freedom. At least the outer peripheral part of the tubular elastic body has an anisotropic characteristic with respect to modulus of elasticity. The axial direction of the tubular elastic body is a direction small in modulus of longitudinal elasticity, while the direction perpendicular to the axial direction of the tubular elastic body is a direction large in modulus of longitudinal elasticity.

Parametrized multifield variational principles in elasticity: II. Hybrid functionals and the free formulation

Abstract: A one-parameter family of d-generalized hybrid/mixed variational principles for linear elasticity is constructed following a domain subdivision. The family includes the d-generalized Hellinger-Reissner and potential energy principles as special cases. The parametrized principle is discretized by independently varied internal displacements, stresses and boundary displacements. The resulting finite element equations are studied following a physically motivated decomposition of the stress and internal displacement fields. The free formulation of Bergan and Nygard is shown to be a special case of this element type, and is obtained by assuming a constant internal stress field. The parameter appears as a scale factor of the higher-order stiffness.

Gasoline, Diesel and Motorfuel Demand in Taiwan

Abstract: The logarithmic flow models generate elasticity estimates for prices that generally exceed estimates of recent studies both for the short run and the long run. This holds true over gasoline, diesel, and total motorfuel models. The linear gasoline results for price elasticity are in the range of previous estimates. In the logarithmic stock flow models, estimates of gasoline price elasticity exceed both short- and long-run estimates of previous studies. The liner stock flow model generates a price elasticity that is no different than zero (statistically) and an income elasticity that appears to be large in the short-ran.

Existence in nonlocal elasticity

Abstract: The displacement boundary value problems of homogeneous, isotropic, linear, nonlocal elasticity are defined. A Hilbert space is defined and an inequality which plays an important role in the existence theory of elasticity is proven. Finally, it is shown that the bilinear form which appears in the weak formulation satisfies the requirements of the fundamental existence lemma (Lax-Milgram's Theorem)

Elastic properties of interfaces. Elasticity moduli and spontaneous geometric characteristics

Abstract: An arbitrarily organized interface with non-uniform curvature is considered. The force factors (surface tension and bending moments) depend on interface geometry. The general definitions of spontaneous geometrical characteristics and elastic moduli of interface are presented. The spontaneous geometrical characteristics correspond to zero values of interface force factors. The elastic moduli are expressed in terms of derivatives of force factors. The expression for energy of interface deformation including the second-order terms is derived.

Cavities vis-à-vis Rigid Inclusions and Some Related General Results in Plane Elasticity

Abstract: The stresses in a body that contains rigid inclusions and is loaded by specified surface tractions depend on the Poisson ratio of the material If the Poisson ratio in this stress field is set equal to +1 for plane strain, or +α for plane stress, the rigd inclusions become cavities for elastic constants within the physical range The paper pursues this circumstance, and in doing so also produces several useful by-products that are connected with the stretching and curvature change of a boundary

Surface Waves in Vertically Inhomogeneous Media

Abstract: Surface waves are considered within the framework of linear elasticity theory, mainly for perfectly elastic bodies. Internal sources of disturbance are described in Section 1.2 by means of equivalent forces. Small departures from perfect elasticity in wave propagation theory can be treated as shown in Section 1.6.

Interpretation of the complex viscosity of dense hard-sphere dispersions

Abstract: The complex viscosity of dense hard-sphere dispersions has been determined recently over a large frequency range. If conceived as a homogeneous system with continuously distributed elasticity and viscosity, the complex viscosity can be described theoretically with a constant relaxation strength and relaxation times τp=τ1/p2, with p the relaxation number. This is consistent with the empirical analysis of the data. The distributed elasticity can be interpreted microscopically as due to statistical springs acting between the spheres. The springs are modeled as Fraenkel springs to take into account the excluded-volume effect. The relaxation strength has been calculated quantitatively. The resulting deduced relaxation strengths are in fair agreement with the experimentally observed ones. The given interpretation is compared with literature theory.