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Deep-inelastic lepton scattering by nuclei. The pion-exchange model

Description: Quark constituents of nucleons were discovered in deep-inelastic electron scattering. It is not surprising therefore that the nuclear effects in deep-inelastic lepton scattering first observed by the European Muon Collaboration (EMC) have spawned many suggestions of revolutionary changes in our views of nuclear structure. Perhaps quarks play a far more active role in nuclear dynamics than the conventional theory provides. Before following the natural appeal of radical conclusions we believe it … more
Date: January 1, 1985
Creator: Coester, F. & Berger, E. L.
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Partner: UNT Libraries Government Documents Department
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Unitary coupled channel deck model

Description: A unitary Deck model with coupled K*..pi.. and Krho channels, including only one resonance in the Q region is constructed. Adjusting the resonance parameters, one achieves a satisfactory description of the experimental phase variations and structure in the mass spectra. The resonance is determined to belong to the J/sup PC/ = 1/sup + -/ SU(3) octet, and is thus the Q/sub B/. The relative coupling strength K*..pi../Krho is approximately 2/3.
Date: May 1, 1976
Creator: Basdevant, J. L. & Berger, E. L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Seismic Waves in Rocks with Fluids and Fractures

Description: Seismic wave propagation through the earth is often strongly affected by the presence of fractures. When these fractures are filled with fluids (oil, gas, water, CO{sub 2}, etc.), the type and state of the fluid (liquid or gas) can make a large difference in the response of the seismic waves. This paper will summarize some early work of the author on methods of deconstructing the effects of fractures, and any fluids within these fractures, on seismic wave propagation as observed in reflection s… more
Date: February 6, 2006
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Measures of microstructure to improve estimates and bounds on elastic constants and transport coefficients in heterogeneous media

Description: The most commonly discussed measures of microstructure in composite materials are the spatial correlation functions, which in a porous medium measure either the grain-to-grain correlations, or the pore-to-pore correlations in space. Improved bounds based on this information such as the Beran-Molyneux bounds for bulk modulus and the Beran bounds for conductivity are well-known. It is first shown here how to make direct use of this information to provide estimates that always lie between these up… more
Date: October 7, 2004
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Comparison of up-scaling methods in poroelasticity and its generalizations

Description: Four methods of up-scaling coupled equations at the microscale to equations valid at the mesoscale and/or macroscale for fluid-saturated and partially saturated porous media will be discussed, compared, and contrasted. The four methods are: (1) effective medium theory, (2) mixture theory, (3) two-scale and multiscale homogenization, and (4) volume averaging. All these methods have advantages for some applications and disadvantages for others. For example, effective medium theory, mixture theory… more
Date: December 13, 2003
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Effective Medium Theories for Multicomponent Poroelastic Composites

Description: In Biot's theory of poroelasticity, elastic materials contain connected voids or pores and these pores may be filled with fluids under pressure. The fluid pressure then couples to the mechanical effects of stress or strain applied externally to the solid matrix. Eshelby's formula for the response of a single ellipsoidal elastic inclusion in an elastic whole space to a strain imposed at a distant boundary is a very well-known and important result in elasticity. Having a rigorous generalization o… more
Date: February 8, 2005
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Pore Fluid Effects on Shear Modulus in a Model of Heterogeneous Rocks, Reservoirs, and Granular Media

Description: To provide quantitative measures of the importance of fluid effects on shear waves in heterogeneous reservoirs, a model material called a ''random polycrystal of porous laminates'' is introduced. This model poroelastic material has constituent grains that are layered (or laminated), and each layer is an isotropic, microhomogeneous porous medium. All grains are composed of exactly the same porous constituents, and have the same relative volume fractions. The order of lamination is not important … more
Date: March 23, 2005
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Poroelastic Analysis of Thomsen Parameters in Finely Layed VTI Media

Description: Thomsen's anisotropy parameters for weak elastic and poroelastic anisotropy are now commonly used in exploration, and can be conveniently expressed in terms of the layer averages of Backus. Although there are five effective shear moduli for any layered VTI medium, only one effective shear modulus for the layered system contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves in VTI media. The effects of the pore … more
Date: March 17, 2003
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Bounds and Estimates for Elastic Constants of Random Polycrystals of Laminates

Description: In order to obtain formulas providing estimates for elastic constants of random polycrystals of laminates, some known rigorous bounds of Peselnick, Meister, and Watt are first simplified. Then, some new self-consistent estimates are formulated based on the resulting analytical structure of these bounds. A numerical study is made, assuming first that the internal structure (i.e., the laminated grain structure) is not known, and then that it is known. The purpose of this aspect of the study is to… more
Date: August 25, 2004
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Fluid Effects on Shear Waves in FInely Layered Porous Media

Description: Although there are five effective shear moduli for any layered VTI medium, one and only one effective shear modulus for the layered system contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves. Pore fluids can increase the magnitude the shear energy stored by this modulus by a term that ranges from the smallest to the largest shear moduli of the VTI system. But, since there are five shear moduli in play, the i… more
Date: May 21, 2004
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Fluid Effects on Shear for Seismic Waves in Finely Layered Porous Media

Description: Although there are five effective shear moduli for any layered VTI medium, one and only one effective shear modulus of the layered system (namely the uniaxial shear) contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves. Pore fluids can increase the magnitude the shear energy stored in this modulus by an amount that ranges from the smallest to the largest effective shear moduli of the VTI system. But, since th… more
Date: July 22, 2004
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Up-scaling analysis with rigorous error estimates for poromechanics in random polycrystals of porous laminates

Description: A detailed analytical model of random polycrystals of porous laminates has been developed. This approach permits detailed calculations of poromechanics constants as well as transport coefficients. The resulting earth reservoir model allows studies of both geomechanics and fluid permeability to proceed semi-analytically. Rigorous bounds of the Hashin-Shtrikman type provide estimates of overall bulk and shear moduli, and thereby also provide rigorous error estimates for geomechanical constants ob… more
Date: January 3, 2005
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Bounds and Estimates for Transport Coefficients of Random and Porous Media with High Contrasts

Description: Bounds on transport coefficients of random polycrystals of laminates are presented, including the well-known Hashin-Shtrikman bounds and some newly formulated bounds involving two formation factors for a two-component porous medium. Some new types of self-consistent estimates are then formulated based on the observed analytical structure both of these bounds and also of earlier self-consistent estimates (of the CPA or coherent potential approximation type). A numerical study is made, assuming f… more
Date: September 24, 2004
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Scale-up in Poroelastic System and Applications to Reservoirs

Description: A fundamental problem of heterogeneous systems is that the macroscale behavior is not necessarily well-described by equations familiar to us at the meso- or microscale. In relatively simple cases like electrical conduction and elasticity, it is hue that the equations describing macroscale behavior take the same form as those at the microscale. But in more complex systems, these simple results do not hold. Consider fluid flow in porous media where the microscale behavior is well-described by Nav… more
Date: July 1, 2003
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Bounds on Elastic Constants for Random Polycrystals of Laminates

Description: A well-known result due to Hill provides an exact expression for the bulk modulus of any multicomponent elastic composite whenever the constituents are isotropic and the shear modulus is uniform throughout. Although no precise analog of Hill's result is available for the opposite case of uniform bulk modulus and varying shear modulus, it is shown here that some similar statements can be made for shear behavior of random polycrystals composed of laminates of isotropic materials. In particular, t… more
Date: April 30, 2004
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Comparison of two up-scaling methods in poroelasticity and its generalizations

Description: Two methods of up-scaling coupled equations at the microscale to equations valid at the mesoscale and/or macroscale for fluid-saturated and partially saturated porous media are discussed, compared, and contrasted. The two methods are: (1) two-scale and multiscale homogenization, and (2) volume averaging. Both these methods have advantages for some applications and disadvantages for others. For example, homogenization methods can give formulas for coefficients in the up-scaled equations, whereas… more
Date: March 16, 2004
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Some Nonlinear Reconstruction Algorithms for Electrical Impedance Tomography

Description: An impedance camera [Henderson and Webster, 1978; Dines and Lytle, 1981]--or what is now more commonly called electrical impedance tomography--attempts to image the electrical impedance (or just the conductivity) distribution inside a body using electrical measurements on its boundary. The method has been used successfully in both biomedical [Brown, 1983; Barber and Brown, 1986; J. C. Newell, D. G. Gisser, and D. Isaacson, 1988; Webster, 1990] and geophysical applications [Wexler, Fry, and Neur… more
Date: March 9, 2001
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Bounds on Transport Coefficients of Porous Media

Description: An analytical formulation of conductivity bounds by Bergman and Milton is used in a different way to obtain rigorous bounds on the real transport coefficients (electrical conductivity, thermal conductivity, and/or fluid permeability) of a fluid-saturated porous medium. These bounds do not depend explicitly on the porosity, but rather on two formation factors--one associated with the pore space and the other with the solid frame. Hashin-Shtrikman bounds for transport in random polycrystals of po… more
Date: March 21, 2005
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Pore Fluid Effects on Shear Modulus for Sandstones with Soft Anisotropy

Description: A general analysis of poroelasticity for vertical transverse isotropy (VTI) shows that four eigenvectors are pure shear modes with no coupling to the pore-fluidmechanics. The remaining two eigenvectors are linear combinations of pure compression and uniaxial shear, both of which are coupled to the fluid mechanics. After reducing the problem to a 2x2 system, the analysis shows in a relatively elementary fashion how a poroelastic system with isotropic solid elastic frame, but with anisotropy intr… more
Date: April 15, 2004
Creator: Berger, E. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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