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Correlation-induced anomalies and extreme sensitivity in fcc-PU1

Description: We have used GGA + U density functional theory to study the effects of correlation on the properties offcc-Pu. We found that the structural and elastic properties offcc-Pu are highly sensitive to the Hubbard U parameter. Within an interval of 0.1 eV ofthe U parameter, the equilibrium lattice constants offcc-Pu can change from 0.44 to 0.47 nm. While the bulk modulus can drop by a factor of5 to 10. The pressure derivative, dB/dp, ofthe bulk modulus can rise dramatically from 5 to 16 and then drop to a negative value before recovering to a more normal value. These observations are partially supported by existing experiments and the prediction of a negative dB/dp needs to be tested in future experiments.
Date: January 1, 2009
Creator: Chen, Shao-ping
Partner: UNT Libraries Government Documents Department

Elastic Scattering of 14 Mev Neutrons (Theoretical Curves)

Description: Abstract: "Theoretical differential cross-sections computed from the optical model for 14 Mev neutrons are presented for a large number of nuclei. The parameters used for the calculations were selected on the basis of best fit to existing experimental data."
Date: July 1957
Creator: Bjorklund, F. & Fernbach, Sidney, 1917-1991
Partner: UNT Libraries Government Documents Department

Stress and strain concentration at a circular hole in an infinite plate

Description: The theory of elasticity shows that the maximum stress at a circular hole in an infinite plate in tension is three times the applied stress when the material remains elastic. The effect of plasticity of the material is to lower this ratio. This paper considers the theoretical problem of the stress distribution in an infinitely large sheet with a circular hole for the general case where the material may have any stress-strain curve. The plate is assumed to be under uniform tension at a large distance from the hole. The material is taken to be isotropic and incompressible. (author).
Date: April 1950
Creator: Stowell, Elbridge Z.
Partner: UNT Libraries Government Documents Department

The Elastic Constants for Wrought Aluminum Alloys

Description: There are several constants which have been devised as numerical representations of the behavior of metals under the action of loadings which stress the metal within the range of elastic action. Some of these constants, such as Young's modulus of elasticity in tension and compression, shearing modulus of elasticity, and Poisson's ratio, are regularly used in engineering calculations. Precise tests and experience indicate that these elastic constants are practically unaffected by many of the factors which influence the other mechanical properties of materials and that a few careful determinations under properly controlled conditions are more useful and reliable than many determinations made under less favorable conditions. It is the purpose of this paper to outline the methods employed by the Aluminum Research Laboratories for the determination of some of these elastic constants, to list the values that have been determined for some of the wrought aluminum alloys, and to indicate the variations in the values that may be expected for some of the commercial products of these alloys.
Date: January 1, 1945
Creator: Templin, R. L. & Hartmann, E. C.
Partner: UNT Libraries Government Documents Department

Free-Flight Longitudinal-Stability Investigation Including Some Effects of Wing Elasticity From Mach Numbers of 0.85 to 1.34 of a Tailless Missile Configuration Having a 45 Degree Sweptback Wing of Aspect Ratio 5.5

Description: Report presenting a free-flight longitudinal-stability investigation between Mach numbers of 0.85 and 1.34 to obtain the aerodynamic characteristics of a long-range, jet-propelled, ground-to-ground missile with a wing of aspect ratio 5.5, 45 degrees of sweepback, and taper ratio 0.4 on a body with a vertical tail. Two models with two different wing materials were flown. Results regarding trimmed flight, pitching flight, and aeroelastic calculations are provided.
Date: August 10, 1953
Creator: Arbic, Richard G. & Gillespie, Warren, Jr.
Partner: UNT Libraries Government Documents Department

Customer Response to RTP in Competitive Markets: A Study ofNiagara Mohawk's Standard Offer Tariff

Description: Utilizing load, price, and survey data for 119 largecustomers that paid competitively determined hourly electricity pricesannounced the previous day between 2000 and 2004, this study providesinsight into the factors that determine the intensity of price response.Peak and off-peak electricity can be: perfect complements, substitutes,or substitutes where high peak prices cause temporary disconnection fromthe grid, as for some firms with on-site generation. The averageelasticity of substitution is 0.11. Thirty percent of the customers usepeak and off-peak electricity in fixed proportions. The 18 percent withelasticities greater than 0.10 provide 75 percent of the aggregate priceresponse. In contrast to Industrial customers, Commercial/Retail andGovernment/Education customers are more price responsive on hot days andwhen the ratio of peak to off-peak prices is high. Price responsivenessis not substantially reduced when customers operate near peak usage.Diversity of customer circumstances and price response suggest dynamicpricing is suited for some, but not all customers.
Date: June 1, 2006
Creator: Boisvert, Richard N.; Cappers, Peter; Goldman, Charles; Neenan,Bernie & Hopper, Nicole
Partner: UNT Libraries Government Documents Department

Transversely isotropic elasticity and poroelasticity arising from thin isotropic layers

Description: Since the classic work of Postma [1955] and Backus [1962], much has been learned about elastic constants in vertical transversely isotropic (VTI) media when the anisotropy is due to fine layering of isotropic elastic materials. However, new results are still being discovered. For example, the P-wave anisotropy parameter c{sub 11}/c{sub 33} lies in the range 1/4 {<=} c{sub 11}/c{sub 33} {<=} <{lambda}+2{mu}><1/({lambda}+2{mu})>, when the layers are themselves composed of isotropic elastic materials with Lame constants {lambda} and {mu} and the vertical average of the layers is symbolized by <{center_dot}>. The lower bound corrects a result of Postma. For porous layers, a connected solid frame forms the basis of the elastic behavior of a poroelastic medium in the presence of confining forces, while connected pores permit a percolating fluid (if present) to influence the mechanical response of the system from within. For isotropic and anisotropic poroelastic media, we establish general formulas for the behavior of transversely isotropic poroelasticity arising from laminations of isotropic components. The Backus averaging method is shown to provide elementary means of constructing general formulas. The results for confined fluids are then compared with the more general Gassmann [1951] formulas that must be satisfied by any anisotropic poroelastic medium and found to be in complete agreement. Such results are important for applications to oil exploration using AVO (amplitude versus offset) since the presence or absence of a fluid component, as well as the nature of the fluid, is the critical issue and the ways in which the fluid influences seismic reflection data still need to be better understood.
Date: July 1, 1997
Creator: Berryman, J.G.
Partner: UNT Libraries Government Documents Department

Fracture imaging with converted elastic waves

Description: This paper examines the seismic signatures of discrete, finite-length fractures, and outlines an approach for elastic, prestack reverse-time imaging of discrete fractures. The results of this study highlight the importance of incorporating fracture-generated P-S converted waves into the imaging method, and presents an alternate imaging condition that can be used in elastic reverse-time imaging when a direct wave is recorded (e.g., for crosswell and VSP acquisition geometries).
Date: May 29, 2001
Creator: Nihei, K.T.; Nakagawa, S. & Myer, L.R.
Partner: UNT Libraries Government Documents Department

Principle and Application of Complementary Energy Method for Thin Homogeneous and Sandwich Plates and Shells With Finite Deflections

Description: Note presenting the principle of complementary energy in the nonlinear elasticity theory, which is shown to be derivable from the principle of potential energy by a Legendre type of transformation. The expression of the complementary energy is derived for homogeneous and sandwich plates and shells with large deflections. The stress-strain relations are derived for homogeneous shells, sandwich plates, and sandwich shells.
Date: February 1952
Creator: Wang, Chi-Teh
Partner: UNT Libraries Government Documents Department

Continuum simulation of dislocation dynamics: Predictions for internal friction response

Description: The amplitude dependent mechanical loss due to bosing of an idealized Frank-Read Source is studied using both simulation and analytical techniques. Dislocations are modeled within isotropic elasticity theory, and are assumed to be in the over-damped limit.
Date: February 19, 2002
Creator: Greaney, P. Alex; Friedman, Lawrence H. & Chrzan, D.C.
Partner: UNT Libraries Government Documents Department

Formation mechanism and properties of CdS-Ag2S nanorod superlattices

Description: The mechanism of formation of recently fabricated CdS-Ag{sub 2}S nanorod superlattices is considered and their elastic properties are predicted theoretically based on experimental structural data. We consider different possible mechanisms for the spontaneous ordering observed in these 1D nanostructures, such as diffusion-limited growth and ordering due to epitaxial strain. A simplified model suggests that diffusion-limited growth partially contributes to the observed ordering, but cannot account for the full extent of the ordering alone. The elastic properties of bulk Ag{sub 2}S are predicted using a first principles method and are fed into a classical valence force field (VFF) model of the nanostructure. The VFF results show significant repulsion between Ag{sub 2}S segments, strongly suggesting that the interplay between the chemical interface energy and strain due to the lattice mismatch between the two materials drives the spontaneous pattern formation.
Date: August 11, 2008
Creator: Wang, Lin-Wang; Demchenko, Denis O.; Robinson, Richard D.; Sadtler, Bryce; Erdonmez, Can K.; Alivisatos, A. Paul et al.
Partner: UNT Libraries Government Documents Department

Waste Materials from Tetra Pak Packages as Reinforcement of Polymer Concrete

Description: This article discusses how compressive and flexural strength and modulus of elasticity decrease gradually, when either Tetra Pak particle concentration or particle size is increased.
Date: September 28, 2015
Creator: Martínez-López, Miguel; Martínez-Barrera, Gonzalo; Barrera-Díaz, Carlos; Ureña-Núñez, Fernando & Brostow, Witold, 1934-
Partner: UNT College of Engineering

Rocks as 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 infinity is a very well-known and important result in elasticity. Having a rigorous generalization of Eshelby's results valid for poroelasticity means that the hard part of Eshelby' work (in computing the elliptic integrals needed to evaluate the fourth-rank tensors for inclusions shaped like spheres, oblate and prolate spheroids, needles and disks) can be carried over from elasticity to poroelasticity - and also thermoelasticity - with only trivial modifications. Effective medium theories for poroelastic composites such as rocks can then be formulated easily by analogy to well-established methods used for elastic composites. An identity analogous to Eshelby's classic result has been derived [Physical Review Letters 79:1142-1145 (1997)] for use in these more complex and more realistic problems in rock mechanics analysis. Descriptions of the application of this result as the starting point for new methods of estimation are presented.
Date: April 30, 1998
Creator: Berryman, J G
Partner: UNT Libraries Government Documents Department

Linking continuum mechanics and 3D discrete dislocation simulations

Description: A technique is developed for linking the methods of discrete dislocation dynamics simulation and finite element to treat elasto-plasticity problems. The overall formulation views the plastically deforming crystal as an elastic crystal with continuously changing dislocation microstructure which is tracked by the numerical dynamics simulation. The FEM code needed in this regard is based on linear elasticity only. This formulation presented here is focused on a continuous updating of the outer shape of the crystal, for possible regeneration of the FEM mesh, and adjustment of the surface geometry, in particular the surface normal. The method is expected to be potentially applicable to the nano- indentation experiments, where the zone around the indenter-crystal contact undergoes significant permanent deformation, the rigorous determination of which is very important to the calculation of the indentation print area and in turn, the surface hardness. Furthermore, the technique is expected to account for the plastic history of the surface displacement under the indenter. Other potential applications are mentioned in the text.
Date: October 18, 1998
Creator: El-Azab, A. A. & Fivel, M.
Partner: UNT Libraries Government Documents Department

Differential Thermal-Expansion Effects on Brazed Joints

Description: Abstract: "Differential thermal-expansion effects in brazed joints involving Type 310 stainless steel and GE-62 brazing alloy were investigated. The work included dilation and modulus-of-elasticity measurements using homogenous cast specimens and observations on bimetallic cantilevers made of the two constituents. No anomalies were found, although there were irregularities in the expansion of the brazing alloy which were ascribed to a solubility phenomenon. The elastic modulus of the brazing alloy was determined. Cantilever deflections with temperature and with load were measured, and the results were interpreted using equations which treat the specimens as true bimetals consisting of two homogeneous components. The difference in thermal-expansion coefficients obtained in this way from the temperature-deflection data was consistent with the dilation measurements. The load measurements yielded an average elastic modulus for the bimetal which was about two-thirds of what would have been expected from knowledge of the components. This discrepancy probably arose from porosity which was observed in the braze components."
Date: September 4, 1953
Creator: Saller, Henry A.; Baroody, Eugene Michael, 1914-1982; Deem, H. W.; Stacy, J. T. & Klebanow, H. L.
Partner: UNT Libraries Government Documents Department

Effects of wing elasticity on the aerodynamic characteristics of a 45 degree sweptback-wing-fuselage combination measured in the Langley 8-foot transonic tunnel

Description: Report presenting testing of a wing-fuselage configuration with a wing of 45 degrees sweepback of the 0.25-chord line, aspect ratio of 4, taper ratio of 0.6, and NACA 65A006 airfoil sections in aluminum and steel at a range of Mach numbers and angles of attack to determine effects of wing elasticity. Results regarding the relative effects of bending and torsion, wing-tip twist, aerodynamic characteristics, and some theoretical considerations are provided.
Date: September 17, 1952
Creator: Osborne, Robert S. & Mugler, John P., Jr.
Partner: UNT Libraries Government Documents Department

Malaysian Natural Rubber Industry: An Econometric Analysis on the Elasticity of Supply and Demand Approaches

Description: The popularity of natural rubber as an important raw material was distorted in the post-World War Two period. It received heavy competition from synthetic rubber. The main purpose of this paper is to determine and to study supply elasticity and demand elasticity of natural rubber in the case of Malaysia. The main aim of analyzing the period since 1971 is that both price and quality competitiveness of Malaysian natural rubber have drastically improved. Therefore, in order for Malaysia to maintain her position as the leading producer and exporter of natural rubber in the world, supportive policies and incentives from the government would further enhance the prospects for improvements in this industry.
Date: December 1989
Creator: Mohd Ismail, Harun Mizam bin
Partner: UNT Libraries