A limit load solution for highly weld strength undermatched DE(T) specimens

A new upper bound solution for highly undermatched welded DE(T) specimens is proposed. A distinguished feature of this solution is that it accounts for the thickness of the specimen. Even though this case is more general than plane-strain and plane-stress solutions, the final result is given in terms of ordinary and double integrals. Comparison with a plane strain solution shows that the thickness of the specimen has a great effect of the limit load.     

Comparison of solution behaviour for three models of pressure-dependent plasticity: A simple analytical example

The main objective of the present paper is to compare, by means of a problem permitting a closed-form solution, qualitative behaviour of solutions based on three models of pressure-dependent plasticity, the coaxial model, the double-shearing model, and the double-slip and rotation model. The constitutive equations of each model reduce to classical metal plasticity at specific values of input parameters. Nevertheless, the solution behaviour essentially depends on the model chosen, independently of how close the input parameters are to these specific values. In particular, such features of the solutions as non-uniqueness, non-existence and singularity are emphasized. It is concluded that the double-slip and rotation model only retains all features inherent to classical plasticity.     

Theory of High Temperature Superconductivity in Cuprates and Other Doped Polar Insulators

In the last two decades, there have been tremendous attempts to build an adequate theory of high-temperature superconductivity. Most studies used some model Hamiltonians with input parameters not directly related to the material. The dielectric response function of electrons in strongly correlated high-temperature superconductors is a priori unknown. Hence, one has to start with the generic Hamiltonian including unscreened Coulomb and Fr?hlich electron?Cphonon interactions operating on the same scale since any ad-hoc assumption on their range and relative magnitude might fail. Using such a generic Hamiltonian, the analytical theory of high-temperature superconductivity in doped polar insulators predicting the critical temperature in excess of a hundred Kelvin without any adjustable parameters has been built. The many-particle electron system is described by an analytically solvable polaronic t?CJ _p Hamiltonian with reduced hopping integral, t, allowed double on-site occupancy, large phonon-induced antiferromagnetic exchange, J _p >t, and a high-temperature superconducting state of small superlight bipolarons protected from clustering. Here, major steps of the theory are outlined suggesting that the true origin of high-temperature superconductivity is found in a proper combination of strong electron?Celectron correlations with a significant finite-range (Fr?hlich) EPI, and that the theory is fully compatible with the key experiments.     

Flow-induced morphological instability and solidification with the slurry and mushy layers in the presence of convection

The linear analysis of convective morphological instability of the planar liquid–solid phase transition boundary is developed. The new stability criterion, dependent on the main parameter–extension rate (proportional to the vertical derivative of the fluid velocity), is deduced. This criterion generalizes analytical results of the recent works [H. Shimizu, J.P. Poirier, J.L. Le Mouël, Phys. Earth Planet. Inter. 151 (2005) 37–51; R. Deguen, T. Alboussière, D. Brito, Phys. Earth Planet. Inter. 164 (2007) 36–49], where convective mechanisms were only partially introduced in the model equations and stability analysis. The convective stability criterion demonstrates that the neutral stability curve divides two possible domains of morphologically stable and unstable solidification. These domains existing in the constitutionally supercooled conditions lead to two different crystallization scenarios “constitutional supercooling + morphological stability” and “constitutional supercooling + morphological instability”, which are described by idealized nonlinear slurry and mushy layer models with convection. Analytical solutions of these models taking into account nucleation and kinetic mechanisms of the growing solid phase are constructed for the steady-state solidification conditions.     

Time-dependent crystallization in magma chambers and lava lakes cooled from above: The role of convection and kinetics on nonlinear dynamics of binary systems

Motivated by geophysical applications we develop a number of mathematical models of the time-dependent crystallization in magma chambers, lava lakes and similar systems which involve nonlinear mechanisms of the melt convection and interfacial kinetics. The Stefan-type moving boundary models including important nonlinear physical dependences are solved analytically for different solidification stages. An influence of the convection intensity and undercooling degree on nonlinear solidification dynamics is discussed.     

Controllable bimodal structures in hypo-eutectoid Cu–Al alloy for both high strength and tensile ductility

To effectively demonstrate the dependence of ductility improvement on the scheme of introducing bimodal structure into nanostructured materials, a three-step processing was adopted in hypo-eutectoid Cu–Al alloys to obtain controllable bimodal structure of micrometer-grained pre-eutectoid phase embedded on ultrafine-grained (UFG) matrix with eutectoid composition: (1) pre-deformation heat-treatment was proposed to achieve controlled distribution of pre-eutectoid phase in the matrix with eutectoid composition, (2) both pre-eutectoid phase and eutectoid matrix were refined to submicrometer level by usage of high-pressure torsion (HPT), (3) annealed HPT-processed samples at selected temperature. All samples subjected to this novel processing route imparted a high strength, meanwhile obvious uniform plastic elongation in tensile deformation was also observed at those with bimodal structure.     

Optical Fluoride Nanoceramics

Inorganic Materials - This paper examines methods for the fabrication of optical fluoride nanoceramics and the compaction behavior of precursor powders. We discuss the basic drawbacks to the...     

Solidification of a ternary melt from a cooled boundary, or nonlinear dynamics of mushy layers

We present a mathematical model and its analytical solution describing directional solidification of a ternary (three-component) system cooled from below. We focus on the solidification theory in the presence of two distinct mushy layers: (1) solidification along a liquidus surface is characterized by a primary mushy layer, and (2) solidification along a cotectic line is characterized by a secondary (cotectic) mushy layer. We consider the case when the phase transition temperatures in two mushy layers represent arbitrary functions of the compositions. We obtain an exact analytical solution of the nonlinear set of equations and boundary conditions in the case of a self-similar solidification scenario. Model predictions are in good agreement with existing experimental data.     

Effects of increased supply of essential amino acids on the metabolism of the isolated perfused guinea-pig mammary gland.

The effects of high rates of infusion of essential amino acids on amino acid uptake by the isolated perfused guinea-pig mammary gland were studied. Infusion of methionine, tyrosine, phenylalanine, histidine and tryptophan (designated group 1) resulted in significant increases in the uptakes of tyrosine, phenylalanine and histidine. Methionine, tryptophan and other essential amino acids were not significantly affected. Infusion of threonine, valine, isoleucine, leucine, lysine and arginine (designated group 2) resulted in significant increases in uptake of all these amino acids. Group 1 amino acid uptake was not significantly affected. Infusion of all the essential amino acids (i.e. groups 1 and 2 together) resulted in significant increases in all their uptakes. Using as index 'the predicted rate of protein synthesis', infusion of group 1 and 2 together led to an apparent 27% increase in protein synthesis. The above results are discussed in relation to the control of milk protein synthesis by limiting essential amino acids.