Loop Quantum Cosmology corrections to inflationary models

In the recent years the quantization methods of Loop Quantum Gravity have been successfully applied to the homogeneous and isotropic Friedmann-Robertson-Walker space-times. The resulting theory, called Loop Quantum Cosmology (LQC), resolves the Big Bang singularity by replacing it with the Big Bounce. We argue that LQC generates also certain corrections to field theoretical inflationary scenarios. These corrections imply that in the LQC the effective sonic horizon becomes infinite at some point after the bounce and that the scale of the inflationary potential implied by the COBE normalisation increases. The evolution of scalar fields immediately after the Bounce becomes modified in an interesting way. We point out that one can use COBE normalisation to establish an upper bound on the quantum of length of LQG.Comment: 16 pages, 1 figure, plain Late

On the Disintegration of A1050/Ni201 Explosively Welded Clads Induced by Long-Term Annealing

The paper presents the microstructure and phase composition of the interface zone formed in the explosive welding process between technically pure aluminum and nickel. Low and high detonation velocities of 2000 and 2800 m/s were applied to expose the differences of the welded zone directly after the joining as well as subsequent long-term annealing. The large amount of the melted areas was observed composed of a variety of Al-Ni type intermetallics; however, the morphology varied from nearly flat to wavy with increasing detonation velocity. The applied heat treatment at 500 °C has resulted in the formation of Al3Ni and Al3Ni2 layers, which in the first stages of growth preserved the initial interface morphology. Due to the large differences in Al and Ni diffusivities, the porosity formation occurred for both types of clads. Faster consumption of Al3Ni phase at the expense of the growing Al3Ni2 phase, characterized by strong crystallographic texture, has been observed only for the weld obtained at low detonation velocity. As a result of the extended annealing time, the disintegration of the bond occurred due to crack propagation located at the A1050/Al3Ni2 interface

Local structure of explosively welded titanium-stainless steel bimetal

Bimetals targeted for industrial applications are usually designed to combine the properties of two dissimilar metals, e.g. high strength, high hardness and low cost of steels with chemically resistive titanium. In this work the structure of one particular, but for industries very interesting, bimetallic system – Cr/Ni stainless steel clad with titanium has been studied. The material was prepared by explosion welding, a method capable of joining a wide variety of similar or dissimilar materials. Our analysis is based on X-ray micro-diffraction experimentation utilizing hard monochromatic X-rays focused down to micrometer size. In this way the bimetal in bulk form was analyzed and microstructural differences between the joined materials and their interface were determined.Web of Science106662762

Microstructural and Phase Composition Differences Across the Interfaces in Al/Ti/Al Explosively Welded Clads

The microstructure and phase composition of Al/Ti/Al interfaces with respect to theirlocalization were investigated. An aluminum-flyer plate exhibited finer grains located close tothe upper interface than those present within the aluminum-base plate. The same tendency, butwith a higher number of twins, was observed for titanium. Good quality bonding with a wavyshape and four intermetallic phases, namely, TiAl3, TiAl, TiAl2, and Ti3Al, was only obtained atthe interface closer to the explosive material. The other interface was planar with threeintermetallic compounds, excluding the metastable TiAl2 phase. As a result of a 100-hourannealing at 903 K (630 C), an Al/TiAl3/Ti/TiAl3/Al sandwich was manufactured, formed withsingle crystalline Al layers. A substantial difference between the intermetallic layer thicknesseswas measured, with 235.3 and 167.4 lm obtained for the layers corresponding to the upper andlower interfaces, respectively. An examination by transmission electron microscopy of a thin foiltaken from the interface area after a 1-hour annealing at 825 K (552 C) showed a mixture ofrandomly located TiAl3 grains within the aluminum. Finally, the hardness results werecorrelated with the microstructural changes across the samples