Modeling and thermal analysis of solidification in a low alloy steel

In this study, solidification of a low alloyed steel used for armor material was simulated at various transformation temperatures by the help of thermodynamical calculations using Thermo-Calc software. Differential thermal analysis (DTA) was carried out to determine the critical transformation temperatures for the phases and results were compared with those calculated by Thermo-Calc. It is concluded that the temperatures calculated by Thermo-Calc software are in good agreement with the results obtained from DTA. These results will be very useful to determine the proper austenization temperature having an important effect on the properties of steel serving as an armor material.     

The propagation of discontinuities in non-homogeneous thermoviscoelastic media

In this study, the propagation of plane, cylindrical and spherical dilatational waves in non-homogeneous thermoviscoelastic media is investigated by employing the notion of singular surfaces and the method of characteristics. The inhomogeneity of the medium is such that the material properties depend in an arbitrary manner on the co-ordinate coinciding with the direction of the propagation. An integral type constitutive equation is considered for the heat flux which permits a finite propagation speed for thermal disturbances. It is found that the application of a dynamic input on the boundary surface gives rise to two different wave fronts along which mechanical and thermal effects are coupled. The growth and decay equations describing the change of the strength of the discontinuities on these two wave fronts are then obtained. By integrating the growth and decay equations along the rays the solutions valid at the wave fronts are found. The solutions are then reduced to two special cases: in one the heat flux equation is taken as the so-called modified Fourier equation, and in the other as the classical Fourier equation. The effects of inhomogeneity, geometry of the wave front, thermomechanical coupling and material internal friction on the strength of the discontinuity are discussed.     

Electron spectroscopic investigation of Sn coatings on glasses

Float glasses of different thicknesses and a conducting tin oxide glass have been investigated using Photo and Auger Electron Spectroscopy induced by AlKalpha X-rays. On the basis of measured chemical XPS shifts in the binding energies the chemical state of Sn (+2 or +4) incorporated on the float glasses could not be assigned. The use of the Auger parameter allows to separate relaxation and chemical contributions. The derived true chemical shifts of Sn on float-glasses are larger than those of SnO and/or SnO(2) due to the larger ionic environment of the glass matrix. Ar(+) or HF etching reveals that the concentration of Sn decreases exponentially as a function of depth from the surface.     

The energy localization problem and the renormalized vacuum energy in static Robertson-Walker universes

We calculate the renormalized quantum vacuum energy inside a spherical boundary for the massless conformal scalar field in curved background Robertson-Walker geometry. We use the mode sum method with an exponential cutoff. In our calculations we do not make assumptions about the exterior geometry or the global topology of the universe.     

New Heterocyclic Phosphorus Ylides: Synthesis,Crystal Structure,and Theoretical Calculation of Alkyl Substituted 3-(4-Benzoyl-1,5-diphenyl-2,3-dihydro-1H-pyrazol-3-yl)-3-oxo-2-(triphenylphosphoranylidene) Propanoates

Novel alkyl substituted 3-(4-benzoyl-1,5-diphenyl-2,3-dihydro-1H-pyrazol-3-yl)-3-oxo-2-(triphenylphosphoranylidene) propanoates (3) were synthesized from 4-benzoyl-1,5-diphenyl-1H-pyrazole-3-carbonylchloride (1) and alkyl (triphenylphosphoranylidene) acetates (2a–b). The synthesized compounds were characterized by elemental analysis, spectroscopic studies (3a–b), and single crystal X-ray diffraction (3a). The mechanism of the reaction between (1) and (2a) was studied by AM1, and the geometrical parameters of the studied molecules were also carried out in B3LYP methods with the standard 6–31G (d,p) basis set. NBO analysis were studied for 1 and 2a B3LYP methods with the standard 6–31G (d,p) basis set.