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[en] In the present work, we prove that there exists a relation between a physical inconsistence known as second spectrum of frequency or non-physical spectrum and the exponential decay of a dissipative Timoshenko system where the damping mechanism acts on angle rotation. The so-called second spectrum is addressed into stabilization scenario and, in particular, we show that the second spectrum of the classical Timoshenko model can be truncated by taking a damping mechanism. Also, we show that dissipative Timoshenko type systems which are free of the second spectrum [based on important physical and historical observations made by Elishakoff (Advances mathematical modeling and experimental methods for materials and structures, solid mechanics and its applications, Springer, Berlin, pp 249–254, 2010), Elishakoff et al. (ASME Am Soc Mech Eng Appl Mech Rev 67(6):1–11 2015) and Elishakoff et al. (Int J Solids Struct 109:143–151, 2017)] are exponential stable for any values of the coefficients of system. In this direction, we provide physical explanations why weakly dissipative Timoshenko systems decay exponentially according to equality between velocity of wave propagation as proved in pioneering works by Soufyane (C R Acad Sci 328(8):731–734, 1999) and also by Muñoz Rivera and Racke (Discrete Contin Dyn Syst B 9:1625–1639, 2003). Therefore, the second spectrum of the classical Timoshenko beam model plays an important role in explaining some results on exponential decay and our investigations suggest to pay attention to the eventual consequences of this spectrum on stabilization setting for dissipative Timoshenko type systems.
[en] A general method for determination of the atomization energy of gaseous dicarbides has been developed. The method is based on measurements of the relative absorbance change during the element evaporation in the common graphite tube and in the tube lined with a tantalum foil, from a probe of tungsten wire. The atomization energy of DyC2 molecules determined by this method is equal to 1268+-100 kJ/mole (2nd Law) and 1279+-27 kJ/mole (3rd Law)
[en] Dysprosium monotelluride is a metallic substance with one valence electron per formula unit belonging to the conduction band. It crystallizes in the defected NaCl-type structure (a = 0,6070) with cation deficiency in the metal sublattice. AC and DC susceptibilities exhibit a maximum at 15 K and a second maximum at higher temperatures which position is field dependent. (author)
[en] Photo-induced quasi-particle (QP) relaxation dynamics with different symmetries have been investigated for the multiple charge–density–wave (CDW) compound DyTe_3 by using ultrafast polarized pump-probe spectroscopy. By performing symmetry analysis, the QP dynamics with isotropic A_1_g and anisotropic B_2_g symmetry were found to show unique anomalies at the first and second CDW transitions. Both the temperature dependence and pump fluence dependence indicate that the B_2_g response is very sensitive to the underlying lattice deformation, which provides critical insight into the multiple CDW formations. (paper)
[en] Spectroscopic studies of rare earth ions in glass matrices exhibit characteristic properties for potential applications as laser materials. Lead antimony borate (LAB) glasses doped with rare earth ions have the ability to emit intense radiation in the visible, near infra-red and infrared spectral regions make them suitable for many practical applications for photonics and electrochemical devices such as solid-state lasers, optical amplifiers, optical memory devices, magneto optical device and advanced batteries. For the present study, glasses of composition 30 PbO - 25 Sb2O3-(45-x)B2O3-xDy2O3 where x=0, 0.2, 0.4, 0.6, 0.8, 1 mol% are taken. The glasses are prepared by the melt quenching method with AR grade chemicals as starting materials. The amorphous nature of the samples is conformed by the x-ray diffractograms. Sample densities are calculated by Archimedes method and from these values molar volume, oxygen packing factor and concentration of Dy3+ ions are calculated