Systems of interacting classical harmonic oscillators have received considerable attention in the last years as analog models for describing electromagnetically induced transparency (EIT) and associated phenomena. We review these models and investigate their validity for a variety of physical systems using two-and three-coupled harmonic oscillators. From the simplest EIT-Λ configuration and twocoupled single cavity modes we show that each atomic dipole-allowed transition and a single cavity mode can be represented by a damped harmonic oscillator. Thus, we have established a one-toone correspondence between the classical and quantum dynamical variables. We show the limiting conditions and the equivalent for the EIT dark state in the mechanical system. This correspondence is extended to other systems that present EIT-related phenomena. Examples of such systems are two-and three-level (cavity EIT) atoms interacting with a single mode of an optical cavity, and four-level atoms in a inverted-Y and tripod configurations. The established equivalence between the mechanical and the cavity EIT systems, presented here for the first time, has been corroborated by experimental data. The analysis of the probe response of all these systems also brings to light a physical interpretation for the expectation value of the photon annihilation operator a . We show it can be directly related to the electric susceptibility of systems, the composition of which includes a driven cavity field mode.

Aiming the in situ formation of CA6 (CaO•6Al2O3) at alumina-based macroporous insulators, distinct Ca 2+ sources and contents were used and their effect on some of the refractories properties were investigated. Adding CaCO3, Ca(OH)2 or CaO resulted in the decrease of the strengthening onset temperature (TS) and also of the linear shrinkage. However, a higher amount of Ca(OH)2 and CaO could not be used because of their effect on reducing the insulator total porosity. The composition prepared with 12.9wt% of CaCO3 was the most promising one, leading to an expansion of 0.81% after firing at 1600ºC for 5h, TS of 680ºC and low thermal conductivity. These results point out the potential reduction of sintering temperatures and to the possibility of in situ firing the ceramic insulator. These features enable the development of a macroporous refractory composition with a higher thermal insulating effectiveness, which can help industries to decrease their energy demand.

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