Soil influence on unbalance response and stability of a simple rotor-foundation system

The equations of motion are set up for a simple rotor (Jeffcott or Laval rotor) on a rigid foundation mass resting on an elastic half space (soil). The unbalance response and the stability limit against self-excited vibrations caused by the internal damping of the rotating shaft are calculated. The numerical results presented as response diagrams and stability graphs show that the damping effect of the soil on the system, due to radiation of energy, may have a very positive influence on the smooth running of the rotors.     

Phase transitions in ferroelectric ceramics of the type Sr0.5Ba0.5Nb2O6

The ferro-paraelectric transition in Sr_0.5Ba_0.5Nb₂O₆ ceramics has been studied by measuring the dielectric pennitivity as a function of temperature at different frequencies. Experimental results in the transition region over ?'_max fit the relation $\text{1}\text{?'}\text{?}\text{1}\text{?'}{}_{\max }\text{= A(T ?}\text{T}{}_0\text{)}{}^{\mathrm{\gamma }}$ with γ > 1, as is typical for dif transitions. In an interval of temperatures of 17°C over T₀ (=Tfor?'_max), γ = 2. Using the relaxors' model of Kirillov-Isupov an equation is inferred in order to compute the activation energy of the relaxors as a function of parameters directly obtained from the experimental results.