Double diffusion in rotating porous media under general boundary conditions

In this article we study a binary fluid saturating a rotating porous medium; the fluid is modeled according to Darcy–Brinkman law and the boundary conditions are rigid or stress-free on the velocity field and of Robin type on temperature and solute concentration.We determine the threshold of linear instability and its dependence on Taylor and Darcy numbers. Using a Lyapunov function we prove analytically, under certain assumptions, the coincidence of linear and nonlinear thresholds. A second Lyapunov function allows us to prove numerically the coincidence of the two thresholds with weaker assumptions on the parameters.We show that in the particular limit case of fixed heat and solute fluxes this system has a remarkable feature: the wave number of critical cells goes to zero when the Taylor number is below a threshold. Above such threshold, the wave number is non-zero when the Darcy number belongs to a finite interval. These phenomena could perhaps be tested experimentally.     

Parallel efficiency of the C.R.F. method on an IBM RS/6000 cluster platform

A new numerical method for kinetic equations in several dimensions has been recently presented by Motta and Wick (1991). The method has been then applied to simple models to test its applicability to realistic physical situations. In the present paper we discuss the parallel performance of the method on a distributed memory platform based on a cluster of IBM RS/6000 superscalar workstations.     

A variational inequality model of the spatial price network problem with uncertain data

We consider the multicriteria spatial price network equilibrium model in which consumers are allowed to weight both the transportation cost and the transportation time associated with the shipment of a given commodity. In particular, we assume that weights are not deterministic but subject to random fluctuations. Therefore, we formulate the problem as a random variational inequality and prove that under natural assumptions the associated random operator satisfies a uniform monotonicity property. The subsequent analysis is carried out in the framework of the theory of random variational inequalities.     

Rotating porous convection with prescribed heat flux

The problem of thermal convection in a rotating horizontal layer of porous medium is considered. The porous medium is described by the equations of Darcy. A novel aspect of this work is to consider boundary conditions for the temperature of Newton–Robin type with heat flux prescribed as a limiting case. The effect of rotation is found to be crucial. For the Taylor number small enough the critical wave number is zero but we find a threshold such that for Taylor numbers beyond this non-zero critical wave numbers are found. The threshold is verified via a weakly nonlinear analysis. Finally, a sharp global nonlinear stability analysis is given.     

Exposure to magnetic fields of railway engine drivers: a case study in Italy

A case study of exposure assessment of railway workers to static and extremely low frequency (ELF) magnetic fields is presented. A measurement campaign was conducted in aboard Italian main line trains. All measurements were performed on board during regular service (two engine drivers were simultaneously present), in all places potentially accessible to personnel, considering routes ranging from a few tens of kilometres to hundreds of kilometres. The measurement protocol was mostly based on broadband metres and personal metres were employed to assess individual exposure. Surveys on static and ELF magnetic fields were performed for seven different models of engine or electrified train. Traction motors were fed by alternating current (AC) current, except for two engines, where AC current fed only auxiliary services. The final result is that the average exposure to static magnetic field was a little higher than the background geomagnetic field; occasionally in few areas it could reach levels of the order of millitesla. The average exposure to ELF magnetic fields was in the order of 1-2 μT, with higher levels (few microtesla) only for one engine; occasionally in hot spots, close to wiring or specific equipment, the field values could reach several tens of microtesla.     

Early-onset hyperthyroidism with muscle involvement: a report on a patient

A case of Graves' disease in a 2 years child old is reported. He presented tachycardia, loss of weight, anxiety and gait abnormality. The serum free T3 and T4 and thyrotropin receptor antibodies values were elevated, TSH was not measurable. The EMG was abnormal with short duration motor unit potentials.     

Inertia effects on rotating porous convection

The problem of thermal convection in a rotating horizontal layer of porous medium is considered. The porous medium is described by the equations of Darcy with the fluid inertia retained. The aim of this paper is to investigate the effect of inertia when the boundary conditions are of Robin type, with special emphasis on the case of prescribed heat flux. A detailed explanation is provided for the inertia effect coupled with the effects of rotation and the thermal boundary conditions.