Showing papers by "University of Minho published in 1982"

On the Magnetization and Magnetostriction of ErZn

Abstract: Magnetisation and paramagnetic susceptibility measurements are presented for a single crystal of ErZn along the main symmetry directions. Magnetostriction is measured along the 〈100〉 and 〈111〉 directions. From the analysis of the field dependence of the forced magnetostriction at the ordered-phase the single-ion and pseudodipolar magnetoelastic interaction parameters associated with the tetragonal distortion are obtained, being respectively M = 12 K/atom and D ≈ 0.8 K/atom. The transverse magnetostriction along the 〈100〉 direction is analyzed in terms of effective conventional magnetostriction parameters hi. From parastriction experiment values for M and the quadrupolar effective interaction parameter are deduced, viz. M = (15 ± 1) K/atom and G1 = (2.5 ± 1) mK/atom. L'aimantation et la susceptibilite paramagnetique ont ete mesurees dans un monocristal de ErZn selon les principales directions de symmetrie. La magnetostriction a ete mesuree selon les directions 〈100〉 et . De l'analyse de la dependence avec le champ magnetique de la magnetostriction forcee – dans le domaine ordone nous avons obtenu les parametres a un-ion et pseudodipolaire de l'interaction magnetoelastique, etant respectivement M = 12 K/atome et D ≈ 0,8 K atome. La magnetostriction transversal selon la direction 〈100〉 est analysee en fonction de parametres conventionnels effectifs, hi. De la mesure de la parastriction les valeurs de M et le parametre l'interaction effectif quadropolaire sont obtenus, M = (15 ± 1) K/atome et G1 = (2,5 ± 1) mK/atome.

Embankments and Slopes by Mathematical Programming

Abstract: Since Coulomb (1776) and Rankine (1857) that the stability of slopes has been calculated resorting to limit equilibrium methods, using friction and cohesion as strenght characteristics for the soils. However the major advance has been obtained by Fellenius (1927) with his method of slices.The further important step was done by Bishop (1956) who made a better static approach and introduced pore pressures. Both these methods assume circular surfaces of sliding. Janbu (1957) and Morgenstern and Price (1965) have generalized the slices method to non-circular sliding surfaces, taking into account at the same time the interslices forces. However, to make the problem statically determinated Janbu has fixed the line of thrust interslices and Morgenstern and Price have fixed the ratio between shear and normal force at the slices interfaces. Defining safety by a reduction factor F for cohesion c and friction tan ɸ, which brings the slope to the verge of failure, both these authors have to make a number of iterations to obtain F. Since F comes in the denominator in the constitutive equations sometimes difficulties arrise in the convergence of the process.

The Effect of Fluoride on the Aqueous Iron–Thionine Photogalvanic System

Abstract: The influence of fluoride ions on the photocurrent and photostationary state composition of the acid, aqueous iron-thionine system at bare and thionine-coated platinum electrodes was investigated. Observed photocurrents are in some circumstances increased by the addition of fluoride, in accordance with the theory of characteristic lengths of Albery et al. However, the Gibbs energy of the forward reaction, and hence the open-circuit voltage available from a differential photogalvanic cell, are sharply decreased.