104 research outputs found
Existence theorems in the geometrically non-linear 6-parametric theory of elastic plates
In this paper we show the existence of global minimizers for the
geometrically exact, non-linear equations of elastic plates, in the framework
of the general 6-parametric shell theory. A characteristic feature of this
model for shells is the appearance of two independent kinematic fields: the
translation vector field and the rotation tensor field (representing in total 6
independent scalar kinematic variables). For isotropic plates, we prove the
existence theorem by applying the direct methods of the calculus of variations.
Then, we generalize our existence result to the case of anisotropic plates. We
also present a detailed comparison with a previously established Cosserat plate
model.Comment: 19 pages, 1 figur
Local stability of hydrostatic compression states of non-linearly thermo-visco-elastic bodies of differential type
Comparison of pressure, magnetic field and excess manganese effects on transport properties of film and bulk ceramic La–Ca manganites
The pressure, magnetic field and excess manganese effects on transport and magnetoresistance
effect (MRE) have been studied in both the epitaxial films and bulk ceramics of manganites
(La₀.₇Ca₀.₃)₁₋xMn₁₊xO₃₋y (x = 0–0.2). A comparison of electrical behavior in both kinds of samples
of similar composition at hydrostatic pressures of up to 1.8 GPa and in a magnetic fields of up
to 8 kOe has been performed. The pressure and magnetic field effects are shown to increase with
increasing manganese content. Experimental data show that the pressure and magnetic field effects
on temperatures of both metal–insulator transition (TMD) and MRE peak (TMR) are considerably
stronger in the films than in ceramics. The hydrostatic pressure increases TMD and TMR.
Magnetoresistance effect for both types of samples was shown to be favored by the pressure and
magnetic field in an opposite way. A direct correlation is established between TMD and conductivity
bandwidth as well as between MRE and concentration of charge carriers at applied pressure.
The differences in the values of pressure effect on resistance, MRE and TMD temperature in the
films and ceramics are connected with both granular structure of ceramics and the oxygen
nonstoichiometry in ceramic and film samples of the same content as well as with the film strain
induced by lattice mismatch between the film and the substrate. The origin of pressure–magnetic
field effects is analyzed in the framework of double exchange interaction and small polaron hopping,
and variable range hopping models
Effect of the structural and mechanical characteristics of polyurethane solutions on the supermolecular structure of films
Study of the mechanism of formation of supermolecular structures arising in epoxy coatings
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