University of Architecture, Civil Engineering and Geodesy

About: University of Architecture, Civil Engineering and Geodesy is a education organization based out in Sofia, Bulgaria. It is known for research contribution in the topics: Finite element method & Beam (structure). The organization has 3808 authors who have published 3822 publications receiving 30736 citations. The organization is also known as: Sofia Polytechnic.

Dynamic response of a viscoelastic beam impacted by a viscoelastic sphere

Abstract: In the present paper, we consider the problem on a transverse impact of a viscoelastic sphere upon a viscoelastic BernoulliEuler beam, the viscoelastic features of which are defined via the fractional derivative standard linear solid models. As this takes place, only Youngs time-dependent operators are preassigned, while the bulk moduli are considered to be constant values, since the bulk relaxation for the majority of materials is far less than the shear relaxation. Beams displacement subjected to the concentrated contact force is found by the method of expansion in terms of eigen (beam) functions. The contact force driven displacement of the impactor, which is the sum of the beams displacement at the place of contact and the indentation of the impactor into the target, is defined from the equation of motion of the material point with the mass equal to spheres mass. Within the contact domain, the contact force is defined by the modified Hertzian contact law with the time-dependent rigidity function. For decoding the viscoelastic operators involving in the problem under consideration, the algebra of Rabotnovs fractional operators is employed. A nonlinear integro-differential equation is obtained either in terms of the contact force or in the local bearing of the target and impactor materials. Using the duration of contact as a small parameter, approximate analytical solutions have been found, which allow one to define the maximal contact force and the duration of contact for colliding bodies.

Dielectric properties of multiferroic CuCrO2

Abstract: We propose a microscopic model in order to study the multiferroic properties of the triangular compound CuCrO2 taking into account antiferromagnetic interactions in the ab plane, spin-phonon interactions and quadratic magnetoelectric (ME) coupling. The temperature and magnetic field dependence of the polarization P ab and dielectric constant ϵ ab is calculated. P ab increases when h is parallel to its direction and decreases when h is perpendicular to it. We show that ϵ ab has a kink near the magnetic phase transition T N = 24 K which disappears with increasing of an external magnetic field h ab . This behavior is an evidence for a strong ME coupling and in qualitative agreement with the experimental data.

PEG/PVDF membranes for separating organosulphur compounds from n‐heptane: Effect of PEG molecular weight

Abstract: Polyethylene glycol (PEG) of three different molecular weights were used to prepared PEG/PVDF composite membranes for separating organosulphur compounds from n-heptane by pervaporation. All the composite membranes were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) X-ray diffraction (XRD) and positron annihilation spectroscopy (PAS). The effects of operating temperature, feed sulphur content and organosulphur species on performance of PEG/PVDF composite membranes with different molecular weights were investigated. When the feed organosulphur was thiophene, the fluxes decreased with an increase in PEG molecular weights, however, the enrichment factors were in the different order, PEG membrane with molecular weight of 35 000 exhibited highest enrichment factor of 12.59 for thiophene at 85 °C. When the feed organosulphur was 2-Methylthiophene or 2, 5-Dimethylthiophene, it was found that PEG membrane with molecular weight of 100 000 showed highest enrichment factor. The results showed that PEG molecular weights have a considerable effect on separation performance for pervaporation desulphurization. This article is protected by copyright. All rights reserved