Opis: In this paper an improved measurement system for experimental assessment of magnetic fluid losses is presented. When fluid is exposed to AC magnetic field, three different losses mechanisms are active; relaxation, hysteresis and resonance mechanism. In this paper not individual contributions where studied but combine acting which can be determine as specific power losses (SPL). SPL of the sample is obtained for a variety of amplitudes and frequencies of magnetic field with presented method of measurement of field parameters where results revealed f H2 dependence for fixed temperature of the sample. Temperature dependence of SPL is examined with calorimetrical measurements, where heating of magnetic fluid at fixed value of applied field and various frequencies is examined and results revealed linearly decreasing temperature dependence. Ključne besede:magnetic fluid loss, magentic field, hysteresis loop Objavljeno v DKUM: 30.06.2017; Ogledov: 816; Prenosov: 343 Celotno besedilo (495,15 KB) Gradivo ima več datotek! Več...

Opis: We make a numerical study of hysteresis loop shapes within a generalized two-dimensional Random Anisotropy Nematic (RAN) model at zero temperature. The hysteresis loops appear on cycling a static external ordering field. Ordering in these systems is history dependent and involves the interplay between the internal coupling constant J, the anisotropy random field D, and the ordering external field H. Here the external field is represented by a traceless tensor, analogous to extension-type fields in continuum mechanics. The calculations use both a mean field approach and full lattice simulations. Our analysis suggests the existence of two qualitatively different solutions, which we denote as symmetric and symmetry breaking. For the set of parameters explored, only the symmetric solutions are stable. Both approaches yield qualitatively similar hysteresis curves, which are manifested either by single or double loops. But the quantitative differences indicate that mean field estimates are only of limited predictive value. Ključne besede:hysteresis loop, liquid crystals, lattice simulations, mean field Objavljeno v DKUM: 14.06.2017; Ogledov: 812; Prenosov: 321 Celotno besedilo (1,41 MB) Gradivo ima več datotek! Več...