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Ambrozic M.,Jozef Stefan Institute | Sluckin T.J.,University of Southampton | Cvetko M.,Regional Development Agency Mura Ltd | Cvetko M.,University of Maribor | And 2 more authors.
NATO Science for Peace and Security Series A: Chemistry and Biology | Year: 2010

The influence of randomly distributed impurities on liquid crystal (LC) orientational ordering is studied using a simple Lebwohl-Lasher type lattice model in two (d=2) and three (d=3) dimensions. The impurities of concentration p impose a random anisotropy field-type of disorder of strength w to the LC nematic phase. Orientational correlations can be well presented by a single coherence length ξ for a weak enough w. We show that the Imry-Ma scaling prediction w ξ α w -/2(4 -d) holds true if the LC configuration is initially quenched from the isotropic phase. For other initial configurations the scaling is in general not obeyed.


Hribersek M.,University of Maribor | Zajdela B.,Regional Development Agency Mura Ltd. | Hribernik A.,University of Maribor | Zadravec M.,University of Maribor
Water Research | Year: 2011

The paper studies the properties and sedimentation characteristics of sludge flocs, as they appear in biological wastewater treatment (BWT) plants. The flocs are described as porous and permeable bodies, with their properties defined based on conducted experimental study. The derivation is based on established geometrical properties, high-speed camera data on settling velocities and non-linear numerical model, linking settling velocity with physical properties of porous flocs. The numerical model for derivation is based on generalized Stokes model, with permeability of the floc described by the Brinkman model. As a result, correlation for flocs porosity is obtained as a function of floc diameter. This data is used in establishing a CFD numerical model of sedimentation of flocs in test conditions, as recorded during experimental investigation. The CFD model is based on Euler-Lagrange formulation, where the Lagrange formulation is chosen for computation of flocs trajectories during sedimentation. The results of numerical simulations are compared with experimental results and very good agreement is observed. © 2010 Elsevier Ltd.


Krasna M.,University of Maribor | Krasna M.,University of El Salvador | Cvetko M.,University of Maribor | Cvetko M.,Regional Development Agency Mura Ltd. | Ambrozic M.,University of Maribor
Beilstein Journal of Organic Chemistry | Year: 2010

Orientational ordering of a homogeneous mixture of uniaxial liquid crystalline (LC) molecules and magnetic nanoparticles (NPs) is studied using the Lebwohl-Lasher lattice model. We consider cases where NPs tend to be oriented perpendicularly to LC molecules due to elastic forces. We study domain-type configurations of ensembles, which are quenched from the isotropic phase. We show that for large enough concentrations of NPs the long range uniaxial nematic ordering is replaced by short range order exhibiting strong biaxiality. This suggests that the impact of NPs on orientational ordering of LCs for appropriate concentrations of NPs is reminiscent to the influence of quenched random fields which locally enforce a biaxial ordering. © 2010 Krasna et al; licensee Beilstein-Institut.


Svetec M.,University of Maribor | Svetec M.,Regional Development Agency Mura Ltd. | Slavinec M.,University of Maribor
Advances in Condensed Matter Physics | Year: 2013

We study meniscus driven locking of point defects of nematic liquid crystals confined within a cylindrical tube with free ends. Curvilinear coordinate system is introduced in order to focus on the phenomena of both (convex and concave) types of menisci. Frank's description in terms of the nematic director field is used. The resulting Euler-Lagrange differential equation is solved numerically. We determine conditions for the defects to be trapped by the meniscus. © 2013 Milan Svetec and Mitja Slavinec.


Repnik R.,University of Maribor | Cvetko M.,University of Maribor | Cvetko M.,Regional Development Agency Mura Ltd. | Gerlic I.,University of Maribor
Molecular Crystals and Liquid Crystals | Year: 2011

Understanding physical phenomena often requires a comprehensive imagination of the subject. Visualization software uses two main approaches for presenting three-dimensional (3D) physical systems in two dimensions (2D): 3D virtual simulation (3D view) or 2D cross-sections (2D view). We focused on liquid crystals (LCs) in our comparative study of comprehension of both views for two groups of students: unfamiliar and familiar with LCs. We found that students with experiences in this field prefer the use of 2D view while other students are significantly worse in interpretation of 2D views. Copyright © Taylor & Francis Group, LLC.

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