Showing papers by "University of Maribor published in 1998"
TL;DR: A survey of the most widely used and, according to many researchers, the most promising textile wastewaters decoloration methods is presented in this paper, where data on decolloration rates of different dye classes, obtained by means of different methods is gathered.
957 citations
TL;DR: In this article, generalized derivations in rings are discussed and generalized derivation in rings can be found in the paper "Generalized derivations of rings in rings: Generalization in rings".
Abstract: (1998). Generalized derivations in rings. Communications in Algebra: Vol. 26, No. 4, pp. 1147-1166.
339 citations
TL;DR: In this article, the authors present a new model for heat integration that overcomes difficulties experienced either with direct integration approaches, or with the Duran and Grossmann (1986) model when handling isothermal streams.
94 citations
TL;DR: It is demonstrated with the help of this extended model that mitochondria are likely to act in favour of frequency encoding by enabling the maintenance of fairly constant amplitudes over wide ranges of frequency.
70 citations
TL;DR: In this paper, the authors used a batch stirred tank reactor in dense carbon dioxide for the esterification of oleic acid with oleyl alcohol catalyzed by lipase from Rhizomucor miehei (Lipozyme IM ) was used as a model system.
Abstract: Dense gases were used as a biochemical reaction medium. Esterification of oleic acid with oleyl alcohol, catalyzed by lipase from Rhizomucor miehei (Lipozyme IM ) was used as a model system. Due to the limitation of the process that may arise from the non-polarity of carbon dioxide, which preferentially dissolves hydrophobic compounds, studies were also performed with other gases (n-butane, n-propane, n-propane/n-butane mixture). The study of the pressure stability of the immobilized lipase showed that the lipase is quite stable; it does not lose its activity when it is exposed to various dense gases at high pressure for a longer time. Esterification rates at high pressure were determined for all systems, and it was found that they were higher than at atmospheric pressure. The studies of thermodynamic properties and mass transfer were performed in a batch stirred tank reactor in dense carbon dioxide for the esterification of oleic acid with oleyl alcohol (catalyzed by lipase). The highest rate and maximum conversion were determined. It was found that in a continuous fixed bed reactor at 150 bar, 40°C and water activity 0.46% w/w, the activity of the enzyme preparation was practically unchanged when CO 2 was used as a solvent. The addition of small amounts of water increases the conversion rate. A higher conversion was also observed at a longer residence time. When n-butane was used as a reaction medium a decrease of conversion was observed.
70 citations
TL;DR: In this article, the pH indicator aminofluorescein was incorporated into various ormosils and the resulting materials were tested for their relative response to pH and dissolved ammonia at constant pH.
Abstract: Ormosils were prepared in different ratios of tetramethoxysilane and organically modified sol-gel precursors of type R′Si(OR) 3 and R′ 2 Si(OR) 2 . The pH indicator aminofluorescein was incorporated into various ormosils and the resulting materials were tested for their relative response to pH and dissolved ammonia at constant pH. R′ 2 Si(OR) 2 -based layers were recognized as the most promising materials because of their high permeability to ammonia, impermeability to ions (protons), long operational lifetime and good photostability.
67 citations
TL;DR: In this article, the effect of triblock copolymer poly(styrene-b-butadiene-bstyrene) (SBS) on the morphology and mechanical properties of immiscible polypropylene/polystyrene (PP/PS) blends were studied.
Abstract: The compatibilizing effect of the triblock copolymer poly(styrene-b-butadiene-b-styrene) (SBS) on the morphology and mechanical properties of immiscible polypropylene/polystyrene (PP/PS) blends were studied. Blends with three different weight ratios of PP and PS were prepared and three different concentrations of SBS were used for investigations of its compatibilizing effects. Scanning electron microscopy (SEM) showed that SBS reduced the diameter of the PS-dispersed particles as well as improved the adhesion between the matrix and the dispersed phase. Transmission electron microscopy (TEM) revealed that in the PP matrix dispersed particles were complex “honeycomblike” aggregates of PS particles enveloped and joined together with the SBS compatibilizer. Wide-angle X-ray diffraction (WAXD) analysis showed that the degree of crystallinity of PP/PS/SBS slightly exceeded the values given by the addition rule. At the same time, addition of SBS to pure PP and to PP/PS blends changed the orientation parameters A110 and C significantly, indicating an obvious SBS influence on the crystallization process in the PP matrix. SBS interactions with PP and PS influenced the mechanical properties of the compatibilized PP/PS/SBS blends. Addition of SBS decreased the yield stress and the Young's modulus and improved the elongation at yield as well as the notched impact strength in comparison to the binary PP/PS blends. Some theoretical models for the determination of the Young's modulus of binary PP/PS blends were used for comparison with the experimental results. The experimental line was closest to the series model line. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 2625–2639, 1998
65 citations
TL;DR: In this article, the authors investigated differences in EEG between gifted individuals and average individuals in resting conditions and while solving different tasks and found that the differences were most pronounced over the frontal brain areas for the tasks involving working memory and arithmetic operations.
57 citations
TL;DR: A new fast three-phase method for object reconstruction from 3D scattered points is presented, founded on a novel fast triangulation algorithm, which generates a base approximation of the object surface.
52 citations
TL;DR: In this paper, fine powders of barium titanate were synthesized hydrothermally from aqueous barium acetate or barium hydroxide and titanium ethoxide solution, with different alkaline media; ammonia, hydrazine and tetramethylammonium hydride.
Abstract: Fine powders of barium titanate were synthesized hydrothermally from aqueous barium acetate or barium hydroxide and titanium ethoxide solution, with different alkaline media; ammonia, hydrazine and tetramethylammonium hydroxide. Barium titanate powder prepared from Ba(OH)2 after synthesis shows BaCO3 impurities. On the other hand, powders prepared from Ba(CH3COO)2, Ti(OC2H5)4 and tetramethylammonium hydroxide exhibit the smallest average grain size and did not contain BaCO3 impurities. However, a relative by large amount of organic disintegration products which delay the sintering process were identified in the BaTiO3 powders from Ba acetate. The BaTiO3 powders were characterized by scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), thermogravimetric analysis (TGA), mass spectroscopy and dilatometric analyses.
51 citations
TL;DR: In this article, a spur gear pair from the first stage of an industrial vehicle gear box has been subjected to experimental testing and the effects of different load distributions along the gear tooth width on the fatigue crack growth in gear tooth root were measured on an appropriate testing device.
TL;DR: A convexity lemma is proved and used to derive a simple algorithm of complexityO(mn) for recognizing median graphs.
Abstract: A hierarchy of classes of graphs is proposed which includes hypercubes, acyclic cubical complexes, median graphs, almost-median graphs, semi-median graphs and partial cubes. Structural properties of these classes are derived and used for the characterization of these classes by expansion procedures, for a characterization of semi-median graphs by metrically defined relations on the edge set of a graph and for a characterization of median graphs by forbidden subgraphs. Moreover, a convexity lemma is proved and used to derive a simple algorithm of complexityO(mn) for recognizing median graphs.
TL;DR: The results of research in the use of cellular automata for image recognition purposes in general are presented, along with the details of how the follicle recognition problem was solved.
TL;DR: In this paper, a general computational model for modeling subsurface fatigue crack growth under cyclic contact loading of mechanical elements is described, where the model assumes that the initial fatigue crack develops along the slip line in a single crystal grain at the point of the maximum equivalent stress.
TL;DR: In this article, a method and an instrument are described to measure the electrokinetic potential of textile materials, either fibers or fabrics, based on the established principles of stream ing potential/current...
Abstract: A method and an. instrument are described to measure the electrokinetic potential of textile materials, either fibers or fabrics. Based on the established principles of stream ing potential/current...
TL;DR: In this article, a computational model for simulation of surface pitting of mechanical elements subjected to rolling and sliding contact conditions is presented, where the cracks leading to pitting are initiated in the area of largest contact stresses at a certain depth under the contacting surface.
Abstract: A computational model for simulation of surface pitting of mechanical elements subjected to rolling and sliding contact conditions is presented. The two-dimensional computational model is restricted to modelling of high-precision mechanical components with fine surface finishing and good lubrication, where the cracks leading to pitting are initiated in the area of largest contact stresses at certain depth under the contacting surface. Hertz contact conditions with addition of friction forces are assumed and the position and magnitude of the maximum equivalent stress is determined by the finite element method. When the maximum equivalent stress exceeds the local material strength, it is assumed that the initial crack develops along the slip line in a single-crystal grain. The Virtual Crack Extension method in the framework of finite element analysis is then used for two-dimensional simulation of the fatigue crack propagation under contact loading from the initial crack up to the formation of the surface pit. The pit shapes and relationships between the stress intensity factor and crack length are determined for various combinations of contacting surface curvatures and loadings. The model is applied to simulation of surface pitting of two meshing gear teeth. Numerically predicted pit shapes in the face of gear teeth show a good agreement with the experimental observations. © 1998 John Wiley & Sons, Ltd.
TL;DR: In this article, a modified induced-dipolem type coupling was used to simulate microscopic liquid crystal structures confined to a submicron cylindrical cavity and stability regions of characteristic nematic structures were determined as functions of the cylinder radius, homeotropic anchoring strength, and degree of the interaction anisotropy.
Abstract: Molecular dynamics is used to simulate nematic liquid crystal structures confined to a submicron cylindrical cavity. Molecules, fixed at the lattice points, are set to interact via a modified induced-dipole--induced-dipole type coupling. Stability regions of characteristic nematic structures are determined as functions of the cylinder radius, homeotropic anchoring strength, and degree of the interaction anisotropy. A connection linking elastic and microscopic approaches is established. Results confirm most of the predictions of the elastic free energy deep in the submicron regime.
TL;DR: An algorithm is presented which, for a given benzenoid system G bounded by a simple circuit Z with n vertices, computes the Wiener index of G in O( n ) time.
TL;DR: In this article, the phase behavior of pentylcyanobiphenyl (5CB) and octylcyane-binear (8CB) liquid crystals confined to controlled porous glass of different characteristic void sizes was studied using deuteron NMR.
Abstract: The phase behavior of pentylcyanobiphenyl (5CB) and octylcyanobiphenyl (8CB) liquid crystals confined to controlled porous glass of different characteristic void sizes $R$ is studied using deuteron NMR. In samples with the 5CB liquid crystal the discontinuous isotropic-nematic $(I\ensuremath{-}N)$ transition becomes gradual for $Rl0.025\ensuremath{\mu}\mathrm{m}.$ The discontinuous $I\ensuremath{-}N$ phase transition temperature shift $\ensuremath{\Delta}{T}_{\mathrm{IN}}$ scales as $\ensuremath{\Delta}{T}_{\mathrm{IN}}\ensuremath{\propto}{R}^{\ensuremath{-}1.3\ifmmode\pm\else\textpm\fi{}0.3}.$ A detailed theoretical analysis of the origins of the temperature shift and the change of the character of the $I\ensuremath{-}N$ and nematic--smectic-$A$ phase transition is given. The influence of the surface treatment is studied for the 8CB liquid crystal immersed in a $R=0.2\ensuremath{\mu}\mathrm{m}$ matrix. The results suggest that for the silane-treated sample the anchoring is homeotropic, whereas it is planar for the nontreated surface. In both cases the corresponding anchoring strength is estimated to be larger than ${10}^{\ensuremath{-}5}{\mathrm{J}/\mathrm{m}}^{2}.$ The smectic-$A$ ordering seems to be more affected by the confinement in the nontreated sample than the one treated by silane.
TL;DR: In this article, the solubility of s-triazine derivatives in supercritical CO2 was measured by a static-analytic method in the pressure range from 100 to 300 bar at temperatures of 40, 60 and 80°C.
TL;DR: In this paper, the authors extended existing models of calcium oscillations by allowing for two types of proteins differing in their calcium-binding properties, i.e., low-affinity proteins with slow binding kinetics (e.g., parvalbumin or the C-domains of calmodulin and troponin C).
31 Aug 1998
TL;DR: In this article, a robust position tracking control algorithm for a belt-driven servomechanism of a laser cutting machine is described, which is tested by simulations and used in the industrial application of a motion controller for the CNC machine.
Abstract: The position control algorithm for a belt-driven servomechanism of a laser cutting machine is described. A high-accuracy position tracking control procedure for systems with inherent elasticity due to the low-cost belt-driven servomechanism is derived based on a continuous sliding mode technique. The proposed robust position tracking control algorithm was tested by simulations and used in the industrial application of a motion controller for the CNC machine. Simulation and experimental results are also reported.
TL;DR: In this paper, the rheological and the technological behavior of different guar thickeners was studied during the printing process and compared with the behaviour of other available printing pastes.
TL;DR: In this article, the synthesis of roller and sliding hydraulic steel gate structures performed by the Mixed-Integer Non-linear Programming (MINLP) approach is described, which enables the determination of the optimal number of gate structural elements (girders, plates), optimal gate geometry, optimal intermediate distances between structural elements and all continuous and standard crossectional sizes.
Abstract: Part III of this three-part series of papers describes the synthesis of roller and sliding hydraulic steel gate structures performed by the Mixed-Integer Non-linear Programming (MINLP) approach. The MINLP approach enables the determination of the optimal number of gate structural elements (girders, plates), optimal gate geometry, optimal intermediate distances between structural elements and all continuous and standard crossectional sizes. For this purpose, special logical constraints for topology alterations and interconnection relations between the alternative and fixed structural elements are formulated. They have been embedded into a mathematical optimization model for roller and sliding steel gate structures GATOP. GATOP has been developed according to a special MINLP model formulation for mechanical superstructures (MINLP-MS), introduced in Parts I and II. The model contains an economic objective function of self-manufacturing and transportation costs of the gate. As the GATOP model is non-convex and highly non-linear, it is solved by means of the Modified OA/ER algorithm accompanied by the Linked Two-Phase MINLP Strategy, both implemented in the TOP computer code. An example of the synthesis is presented as a comparative design research work of the already erected roller gate, the so-called Intake Gate in Aswan II in Egypt. The optimal result yields 29·4 per cent of net savings when compared to the actual costs of the erected gate. © 1998 John Wiley & Sons, Ltd.
TL;DR: In this article, the authors introduce typical tourist programs of health resorts in Slovenia, their competitive advantage and possible routes of development, and present certain elements of perceived quality of health resort in Slovenia stemming from the national visitor survey.
Abstract: First part introduces typical tourist programs of health resorts in Slovenia, their competitive advantage and possible routes of development. In the second part certain elements of perceived quality of health resorts in Slovenia are presented, stemming from the national visitor survey. Third part is concerned with the empirical analysis of the profiles of tourists satisfaction with the elements of service quality in two health resorts in Slovenia, and of the correlation between the perceived service quality and tourists loyalty.
Journal Article•
TL;DR: The decision tree concept and automatic learning can be successfully used in real world situations, constrained with the real world limitations, but they should be used only with the guidelines of appropriate medical experts.
Abstract: The decision tree approach is one of the most common approaches in automatic learning and decision making. It is popular for its simplicity in constructing, efficient use in decision making and for simple representation, which is easily understood by humans. The automatic learning of decision trees and their use usually show very good results in various "theoretical" environments. The training sets are usually large enough for learning algorithm to construct a hypothesis consistent with the underlying concept. But in real life it is often impossible to find the desired number of training objects for various reasons. The lack of possibilities to measure attribute values, high cost and complexity of such measurements, unavailability of all attributes at the same time are the typical representatives. There are different ways to deal with some of these problems, but in a delicate field of medical decision making, we cannot allow ourselves to make any inaccurate decisions. We have measured the values of 24 attributes before and after the 82 operations of children in age between 2 and 10 years. The aim was to find the dependencies between attribute values and a child's predisposition to acidemia--the decrease of blood's pH. Our main interest was in discovering predisposition to two forms of acidosis, the metabolic acidosis and the respiratory acidosis, which can both have serious effects on child's health. We decided to construct different decision trees from a set of training objects, which was complete (there were no missing attribute values), but on the other hand not large enough to avoid the effect of overfitting. A common approach to evaluation of a decision tree is the use of a test set. In our case we decided that instead of using a test set, we ask medical experts to take a closer look at the generated trees. They examined and evaluated the decision trees branch by branch. Their comments on the generated trees can be found in this paper. The comments show, that trees generated from available training set mainly have surprisingly good branches, but on the other hand some are very "stupid" and no medical explanation could be found. Thereafter we can conclude, that the decision tree concept and automatic learning can be successfully used in real world situations, constrained with the real world limitations, but they should be used only with the guidelines of appropriate medical experts.
TL;DR: In this paper, the room temperature I-U characteristics of the ionized cluster beam, ICB, deposited Agn-Si(111) and Agp-Si (100) Schottky barrier junctions, for non zero Ag ions acceleration voltage Ua > 0 V, have been investigated.