Showing papers by "University of Maribor published in 2001"
TL;DR: In this article, a supersymmetric four-dimensional orientifolds of type IIA on T 6 /( Z 2 × Z 2 ) with D6-branes intersecting at angles was constructed.
563 citations
30 Sep 2001
TL;DR: In this paper, the authors evaluated saturation and cross-magnetization effects in an interior permanent magnet synchronous motor (IPMSM) over the entire range of direct and quadrature-axis excitations.
Abstract: This paper presents the evaluation of saturation and cross-magnetization effects in an interior permanent magnet synchronous motor (IPMSM) over the entire range of direct- and quadrature-axis excitations. The conventional two-axis machine model is modified in order to include the influence of saturation and cross-coupling effects on the variation of self- and cross-coupling inductances in the direct and the quadrature axis. The two-axis machine model parameters are evaluated by experiments performed on an IPMSM using a controlled voltage-source inverter and are compared with parameter values evaluated by the finite-element method. The evaluation of two-axis machine model parameters reveals significant saturation and cross-magnetization effects in both axes, especially in the flux-weakening regime.
476 citations
TL;DR: In this paper, the stability and activity of lipases from Pseudomonas fluorescens, Rhizopus javanicus, rhizopus niveus, porcine pancreas and Candida rugosa in a non-solvent system at atmospheric pressure, in supercritical carbon dioxide (SC CO2), and near-critical propane at 100 bar and 40 C were studied.
Abstract: The stability and activity of lipases from Pseudomonas fluorescens, Rhizopus javanicus, Rhizopus niveus, porcine pancreas and Candida rugosa in a non-solvent system at atmospheric pressure, in supercritical carbon dioxide (SC CO2), and near-critical propane at 100 bar and 40 °C were studied. Esterification of n-butyric acid with ethanol and isoamyl alcohol was used as a model system. In supercritical carbon dioxide there was a great loss in activity of the examined lipases. Decreased relative activity of lipases in SC CO2 was attributed to the interactions between CO2 and the enzyme. The second reason for this effect was the differences in water partitioning between the enzyme and its surroundings. In contrast, the use of near-critical propane improved the activity of lipases in the comparison to the non-solvent system by four- (porcine pancreas lipase) to nine-times (Rhizopus javanicus lipase). The use of near-critical propane also improved the thermal stability of porcine pancreas lipase compared with the non-solvent system. The calculated deactivation constant for esterification between butyric acid and isoamyl alcohol, catalyzed by porcine pancreas lipase, showed that there was more than twice as much inactive as active enzyme in the non-solvent system studied whereas the ratio in propane was 1.
© 2001 Society of Chemical Industry
116 citations
TL;DR: An optical sensor highly sensitive to hydrogen peroxide has been prepared by incorporating the indicator dye Meldola Blue (MB) into sol-gel layers, prepared from (a) pure tetramethoxysilane (TMOS) and (b) variation of TMOS and Me-TriMOS as mentioned in this paper.
Abstract: An optical sensor highly sensitive to hydrogen peroxide has been prepared by incorporating the indicator dye Meldola Blue (MB) into sol–gel layers, prepared from (a) pure tetramethoxysilane (TMOS) and (b) variation of TMOS and methyltrimethoxysilane (Me-TriMOS). Sensor layers based on TMOS doped with MB were found to be most appropriate for purposes of sensing hydrogen peroxide in giving large signal changes and displaying rapid response times over the wide concentration range of 10 −8 –10 −1 M.
105 citations
TL;DR: In this paper, the efficiency of high pressure extraction in the production of oil with a high concentration of vitamin E, from seeds of Silybum marianum, was investigated and the influence of process parameters on the total yield of extraction, vitamin E composition and acid value of the extracts was investigated.
96 citations
TL;DR: In this paper, the structure of Ni-based superalloy IN 713C (∅ 10 mm, water cooled Cu-Be mold, argon atmosphere) was characterized using several microstructural characterization techniques (LM, SEM, TEM, EDS, XRD).
92 citations
TL;DR: In this paper, the problem of solving Herstein's Lie Map Conjectures was solved in full generality under the assumption that the algebras involved were of sufficiently high dimension.
90 citations
TL;DR: In this article, the NH3 plasma treatment of PA 6 foils and the evaluation of surface modification as a function of treatment time is presented. But the results show that the introduction of N-containing groups is increasing with longer treatment time only to a certain extent where the negative effect of surface destruction prevails over the positive effect of introduction of functional groups.
83 citations
TL;DR: The approach has been shown to be viable and increases the education and training possibilities for key workers while maintaining a low cost of ownership and the downtime of mission-critical equipment is minimized while the gaining of valuable experience is maximized.
Abstract: Many enterprises experience difficulty in training people to work with expensive equipment, which is needed for carrying out profitable work tasks (e.g., production line robots). Similar problems are found when work is of a complex and safety-critical nature (e.g., nuclear environments, explosive placement, surgery). This paper describes a method of education and training involving offline usage of virtual environments for task planning. When tasks are developed to the satisfaction of the trainee, they are exported to remote physical hardware, via the Internet, for real-world execution. Development of the system and the training experiments is discussed, along with some of the issues raised for telerobotics and solutions to the problem of detecting collisions in the virtual world. The approach has been shown to be viable and increases the education and training possibilities for key workers while maintaining a low cost of ownership. The downtime of mission-critical equipment is minimized while the gaining of valuable experience is maximized.
83 citations
TL;DR: Kreze et al. as discussed by the authors analyzed the structural characteristics of regenerated cellulose fibres and their comparison with viscose and modal fibres, showing that the new lyocell fibres have a greater degree of crystallinity and molecular orientation.
83 citations
TL;DR: High (emotional intelligence scores) and average emotional intelligent individuals were solving tasks from an emotional intelligence test while their electroencephalogram was recorded and a significant positive correlation between the mean frequency and emotional intelligence was observed.
01 Apr 2001
TL;DR: Numerical results (based on an electrical double-layer theory) for the theoretical model of surface neutralization due to ion shifts from the bulk of the solution toward the particle surfaces, are presented to show the theoretical possibility of accelerated coagulation of scale-forming particles during and after MWT.
Abstract: The destabilization of fine nonmagnetic particles as one of the possible mechanisms for magnetic water treatment (MWT), an alternative method for scale control in industrial water processing and amelioration of dispersion separations, is discussed. Numerical results (based on an electrical double-layer theory) for the theoretical model of surface neutralization due to ion shifts from the bulk of the solution toward the particle surfaces, are presented to show the theoretical possibility of accelerated coagulation of scale-forming particles during and after MWT.
TL;DR: In this paper, the authors present a paper by the American Mathematical Society in which the authors propose a method to solve a set of problems in the context of algebraic geometry.
Abstract: First published in Transactions- American Mathematical Society in Vol.353, No.10, pp.4235-4260, published by the American Mathematical Society
TL;DR: A transit function R on a set V is characterized by transit axioms as mentioned in this paper, where R(u, u, u) is a transit function satisfying the axiomatization of U(U, U) for all paths in a connected graph.
Abstract: A transit function R on a set V is a function
$$R:VxV \to 2^2 $$
satisfying the axioms
$$u \in R(u,\upsilon ),R(u,\upsilon ) = R(\upsilon ,u)$$
and
$$R(u,u) = \{ u\} $$
, for all
$$u,\upsilon \in V$$
. The all-paths transit function of a connected graph is characterized by transit axioms.
TL;DR: This work has investigated the occurrence of different types of Ca2+ oscillations obtained by the model, i.e. simple oscillations, bursting, and chaos, and shown that all these various modes of oscillatory behavior are obtained by a change of only one model parameter, which corresponds to the physiological variability of an agonist.
TL;DR: In this article, bimetallic γ-alumina-supported Pd-Cu catalysts with different Pd:Cu atomic ratios and different total metal loadings were prepared by pore volume successive impregnation technique.
Abstract: Bimetallic γ-alumina-supported Pd–Cu catalysts with different Pd:Cu atomic ratios (2:1, 1:1, 1:2) and different total metal loadings (Pd+Cu: 6.1, 1.3, 0.65 wt.% at constant Pd:Cu=2:1) were prepared by pore volume successive impregnation technique. The materials were characterized by means of X-ray powder diffraction (XRD), extended X-ray absorption fine structure (EXAFS) spectroscopy, chemisorption of hydrogen, transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDX). TEM/EDX, H 2 chemisorption, and EXAFS results gave strong evidence that particles of nearly spherical shape, dispersed on supporting γ-alumina crystallites, are bimetallic. Comparison with Pd/γ-alumina prepared under identical conditions clearly suggests that the addition of copper decreases the amount of palladium atoms that chemisorb hydrogen. The H 2 chemisorption and EXAFS data indicated a dilution effect of Pd ensembles by copper atoms. It was found that both surface composition and bulk structure of the bimetallic particles varied with the Pd:Cu atomic ratio, while the size of particles did not change significantly. On the other hand, the Pd–Pd and Pd–Cu coordination values demonstrated that higher total metal loading at a constant Pd:Cu atomic ratio resulted in the formation of larger bimetallic particles. The highest H 2 chemisorption ability and the smallest bimetallic nanoparticles with nonuniform distribution of Pd and Cu were observed for Pd–Cu catalyst (Pd:Cu=2:1) previously reported, that exhibited the highest selectivity in a liquid-phase nitrate reduction.
01 Apr 2001-Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology
TL;DR: In this article, a new high precision measuring device for testing and calibration of portable coordinate measuring arms is presented, which can be used for measuring along a straight line adjusted in various spatial directions.
Abstract: Portable coordinate measuring arms with rotational axes have found their place in many industrial areas. To establish and confirm the accuracy of these measuring devices, related test methods and appropriate devices are needed. After an introduction, a new high precision measuring device for testing and calibration of portable coordinate measuring arms is presented. Analysis showed that the best results can be obtained with a device for measuring along a straight line adjusted in various spatial directions. We discuss the design and construction of this measuring system and provide a theoretical calculation of its measurement accuracy, which was confirmed by experiments carried out on a prototype of a high precision measuring device in both unloaded and loaded conditions.
TL;DR: In this paper, a new up to the visible range absorbing and at 460nm fluorescing 4-trifluoromethylcarbostyril derivative of diethylenetriaminepentaacetic acid (DTPA) was synthesized.
Abstract: A new up to the visible range absorbing and at 460 nm fluorescing 4-trifluoromethylcarbostyril derivative of diethylenetriaminepentaacetic acid (DTPA) was synthesized. After formation of an europium (III)-complex intense antenna mediated lanthanide luminescence was observed. Without loss of the antenna function, the complex was entrapped into various sol–gel and ormosil (organically modified siloxanes) matrices. Luminescence spectra were then found to be independent of pH changes in the range 1–10. No leaching was observed and photostability was excellent. This stability allowed us to study the influence and pH response of bromothymolblue (BTB) as co-immobilized non-fluorescent indicator by fluorescence. A single sensor layer based on tetramethoxysilane (TMOS) doped with the Eu +3 -complex and about 3.5 equivalents BTB was found to be most appropriate for purposes of sensing pH over the broad pH range 5–9. The apparent p K a was 7.29 at ionic strength 0.1 and 6.05 at ionic strength 1.0 (KCl).
TL;DR: This paper proposes a decomposed proportional–integral–derivative fuzzy logic controllers (PID FLC) that uses three one-input one-output inferences with three separate rule bases and is compared with several PID FLCs structures.
TL;DR: Low resolution brain electromagnetic tomography data suggest that high intelligent individuals more efficiently distributed their cognitive resources needed to cope with the oddball tasks.
TL;DR: SiO2 and Al2O3 aerogels and mixed SiO2−Al 2O3 alogels exhibit excellent adsorption capacities of water vapor in the range above 1.0 kg of water/kg of aerogel as mentioned in this paper.
Abstract: SiO2 and Al2O3 aerogels and mixed SiO2−Al2O3 aerogels exhibit excellent adsorption capacities of water vapor in the range above 1.0 kg of water/kg of aerogel. Adsorption properties of mixed SiO2−Al2O3 aerogels remain stable even after 25 repeated adsorption/desorption cycles.
TL;DR: In this article, a two-dimensional numerical simulation of laminar and turbulent natural convection in a fluid with internal heat generation in a square cavity is presented, at Rayleigh numbers 106-1011 and Prandtl numbers 0.25 and 0.6.
TL;DR: In this article, a two-dimensional computational model for simulation of surface pitting of mechanical elements subjected to contact loading conditions is presented, where the initial crack of length 0.015 mm is initiated at the contacting surfaces due to previously thermal or mechanical treatment of the material.
TL;DR: It is shown that it is possible to use the same rate laws for Ca(2+) fluxes across the inner mitochondrial membrane as a plug-in element in other existing mathematical models and obtain the same effect on amplitude regulation, which appears to be universal.
TL;DR: A new algorithm for solving the point-in-polygon problem, especially suitable when it is necessary to check whether many points are placed inside or outside a polygon, which works with O ( n ) space complexity.
TL;DR: The main contribution of this paper is the introduction of the integrated computerized environment DIAPRO enabling the diagnostic process optimization.
Abstract: Efficiency in hospital performance is becoming more and more important. Studies showed that diagnosis can considerably reduce the inefficiency, so one of the most important tasks in achieving greater hospital efficiency is to optimize the diagnostic process. For the best of the patient the diagnostic process has to be optimized regarding the number of the examinations and individualized in order to maximize accuracy, sensitivity and specificity. In addition the duration of the diagnostic process has to be minimized and the process has to be performed on the most reliable equipment. The main contribution of our paper is the introduction of the integrated computerized environment DIAPRO enabling the diagnostic process optimization. The DIAPRO is based on a single approach—evolutionary algorithms.
TL;DR: In this paper, the zeta potential of natural and regenerated cellulose fibres changes noticeably during the pre-treatment and finishing process and it is important for the quality of the final product (whiteness, colour, hydrophilicity).
Abstract: The electrokinetic properties of macroscopic solids can describe both the surface modifications as well as the interaction abilities during processing. Normally the zeta potential (ξ) is measured and can be used to develop, optimise and control the manufacturing process. The zeta potential of natural and regenerated cellulose fibres changes noticeably during the pre-treatment and finishing process and it is important for the quality of the final product (whiteness, colour, hydrophilicity). The pre-treatment of cellulose fibres improves the accessibility of dissociables groups. Further improvement of hydrophilicity (mercerisation) causes a pronounced increase in the surface charge density and a reduction in the degree of crystallinity and structural modifications. The progress of the chemical as well as the enzymatic treatment correlates with ξ. These data correlate very well with the results obtained using tensiometry, water retention, and water vapour and iodine adsorption. The changes in crystallinity index and the accessibility for low molecular components are well described by the latter methods.
TL;DR: In this article, Mouter derivations and automorphisms were studied and a version of the Chevalley-Jacobson density theorem for rings with such derivations was proved.
Abstract: We introduce and studyM-outer derivations and automorphisms and prove a version of the Chevalley-Jacobson density theorem for rings with such derivations and automorphisms.
TL;DR: In this article, a supersymmetric four-dimensional orientifolds of type IIA on T^6/(Z_2 x Z_2) with D6-branes intersecting at angles was constructed.
Abstract: We construct N=1 supersymmetric four-dimensional orientifolds of type IIA on T^6/(Z_2 x Z_2) with D6-branes intersecting at angles. The use of D6-branes not fully aligned with the O6-planes in the model allows for a construction of many supersymmetric models with chiral matter, including those with the Standard Model and grand unified gauge groups. We perform a search for realistic gauge sectors, and construct the first example of a supersymmetric type II orientifold with SU(3)_C x SU(2)_L x U(1)_Y gauge group and three quark-lepton families. In addition to the supersymmetric Standard Model content, the model contains right-handed neutrinos, a (chiral but anomaly-free) set of exotic multiplets, and diverse vector-like multiplets. The general class of these constructions are related to familiar type II orientifolds by small instanton transitions, which in some cases change the number of generations, as discussed in specific models. These constructions are supersymmetric only for special choices of untwisted moduli. We briefly discuss the supersymmetry breaking effects away from that point. The M-theory lift of this general class of supersymmetric orientifold models should correspond to purely geometrical backgrounds admitting a singular G_2 holonomy metric and leading to four-dimensional M-theory vacua with chiral fermions.
TL;DR: In this article, a systematic analysis of structure characteristics and the influence of aqueous medium on the mechanical properties of lyocell fibers was performed. But the results showed that the water influence on mechanical properties is considerably smaller compared to the viscose and modal fibers.
Abstract: Comparative investigations between the new lyocell fibers and the regular viscose and modal types were made in order to explain the reasons for the differences in the mechanical properties of the fibers. The purpose was a systematic analysis of structure characteristics and of influence of aqueous medium on the mechanical properties. The properties determined in the wet state reflect the effect of the aqueous medium on the changes in the supermolecular structure during wet treatments [1, 2]. The new lyocell fibers consist of longer molecules and have a higher degree of crystallinity. Smaller but longer crystallites are oriented in the fiber axis direction and the voids structure is similar to that of viscose fibers [3]. Good mechanical properties are conditioned by the structure of the lyocell fibers, above all by high values of the orientation factor and crystallinity index. Sorption properties place lyocell fibers between the viscose and modal fibers. The water influence on the mechanical properties of lyocell fibers is considerably smaller compared to the viscose and modal fibers.