Showing papers by "University of Maribor published in 1996"
TL;DR: In this article, a formula for the Szeged index of Cartesian product graphs is obtained and some other composite graphs are considered, and for all connected graphs, Sz is greater than or equal to the sum of distances between all vertices.
136 citations
TL;DR: The Schultz molecular topological index (MTI) is compared with the Wiener index (W) of a molecular graph and it is shown that 2vminW < MTI ≤ 4vmaxW holds for any (connected) graph Γ.
Abstract: The Schultz molecular topological index (MTI) is compared with the Wiener index (W) of a molecular graph. It is shown that 2vminW < MTI ≤ 4vmaxW holds for any (connected) graph Γ, with vmin and vma...
94 citations
01 Jan 1996
92 citations
TL;DR: In this article, the authors consider complex Banach spaces and show that if Φ = cΘ where Θ is either an algebra-automorphism or an antiautomorphism of B ( X ) and c is a complex constant such that | c |=1.
76 citations
TL;DR: In this paper, the Delphi technique was used by the authors to compile a list of the key issues in information systems (IS) management in Slovenia, to quantify them, and, through iterations, to strengthen consensus about their importance.
75 citations
TL;DR: The main result of as mentioned in this paper is that [D(x, x, x] = 0 holds for all x ∈ R. In this case, the derivation is a derivation of a 2-torson free semiprime ring.
Abstract: The main result: Let R be a 2-torson free semiprime ring and let D: R → R be a derivation. Suppose that [[D(x), x], x] = 0 holds for all x ∈ R. In this case [D(x), x] = 0 holds for all x ∈ R.
75 citations
TL;DR: In this article, the cross-section morphologies of polymeric membranes obtained by scanning electron microscopy are presented and qualitatively correlated with the turbidity appearance and its intensity during the (proto)membrane formation process and with their permeability to pure water.
Abstract: The cross-section morphologies of polymeric membranes obtained by scanning electron microscopy are presented. Membranes are prepared by a wet phase inversion process from cellulose acetate, polysulfone, polyester and a polyether type of elastomeric polyurethanes, poly(methylmethacrylate), and polyamide—nylon 4,6. Morphologies are qualitatively correlated with the turbidity appearance and its intensity during the (proto)membrane formation process and with their permeability to pure water. From the morphological characteristics, such as different cellular or dense structures, macrovoids, and polymer beads, and from the turbidity phenomena during the (proto)membrane formation, the nucleation and growth of polymer-lean or polymer-rich phase and the spinodal modes of polymer-solvent-nonsolvent ternary system decomposition are postulated. © 1996 John Wiley & Sons, Inc.
73 citations
TL;DR: The classical diffusive process which takes place in a chaotic billiard is studied analytically and numerically to estimate the conditions under which the statistical properties of eigenvalues and eigenfunctions can be described by Random Matrix Theory.
Abstract: We study analytically and numerically the classical diffusive process which takes place in a chaotic billiard. This allows one to estimate the conditions under which the statistical properties of eigenvalues and eigenfunctions can be described by random matrix theory. In particular, the phenomenon of quantum dynamical localization should be observable in real experiments.
71 citations
TL;DR: In this article, an improved MINLP approach is proposed for the synthesis of complex problems, which uses smaller and more compact superstructures of the distillation sequences included in the flowsheet superstructure rather than the usual tree and network representations.
70 citations
TL;DR: In this article, a case study of waste minimization in the textile industry is presented, where several options for waste minimisation were proposed and their implementation was able to decrease waste water production by 21%, consumption of dyes by 24%, textile auxiliaries and chemicals by 14%, and steam usage by 25%.
Abstract: This paper describes the methods and procedures of pollution prevention which have been applied in process industries with a case study of waste minimization in the textile industry. The waste minimization procedure developed by the United States Environmental Protection Agency (US EPA) was first used and later extended by additional steps which were found appropriate for use in process industries in order to obtain optimal waste minimization options. Mass and energy balances were produced, and the whole process was examined in a machine and piece dyeing mill. The analysis of steam distribution, steam utilization, and the condensate system was carried out. Several options for waste minimization were proposed and their implementation was able to decrease waste water production by 21%, consumption of dyes by 24%, textile auxiliaries and chemicals by 14%, and steam usage by 25%. The flue gas and greenhouse effect gases could also be reduced a great deal. The payback period of the proposed options is less than 1 year. Some practical improvements were introduced directly, while the implementation of other options depended on the financial ability of the factory. Some of them (good housekeeping and regular maintenance) will be introduced through the introduction of the Total Quality Management system.
68 citations
TL;DR: The chromatic number turned out to be an interesting parameter on all these products, except on the Cartesian one, and some applications of product colorings are also included.
TL;DR: The decision-making algorithm implemented in the bar is described and the bar's self-adaptive behavior of displaying the frequency of each icon's use through the icon's size is described, allowing the user to maintain a clear general model of the system.
Abstract: As information systems become increasingly important in many different domains, the potential to adapt them to individual users and their needs also becomes more important. Adaptive user interfaces offer many possible ways to adjust displays and improve procedures for a user's individual patterns of work. This paper describes an attempt to design an adaptive user interface in a computer environment familiar to many users. According to one classification of adaptive user interfaces, the adaptive bar described in this paper would be classified as a user-controlled self-adaptation system.
TL;DR: By combining the variable structure systems and Lyapunov designs a new algorithm is developed which has all the good properties of the sliding mode systems while avoiding unnecessary discontinuity of the control thus eliminating chattering.
Abstract: In this paper sliding mode motion design is considered for nonlinear plants which are linear with respect to control input. The dynamics of the robotic manipulators is treated with and without those of the actuators. When the dynamics of the actuators is included a design of the sliding modes for the systems with discontinuous control is performed. If actuators' dynamics is negelected the control is assumed to be continuous quantity. By combining the variable structure systems and Lyapunov designs a new algorithm is developed which has all the good properties of the sliding mode systems while avoiding unnecessary discontinuity of the control thus eliminating chattering. Neither the explicit calculation of the equivalent control, nor high gain inside the boundary layer are used. The parameters of the control depend on the plant's gain matrix, and the gradients of the sliding mode manifold. This control method is then applied to develop a unified control strategy for the motion control systems including the path tracking control, the impedance control and the force control of a robotic manipulator. It is shown that all these tasks can be formulated in the same mathematical form in which selected so-called sliding mode functions must track their references. In this way the systems state is forced to remain on the selected manifold in the state space after reaching it. The solution is interpreted in both the Joint space and the Work space for n -degrees of freedom robotic manipulators.
TL;DR: Test computation results show that BDIM is an accurate approximation technique which, together with the subdomain technique and powerful iterative solvers, can exhibit some significant savings in storage and CPU time requirements.
Abstract: The solution of Navier–Stokes equations of time-dependent incompressible viscous fluid flow in planar geometry by the Boundary Domain Integral Method (BDIM) is discussed. The introduction of a subdomain technique to fluid flow problems is considered and improved in order to maintain the stability of BDIM. To avoid problems with flow kinematics computation in the sudomain mesh, a segmentation technique is proposed which combines the original BDIM with its subdomain variant and preserves its numerical stability. In order to reduce the computational cost of BDIM, which greatly depends on the solution of systems of linear equations, iterative methods are used. Conjugate gradient methods, conjugate gradients squared and an improved version of the biconjugate gradient method BiCGSTAB, together with the generalized minimal residual method, are used as iterative solvers. Different types of preconditioning, from simple Jacobi to incomplete LU factorization, are carried out and the performance of chosen iterative methods and preconditioners are reported. Test examples include backward facing step flow and flow through tubular heat exchangers. Test computation results show that BDIM is an accurate approximation technique which, together with the subdomain technique and powerful iterative solvers, can exhibit some significant savings in storage and CPU time requirements.
01 Jan 1996
TL;DR: The PGSS-process as mentioned in this paper is a simple and simple method to produce fine dispersed powder of polyetheneglycols, which allows to treat polymers with higher molar mass (up to 35.000 g/mol), which are too hard for grinding in conventional machines.
Abstract: 5. Summary The PGSS-Process is a versatile and simple method to produce fine dispersed powder of Polyetheneglycols. Compared to milling processes it allows to treat not only PEG with lower molar mass (which are too greasy), but also polymers with higher molar mass (up to 35.000 g/mol), which are too hard for grinding in conventional machines. The particles are relatively small (150 to 400 μm), with bulk densities between 100 and 180 kg/m 3 . By adjusting suitable process parameters (temperature, nozzle, CO 2 -addition) the particles, particle size distribution and the morphology can be adapted to specific requirements. Due to the good solubility of CO 2 in PEG the gas consumption is low. Typical ratios are between 0,17 to 0,8 kg of gas per 1 kg of PEG powder. These values are also low compared to classical processes like spray drying, solvent crystallisation or freeze grinding. Typical values of gas consumption (e.g. drying or cooling gas) for such processes are from 2 to 20 kg gas/kg solid. The PGSS-produced PEG powders are solvent free, which is an important boundary condition e.g. for pharmaceutical applications.
TL;DR: In this paper, a new apparatus incorporating dual high pressure syringe pumps and a high pressure UV cell was constructed to measure the supercritical adsorption isotherms at pressures between 90 and 250 bar and 308.1 and 328.1 K.
TL;DR: In this paper, the authors used graphite furnace atomic absorption spectrometry (standard addition method) to determine the total arsenic in wild-growing mushrooms after digestion with nitric acid, then with perchloric acid and in associated soils.
Abstract: Graphite furnace atomic absorption spectrometry (standard addition method) was used to determine the total arsenic in wild-growing mushrooms after digestion with nitric acid, then with perchloric acid and in associated soils after digestion with mixtures of nitric and hydrofluoric acids in a microwave system. Among 83 species of mushrooms the highest concentrations of arsenic on a dry mass basis were found in Laccaria amethystea (26–125 mg kg−1), Laccaria laccata (11–33 mg kg−1), Thelephora terrestris (38 mg kg−1), Boletus cavipes (11.6 mg kg−1) and Ramaria botrytis (10 mg kg−1). Mushroom caps of L. laccata, L. amethystea, and B. cavipes had approximately double the arsenic concentrations found in stems. The arsenic concentrations in caps of L. amethystea and L. laccata were directly proportional to the concentrations in the soils. The concentrations of arsenic in the soils were in the range 6.5–65 mg kg−1. Among the 19 mushroom caps with arsenic concentrations above the method detection limit of ...
TL;DR: In this article, a quantum SOS coherent state representation (SOS Husimi distribution) of an arbitrary (either stationary or evolving) quantum SOS state (vestor from the Hilbert space over the configurational SOS) is introduced.
TL;DR: A particular instance of this method computes the domination number of fasciagraphs and rotagraphs in O(log n) time, where n is the number of monographs of such a graph.
17 Jun 1996
TL;DR: In this paper, the sensitivity of the capacitive-dependent capacitive crystal of the humidity sensor with stochastic test signals has been investigated, including the influence of test signals of the weighting function uncertainty and of the A/D-D/A conversion.
Abstract: The humidity sensor using the sensitive capacitive-dependent crystal is described. Presented is the probe sensitivity (dependence of df on the dC/sub x/). In addition, the new idea of excitation of the entire humidity sensor with stochastic test signals is described, and the humidity surface-measuring method is given. It includes the influence of test signals of the weighting function uncertainty and of the A/D-D/A conversion. The results of humidity measurement with the excitation signals are shown experimentally. The uncertainty of the surface humidity measurement is less than 0.2% (T=15-25/spl deg/C and humidity=50-98%).
TL;DR: This paper contains a new algorithm that recognizes whether a given graph G is a Hamming graph, i.e. a Cartesian product of complete graphs, in O(m) time and O(n 2 ) space.
TL;DR: It is shown that for any k ⩾ 0 there exists a graph G such that γ ( G × G ) ⩽ ( G ) 2 − k .
TL;DR: In this paper, a multiplicative derivation of a topological space satisfying the first axiom of countability with no isolated points is studied. But the assumption of linearity or continuity of the space is not considered.
Abstract: LetX be a completely regular topological space satisfying the first axiom of countability with no isolated points, and letC(X) be the algebra of all continuous functions onX. A mappingd:C(X)→C(X) is called a multiplicative derivation ifd(fg)=fd(g)+gd(f) for every pair of functionsf, g∈C(X) (no linearity or continuity ofd is assumed). We obtain a complete description of such mappings and give examples to show that the above assumptions on the spaceX are essential.
Journal Article•
TL;DR: In this paper, a capacitance-dependent crystal-based humidity sensor with stochastic test signals is described, including the influence of test signals on the weighting-function uncertainty and on the A/D-D/A conversion.
Abstract: A humidity sensor using a sensitive capacitance-dependent crystal is described. The probe sensitivity (dependence of d f on d C 1 ) is presented. In addition, the new idea of excitation of the entire humidity sensor with stochastic test signals is described, and the humidity surface-measuring method is given. It includes the influence of test signals on the weighting-function uncertainty and on the A/D-D/A conversion. The results of humidity measurement with the excitation signals are shown experimentally. The uncertainty of the surface humidity measurement is less than 0.2% ( T − 15–25°C and humidity = 50 to 98%).
TL;DR: It is demonstrated that smectic elasticity can cause strong deviations from the preferred surface anchoring direction and the chevron and bookshelf structures are found to be the most stable in the weak anchoring regime.
Abstract: Model structures of a smectic-A liquid crystal confined to a long cylindrical cavity enforcing homeotropic surface anchoring are studied theoretically. The structures are obtained numerically through minimization of the Landau--de Gennes type free energy. We limit our discussion to cylinders with submicrometer radia. Five qualitatively different smectic-A configurations are proposed: the smectic-planar-radial, smectic-escaped-radial, chevron, bookshelf, and hybrid structures. Our analysis suggests that in the strong anchoring regime the smectic--escaped-radial structure is the most stable. For this structure relatively large temperature shifts of the nematic--smectic-A phase transition are expected. In the weak anchoring regime the chevron and bookshelf structures are found to be the most stable. We demonstrate that smectic elasticity can cause strong deviations from the preferred surface anchoring direction. \textcopyright{} 1996 The American Physical Society.
TL;DR: In this article, a systematic WKB expansion to all orders for a one-dimensional system with potential $V(x)=U_0/\cos^2{(\alpha x)} was performed.
Abstract: We perform a systematic WKB expansion to all orders for a one-dimensional system with potential $V(x)=U_0/\cos^2{(\alpha x)}$. We are able to sum the series to the exact energy spectrum. Then we show that at any finite order the error of the WKB approximation measured in the natural units of the mean energy level spacing does not go to zero when the quantum number goes to infinity. Therefore we make the general conclusion that the semiclassical approximations fail to predict the individual energy levels within a vanishing fraction of the mean energy level spacing.
TL;DR: In this paper, a thermoplastic polyurethane (TPU) with poly(styrene-co-acrylonitrile) (SAN) was investigated by differential scanning calorimetry (DSC) and dielectric spectroscopy.
TL;DR: In this article, a new simple proof of Semrl's recent representation theorem for quasi-quadratic functions acting on unital modules is given, and a certain extension of SemRL's result is also given.
Abstract: We give a new simple proof of Semrl’s recent representation theorem for quasi-quadratic functions acting on unital modules and then show that our approach also gives a certain extension of Semrl’s result
TL;DR: This paper considers only sweep surfaces, generated by sweeping one curve (cross-section) along the other curve (trajectory), and their existing construction methods: the Frenet frame method, the discrete approach, the offset method, and the projection technique.
TL;DR: The use of supercritical fluid chromatography for determining partial molar volumes of alcohols and terpenes at infinite dilution in supercritical CO2 is presented and discussed in this article.
Abstract: The use of supercritical fluid chromatography for determining partial molar volumes of alcohols and terpenes at infinite dilution in supercritical CO2 is presented and discussed. Partial molar volumes at infinite dilution are obtained from the variation of the retention properties with the density of mobile phase at 313.15 K and in the pressure range from 85 to 280 bar.