Showing papers by "Johannes Kepler University of Linz published in 1997"
TL;DR: The algorithms of the automatic mesh generator NETGEN are described and emphasis is given to the abstract structure of the element generation rules.
Abstract: In this paper, the algorithms of the automatic mesh generator NETGEN are described. The domain is provided by a Constructive Solid Geometry (CSG). The whole task of 3D mesh generation splits into four subproblems of special point calculation, edge following, surface meshing and finally volume mesh generation. Surface and volume mesh generation are based on the advancing front method. Emphasis is given to the abstract structure of the element generation rules. Several techniques of mesh optimization are tested and quality plots are presented.
1,150 citations
616 citations
TL;DR: For example, this paper found that owners who had personally set up their business (founders) were emotionally more stable and more independent than owners who took over their business from parents, relatives, or by marriage.
352 citations
TL;DR: In this article, the convergence and logarithmic convergence rate of the Gauss-Newton method in a Hilbert space setting were proven provided a log-linear source condition is satisfied.
Abstract: Convergence and logarithmic convergence rates of the iteratively regularized Gauss - Newton method in a Hilbert space setting are proven provided a logarithmic source condition is satisfied. This method is applied to an inverse potential and an inverse scattering problem, and the source condition is interpreted as a smoothness condition in terms of Sobolev spaces for the case where the domain is a circle. Numerical experiments yield convergence and convergence rates of the form expected by our general convergence theorem.
198 citations
TL;DR: In this paper, the authors show that the major causes of the shadow economy are the direct and indirect tax burden and government regulation, and that the size of shadow economy in 1990 was more than 10% of GNP.
Abstract: The latest empirical research indicates a strong increase in the size of the shadow economy in Western Europe, over the period 1970 to 1990. For 11 of the 17 investigated OECD-countries the size of the shadow economy in 1990 was more than 10% of GNP. Analysis shows that the major causes of the shadow economy are the direct and indirect tax burden, and government regulation.
197 citations
TL;DR: In this article, the authors reported the direct observation of a bottleneck in electron cooling in wide GaAs quantum wells and their dependence on intensity, lattice temperature, and well width have been measured using a ps excite-probe technique.
Abstract: We report the direct observation of a bottleneck in electron cooling in wide GaAs quantum wells. Intersubband lifetimes \ensuremath{\tau} and their dependence on intensity, lattice temperature ${\mathrm{T}}_{\mathrm{L}}$ , and well width have been measured using a ps excite-probe technique in wells with subband separation less than the longitudinal optical (LO) phonon energy. Above an electron temperature of about ${\mathrm{T}}_{\mathrm{e}}$ =35 K the lifetime depends on ${\mathrm{T}}_{\mathrm{e}}$ and is determined by LO-phonon emission. Below this bottleneck temperature acoustic phonons dominate the plasma cooling. An energy balance model of these interactions, with no adjustable parameters, gives good agreement with our results. At electron temperatures below 35 K we determine \ensuremath{\tau}=500 and 200 ps for samples of subband energy 19.5 and 26.6 meV, respectively.
119 citations
TL;DR: In this paper, a multilayers of self-assembled Ge-rich dot embedded in silicon grown by molecular-beam epitaxy using high resolution x-ray reciprocal space mapping and reflectivity was studied.
Abstract: We have studied multilayers of self-assembled Ge-rich dots embedded in silicon grown by molecular-beam epitaxy using high resolution x-ray reciprocal space mapping and reflectivity. The Si spacer thicknesses between the dot arrays were in the range of 10‐40 nm, the typical dot size was about 150 nm for the diameter and 7 nm for the height. The measured reciprocal space maps were simulated using statistical kinematical x-ray-diffraction theory, and a good agreement between experimental and simulated data has been achieved. From the measurements, the in-plane strain in the dot lattice was determined. We derived the degree of the vertical correlation of the dot positions ~‘‘stacking’’ ! and a lateral ordering of the dots in a square array with main axes parallel to the ^100& directions, with an array lattice constant of about 500 nm. @S0163-1829~97!05623-3#
107 citations
TL;DR: This paper shows how to write all common stability problems as quantifier-elimination problems, and develops a set of computer-algebra tools that allows us to find analytic solutions to simple stability problems in a few seconds, and to solve some interesting problems in from a few minutes to a few hours.
103 citations
TL;DR: Comparison to NMR-spectra of lysozyme with a bound inhibitor shows that the interaction with sorbitol affects spatially disparate regions of the protein, and most significant changes are manifest in the anomalous relaxation properties of Ala and Thr methyl groups.
85 citations
16 Jun 1997
TL;DR: This paper proposes a simple augmentation to texture mapping hardware which produces the correct depth buffer content and hence correct visibility when replacing complex objects by partially transparent textured polygons.
Abstract: This paper proposes a simple augmentation to texture mapping hardware which produces the correct depth buffer content and hence correct visibility when replacing complex objects by partially transparent textured polygons. Rendering such polygons exploits frame-to-frame coherence in image sequences of dynamic scenes.
75 citations
TL;DR: Magnetotransport studies of the unusual two-dimensional metallic phase in highmobility Si-MOS structures are reported in this article, where it is found that a magnetic field applied in the 2D plane suppresses the metallic state, causing the resistivity to increase dramatically.
Abstract: Magnetotransport studies of the unusual two-dimensional metallic phase in high-mobility Si-MOS structures are reported. It is found that a magnetic field applied in the 2D plane suppresses the metallic state, causing the resistivity to increase dramatically (by more than 30 times). The total existence range of the metallic state is found to contain three distinct types of magnetoresistance, related to the corresponding quantum corrections to the conductivity. The data suggest that the unusual metallic state is a consequence of both spin and Coulomb interaction effects.
TL;DR: An efficient algorithm for computing optimal parametrizations of plane algebraic curves over an algebraic extension of least degree over the field of definition is presented and a classical theorem of Hilbert and Hurwitz about birational transformations is generalized.
TL;DR: In this paper, the electronic stopping cross section of slow hydrogen projectiles in large-band-gap insulators has been measured at energies of a few keV, and it has been shown that electron promotion processes contribute substantially to stopping due to formation of molecular orbitals.
Abstract: The electronic stopping cross section « of slow hydrogen projectiles in large-band-gap insulators has been measured at energies of a few keV. Even at velocities as low as y0y3 sy0 › cy137d ,w e find no influence of the band gap on the velocity dependence of «, contrary to the case of gaseous targets with similar minimum excitation energy. The magnitude of « and its essentially linear velocity dependence allow us to arrive at the following conclusion: Electron promotion processes contribute substantially to stopping due to formation of molecular orbitals. This points towards the existence of a bound electron state at a proton that moves slowly in an insulator. A simple model based on the calculation of molecular orbital correlation diagrams for the HyLiF collision system supports the idea of local reduction of the band gap of an insulating target. [S0031-9007(97)04585-7]
TL;DR: The plasma membrane of rat erythrocytes contains a 47‐kDa glycoprotein that binds the channel‐forming toxin aerolysin with high affinity and accounts for the sensitivity of these cells to the toxin, and the receptor was purified so that its N‐terminal sequence could be determined after Western blotting and did not match any sequences in the databases.
Abstract: The plasma membrane of rat erythrocytes contains a 47-kDa glycoprotein that binds the channel-forming toxin aerolysin with high affinity and accounts for the sensitivity of these cells to the toxin. The receptor was purified so that its N-terminal sequence could be determined after Western blotting. The sequence did not match any sequences in the databases, indicating that the receptor is a novel erythrocyte surface protein. However, it exhibited considerable homology to the N-termini of a group of membrane proteins that are thought to be involved in ADP-ribosyl transfer reactions. A common property of these proteins is that they are attached to plasma membranes by C-terminal glycosylphosphatidylinositol (GPI) anchors. The aerolysin receptor was shown to be anchored in the same way by treating rat erythrocytes with phosphatidylinositol-specific phospholipase C. This caused the selective release of the receptor and a reduction in the rodent cells' sensitivity to aerolysin. Human and bovine erythrocytes were shown to contain an aerolysin-binding protein with similar properties to the rat erythrocyte receptor. Proteins with GPI anchors are thought to have unusually high lateral mobility, and this may be an advantage for a toxin, such as aerolysin, which must oligomerize after binding to become insertion competent.
02 Dec 1997
TL;DR: The proposed combination of a more formal approach with a slim programming language provides a good basis for elicitation and documentation tasks in the analysis and design phase, especially in cases of a prototyping-oriented software development approach.
Abstract: The idea of design by contract (DEC), realized in the statically typed object-oriented programming language Eiffel, can be viewed as a systematic approach to specifying and implementing object-oriented software systems. We believe that a statically typed programming language is not suitable in the analysis and design phase of a prototyping-oriented software life cycle. For this purpose, dynamically typed interpreted programming languages are better suited. Unfortunately, dynamically typed programming languages usually do not support the concept of DEC. Therefore we integrated DEC into the programming language Python by using a metaprogramming approach, i.e., without changing the language or the run-time system. We adopted the DEC concept by adding mechanisms for dynamic type checking for method parameters and instance variables. The proposed combination of a more formal approach with a slim programming language provides a good basis for elicitation and documentation tasks in the analysis and design phase, especially in cases of a prototyping-oriented software development approach. Although the approach presented provides basic tool support for the analysis and design phase, further tool support especially for browsing assertions, is desirable.
02 Feb 1997-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: Physical mechanisms of UV-laser ablation of polyimide (Kapton H) are discussed for different laser pulse duration from long (μs) to ultra-short (ps) laser pulses as mentioned in this paper.
Abstract: Physical mechanisms of UV-laser ablation of polyimide (Kapton H) are discussed for different laser pulse duration from long (μs) to ultra-short (ps) laser pulses. Theoretical analysis of experimental data suggests that with long laser pulses the mechanism appears to be thermal. The activation energies for ablation are about 1.5 eV, and typical temperatures lie in the range 1400–1800 K. With ns pulses one can distinguish between the mass loss due to depletion of light volatile species from the bulk of the polymer, and the real ablation. The former is especially important near the ablation threshold. For sub-ps laser pulses ablation may proceed via preferential removal of electronically excited species. Here, decrease in delay time between two subsequent laser pulses may result in a decrease in ablation rate due to saturation and bleaching effects.
TL;DR: The data demonstrate that besides the specific distribution of hydrophobic residues, interchain ionic interactions can be crucial in modulating the association behavior of α‐helical coiled‐coil domains.
Abstract: We have studied the oligomerization of an alpha-helical coiled-coil using as an example a peptide corresponding to the C-terminal domain of cartilage matrix protein. By replacing one arginine residue, which forms an interchain ionic interaction with a glutamic acid residue, with glutamine, we found that this peptide assembles into a homotetramer at neutral pH in contrast to the native molecule which forms homotrimers. At acidic and basic pH, however, we again observed the trimer conformation. Another arginine, which is probably involved in an intrachain salt bridge, has no effect on the assembly. Our data demonstrate that besides the specific distribution of hydrophobic residues, interchain ionic interactions can be crucial in modulating the association behavior of alpha-helical coiled-coil domains.
TL;DR: The advances in detection techniques for ion chromatography that have been achieved within the last five years are reviewed, with special attention to conductivity, amperometric and potentiometric detection, post-column reaction detection including UV-Vis absorbance, fluorescence and luminescence measurements, atomic spectroscopic detection and combination with mass spectrometry as mentioned in this paper.
03 Nov 1997
01 Mar 1997-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, the surface morphology and the structure of the ion beam modified polyimide upilex R were examined using atomic force microscopy and X-ray difraction sheet resistance as a function of ion fluence and the sample temperature was measured by standard two point technique.
Abstract: Polyimide Upilex R was irradiated with 90 keV N + ions to the fluences of 1 × 10 14 –2 × 10 17 cm −2 The surface morphology and the structure of the ion beam modified PI were examined using atomic force microscopy and X-ray difraction Sheet resistance as a function of the ion fluence and the sample temperature was measured by standard two point technique Significant changes of the surface morphology and production of graphitic phase in the sample surface layer modified by the ion irradiation were observed Strong decrease of the sheet resistance (by 11 orders of magnitude) in the ion beam modified samples is connected with progressive carbonization and graphitization of the degraded polymer Electrical charge transport is mediated by variable-range hopping mechanism Drastic structural changes initiated by the ion irradiation to high fluences are similar to those observed in polymer pyrolysis
01 Apr 1997
TL;DR: All the tools in the MAD environment follow an extensible and modular debugging strategy based on a graphical user interface that helps the user in monitoring and analyzing message passing programs.
Abstract: Debugging parallel programs can be tedious and difficult. Therefore the programmer needs support from tools, that provide features for error detection and performance analysis. The MAD environment is such a toolset. It helps the user in monitoring and analyzing message passing programs. Communication errors and performance bottlenecks are visualized based on an event graph. Source code connection provides a combination between visualized events and the original lines of code or a control and data flow representation. A main part of the environment is dedicated to race conditions. After evaluation of events, which might be reordered during successive program runs, localization of message races can be performed by means of trace driven simulation. All the tools in the MAD environment follow an extensible and modular debugging strategy based on a graphical user interface.
TL;DR: In this article, the ablation threshold in air, Φth, is around 0.3±0.4 J/cm2 with ArF-laser radiation.
Abstract: N4 has been investigated. The ablation threshold in air, Φth, is around 0.3±0.1 J/cm2 with ArF- and 0.9±0.2 J/cm2 with KrF-laser radiation. With fluences Φth<Φ<4 J/cm2 the irradiated surface is either very flat or it exhibits a cone-type structure, depending on the number of laser pulses employed. With fluences of 5 to 10 J/cm2, the sample surface becomes very smooth, much smoother than the original mechanically polished surface. Pores, scratches, and cracks observed on the non-irradiated surface are absent within the illuminated area. In this regime, the ablation rates are typically 0.1 to 0.2 μm/pulse.
01 Mar 1997
TL;DR: This work introduces a new class of polygonal simplification: Smooth LODs, a very large number of small details encoded in a data stream that allows a progressive refinement of the object from a very coarse approximation to the original high quality representation.
Abstract: Levels of detail (LODs) are used in interactive computer graphics to avoid overload of the rendering hardware with too many polygons. While conventional methods use a small set of discrete LODs, we introduce a new class of polygonal simplification: Smooth LODs. A very large number of small details encoded in a data stream allows a progressive refinement of the object from a very coarse approximation to the original high quality representation. Advantages of the new approach include progressive transmission and encoding suitable for networked applications, interactive selection of any desired quality, and compression of the data by incremental and redundancy free encoding.
TL;DR: In this paper, the authors examined various properties of the two-dimensional plasma of charged bosons over an extensive range of densities, especially in the previously less studied low-density regime using a microscopic, variational approach.
Abstract: We examine various properties of the two- and three-dimensional plasma of charged bosons over an extensive range of densities, especially in the previously less studied low-density regime using a microscopic, variational approach. We calculate the ground-state structure and energetics and compare both our analytical and numerical results with earlier theoretical work. Throughout the entire density regime investigated, good agreement with the results of several Monte Carlo calculations is obtained. Triplet correlations are found to be important for the consistency of the equation of state at high densities. To study excitations we then allow for {ital time-dependent} interparticle correlations. Special attention is paid to the question of a microscopic justification for the {open_quotes}local-field factor,{close_quotes} and the consistency demands imposed by sum rules on microscopic excitation theories. Results for the static dielectric function {epsilon}(k,0) and the dynamic structure function S(k,{omega}) are presented in three and two dimensions. {copyright} {ital 1997} {ital The American Physical Society}
TL;DR: In this paper, a regionally specified general equilibrium model is used to derive the efficiency conditions for a competitive equilibrium to guarantee a Pareto optimal outcome for nonmarket services provided by farmers for recreational purposes in several Central European regions.
Abstract: This paper covers nonmarket services provided by farmers for recreational purposes in several Central European regions. A regionally specified general equilibrium model is used to derive the efficiency conditions for a competitive equilibrium to guarantee a Pareto optimal outcome. Moreover, we present green agricultural compensation programmes in Europe and their assessment from an economic perspective. The empirical analysis focuses on tourists' willingness to pay (WTP) for the provision of agricultural landscape-enhancing services in Austria. A comparison of these measures with current voluntary compensation payments made to farmers for the preservation of an agricultural countryside in several Austrian tourism communities suggests that the hypothetical contingent valuation (CV) results represent a valid order of magnitude for the value of recreation-related agricultural services. As far as agricultural policy is concerned, environmental improvement, the stabilization of agricultural income levels, diminishing intrasectoral income differences, and the development of economically disadvantaged rural regions can be expected from directly subsidizing farmers for the provision of countryside amenities.
TL;DR: In this article, Ge-rich dots on Si(100), grown by molecular beam epitaxy, were analyzed by atomic force microscopy, determining the areal density, height and diameter of the dots.
TL;DR: In this article, a method for the determination of traces of metallo-cyanide complexes by capillary zone electrophoresis is described, and the suitability of preconcentration procedures based on supported liquid membranes in a flow system is investigated.
TL;DR: Different modes of CZE such as co-and counterelectroosmotic electrophoresis as well as different detection methods like direct and indirect UV detection or conductivity detection are reviewed for these solutes in this paper.
Abstract: Within the last few years capillary zone electrophoresis (CZE) has been recognized as an attractive technique for the separation and quantification of low-molecular-mass organic acids, thereby complementing established chromatographic methods. Different modes of CZE such as co- and counterelectroosmotic electrophoresis as well as different detection methods like direct and indirect UV detection or conductivity detection are reviewed for these solutes. Systematic optimization of carrier electrolytes containing complexing reagents such as alkaline earth metals or cyclodextrines is discussed with respect to the separation selectivity. Applications to various classes of organic acids in real samples of complex composition are demonstrated.
TL;DR: This work simplifies the result of Schweizer and Sklar (1983), proving a sufficient condition which involves only one argument of a one-place function rather than two arguments, and applies it to show the monotonicity of some well-known classes of t -norms.
TL;DR: A classification is given of some optimal ternary linear codes of small length of up to minimum distance 12 for higher dimension where possible.
Abstract: A classification is given of some optimal ternary linear codes of small length. Dimension 2 is classified for every minimum distance. Dimension 3, 4 and 5 is classified up to minimum distance 12. For higher dimension a classification is given where possible.