Showing papers by "Johannes Kepler University of Linz published in 1979"
01 Jun 1979
TL;DR: A new criterion is presented that may be applied in an algorithm for constructing Grobner-bases of polynomial ideals and allows to derive a realistic upper bound for the degrees of the polynomials in the GroBner-Bases computed by the algorithm in the case of poylemials in two variables.
Abstract: We present a new criterion that may be applied in an algorithm for constructing Grobner-bases of polynomial ideals. The application of the criterion may drastically reduce the number of reductions of polynomials in the course of the algorithm. Incidentally, the new criterion allows to derive a realistic upper bound for the degrees of the polynomials in the Grobner-bases computed by the algorithm in the case of polynomials in two variables.
374 citations
TL;DR: In this article, the critical dynamics at elastic phase transitions of second order is studied by the renormalization-group theory, where the dynamical susceptibility and the characteristic frequency depend singularly on an irrelevant parameter, which diverges at the fixed point.
Abstract: The critical dynamics at elastic phase transitions of second order is studied by the renormalization-group theory. The dynamical theory is based on a stochastic equation of motion for damped phonons. For systems with one-dimensional soft sectors usual dynamical scaling holds with the critical dynamical exponent $z=2$. For two-dimensional sectors logarithmic corrections appear. Novel features are found for an isotropic-phonon model. The dynamical susceptibility and the characteristic frequency depend singularly on an irrelevant parameter, which, however, diverges at the fixed point. Consequently dynamical scaling breaks down; e.g., the characteristic frequency is no longer a homogeneous function of the wave number $k$ and the inverse correlation length ${\ensuremath{\xi}}^{\ensuremath{-}1}$. Instead it is a homogeneous function of these variables and an irrelevant parameter. Consequently, the critical dynamics can be characterized by the relaxational exponent $z=2+c\ensuremath{\eta}$ at ${T}_{c}$, while in the hydrodynamic region the sound frequency is characterized by $z=2\ensuremath{-}\frac{1}{2}\ensuremath{\eta}$ and the damping by yet another exponent. This breakdown of scaling is also reflected by the fact that different fixing conditions, i.e., different choices of the frequency, lead to different values of $z$. All of these apparently different transformations lead to the same modified dynamical scaling relations.
46 citations
TL;DR: In this paper, experimental K-shell ionization cross sections from the 1978 compilation by Gardner and Gray, and from some more recent publications are presented graphically, for projectiles from 1 H up to 19 F. In spite of some obvious discrepancies between different experiments, almost all the cross sections agree with the corrected PWBA theory within 60%.
42 citations
TL;DR: In this paper, the electrical properties of CdTe thin films on BaF 2 substrates were investigated, and different treatments of the substrates prior to deposition were tried, showing that the mobility increased exponentially with temperature in the temperature range 200-300 K and decreased with increasing carrier concentration.
33 citations
TL;DR: In this article, a simple analytical expression is derived in closed form for the thickness distribution of the "freeze-off" layer which is vitrified at the (flat) wall of an oblong rectangular cavity.
Abstract: In continuation of a previous investigation a simple analytical expression is derived in closed form for the thickness distribution of the “freeze-off” layer which is vitrified at the (flat) wall of an oblong rectangular cavity. As has been pointed out previously, this layer is marked for amorphous polymers by the molecular orientation (birefringence pattern) in the moulded sample. One can show that a more detailed study with the aid of the coupled equations of energy and of motion will not furnish essential improvements. Problems of polymer physics like glass transition or crystallization kinetics at extreme rates of cooling and shearing must be solved first.
28 citations
TL;DR: In this article, a single integral constitutive equation with strain dependent and factorized memory function is applied to describe the time dependence of the shear stress, the primary normal-stress difference, and, by using the stress-optical law, also the extinction angle and flow birefringence of a polystyrene melt in intermittent shear flows.
Abstract: A single integral constitutive equation with strain dependent and factorized memory function is applied to describe the time dependence of the shear stress, the primary normal-stress difference, and, by using the stress-optical law, also the extinction angle and flow birefringence of a polystyrene melt in intermittent shear flows. The theoretical predictions are compared with measurements. The nonlinearity of the viscoelastic behaviour which is represented by the so called damping function, is approximated by a single exponential function with one parametern. The damping constantn as well as a discrete relaxation time spectrum of the melt can be determined from the frequency dependence of the loss and storage moduli.
25 citations
14 citations
14 citations
TL;DR: In this article, a microscopic model for the anomalous phase transition behavior of these compounds is suggested, and the temperature-dependent optical second-harmonic generation in thermally depoled La-doped lead zirconate titanate (PLZT) ceramics was studied.
Abstract: The temperature-dependent optical second-harmonic generation in thermally depoled La-doped lead zirconate titanate (PLZT) ceramics of composition 8/65/35 and 9/65/35 has been studied. A microscopic model for the anomalous phase transition behaviour of these compounds is suggested.
13 citations
TL;DR: In this article, the amplitudes of magnetophonon (MP) and Shubnikov-de Haas (SdH) oscillations have been measured in five n-type PbTe films grown epitaxially on BaF2 substrates.
10 citations
TL;DR: This paper shows a novel and intriguing idea: Several processors are started with the same task, using different algorithms, and the one which finishes first returns the results and stops the others.
TL;DR: In this paper, Heilmann proved that a certain class of stochastic linear programs possesses an optimal solution which depends on the random parameter in a measurable way, and that the optimal value is measurable.
Abstract: Recently W. Heilmann proved that a certain class of stochastic linear programs possesses an optimal solution which depends on the random parameter in a measurable way, and that the optimal value is measurable. We prove a result of this type for much more general problems, including stochastic nonlinear programming and stochastic optimal control problems.
TL;DR: In this paper, it was shown that no local symmetry breaking occurs in the high temperature phase of the optical second harmonic generation in squaric acid, and the same conclusion was also held for the high-temperature phase of this material.
TL;DR: In this article, the use of two types of wires, tungsten wires and tantalum coated quartz wires, is discussed, and the wires are moved by a stepping motor for high reproducibility.
TL;DR: A simple hardware implementation of the multimicrocomputer concept called ‘computer tree’ is described, and a proposal for a future hardware implementation that goes beyond the capabilities of the first in that a flexible connection of processor modules and, thereby, an adaptation of the hardware structure to the structure of the algorithm during execution time is provided.
TL;DR: In this paper, magneto-reflectivity and -transmission measurements were performed on Pb1−xSnxTe (0 ⩽ x⩽ 0.16) in the frequency range 10 to 400 cm-1 and magnetic fields up to 60 kG in Faraday configuration.
TL;DR: In this article, the authors performed magnetic measurements on Heusler alloys Ni2(Ti, Mn)Sn and Co2(T,N)Sn in the ferro- and para-magnetic region.
01 Jan 1979
TL;DR: In this paper, a wire scanner driven by a stepping motor was built to measure beam profiles of a low energy ion accelerator by Rutherford backscattering, which allowed use of the system also in the undeflected beam where ions of different mass and energy are present.
Abstract: A wire scanner driven by a stepping motor was built to measure beam profiles of a low energy ion accelerator by Rutherford back-scattering. This permits use of the system also in the undeflected beam where ions of different mass and energy are present. With this monitor, emittance and luminosity of a beam produced by a radio-frequency ion source were measured.
TL;DR: In this paper, polarographische Verhalten neuer Verbindungen vom substituierten Phenylpyridazine wurde untersucht, e.g.
Abstract: Das polarographische Verhalten neuer Verbindungen vom Typus der substituierten Phenylpyridazine wurde untersucht. Ein polarographischer Reduktionsmechanismus wurde vorgeschlagen. Fur die praktische Anwendung wurde ein Analysenverfahren angegeben, um nach dunnschichtchromatographischer Vortrennung Gehaltsbestimmungen von O-[3-Phenyl-6-chlorpyridazinyl(4)]-S-n-octylthiocarbonat in technischen Produkten durchzufuhren.
01 Jan 1979
TL;DR: In this paper, a Pradiktor-Korrektor Verfahren (hier: trivialer, allgemeiner Korrektor) wird ein Modell aufgestellt, welches den Rechenaufwand (=Gesamtzahl der Pradiconceptorschritte) minimiert.
Abstract: Bei der Losung nichtlinearer Probleme mit Einbettungsmethoden hat die Schrittweitensteuerung wesentlichen Einflus auf den Aufwand. Fur ein Pradiktor-Korrektor Verfahren (hier: trivialer Pradiktor, allgemeiner Korrektor) wird ein Modell aufgestellt, welches den Rechenaufwand (=Gesamtzahl der Pradiktor-Korrektorschritte) minimiert. Das auf globalen Grosen basierende Modell kann explizit gelost werden. Fur das Newtonverfahren als Korrektor last sich eine implementierbare Version formulieren. Die Wirksamkeit der Schrittweitensteuerung wird mit einer bekannten Methode von W.C. Rheinboldt an Hand einiger Beispiele verglichen.
01 Jan 1979
TL;DR: Magneto-optical experiments on As and implanted PbTe epitaxial layers were performed in the magnetic field range around the mt cyclotron resonance using the radiation of the DCN and the H2O laser as discussed by the authors.
Abstract: Magneto-optical experiments on As and In implanted PbTe epitaxial layers were performed in the magnetic field range around the mt cyclotron resonance using the radiation of the DCN and the H2O laser. Additional structure of the transmission spectrum was observed near the cyclotron resonance in the As implanted sample. This seems to indicate that As can produce shallow impurity levels above the valence band edge in high magnetic fields.