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Showing papers by "Johannes Kepler University of Linz published in 1978"


Journal ArticleDOI
TL;DR: In this article, a hot wall epitaxy approach is used to grow epitaxial layers under conditions as near as possible to thermodynamic equilibrium, which has achieved the development of high quality luminescent and electro-optic films of II-VI materials.

386 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a universal form for the calculation of plane-wave Born cross sections for proton-impact ionization of the K -shell and of individual L -subshells.

101 citations


Book ChapterDOI
01 Jan 1978
TL;DR: The study of random fixed point theorems was initiated by the Prague school of probabilists around Spacek and Hans in the 1950s and has been revived in the last years as discussed by the authors.
Abstract: Publisher Summary This chapter presents random fixed point theorems. The study of random operator equations was initiated by the Prague school of probabilists around Spacek and Hans in the 1950s. As it seems to be a current trend to use stochastic models rather than deterministic ones, it is not surprising that the interest in random operator equations has been revived in the last years. The basic questions asked about random operator equations contain all problems that are interesting for deterministic operator equations, such as existence, uniqueness, stability, and approximation of solutions. However, the randomization leads to several new questions, such as the measurability of solutions and their statistical properties. The chapter presents the question of single- and multivalued random operators on randomly varying domains of definition.

66 citations


Journal ArticleDOI
TL;DR: In this paper, ultrasonic velocity measurements were used to find that the temperature for the structural phase transition is lower in samples reduced in hydrogen, and increased in Nb-doped samples.

39 citations


Journal ArticleDOI
TL;DR: In this paper, three parameters of an unknown distribution of foreign atoms in bulk material can be determined by relative X-ray yield measurements at three proton impact energies, and a method of evaluation is presented and its reliability is demonstrated by analyzing AgCuAg sandwich targets.

23 citations


Journal ArticleDOI
01 Feb 1978-Kyklos

22 citations


Journal ArticleDOI
TL;DR: Some new theoretical results are presented by which the complexity of this algorithm for the construction of Gröbner-bases of polynomial ideals may drastically be reduced in many cases.
Abstract: In /1/, /2/ we gave an algorithm for the construction of so called Grobner-bases of polynomial ideals. In this paper we present some new theoretical results by which the complexity of this algorithm may drastically be reduced in many cases.

19 citations


Journal ArticleDOI
TL;DR: In this paper, the Ginzburg-Landau model is used to model the influence of defects on the properties of nearly ferromagnetic systems (giant moment formation, as proposed by Suhl) and solids near a displacive phase transition.
Abstract: The one-dimensional single component Ginzburg-Landau (GL) model where the order parameter couples either linearly to an internal degree of freedom of localized defects or quadratically to rigid defects is studied. It is a model for the influence of defects on the properties of nearly ferromagnetic systems (“giant moment” formation, as proposed by Suhl) and of solids near a displacive phase transition. For isolated defects the nonlinear GL equation can be solved analytically. The exact strength and shape of the localized condensate and the conditions for its existence are calculated and used as a test for previous approximations applicable in three dimensions. Near the local “transition temperature” a localized order parameter mode becomes soft. The temperature dependence of its spectrum and shape and the phase shifts for the scattering of order parameter waves in the regions with and without localized condensate are calculated exactly. The stationary states for a system with two defects are presented. Apart from the stable states, the saddle points across which the system has to pass in going from one stable configuration to another are also discussed. The interactions between the defects induced by the order parameter field, between the localized moments corresponding to the condensate and between the defects and Bloch walls are given.

19 citations


Journal ArticleDOI
TL;DR: In this article, reflectivity measurements on Pb 1− x Ge x Te (0 ≤ x ≤ 0.013) epitaxial layers in the frequency range of 5 −500 cm −1 and the temperature range of 10 −300K were performed.

15 citations


Journal ArticleDOI
TL;DR: The electrical properties of as-grown CdTe thin films deposited on BaF 2 substrates have been investigated in this article, and the electron mobilities seem to be the largest reported for CdTE thin films.

14 citations


Journal ArticleDOI
TL;DR: In this article, a method for measuring specific energy losses in pure polycrystalline materials is presented and applied to the stopping of protons in gold in the range 350-650 keV.

Journal ArticleDOI
TL;DR: In this paper, a strong resonantlike increase of the electron damping parameter was observed in the region of the coupled LO-phonon-plasmon excitations in $n$-PbTe at low temperatures.
Abstract: A strong resonantlike increase of the electron damping parameter was observed in the region of the coupled LO-phonon-plasmon excitations in $n$-PbTe at low temperatures. This behavior is interpreted as evidence of a generation of collective coupled plasmon-phonon excitations. The experimental results can be interpreted very well by a model calculation as reported recently by Mycielski et al.

Journal ArticleDOI
TL;DR: The drift velocity and Hall coefficient of tn and p-type PbTe at 77K were measured for various crystallographic directions of current up to field strengths of 1.5 kV/cm as mentioned in this paper.
Abstract: The drift velocity and Hall coefficient of tn and p -type PbTe at 77K were measured for various crystallographic directions of current up to field strengths of 1.5 kV/cm. Both the conductivity and the Hall effect are anisotropic with the latter depending also strongly on the magnetic field. These effects are attributed to nonuniform heating of the equivalent conduction band L -valleys of PbTe and equivalent intervalley transfer. For field strengths beyond 1 kV/cm oscillations of the current and the potential distribution occur. The Hall coefficient decreases sharply above this threshold indicating avalanche breakdown. At still higher field strengths a sign reversal of the Hall coefficient is observed. Probing the potential distribution, it could be shown that this instability is caused by high field domains, which travel along the sample with the drift velocity of the carriers. Possible mechanisms for the formation of high field domains are discussed.

Journal ArticleDOI
TL;DR: In this paper, the cyclotron resonance of bound carriers in inversion and accumulation layers on p -PbTe was observed as an electric-field induced change in the magnetoreflectivity.

Journal ArticleDOI
01 Mar 1978
TL;DR: In this paper, the authors compared the nonrelativistic plane wave Born approximation (PWBA), the PWBA with corrections for Coulomb deflection and binding effects, and the binary-encounter approximation (BEA) with relative k-shell x-ray production cross sections.
Abstract: RelativeK-shell x-ray production cross sections have been measured for thin targets of Cu and Ag for proton and He+ impact in the energy range 150 to 800 keV. The experimental values are compared to the nonrelativistic plane wave Born approximation (PWBA), the PWBA with corrections for Coulomb deflection and binding effects (PWBABC), and the binary-encounter approximation (BEA). The PWBABC theory provides the best agreement with relative experimental cross sections. For protons, the agreement is within 2% for values of the scaled energy variableγ=η/(eθ)2>0.011; forψ<0.009, however, the deviation reaches about 10%. For helium a 10% deviation appears atγ∼0.007. An explanation for these deviations is given.

Book ChapterDOI
01 Jan 1978
TL;DR: In this paper, the Tschebyscheff polynomial Un of 2 type was shown to be the best approximation for piecewise continuous functions with jumps in the L1-norm.
Abstract: Markoff proved the following theorem: Let \(f \in {L^1}[ - 1, + 1],\;q \in {P_{n - 1}},\;\lambda (Z(f - q)) = 0\) (Z the zero set). If f-q changes sign exactly at the zeros of the Tschebyscheffpolynomial Un of 2 type, then q is the best approximation for f on [-l,+l] with respect to Pn-1 in the L1-norm. Corresponding results are deduced for the case when f-q changes sign more than n times on (-1,+1), using properties of generalised Tschebyscheff-polynomials of the 2nd type. In addition, applications to 1) the Solotareff-problem, 2) the uniqueness of the best approximation of piecewise continuous functions with jumps are given.

Journal ArticleDOI
TL;DR: In this paper, the critical dynamics of a relaxational model near the Lifshitz point are studied by the e expansion, and the dynamical exponents z are calculated numerically for the uniaxial (m = 1) and biaxially (m=2) cases.

Journal ArticleDOI
TL;DR: In this article, a precision gated current integrator and live time meter system (CILT) was designed which permits accurate determination of counting rates from multichannel analyzer spectra measured in accelerator experiments where counting rates may vary during a run.


Book ChapterDOI
01 Jan 1978
TL;DR: In this article, the authors discuss decomposition methods for decomposing I/O relations, and develop some ideas for decomposition of parameterized and fuzzy-fied relations, which are seen from the viewpoint of general systems theory.
Abstract: In problem-solving (in the widest sense) using a (mathematical) model the following can be seen: (a) the problem-solver must concentrate his attention on certain “parts” of the model, (b) he is interested to get “parts” in the right “form” so that effective methods for problem solution are available, (c) since each “part” has to be seen in connection with the model as a whole, knowledge on how the parts are coupled is essential. Decomposition methods are one help in this direction. My paper discusses this topic and develops some ideas for decomposing I/O relations, parameterized I/O relations, fuzzyfied I/O relations and finally finite discrete dynamical systems. These ideas are seen from the viewpoints of mathematics, more or less well-known and not really exciting. But from the viewpoint of general systems theory they may deserve interest.