OPEN FAU

Online publication system of Friedrich-Alexander-Universität Erlangen-Nürnberg

The online publication system OPEN FAU is the central publication platform for Open Access publishing for all members of Friedrich-Alexander-Universität. Qualified works from research and teaching may be published here free of charge, either as a primary or secondary publication. The full texts are permanently available worldwide and are findable and citable via catalogues and search engines.

To search for documents in OPEN FAU, please select "Search" (via the magnifying glass at the top right); this will provide you with various search options. If you want to publish a document, go to "Login" and "My Publications". Then drag you document into the field provided and enter the metadata. In just a few steps, you can submit your document. Please note our guidelines, the publication contract and FAQs.

Recent Submissions

Article

Open Access

Molekulardynamische Untersuchung von Zerkleinerungsprozessen in Kugelmühlen

(Vogel Business Media, 2000) Buchholtz, Volkhard; Freund, Jan Alfred; Pöschel, Thorsten

Molekulardynamische Untersuchungen eignen sich zur Simulation des Verhaltens makroskopischer Mengen granularen Materials unter bestimmten, technologisch relevanten Beanspruchungen. Wir untersuchen das Zerkleinerungsverhalten von Mahlgut in einer Kugelmühle, insbesondere im Hinblick auf die Effizienz als Funktion der Drehzahl und auf die räumliche Verteilung von Beanspruchungen. Die Untersuchung der Verteilung von Kraflketten (force chains) liefert eine Erklärung des Experiments von Rothkegel und Rolf [3].

Book part

Open Access

Die Kühlrate eines granularen Gases

(Köster, 1996) Schwager, Thomas; Pöschel, Thorsten; Freund, Jan Alfred

Book part

Open Access

A measure of the information content of neural spike trains

(DIRAC, 1997) Jiménez-Montaño, Miguel Angel; Pöschel, Thorsten; Rapp, Paul; Mizraji, Eduardo; Acerenza, Luis; Alvarez, Fabián; Pomi, Andrés

Conference object

Open Access

From “solid” to “fluid”: Time-dependent hydrodynamic analysis of dense granular flows

(Kluwer Academic Press, 2001-09-30) Salueña, Clara; Pöschel, Thorsten; Esipov, Sergei E.; Aref, Hassan; Phillips, James W.

When dealing with dense granular flows (not far above the ''fluidization point'' of the granular material), which cannot be regarded as granular gases, multiple unresolved questions arise. Many of them are related to the necessity of constructing the right framework to handle the dynamics of void occupation, which governs granular flow at high densities. This is a formidable task. However, hydrodynamic fields such as density, velocity, pressure and granular temperature, are easy to produce and study in numerical simulations of particles.

Conference object

Open Access

Entropy and Compressibility of Symbol Sequences

(Complex Systems Institute, 1996-11-22) Ebeling, Werner; Pöschel, Thorsten; Neiman, Alexander

The purpose of this paper is to investigate long-range correlations in symbol sequences using methods of statistical physics and nonlinear dynamics. Beside the principal interest in the analysis of correlations and fluctuations comprising many letters, our main aim is related here to the problem of sequence compression. In spite of the great progress in this field achieved in the work of Shannon, Fano, Huffman, Lempel, Ziv and others [1] many questions still remain open. In particular one must note that since the basic work by Lempel and Ziv the improvement of the standard compression algorithms is rather slow not exceeding a few percent per decade. One the other hand several experts expressed the idee that the long range correlations, which clearly exist in texts, computer programs etc. are not sufficiently taken into account by the standard algorithms [1]. Thus, our interest in compressibility is twofold: (i) We would like to explore how far compressibility is able to measure correlations. In particular we apply the standard algorithms to model sequences with known correlations such as, for instance, repeat sequences and symbolic sequences generated by maps. (ii) We aim to detect correlations which are not yet exploited in the standard compression algorithms and belong therefore to potential reservoirs for compression algorithms. First, the higher-order Shannon entropies are calculated. For repeat sequences analytic estimates are derived, which apply in some approximation to DNA sequences too. For symbolic strings obtained from special nonlinear maps and for several long texts a characteristic root law for the entropy scaling is detected. Then the compressibilities are estimated by using grammar representations and several standard computing algorithms. In particular we use the Lempel-Ziv compression algorithm. Further the mean square fluctuations of the composition with respect to the letter content and several characteristic scaling exponents are calculated. We show finally that all these measuresare able to detect long-range correlations. However, as demonstrated by shuffling experiments, different measuring methods operate on different length scales. The algorithms based on entropy or compressibility operate mainly on the word and sentence level. The characteristic scaling exponents reflect mainly the long-wave fluctuations of the composition which may comprise a few hundreds or thousands of letters.