928 research outputs found
Linear reduced order modelling for gust response analysis using the DLR-TAU code
No full textA unified modelling approach, using computational fluid dynamics, to calculate the flutter stability and dynamic gust response of realistic aircraft models is outlined. The approach uses an eigenmode decomposition of the coupled problem combined with a (linear or nonlinear) Taylor expansion of the nonlinear, full order residual function. The necessary information for the flutter stability analysis, aerodynamic influence coefficients, is readily calculated. The aerodynamic influence is presented in a form which is in line with industrial practice using corrected doublet lattice method aerodynamics. Based on the stability analysis, eigenmodes are used to produce a reduced model for the gust response analysis. With the projection of the full order system on the eigenmode basis, a small set of equations governing the dominant dynamics is found. The approach is general to work with a variety of numerical schemes for the different physics involved in the coupled problem. In addition, arbitrary parameter variations can be included in the reduced model. The methods are used herein for the computational fluid dynamics solver DLR–TAU, which is adopted by industry throughout Europe, for aerodynamics. Structures are described by the standard modal form of a finite–element model. While pre–computations to evaluate the reduced order model require heavy computational resources, the reduced model can be solved in a matter of seconds on a desktop machine. The test cases presented to demonstrate the modelling capability include a wing structure and a realistic passenger aircraf
Revealing Network Connectivity From Response Dynamics
No full textWe present a method to infer the complete connectivity of a network from its stable response dynamics. As a paradigmatic example, we consider networks of coupled phase oscillators and explicitly study their long-term stationary response to temporally constant driving. For a given driving condition, measuring the phase differences and the collective frequency reveals information about how the units are interconnected. Sufficiently many repetitions for different driving conditions yield the entire network connectivity (the absence or presence of each connection) from measuring the response dynamics only. For sparsely connected networks, we obtain good predictions of the actual connectivity even for formally underdetermined problems
Data supporting the article, "Transonic buffet characteristics under conditions of free and forced transition" published in the AIAA Journal, 2022
No full textThis dataset supports the publication by Moise, P., Zauner, M., Sandham, N. D., Timme, S. & Wei, H "Transonic Buffet Characteristics Under Conditions of Free and Forced Transition", AIAA Journal, https://doi.org/10.2514/1.J062362.
The data contains
DataSets.zip, containing ".csv" (comma separated values, CSV) files in ASCII format. These CSV files correspond to several plots presented in the article, "Transonic Buffet Characteristics Under Conditions of Free and Forced Transition" published in the AIAA Journal, 2022. Plots with aerofoil geometry are not provided due to copyright reasons. All CSV files are named in a "fig[No][subfigure][description].csv" format (e.g. fig30d_X.csv refers to figure 30d in the article with X being the variable stored). The figures for which data is provided are:
3,6,7,8,11,12,13,18,A1,B1.
A sample MATLAB script, sample Code.m is provided for plotting the data in the .csv files.
Padeep Moise is an Assistant Professor, Department of Aerospace Engineering, Indian Institute of Technology Kanpur, Uttar Pradesh 208016, India (email [email protected])
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Lebenswege - Fluchtwege. Kantaten und Liedpredigten an der Universität Bielefeld 1995
No full textAxmacher E, Hoyer M. Lebenswege - Fluchtwege. Kantaten und Liedpredigten an der Universität Bielefeld 1995. Theologie, Religionswissenschaft. Vol 5. Berlin: Frank & Timme; 2008
Nonlocal failures in complex supply networks by single link additions
No full textHow do local topological changes affect the global operation and stability of complex supply networks? Studying supply networks on various levels of abstraction, we demonstrate that and how adding new links may not only promote but also degrade stable operation of a network. Intriguingly, the resulting overloads may emerge remotely from where such a link is added, thus resulting in nonlocal failures. We link this counter-intuitive phenomenon to Braess’ paradox originally discovered in traffic networks. We use elementary network topologies to explain its underlying mechanism for different types of supply networks and find that it generically occurs across these systems. As an important consequence, upgrading supply networks such as communication networks, biological supply networks or power grids requires particular care because even adding only single connections may destabilize normal network operation and induce disturbances remotely from the location of structural change and even global cascades of failures
Bibliophile Cyborgs. Mediendispositiv und diskursives Grenzmanagement in Buch-Blogs
No full textPetzold K. Bibliophile Cyborgs. Mediendispositiv und diskursives Grenzmanagement in Buch-Blogs. In: Oberle I, Schellens D, Frey M, Braune C, Römer D, eds. Literaturkontakte. Kulturen – Medien – Märkte. Berlin: Frank & Timme; 2018: 217-237
How chaotic is the balanced state?
No full textLarge sparse circuits of spiking neurons exhibit a balanced state of highly irregular activity under a wide range of conditions. It occurs likewise in sparsely connected random networks that receive excitatory external inputs and recurrent inhibition as well as in networks with mixed recurrent inhibition and excitation. Here we analytically investigate this irregular dynamics in finite networks keeping track of all individual spike times and the identities of individual neurons. For delayed, purely inhibitory interactions we show that the irregular dynamics is not chaotic but in fact stable. Moreover, we demonstrate that after long transients the dynamics converges towards periodic orbits and that every generic periodic orbit of these dynamical systems is stable. We investigate the collective irregular dynamics upon increasing the time scale of synaptic responses and upon iteratively replacing inhibitory by excitatory interactions. Whereas for small and moderate time scales as well as for few excitatory interactions, the dynamics stays stable, there is a smooth transition to chaos if the synaptic response becomes sufficiently slow (even in purely inhibitory networks) or the number of excitatory interactions becomes too large. These results indicate that chaotic and stable dynamics are equally capable of generating the irregular neuronal activity. More generally, chaos apparently is not essential for generating high irregularity of balanced activity, and we suggest that a mechanism different from chaos and stochasticity significantly contributes to irregular activity in cortical circuits
Tiere(n) auf der Spur. Entwurf einer tierästh-ethisch bildenden Hörspieldidaktik.
No full textBondzio-Becker M. Tiere(n) auf der Spur. Entwurf einer tierästh-ethisch bildenden Hörspieldidaktik. In: Bernhardt S, ed. Literaturunterricht in den Sekundarstufen zwischen Themenorientierung und Ästhetik. Literatur – Medien – Didaktik. Vol 19. Berlin: Frank & Timme; 2025: 261-282
Frühe Kindheit als "Grundstein für eine erfolgreiche Bildungsbiografie". Deutungen guter Kindheit im politischen Diskurs
No full textBischoff S, Pardo-Puhlmann M, de Moll F, Betz T. Frühe Kindheit als "Grundstein für eine erfolgreiche Bildungsbiografie". Deutungen guter Kindheit im politischen Diskurs . In: Grubenmann B, Schöne M, eds. Frühe Kindheit im Fokus. Entwicklungen und Herausforderungen (sozial-)pädagogischer Professionalisierung. Berlin: Frank & Timme; 2013: 15-34
The simplest problem in the collective dynamics of neural networks: is synchrony stable?
No full textFor spiking neural networks we consider the stability problem of global synchrony, arguably the simplest non-trivial collective dynamics in such networks. We find that even this simplest dynamical problem—local stability of synchrony—is non-trivial to solve and requires novel methods for its solution. In particular, the discrete mode of pulsed communication together with the complicated connectivity of neural interaction networks requires a non-standard approach. The dynamics in the vicinity of the synchronous state is determined by a multitude of linear operators, in contrast to a single stability matrix in conventional linear stability theory. This unusual property qualitatively depends on network topology and may be neglected for globally coupled homogeneous networks. For generic networks, however, the number of operators increases exponentially with the size of the network.We present methods to treat this multi-operator problem exactly. First, based on the Gershgorin and Perron–Frobenius theorems, we derive bounds on the eigenvalues that provide important information about the synchronization process but are not sufficient to establish the asymptotic stability or instability of the synchronous state. We then present a complete analysis of asymptotic stability for topologically strongly connected networks using simple graph-theoretical considerations.For inhibitory interactions between dissipative (leaky) oscillatory neurons the synchronous state is stable, independent of the parameters and the network connectivity. These results indicate that pulse-like interactions play a profound role in network dynamical systems, and in particular in the dynamics of biological synchronization, unless the coupling is homogeneous and all-to-all. The concepts introduced here are expected to also facilitate the exact analysis of more complicated dynamical network states, for instance the irregular balanced activity in cortical neural networks
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