Pet Projects

Superzon can be used to find the really best products on Amazon. It does that by reranking the Amazon search results using a bayesian average of the reviews taking the number of reviewers into account. It is implemented as a small webservice written with Flask in Python and deployed on Heroku.
Correl-O-Mat is a python script for analyzing correlations from the data of the wahl-o-mat. It generates a correlation matrix counting all questions where the parties agree with each other. This shows, which parties share opinions and therefor are similar to each other (with sometimes surprising results!).
Semaeval is a python package to evaluate the quality of semantic engines. It supports evaluation of the natural language processing capabilities of many engines like alchemyapi, semantria, textrazor. It also offers tools to get example texts in many languages from sources like, or
show more
Python scripts for finding free conference rooms from a Microsoft Exchange Server.
This project offers some python scripts for generating a bilingual dictionary from a wikipedia dump.
More on Github
Even more pet projects are on github.


Towards Sustainable IaaS Pricing
In this paper we argue that the predominant flat rate billing in conjunction with the practice of overbooking and its associated mismatch between actual costs and billed posts results in a substantial misalignment between the interests of providers and customers that stands in the way of trustworthy and sustainable cloud computing. On these grounds, we propose a hybrid IaaS pricing model that aims to avoid these problems in a non-technical fashion by shifting to consumption based billing on top of credible minimum performance.
Philipp Berndt, Andreas Maier
Economics of Grids, Clouds, Systems, and Services. Springer International Publishing, 2013. 173-184.
Turbulence modeling and the physics of the intra-cluster medium
FEARLESS (Fluid mEchanics with Adaptively Refined Large Eddy SimulationS) is a new numerical scheme arising from the combined use of subgrid scale (SGS) model for turbulence at the unresolved length scales and adaptive mesh refinement (AMR) for resolving the large scales. This tool is especially suitable for the study of turbulent flows in strongly clumped media. In this contribution, the main features of FEARLESS are briefly outlined. We then summarize the main results of FEARLESS cosmological simulations of galaxy cluster evolution. In clusters, the production of turbulence is closely correlated with merger events; for minor mergers, we find that turbulent dissipation affects the cluster energy budget only locally. The level of entropy in the cluster core is enhanced in FEARLESS simulations, in accord with a better modeling of the unresolved flow, and with its feedback on the resolved mixing in the ICM.
L. Iapichino, A. Maier, W. Schmidt and J. C. Niemeyer
AIP Conf. Proc. 1241, 928 (2010)
Adaptively refined large eddy simulations of a galaxy cluster: turbulence modeling and the physics of the intracluster medium.
We present a numerical scheme for modeling unresolved turbulence in cosmological adaptive mesh refinement codes. As a first application, we study the evolution of turbulence in the intracluster medium (ICM) and in the core of a galaxy cluster. Simulations with and without subgrid scale (SGS) model are compared in detail. Since the flow in the ICM is subsonic, the global turbulent energy contribution at the unresolved length scales is smaller than 1% of the internal energy. We find that the production of turbulence is closely correlated with merger events occurring in the cluster environment, and its dissipation locally affects the cluster energy budget. Because of this additional source of dissipation, the core temperature is larger and the density is smaller in the presence of SGS turbulence than in the standard adiabatic run, resulting in a higher entropy core value.
Maier, A., Iapichino, L., Schmidt, W., & Niemeyer, J. C.
The Astrophysical Journal 707.1 (2009): 40.
C+O detonations in thermonuclear supernovae: Interaction with previously burned material
In the context of explosion models for Type Ia Supernovae, we present one- and two-dimensional simulations of fully resolved detonation fronts in degenerate C+O White Dwarf matter including clumps of previously burned material. The ability of detonations to survive the passage through sheets of nuclear ashes is tested as a function of the width and composition of the ash region. We show that detonation fronts are quenched by microscopically thin obstacles with little sensitivity to the exact ash composition. Front-tracking models for detonations in macroscopic explosion simulations need to include this effect in order to predict the amount of unburned material in delayed detonation scenarios.
A. Maier, J.C. Niemeyer
Astronomy & Astrophysics 451.1 (2006): 207-212.


Half alive and half dead, like Schrödingers cat: My old website.

The end

"Computers are useless, they can only give you answers!"