Erland Müller

This is my private home page, set up to provide papers and reports unrelated to my employed work. Currently I'm working as a technician at the DESY particle accelerator centre, helping experiments at FLASH with thier IT infrastructure. I wish to cooperatively create and maintain useful, high quality software and share the consideration “software is text”.

Constraint-Based Refactoring

Refactoring means to alter a software in order to improve its readability without affecting its function. Refactoring manually is tedious and error prone. Tools automating the process massively improve programmers' productivity provided, the tools do refactor correctly. A promising technique is based on constraints.

The objective of my master's thesis in computer science was to develop an efficient algorithm to compute the constraints for a simple refactoring of Java programs. The thesis titled “An Algorithm to Systematically Generate Constraints for Constraint-Based Refactoring” is available (in German) at the University of Hagen. This site contributes the source code of the implemented Eclipse refactoring tool.

Modelling Groundwater Contaminant Transport

Groundwater is a valuable water resource. Its contamination has been of concern for over a century. Towards the end of the last, computer models have become feasible to predict the consequences of contaminant discharge or land use application to soils on fissured porous rock.

My master's thesis in engineering hydrology at the University of Newcastle extends a pollutant transport model to account for dual porosity aquifers. The computational efficiency of the finite element code is considerably improved by deriving an analytic solution for an equation, which was integrated numerically before. The new model is successfully applied to a real pollution problem of the Chalk near Cambridge.

Estimating Low-Flow Discharge

Information on low-flow discharge of small rivers and streams are relevant to water resources planning regards sewage discharge or water abstraction for irrigation or power generation. In absence of long term data statistical extrapolation is employed to estimate low-flow frequencies. However, global warming has obsoleted the underlying assumptions.

Nevertheless, my diploma thesis in agricultural sciences at Kiel University investigated, whether areas of geologic formations in catchments as obtained from geologic maps would improve the accuracy of low-flow estimates. A digital planimeter was constructed, areas measured, low-flow frequency distributions fitted and multivariate statistics employed. In the end, the predictive ability of estimates could be improved, alas better without the geologic map data.

Automating an Assembly Line

The G10 College of Professional Education and Training, Hamburg Altona, has inherited a small Bosh assembly line, which is controlled by a Siemens S5 PLC. The objective of a students' project was to get the line going and visualise the circulation of workpieces on a PC connected to the PLC running Delta-Logic's Accon-ProSys 1131 software.

Together with Andreas Hoeft we invented the concept of an engaged line section. The model was implemented as a function block using IEC 1131-3 structured control language (SCL). This function block made programming the complete assembly line ridiculously easy. Our preliminary report was prepared for the English language class. Don't hesitate to get in touch, if the comprehensive project documentation in German might still be useful to you.

Final Notes


If not stated otherwise, all the material on this site is copyright of the author, 2013. The content is made available according to the GNU Free Documentation License (GFDL) version 1.3 or later.


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