TY  - CHAP
A1  - Alexopoulos, Spiros
A1  - Kluczka, Sven
A1  - Vaeßen, Christiane
A1  - Roeb, M.
A1  - Neises, M.
T1  - Scenario development for efficient methanol production using CO2 and solar energy
T2  - Eurosun 2012 : Solar energy for a brighter future : conference proceedings : Rijeka, 18.-22.09.2012
Y1  - 2012
SP  - ID 99
CY  - Rijeka
ER  - 
TY  - CHAP
A1  - Alexopoulos, Spiros
A1  - Rau, Christoph
A1  - Hoffschmidt, Bernhard
A1  - Breitbach, Gerd
A1  - Latzke, Markus
T1  - Modelling and validation of a transient heat recovery steam generator of the solar tower power plant Juelich
T2  - Eurosun 2012 : Solar energy for a brighter future : conference proceedings : Rijeka, 18.-22.09.2012
Y1  - 2012
SP  - ID 97
CY  - Rijeka
ER  - 
TY  - CHAP
A1  - Alexopoulos, Spiros
A1  - Hoffschmidt, Bernhard
A1  - Rau, Christoph
A1  - Sattler, Johannes Christoph
T1  - Simulation of hybrid solar tower power plants
T2  - 30th ISES Biennial Solar World Congress 2011 : Kassel, Germany, 28 August - 2 September 2011. Vol. 5
Y1  - 2012
SP  - 4044
EP  - 4050
PB  - Curran
CY  - Red Hook, NY
ER  - 
TY  - CHAP
A1  - Fricke, Barbara
A1  - Ziolko, C.
A1  - Anthrakidis, Anette
A1  - Alexopoulos, Spiros
A1  - Hoffschmidt, Bernhard
A1  - Giese, F.
A1  - Dillig, M.
T1  - InnoSol - environmental aspects of the open volumetric receiver technology
T2  - 30th ISES Biennial Solar World Congress 2011 : : Kassel, Germany, 28 August - 2 September 2011. Vol. 5
Y1  - 2012
SP  - 3895
EP  - 3900
PB  - Curran
CY  - Red Hook, NY
ER  - 
TY  - CHAP
A1  - Sauerborn, Markus
A1  - Hoffschmidt, Bernhard
A1  - Telle, R.
A1  - Wagner, M.
T1  - Heatable optical analyse system for high temperature absorbers
T2  - 30th ISES Biennial Solar World Congress 2011 : : Kassel, Germany, 28 August - 2 September 2011. Vol. 5
Y1  - 2012
SN  - 978-1-61839-364-7
SP  - 3852
EP  - 3860
PB  - Curran
CY  - Red Hook, NY
ER  - 
TY  - CHAP
A1  - Baumann, Torsten
A1  - Teixeira Boura, Cristiano José
A1  - Eckstein, Julian
A1  - Dabrowski, Jan
A1  - Göttsche, Joachim
A1  - Hoffschmidt, Bernhard
A1  - Schmitz, Stefan
A1  - Zunft, Stefan
T1  - Properties of bulk materials for high-temperature air-sand heat exchangers
T2  - 30th ISES Biennial Solar World Congress 2011 : Kassel, Germany, 28 August - 2 September 2011. Vol. 2
Y1  - 2012
SN  - 978-1-61839-364-7
SP  - 1270
EP  - 1278
PB  - Curran
CY  - Red Hook, NY
ER  - 
TY  - JOUR
A1  - Ferrein, Alexander
A1  - Meyer, Thomas
T1  - A Brief Overview of Artificial Intelligence in South Africa
JF  - AI Magazine
N2  - South Africa in recent years is the establishment of a number of research hubs involved in AI activities ranging from mobile robotics and computational intelligence, to knowledge representation and reasoning, and human language technologies. In this survey we take the reader through a quick tour of the research being conducted at these hubs, and touch on an initiative to maintain and extend the current level of interest in AI research in the country.
Y1  - 2012
U6  - https://doi.org/10.1609/aimag.v33i1.2357
SN  - 0738-4602
VL  - 33
IS  - 1
SP  - 99
EP  - 101
PB  - AAAI
CY  - Menlo Park
ER  - 
TY  - CHAP
A1  - Ferrein, Alexander
A1  - Kallweit, Stephan
A1  - Lautermann, Mark
T1  - Towards an autonomous pilot system for a tunnel boring machine
T2  - 5th Robotics and Mechatronics Conference of South Africa (ROBMECH) : 26 - 27 November 2012 ; CSIR International Conference Centre Gauteng South Africa
Y1  - 2012
SN  - 978-1-4673-5183-6
N1  - Robotics and Mechatronics Conference of South Africa <5, 2012, Johannesburg> ; ROBOMECH <5, 2012, Johannesburg>
PB  - IEEE
CY  - Piscataway, NJ
ER  - 
TY  - CHAP
A1  - Ganegedara, H.
A1  - Alahakoon, D.
A1  - Mashford, J.
A1  - Paplinski, A.
A1  - Müller, Karsten
A1  - Deserno, T. M.
T1  - Self organising map based region of interest labelling for automated defect identification in large sewer pipe image collections
T2  - The 2012 International Joint Conference on Neural Networks (IJCNN) : 10 - 15 June 2012, Brisbane, Australia ; [part of the] 2012 IEEE World Congress on Computational Intelligence (IEEE-WCCI 2012)
Y1  - 2012
SN  - 978-1-4673-1490-9
PB  - IEEE
CY  - Piscataway, NJ
ER  - 
TY  - JOUR
A1  - Kirstein, Simon
A1  - Müller, Karsten
A1  - Walecki-Mingers, Mark
A1  - Deserno, Thomas M.
T1  - Robust adaptive flow line detection in sewer pipes
JF  - Automation in construction
N2  - As part of a novel approach to automatic sewer inspection, this paper presents a robust algorithm for automatic flow line detection. A large image repository is obtained from about 50,000 m sewers to represent the high variability of real world sewer systems. Automatic image processing combines Canny edge detection, Hough transform for straight lines and cost minimization using Dijkstra's shortest path algorithm. Assuming that flow lines are mostly smoothly connected horizontal structures, piecewise flow line delineation is reduced to a process of selecting adjacent line candidates. Costs are derived from the gap between adjacent candidates and their reliability. A single parameter α enables simple control of the algorithm. The detected flow line may precisely follow the segmented edges (α = 0.0) or minimize gaps at joints (α = 1.0). Both, manual and ground truth-based analysis indicate that α = 0.8 is optimal and independent of the sewer's material. The algorithm forms an essential step to further automation of sewer inspection.
Y1  - 2012
U6  - https://doi.org/10.1016/j.autcon.2011.05.009
SN  - 1872-7891 (E-Journal) ; 0926-5805 (Print)
IS  - 21
SP  - 24
EP  - 31
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - CHAP
A1  - Engels, Elmar
A1  - Schnabel, Holger
T1  - Rapid-control-prototyping of industrial drives for the sercos automation bus
T2  - 13th International Workshop on Mechatronics (MECATRONICS), 2012 9th France-Japan & 7th Europe-Asia Congress on and Research and Education in Mechatronics (REM)
N2  - This article describes the functionality of a MATLAB® library that can be used to develop motion-logic applications in MATLAB programming language for industrial drive and control systems using the well known sercos automation bus. Therewith MATLAB's functionality is extended to designing automation applications from single axis machines up to multi-kinematic robots.
KW  - MATLAB , MLPI , Motion control , Open Core , industrial drives , rapid control prototypin , sercos automation bus
Y1  - 2012
UR  - http://dx.doi.org/10.1109/MECATRONICS.2012.6451005
SN  - 978-1-4673-4771-6
SP  - 177
EP  - 181
ER  - 
TY  - THES
A1  - Schieffer, Andre
T1  - Studies on diversity and coexistence in an experimental microbial community
N2  - Biodiversity and the coexistence of species have puzzled and fascinated biologists since decades and is a hotspot in todays’ natural sciences. Preserving this biodiversity is a great challenge as habitats and environments underlying tremendous changes like climate change and the loss of natural habitats, which are mainly due to anthropogenic influences. The coexistence of numerous species even in homogeneous environments is a stunning feature of natural communities and has been summarized under the term ‘paradox of plankton’. Up to now, there are several mechanisms discussed, which may contribute to local and global diversity of organisms. Several interspecific trade offs have been identified maintaining the coexistence of species like their abilities regarding competition and predator avoidance, their capability to disperse in space and time, and their ability to exploit variable resources. Further, micro-evolutionary dynamics supporting the coexistence of species have been added to our knowledge, and deriving from theoretical deterministic models, non-linear dynamics which describe the temporal fluctuation of abundances of organisms. Whereas competition and predation seem to be clue structural elements within interacting organisms, the intrinsic dynamic behavior – by means of temporal changes in abundance - plays an important role regarding coexistence within a community. The present work sheds light on different factors affecting the coexistence of species using experimental microbial model systems consisting of a bacterivorous ciliate as the predator and two bacteria strains as prey organism. Additionally, another experimental setup consisting of two up to five bacteria species competing for one limiting resource was investigated. Highly controllable chemostat systems were established to exclude extrinsic disturbances. According to theoretical analyses I was able to show - experimentally and theoretically - that phenotypic plasticity of one species within a microbial one-predator-two-prey food web enlarges the range of possible coexistence of all species under different dynamic conditions, compared to a food web without phenotypic plasticity. This was accompanied by non-linear (chaotic) population dynamics within all experimental systems showing phenotypic plasticity. The experiments on the interplay of competition, predation and invasion showed that all aspects have an influence on species coexistence. Under undisturbed controlled conditions all aspects were analyzed in detail and in combination. Populations showed oscillations which were shown by quasi-chaotic attractors in phase space diagrams. Competition experiments with two up to five bacteria species competing for one limiting resource showed that all organisms were able to coexist which was mediated by species oscillations entering a regime of chaos. Besides that fact it was found, that the productivity (biomass) as well as the total cell numbers – under the same nutrition supply – increased by an increasing number of species in the experimental systems. Up to now, the occurrence of non-linear dynamics in well controlled experimental studies has been recognized several times and this phenomenon seemed to be more common in natural systems than generally assumed.
N2  - Biodiversität und die Koexistenz von Arten fasziniert und verblüfft Biologen seit Jahr-zehnten und stellen einen Schwerpunkt in der heutigen Umweltforschung dar. Der Schutz und die Konservierung dieser Mannigfaltigkeit stellen eine große Herausfor-derung dar, da die natürlichen Lebensräume sowie die Umwelt enormen Verände-rungen unterworfen sind, welche meist in einem anthropogenen Ursprung wurzeln. Die Koexistenz vieler Arten, auch in relativ homogenen Habitaten ist ein faszinieren-des Charakteristikum natürlicher Lebensgemeinschaften und wird als ‚Paradox des Planktons‘ bezeichnet. Gegenwärtig werden diverse Ursachen diskutiert, welche vermutlich zur lokalen und globalen Diversität von Organismen beitragen. Einige die-ser möglichen Ursachen, die zur Aufrechterhaltung der Koexistenz der Arten beitra-gen, wurden identifiziert: Das Vermögen der Konkurrenz- und Prädationsvermeidung, die Fähigkeit räumlicher sowie zeitlicher Verteilung, sowie das Vermögen variable Ressourcen zu nutzen. Des Weiteren wurden mikro-evolutionäre Phänomene und Dynamiken identifiziert, sowie, von theoretischen deterministischen Modellen ausge-hend, nichtlineare Dynamiken, welche die zeitlichen Schwankungen der Abundanzen von Organismen beschreiben. Diese Aspekte stellen die Schlüsselkomponenten zwi-schen interagierenden Organismen dar, wobei das intrinsiche, nicht lineare dynami-sche Verhalten in Form von zeitlichen Veränderungen in Abundanzen eine zusätzli-che entscheidende Rolle bezüglich der Koexistenz von Arten spielen kann. Einige dieser Aspekte wurden in der vorliegenden Arbeit untersucht. In Anlehnung an theoretische Analysen konnte experimentell sowie theoretisch gezeigt werden, dass phänotypische Plastizität in einer Bakterienart in einem mikrobiellen Ein-Räuber-zwei-Beute-Nahrungsgewebe den Bereich der möglichen Koexistenz unter sich än-dernden experimentellen Bedingungen (Änderungen der Durchflussraten der Chemostate) – im direkten Vergleich zu einem experimentellen Nahrungsgewebe ohne phänotypische Plastizität – erweitern kann. Dies wurde begleitet durch nicht lineare Abundanzschwankungen in den Populationen aller untersuchten Versuchs-ansätze. In weiteren Untersuchungen wurde das Zusammenspiel von Konkurrenz, Prädation und Invasion in einer experimentellen mikrobiellen Gemeinschaft untersucht. Unter kontrollierten Bedingungen konnten diese Aspekte detailliert untersucht werden und es konnten Aufschlüsse darüber gewonnen werden, welche Reaktionen (Interaktionen) innerhalb der untersuchten Gemeinschaften stattfinden. Im Versuchsverlauf wurden Veränderungen in den Abundanzen sowie chaotische Schwankungen der Zellzahlen festgestellt. In Konkurrenzexperimenten von zwei bis zu fünf um eine limitierende Ressource konkurrierende Bakterienarten konnte gezeigt werden, dass alle Arten – vermittelt durch chaotische Abundanzschwankungen – nebeneinander koexistieren konnten. Begleitend dazu wurde herausgefunden, dass die Produktivität (Biomasse) sowie die Gesamtzellzahl bei gleicher Nahrungsverfügbarkeit der experimentellen Systeme mit steigender Artenzahl zunehmen. Gegenwärtig ist das Auftreten von Chaos in gut kontrollierten experimentellen Studien vereinzelt beobachtet worden, wobei dieses Phänomen jedoch häufiger in der Natur aufzutreten scheint als generell vermutet.
Y1  - 2012
N1  - Köln, Univ., Diss., 2012
ER  - 
TY  - JOUR
A1  - Nomdedeu, Mar Monsonis
A1  - Willen, Christine
A1  - Schieffer, Andre
A1  - Arndt, Hartmut
T1  - Temperature-dependent ranges of coexistence in a model of a two-prey-one-predator microbial food web
JF  - Marine Biology
N2  - The objective of our study was to analyze the effects of temperature on the population dynamics of a three-species food web consisting of two prey bacteria (Pedobacter sp. and Acinetobacter johnsonii) and a protozoan predator (Tetrahymena pyriformis) as model organisms. We assessed the effects of temperature on the growth rates of all three species with the objective of developing a model with four differential equations based on the experimental data. The following hypotheses were tested at a theoretical level: Firstly, temperature changes can affect the dynamic behavior of a system by temperature-dependent parameters and interactions and secondly, food web response to temperature cannot be derived from the single species temperature response. The main outcome of the study is that temperature changes affect the parameter range where coexistence is possible within all three species. This has significant consequences on our ideas regarding the evaluation of effects of global warming.
Y1  - 2012
U6  - https://doi.org/10.1007/s00227-012-1966-x
SN  - 1432-1793
VL  - 159
IS  - 11
SP  - 2423
EP  - 2430
PB  - Springer
CY  - Berlin
ER  - 
TY  - CHAP
A1  - Duong, Minh Tuan
A1  - Nguyen, Nhu Hunyh
A1  - Staat, Manfred
T1  - Finite Element Implementation of a 3D Fung-type Model
T2  - ESMC-2012 - 8th European Solid Mechanics Conference, Graz, Austria, July 9-13, 2012
Y1  - 2012
SN  - 978-3-85125-223-1
PB  - Verlag d. Technischen Universität Graz
CY  - Graz
ER  - 
TY  - CHAP
A1  - Frotscher, Ralf
A1  - Raatschen, Hans-Jürgen
A1  - Staat, Manfred
ED  - Holzapfel, Gerhard A.
T1  - Effectiveness of the edge-based smoothed finite element method applied to soft biological tissues
T2  - ESMC-2012 - 8th European Solid Mechanics Conference, Graz, Austria, July 9-13, 2012
Y1  - 2012
SN  - 978-3-85125-223-1
PB  - Verlag d. Technischen Universität Graz
CY  - Graz
ER  - 
TY  - CHAP
A1  - Streun, M.
A1  - Al-Kaddoum, R.
A1  - Parl, C.
A1  - Pietrzyk, U.
A1  - Ziemons, Karl
A1  - Waasen, S. van
T1  - Simulation studies of optical photons in monolithic block scintillators
T2  - 2011 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)
N2  - The interest in PET detectors with monolithic block scintillators is growing. In order to obtain high spatial resolutions dedicated positioning algorithms are required. But even an ideal algorithm can only deliver information which is provided by the detector. In this simulation study we investigated the light distribution on one surface of cuboid LSO scintillators of different size. Scintillators with a large aspect ratio (small footprint and large height) showed significant position information only for a minimum interaction depth of the gamma particle. The results allow a quantitative estimate for a useful aspect ratio.
Y1  - 2012
SN  - 978-1-4673-0120-6 (electronic ISBN)
SN  - 978-1-4673-0118-3 (print ISBN)
U6  - https://doi.org/10.1109/NSSMIC.2011.6154621
SP  - 1380
EP  - 1382
PB  - IEEE
CY  - New York
ER  - 
TY  - JOUR
A1  - Alexopoulos, Spiros
T1  - Biogas systems: basics, biogas multifunction, principle of fermentation and hybrid application with a solar tower for the treatment of waste animal manure
JF  - Journal of Engineering Science and Technology Review
N2  - Two of the main environmental problems of today’s society are the continuously increasing production of organic wastes as well as the increase of carbon dioxide in the atmosphere and the related green house effect. A way to solve these problems is the production of biogas. Biogas is a combustible gas consisting of methane, carbon dioxide and small amounts of other gases and trace elements. Production of biogas through anaerobic digestion of animal manure and slurries as well as of a wide range of digestible organic wastes and agricultural residues, converts these substrates into electricity and heat and offers a natural fertiliser for agriculture. The microbiological process of decomposition of organic matter, in the absence of oxygen takes place in reactors, called digesters. Biogas can be used as a fuel in a gas turbine or burner and can be used in a hybrid solar tower system offering a solution for waste treatment of agricultural and animal residues. A solar tower system consists of a heliostat field, which concentrates direct solar irradiation on an open volumetric central receiver. The receiver heats up ambient air to temperatures of around 700°C. The hot air’s heat energy is transferred to a steam Rankine cycle in a heat recovery steam generator (HRSG). The steam drives a steam turbine, which in turn drives a generator for producing electricity. In order to increase the operational hours of a solar tower power plant, a heat storage system and/ or hybridization may be considered. The advantage of solar-fossil hybrid power plants, compared to solar-only systems, lies in low additional investment costs due to an adaptable solar share and reduced technical and economical risks. On sunny days the hybrid system operates in a solar-only mode with the central receiver and on cloudy days and at night with the gas turbine only. As an alternative to methane gas, environmentally neutral biogas can be used for operating the gas turbine. Hence, the hybrid system is operated to 100% from renewable energy sources
Y1  - 2012
SN  - 1791-2377
N1  - Special Issue on Renewable Energy Systems
VL  - 5
IS  - 4
SP  - 48
EP  - 55
ER  - 
TY  - GEN
A1  - Baumgartner, Thomas
A1  - Wunderlich, Florian
A1  - Jaunich, Arthur
A1  - Sato, Tomoo
A1  - Bundy, Georg
A1  - Grießmann, Nadine
A1  - Kowalski, Julia
A1  - Burghardt, Stefan
A1  - Hanebrink, Jörg
T1  - Lighting the way: Perspectives on the global lighting market
Y1  - 2012
CY  - McKinsey
ET  - 2nd ed.
ER  - 
TY  - JOUR
A1  - Fischer, Jan-Thomas
A1  - Kowalski, Julia
A1  - Pudasaini, Shiva P.
T1  - Topographic curvature effects in applied avalanche modelling
JF  - Cold Regions Science and Technology
N2  - This paper describes the implementation of topographic curvature effects within the RApid Mass MovementS (RAMMS) snow avalanche simulation toolbox. RAMMS is based on a model similar to shallow water equations with a Coulomb friction relation and the velocity dependent Voellmy drag. It is used for snow avalanche risk assessment in Switzerland. The snow avalanche simulation relies on back calculation of observed avalanches. The calibration of the friction parameters depends on characteristics of the avalanche track. The topographic curvature terms are not yet included in the above mentioned classical model. Here, we fundamentally improve this model by mathematically and physically including the topographic curvature effects. By decomposing the velocity dependent friction into a topography dependent term that accounts for a curvature enhancement in the Coulomb friction, and a topography independent contribution similar to the classical Voellmy drag, we construct a general curvature dependent frictional resistance, and thus propose new extended model equations. With three site-specific examples, we compare the apparent frictional resistance of the new approach, which includes topographic curvature effects, to the classical one. Our simulation results demonstrate substantial effects of the curvature on the flow dynamics e.g., the dynamic pressure distribution along the slope. The comparison of resistance coefficients between the two models demonstrates that the physically based extension presents an improvement to the classical approach. Furthermore a practical example highlights its influence on the pressure outline in the run out zone of the avalanche. Snow avalanche dynamics modeling natural terrain curvature centrifugal force friction coefficients.
KW  - Snow
KW  - Avalanche
Y1  - 2012
U6  - https://doi.org/10.1016/j.coldregions.2012.01.005
SN  - 1872-7441
VL  - 74-75
SP  - 21
EP  - 30
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Olaru, Alexandra Maria
A1  - Kowalski, Julia
A1  - Sethi, Vaishali
A1  - Blümich, Bernhard
T1  - Exchange relaxometry of flow at small Péclet numbers in a glass bead pack
JF  - Journal of Magnetic Resonance (JMR)
N2  - In this paper we consider low Péclet number flow in bead packs. A series of relaxation exchange experiments has been conducted and evaluated by ILT analysis. In the resulting correlation maps, we observed a collapse of the signal and a translation towards smaller relaxation times with increasing flow rates, as well as a signal tilt with respect to the diagonal. In the discussion of the phenomena we present a mathematical theory for relaxation exchange experiments that considers both diffusive and advective transport. We perform simulations based on this theory and discuss them with respect to the conducted experiments.
KW  - NMR exchange relaxometry
KW  - Low-field NMR
Y1  - 2012
U6  - https://doi.org/10.1016/j.jmr.2012.04.015
SN  - 1096-0856
VL  - 220
SP  - 32
EP  - 44
PB  - Elsevier
CY  - Amsterdam
ER  -