@inproceedings{ReckerBosschaertsWagemakersetal.2010, author = {Recker, Elmar and Bosschaerts, Walter and Wagemakers, Rolf and Hendrick, Patrick and Funke, Harald and B{\"o}rner, Sebastian}, title = {Experimental study of a round jet in cross-flow at low momentum ratio}, pages = {13 Seiten}, year = {2010}, abstract = {With the final objective of optimizing the "Micromix" hydrogen combustion principle, a round jet in a laminar cross-flow prior to its combustion is investigated experimentally using Stereoscopic Particle Image Velocimetry. Measurements are performed at a jet to cross-stream momentum ratio of 1 and a Reynolds number, based on the jet diameter and jet velocity, of 1600. The suitability to combine side, top and end views is analyzed statistically. The statistical theory of testing hypotheses, pertaining to the joint distribution of the averaged velocity along intersecting observation planes, is employed. Overall, the averaged velocity fields of the varying observation planes feature homogeneity at a 0.05 significance level. Minor discrepancies are related to the given experimental conditions. By use of image maps, averaged and instantaneous velocity fields, an attempt is made to elucidate the flow physics and a kinematically consistent vortex model is proposed. In the time-averaged flow field, the principal vortical systems were identified and the associated mixing visualized. The jet trajectory and physical dimensions scale with the momentum ratio times the jet diameter. The jet/cross-flow mixture converging upon the span-wise centre-line, the lifting action of the Counter Rotating Vortex Pair and the reversed flow region contribute to the high entrainment and mixedness. It is shown that the jet width is larger on the downstream side as compared to the upstream side of the centre-streamline. The deepest penetration of the particles on the outer boundary occurs in the centre-plane. Meanwhile, with increasing off-centre position, the boundaries all lay further from the centre-line position than does the boundary in the centre-plane, corresponding to a kidney-like shape of the flow cross-section. The generation of the Counter Rotating Vortex Pair and the instability mechanism is documented by instantaneous image maps and vector fields. The necessary circulation for the Counter Rotating Vortex Pair originates from a combined effect of steady in-hole, hanging and wake vortices. The strong cross-flow and jet interaction induces a three-dimensional waving, the stream-wise Counter Rotating Vortex Pair pair, leading to the formation of Ring Like Vortices. A secondary Counter Rotating Vortex Pair forms on top of the primary Counter Rotating Vortex Pair, resulting in mixing by "puffs". Overall, Stereoscopic Particle Image Velocimetry proofed capable of elucidating the Jet in Cross-Flow complex flow field. The gained insight in the mixing process will definitely contribute to the "Micromix" hydrogen combustion optimization.}, language = {en} } @inproceedings{FunkeBoernerRobinsonetal.2010, author = {Funke, Harald and B{\"o}rner, Sebastian and Robinson, A. and Hendrick, P. and Recker, E.}, title = {Low NOx H2 combustion for industrial gas turbines of various power ranges}, year = {2010}, language = {en} } @inproceedings{FunkeRobinsonHendricketal.2010, author = {Funke, Harald and Robinson, A. E. and Hendrick, P. and Wagemakers, R.}, title = {Design and Testing of a Micromix Combustor With Recuperative Wall Cooling for a Hydrogen Fuelled µ-Scale Gas Turbine}, series = {Conference Proceedings ASME Turbo Expo 2010: Power for Land, Sea, and Air. Volume 5: Industrial and Cogeneration; Microturbines and Small Turbomachinery; Oil and Gas Applications; Wind Turbine Technology}, booktitle = {Conference Proceedings ASME Turbo Expo 2010: Power for Land, Sea, and Air. Volume 5: Industrial and Cogeneration; Microturbines and Small Turbomachinery; Oil and Gas Applications; Wind Turbine Technology}, publisher = {ASME}, address = {New York, NY}, isbn = {978-0-7918-4400-7}, doi = {10.1115/GT2010-23453}, pages = {587 -- 596}, year = {2010}, abstract = {For more than a decade up to now there is an ongoing interest in small gas turbines downsized to micro-scale. With their high energy density they offer a great potential as a substitute for today's unwieldy accumulators, found in a variety of applications like laptops, small tools etc. But micro-scale gas turbines could not only be used for generating electricity, they could also produce thrust for powering small unmanned aerial vehicles (UAVs) or similar devices. Beneath all the great design challenges with the rotating parts of the turbomachinery at this small scale, another crucial item is in fact the combustion chamber needed for a safe and reliable operation. With the so called regular micromix burning principle for hydrogen successfully downscaled in an initial combustion chamber prototype of 10 kW energy output, this paper describes a new design attempt aimed at the integration possibilities in a μ-scale gas turbine. For manufacturing the combustion chamber completely out of stainless steel components, a recuperative wall cooling was introduced to keep the temperatures in an acceptable range. Also a new way of an integrated ignition was developed. The detailed description of the prototype's design is followed by an in depth report about the test results. The experimental investigations comprise a set of mass flow variations, coupled with a variation of the equivalence ratio for each mass flow at different inlet temperatures and pressures. With the data obtained by an exhaust gas analysis, a full characterisation concerning combustion efficiency and stability of the prototype chamber is possible. Furthermore the data show a full compliance with the expected operating requirements of the designated μ-scale gas turbine.}, language = {en} } @inproceedings{Ferrein2010, author = {Ferrein, Alexander}, title = {golog.lua: Towards a non-prolog implementation of Golog for embedded systems}, series = {Dagstuhl Seminar Proceedings, Volume 10081}, booktitle = {Dagstuhl Seminar Proceedings, Volume 10081}, doi = {10.4230/DagSemProc.10081.9}, pages = {1 -- 15}, year = {2010}, abstract = {Among many approaches to address the high-level decision making problem for autonomous robots and agents, the robot program¬ming and plan language Golog follows a logic-based deliberative approach, and its successors were successfully deployed in a number of robotics applications over the past ten years. Usually, Golog interpreter are implemented in Prolog, which is not available for our target plat¬form, the bi-ped robot platform Nao. In this paper we sketch our first approach towards a prototype implementation of a Golog interpreter in the scripting language Lua. With the example of the elevator domain we discuss how the basic action theory is specified and how we implemented fluent regression in Lua. One possible advantage of the availability of a Non-Prolog implementation of Golog could be that Golog becomes avail¬able on a larger number of platforms, and also becomes more attractive for roboticists outside the Cognitive Robotics community.}, language = {en} } @article{Ferrein2010, author = {Ferrein, Alexander}, title = {golog.lua: Towards a Non-Prolog Implementation of Golog for Embedded Systems}, publisher = {AAAI}, address = {Menlo Park}, pages = {20 -- 28}, year = {2010}, language = {en} } @inproceedings{FerreinSteinbauer2010, author = {Ferrein, Alexander and Steinbauer, Gerald}, title = {On the Way to High-Level Programming for Resource-Limited Embedded Systems with Golog}, series = {Simulation, Modeling, and Programming for Autonomous Robots}, booktitle = {Simulation, Modeling, and Programming for Autonomous Robots}, publisher = {Springer}, address = {Berlin}, doi = {10.1007/978-3-642-17319-6_23}, pages = {229 -- 240}, year = {2010}, abstract = {In order to allow an autonomous robot to perform non-trivial tasks like to explore a foreign planet the robot has to have deliberative capabilities like reasoning or planning. Logic-based approaches like the programming and planing language Golog and it successors has been successfully used for such decision-making problems. A drawback of this particular programing language is that their interpreter usually are written in Prolog and run on a Prolog back-end. Such back-ends are usually not available or feasible on resource-limited robot systems. In this paper we present our ideas and first results of a re-implementation of the interpreter based on the Lua scripting language which is available on a wide range of systems including small embedded systems.}, language = {en} } @inproceedings{RensVarzinczakMeyeretal.2010, author = {Rens, Gavin and Varzinczak, Ivan and Meyer, Thomas and Ferrein, Alexander}, title = {A Logic for Reasoning about Actions and Explicit Observations}, series = {AI 2010: Advances in Artificial Intelligence}, booktitle = {AI 2010: Advances in Artificial Intelligence}, publisher = {Springer}, address = {Berlin}, doi = {10.1007/978-3-642-17432-2_40}, pages = {395 -- 404}, year = {2010}, abstract = {We propose a formalism for reasoning about actions based on multi-modal logic which allows for expressing observations as first-class objects. We introduce a new modal operator, namely [o |α], which allows us to capture the notion of perceiving an observation given that an action has taken place. Formulae of the type [o |α]ϕ mean 'after perceiving observation o, given α was performed, necessarily ϕ'. In this paper, we focus on the challenges concerning sensing with explicit observations, and acting with nondeterministic effects. We present the syntax and semantics, and a correct and decidable tableau calculus for the logic}, language = {en} } @article{Ferrein2010, author = {Ferrein, Alexander}, title = {Robot controllers for highly dynamic environments with real-time constraints}, series = {K{\"u}nstliche Intelligenz : KI}, volume = {24}, journal = {K{\"u}nstliche Intelligenz : KI}, number = {2}, publisher = {Springer}, address = {Heidelberg}, issn = {1610-1987}, doi = {10.1007/s13218-010-0041-3}, pages = {175 -- 178}, year = {2010}, abstract = {In this extended abstract we describe the robot programming and planning language READYLOG, a GOLOG dialect which was developed to support the decision making of robots acting in dynamic real-time domains like robotic soccer. The formal framework of READYLOG, which is based on the situation calculus, features imperative control structures like loops and procedures, allows for decision-theoretic planning, and accounts for a continuously changing world. We developed high-level controllers in READYLOG for our soccer robots in RoboCup's Middle-size league, but also for service robots and for autonomous agents in interactive computer games.}, language = {en} } @inproceedings{NiemuellerFerreinBecketal.2010, author = {Niem{\"u}ller, Tim and Ferrein, Alexander and Beck, Daniel and Lakemeyer, Gerhard}, title = {Design principles of the component-based robot software framework Fawkes}, series = {Simulation, Modeling, and Programming for Autonomous Robots}, booktitle = {Simulation, Modeling, and Programming for Autonomous Robots}, publisher = {Springer}, address = {Berlin}, doi = {10.1007/978-3-642-17319-6_29}, pages = {300 -- 311}, year = {2010}, abstract = {The idea of component-based software engineering was proposed more that 40 years ago, yet only few robotics software frameworks follow these ideas. The main problem with robotics software usually is that it runs on a particular platform and transferring source code to another platform is crucial. In this paper, we present our software framework Fawkes which follows the component-based software design paradigm by featuring a clear component concept with well-defined communication interfaces. We deployed Fawkes on several different robot platforms ranging from service robots to biped soccer robots. Following the component concept with clearly defined communication interfaces shows great benefit when porting robot software from one robot to the other. Fawkes comes with a number of useful plugins for tasks like timing, logging, data visualization, software configuration, and even high-level decision making. These make it particularly easy to create and to debug productive code, shortening the typical development cycle for robot software.}, language = {en} } @inproceedings{NiemuellerFerreinLakemeyer2010, author = {Niem{\"u}ller, Tim and Ferrein, Alexander and Lakemeyer, Gerhard}, title = {A Lua-based behavior engine for controlling the humanoid robot Nao}, series = {RoboCup 2009: Robot Soccer World Cup XIII}, booktitle = {RoboCup 2009: Robot Soccer World Cup XIII}, publisher = {Springer}, address = {Berlin}, doi = {10.1007/978-3-642-11876-0_21}, pages = {240 -- 251}, year = {2010}, abstract = {The high-level decision making process of an autonomous robot can be seen as an hierarchically organised entity, where strategical decisions are made on the topmost layer, while the bottom layer serves as driver for the hardware. In between is a layer with monitoring and reporting functionality. In this paper we propose a behaviour engine for this middle layer which, based on formalism of hybrid state machines (HSMs), bridges the gap between high-level strategic decision making and low-level actuator control. The behaviour engine has to execute and monitor behaviours and reports status information back to the higher level. To be able to call the behaviours or skills hierarchically, we extend the model of HSMs with dependencies and sub-skills. These Skill-HSMs are implemented in the lightweight but expressive Lua scripting language which is well-suited to implement the behaviour engine on our target platform, the humanoid robot Nao.}, language = {en} } @article{FerreinSiebelSteinbauer2010, author = {Ferrein, Alexander and Siebel, Nils T. and Steinbauer, Gerald}, title = {Hybrid control for autonomous systems — Integrating learning, deliberation and reactive control}, series = {Robotics and Autonomous Systems}, volume = {58}, journal = {Robotics and Autonomous Systems}, number = {9}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0921-8890}, doi = {10.1016/j.robot.2010.06.003}, pages = {1037 -- 1038}, year = {2010}, language = {en} } @article{LeimenaArtmannDachwaldetal.2010, author = {Leimena, W. and Artmann, Gerhard and Dachwald, Bernd and Temiz Artmann, Ayseg{\"u}l and Gossmann, Matthias and Digel, Ilya}, title = {Feasibility of an in-situ microbial decontamination of an ice-melting probe}, series = {Eurasian Chemico-Technological Journal}, volume = {12}, journal = {Eurasian Chemico-Technological Journal}, number = {2}, publisher = {Institute of Combustion Problems}, address = {Almaty}, isbn = {1562-3920}, doi = {10.18321/ectj37}, pages = {145 -- 150}, year = {2010}, abstract = {Autonomous robotic systems for penetrating thick ice shells with simultaneous collecting of scientific data are very promising devices in both terrestrial (glacier, climate research) and extra-terrestrial applications. Technical challenges in development of such systems are numerous and include 3D-navigation, an appropriate energy source, motion control, etc. Not less important is the problem of forward contamination of the pristine glacial environments with microorganisms and biomolecules from the surface of the probe. This study was devoted to establishing a laboratory model for microbial contamination of a newly constructed ice-melting probe called IceMole and to analyse the viability and amount of the contaminating microorganisms as a function of distance. The used bacterial strains were Bacillus subtilis (ATCC 6051) and Escherichia coli (ATCC 11775). The main objective was development of an efficient and reliable in-situ decontamination method of the melting probe. Therefore, several chemical substances were tested in respect of their efficacy to eliminate bacteria on the surface of the melting probe at low temperature (0 - 5 °C) and at continuous dilution by melted water. Our study has shown that at least 99.9\% decontamination of the IceMole can be successfully achieved by the injection of 30\% (v/v) hydrogen peroxide and 3\% (v/v) sodium hypochlorite into the drilling site. We were able to reproduce this result in both time-dependent and depth-dependent experiments. The sufficient amount of 30\% (v/v) H₂O₂ or 3\% (v/v) NaClO has been found to be approximately 18 L per cm² of the probe's surface.}, language = {en} } @misc{BehbahaniMaiWalugaetal.2010, author = {Behbahani, Mehdi and Mai, A. and Waluga, C. and Bergmann, B. and Tran, L. and Vonderstein, K. and Behr, Marek and Mottaghy, K.}, title = {Numerical Modeling of Flow-Related Thrombus Formation under Physiological and Non-Physiological Flow Conditions}, series = {Acta Physiologica}, volume = {198}, journal = {Acta Physiologica}, number = {Supplement 677}, publisher = {Wiley-Blackwell}, address = {Oxford}, issn = {1748-1716}, pages = {185}, year = {2010}, abstract = {Aims: Thrombotic complications due to activation of platelets and plasmatic clotting factors belong still to the most investigated topics in the field of study of patho-physiological mechanisms. Mathematical modeling of thrombotic reactions is established and validated in test cases. Aim of this study is to experimentally evaluate and computationally simulate platelets under the influence of well-defined shear flow conditions. Platelet behaviour and reactions are experimentally reproduced, measured and used for validation of the numerical simulation. Methods: A mathematical model of platelet activation, adhesion and aggregation has been implemented into a finite element CFD (Computational Fluid Dynamics) code. The approach is based on the advective and diffusive transport equations for resting platelets, activated platelets and platelet released agonists. Adhesion rates for the reactive surfaces depend on the hemocompatibility properties of the surface and the local shear rate. Experiments with citrate-anticoagulated freshly-drawn whole blood are performed in a perfusion flow chamber as well as in a system of rotating cylinders for Couette and Taylor-vortex flow. Different biomaterials are used. The activation, drop of platelet concentration, adhesion and aggregation are quantified using scanning electron microscopy (SEM) and flow cytometry. Results: Regions and flow conditions with a high potential for thrombus growth could be identified. The experiments clearly show the influence of the blood contacting material and flow properties. By means of SEM diverse platelet adhesion patterns are observed. Numerical analysis can explain the patterns and the degree of thrombus formation. Conclusion: The numerical method shows good agreement with experimental data indicating a possible prediction of initiation of activation and detection of the local adhesion areas in connection with the role of Von-Willebrand-Factor.}, language = {en} } @article{BehbahaniMaiBergmannetal.2010, author = {Behbahani, Mehdi and Mai, A. and Bergmann, B. and Waluga, C. and Behr, Marek and Tran, L. and Vonderstein, K. and Mottaghy, K.}, title = {Modeling and Numerical Simulation of Blood Damage}, year = {2010}, language = {en} } @article{BehbahaniProbstMaietal.2010, author = {Behbahani, Mehdi and Probst, M. and Mai, A. and Behr, Marek and Tran, L. and Vonderstein, K. and Mottaghy, K.}, title = {Numerical Prediction of Blood Damage in Biomedical Devices}, year = {2010}, language = {en} } @article{ProbstBehbahaniBorrmannetal.2010, author = {Probst, M. and Behbahani, Mehdi and Borrmann, E. and Elgeti, S. and Nicolai, M. and Behr, Marek}, title = {Hemodynamic Modeling for Numerical Analysis and Design of Medical Devices}, year = {2010}, language = {en} } @misc{BehbahaniNamWalugaetal.2010, author = {Behbahani, Mehdi and Nam, J. and Waluga, C. and Behr, Marek and Pasquali, M. and Mottaghy, K.}, title = {Modeling and Numerical Analysis of Platelet Activation, Adhesion and Aggregation in Artificial Organs}, series = {ASAIO Journal}, volume = {56}, journal = {ASAIO Journal}, number = {2}, publisher = {Lippincott Williams \& Wilkins}, address = {Philadelphia}, issn = {1538-943X}, doi = {10.1097/01.mat.0000369377.65122.a3}, pages = {85}, year = {2010}, abstract = {Purpose of Study: Thrombosis-related complications are among the leading causes for morbidity and mortality in patients who depend on artificial organs. For the prediction of platelet behavior both the flow conditions inside the device and the thrombogenic properties of the blood-contacting surfaces must be considered. Platelet reactions under the influence of well-defined shear rates are experimentally evaluated and numerically simulated. The approach is intended for the analysis of VAD and oxygenator design. Methods Used: A mathematical model of platelet activation, adhesion and aggregation has been implemented into a finite element CFD (Computational Fluid Dynamics) code. The approach is based on the advective and diffusive transport equations for resting and activated platelets and platelet released agonists. Experiments with citrate-anticoagulated freshly-drawn whole blood are performed in a perfusion flow chamber as well as in a system of rotating cylinders for Couette and Taylor-vortex flow. Different biomaterials are used. The activation, adhesion and aggregation are quantified using scanning electron microscopy and flow cytometry. Summary of Results: Regions and flow conditions with a high potential for thrombus growth could be identified. The experiments clearly show the influence of the blood contacting material and governing shear rates. Numerical analysis can explain observed adhesion patterns and the degree of thrombus formation}, language = {en} } @article{JansenBehbahaniLaumenetal.2010, author = {Jansen, S. V. and Behbahani, Mehdi and Laumen, M. and Kaufmann, T. and Hormes, M. and Behr, Marek and Schmitz-Rode, T. and Steinseifer, U.}, title = {Investigation of Steady Flow Through a Realistic Model of the Thoracic Human Aorta Using 3D Stereo PIV and CFD-Simulation}, series = {ASAIO Journal}, volume = {56}, journal = {ASAIO Journal}, number = {2}, publisher = {Lippincott Williams \& Wilkins}, address = {Philadelphia}, doi = {10.1097/01.mat.0000369377.65122.a3}, pages = {98}, year = {2010}, language = {en} } @misc{NamAroraBehbahanietal.2010, author = {Nam, J. and Arora, D. and Behbahani, Mehdi and Probst, M. and Benkowski, R. and Behr, Marek and Pasquali, M.}, title = {New computational method in hemolysis analysis for artificial heart pump}, series = {ASAIO Journal}, volume = {56}, journal = {ASAIO Journal}, number = {2}, publisher = {Lippincott Williams \& Wilkins}, address = {Philadelphia}, doi = {10.1097/01.mat.0000369377.65122.a3}, pages = {98}, year = {2010}, abstract = {The MicroMed DeBakey ventricular assist device is an axial flow pump designed for providing long-term support to end-stage heartfailure patients. Previously, we presented computational analysis of the blood pump flow. From the analysis, we were able to identify regions of high shear and recirculating flow that may cause blood damage, for example, deformation and fragmentation of the red blood cell (RBC). This mechanical hemolysis can be predicted using a tensor-based blood damage model that is based on the physical properties of the RBCs, for example, the relaxation time of the RBC membrane. However, an extensive and detailed analysis was complicated by the fact that the previous method predicts hemolysis along a finite number of pathlines traversed by the RBCs, possibly omitting parts of the flow domain. Furthermore, it is computationally expensive and is not easily parallelizable. Here, we propose a new method to estimate hemolysis. The method is based on treating the shape of droplet (tensor) as a field variable, like velocity in the Navier-Stokes system. The governing equation for the RBC shape is treated by least-squares finite element method and the volume conservation of the RBC is augmented by Lagrangian multiplier. Unlike the previous method, the proposed method can visualize areas of high RBC strain that is potentially dangerous for mechanical hemolysis. Also, the amount of plasma-free hemoglobin and, consequently, normalized index of hemolysis can be computed as a byproduct. The method is tested in a simple shear flow for validation and an artery graft flow is chosen to show its potential usefulness. Finally, the method is applied to the blood damage estimation for the pump.}, language = {en} } @article{GoettscheHoffschmidtSchmitzetal.2010, author = {G{\"o}ttsche, Joachim and Hoffschmidt, Bernhard and Schmitz, Stefan and Sauerborn, Markus}, title = {Solar Concentrating Systems Using Small Mirror Arrays}, series = {Journal of solar energy engineering}, volume = {132}, journal = {Journal of solar energy engineering}, number = {1}, publisher = {ASME}, address = {New York}, issn = {0199-6231}, doi = {10.1115/1.4000332}, pages = {4 Seiten}, year = {2010}, abstract = {The cost of solar tower power plants is dominated by the heliostat field making up roughly 50\% of investment costs. Classical heliostat design is dominated by mirrors brought into position by steel structures and drives that guarantee high accuracies under wind loads and thermal stress situations. A large fraction of costs is caused by the stiffness requirements of the steel structure, typically resulting in ~ 20 kg/m² steel per mirror area. The typical cost figure of heliostats (figure mentioned by Solucar at Solar Paces Conference, Seville, 2006) is currently in the area of 150 €/m² caused by the increasing price of the necessary raw materials. An interesting option to reduce costs lies in a heliostat design where all moving parts are protected from wind loads. In this way, drives and mechanical layout may be kept less robust, thereby reducing material input and costs. In order to keep the heliostat at an appropriate size, small mirrors (around 10x10 cm²) have to be used, which are placed in a box with a transparent cover. Innovative drive systems are developed in order to obtain a cost-effective design. A 0,5x0,5 m² demonstration unit will be constructed. Tests of the unit are carried out with a high-precision artificial sun unit that imitates the sun's path with an accuracy of less than 0.5 mrad and creates a beam of parallel light with a divergence of less than 4 mrad.}, language = {en} }