2,160 research outputs found
Interview mit Prof. Kerstin Schill, Professorin an der Universität Bremen
No full textByline: Ubbo Visser (1) Author Affiliation: (1) Department of Computer Science, University of Miami, Coral Gables, FL, 33124, USA Article History: Registration Date: 10/10/2011 Online Date: 19/10/2011Academi
Interview mit Prof. Wolfgang Wahlster, Leiter des DFKI und Professor an der Universität des Saarlandes
No full textByline: Ubbo Visser (1) Author Affiliation: (1) Department of Computer Science, University of Miami, Coral Gables, FL, 33124, USA Article History: Registration Date: 10/10/2011 Online Date: 19/10/2011Academi
KI und Robotik fur das Human Brain Project
No full textByline: Ubbo Visser (1) Author Affiliation: (1) Department of Computer Science, University of Miami, Coral Gables, FL, 33146, USA Article History: Registration Date: 17/09/2014 Online Date: 02/10/2014Academi
Eelco Visser - An Exceptional SLE Researcher
No full textThese notes honor Eelco Visser as an exceptional member of the Software Language Engineering (SLE) community. The notes are authored from the perspective of an SLE co-founder and a continuous SLE supporter. As an inevitable side effect, a short history of SLE is captured. The commemoration begins with Eelco’s role in launching the SLE conference. The commemoration continues with Eelco’s contributions as an author and his involvement with running the conference and working towards an SLE Body of Knowledge (SLEBoK). The commemoration ends with recalling Eelco’s role as the de-facto SLE photographer
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An Omni-Directional Kick Engine for NAO Humanoid Robot
No full textIncorporating a dynamic kick engine that is both fast and effective is pivotal to be competitive in one of the world’s biggest AI and robotics initiative: RoboCup. Using the NAO robot as a testbed, we developed a dynamic kick engine that can generate a kick trajectory with an arbitrary direction without prior input or knowledge of the parameters of the kick. The trajectories are generated using cubic splines, sextic polynomials, and cubic Hermite splines, and the trajectories are executed while the robot is dynamically balancing on one foot. When the robot swings the leg for the kick motion, unprecedented forces might be applied on the robot, and to compensate for these forces, we developed a Zero Moment Point (ZMP) based preview controller that minimizes the ZMP error. Although a variety of kick engines have been implemented by others, there are only a few papers on how kick engine parameters have been optimized to give an effective kick or even a kick that minimizes energy consumption and time. Parameters such as kick configuration, limit of the robot, or shape of the polynomial can be optimized. We propose an optimization framework based on the Webots simulator to optimize these parameters. We also integrated a state-of- the-art walk engine from Seekircher and Visser and kick controller from Pena, Masterjohn, and Visser to generate a kick while walking. Experiments of the physical robot show promising results.</p
Application of sediment transport formulae to sand-dike breach erosion
No full textThe Technical Advisory Committee on Water Defences in the Netherlands has decided to develop a mathematical model for breach erosion in dunes and dikes, with which it will be possible to predict the growth of the breach and the discharge rate through the breach in case of a dike-burst. An essential part of such a mathematical model is the description of the entrainment of the sediment (sand or clay) and its transport through the breach. The process of breach erosion, especially in the first phases, is characterized by relatively steep slopes and large flow velocities. None of the existing sediment transport formulae has been derived and tested for these circumstances. This report presents the results of an investigation into the applicability of sediment transport formulae to sand-dike breach erosion. In view of the steep slopes and the large flow velocities, the following sediment transport conceptions have been included in the study: formulae for sand-water mixture flows: Wilson (1966), Wilson (1987), Mastbergen and Winterwerp (1987); formulae for sediment transport in flows on relatively steep slopes: Mizuyama (1977), Smart and Jaeggi (1983), Bathurst et al. (1987), Takahashi (1987), Rickenmann (1991); formulae for river regimes which have been tested for (relatively) large flow velocities (large shear stress velocities): Engelund and Hansen (1967), Van Rijn (1984a, 1984c); energetics-based sediment transport conceptions: Bagnold (1963, 1966), Yang (1979), Bagnold-Bailard, see Bailard (1981), Bagnold-Visser, see Visser (1988), these last two formulae are modifications of the original conception of Bagnold (1963, 1966); formulae for debris flows: Takahashi (1978, 1980, 1987, 1991). These sediment transport formulae, combined with Galappatti's model (1983) for the pickup of sediment, are compared with the data of two laboratory experiments (Schelde Flume experiments, see Steetzel and Visser, 1992a, 1992b) and the data of a field experiment (Zwin'89 experiment, see Visser et al., 1990). Experimental sediment transport rates have been determined as volumes of sand eroded over a certain period of time. All tests concern super-critical flow (Froude number Fr > 1, i.e. here 2.8<5 Fr<5 4.1), large values for Shields' mobility parameter (10 < theta < 100) and high concentrations (depth-averaged values rising up to about 0.25 by volume). Most of the tested sediment transport formulae predict sand transport rates being much larger than the observed quantities. Only the Bagnold-Visser formula, see Visser (1988), predicts sand transport rates within a factor two of the experimental values. With the formulation of Van Rijn (1984a, 1984c) this is possible within about a factor three. All other formulae give larger deviations from the experimental data. These conclusions hold for the three initial phases of the process of breach erosion, when the flow is supercritical, and confirm the good results obtained up to now with the BagnoldVisser formula, see Visser (1988, 1994). Once more it should be emphasized that this formula has not been derived for a situation where the rate of sand entrainment is so large as in the first three phases of the breach erosion process (this applies to both the energeticsbased method and the semi-empirical determination of the efficiency factor). The relatively large entrainment of sediment causes a relatively large increase of both the flow rate and the sediment concentration of the sand-water mixture along the inner slope (so that the effect of 'hindered entrainment' is possibly not negligible). Further study is necessary to establish the effects of the large rate of sediment entrainment on the breach erosion process. For the time being it is recommended to apply the formula of Bagnold-Visser in a mathematical breach growth model for the description of the first phases (i.e. as long as the flow is supercritical) of the breach erosion process. The present study does not recommend a formula for the important later phases of breach growth (when the flows becomes subcritical), in which most of the breach erosion takes place and in which also the dimensions of the ultimate breach are determined. Probably the data of the recent Zwin'94 field experiment (see Visser et al, 1995) will allow such a recommendation in the near future. For the present the conclusion of Voogt et al. (1991) is still valid, i.e. that the formulae of Engelund and Hansen (1967) and in particular Van Rijn (1984a, 1984c) can also be applied for relatively large current velocities in subcritical flow.Civil Engineering and Geoscience
TopLeague and Bundesliga Manager: New Generation Online Soccer Games
No full textThis paper describes a new generation online soccer manager. More than 210,000 users operate TopLeague and the Official Bundesliga Manager, complex real-time soccer simulators that are based on actual data of real professional soccer players. The underlying technology is a hierarchical three-tier multiagent system that consists of autonomous BDI agents and allows dynamic group structures (e.g. an emergent situation for a wing attack). The German Bundesliga, one of the most prestigious soccer leagues in the world, adopted this AI system for their official web site. The online games run seamlessly in a web browser with a state-of-the-art 3D visualization engine. Fundamental research within the domain of the RoboCup simulation league is the basis for this technology. We will describe the architecture of the multiagent system (MAS) in this paper, discuss motion capture techniques for graphical animation, and reveal details about user acceptance of the games
Discussie. Mondialisering, groei en ongelijkheid. Antwoord aan Hans Visser en Robert Went
No full textGlobalization, Growth, and Inequality: A Response to Hans Visser and Robert Went.
In a reply to criticisms by Hans Visser and Robert Went (2002) of the author\u27s "Mondialisering en de mondiale welvaartskloof: trends in inkomensverschillen in de wereld, 1950-1998" ([Globalization and the Global Welfare Gap: Trends in Income Disparities in the World, 1950-1998] 2002), it is argued that the author and his critics are speaking of different things. Visser approves of globalization "under certain conditions," whereas Went aligns himself with antiglobalists. It is acknowledged that the definition of globalization is a problematic one, and that it can be argued that globalization as a process began in 1492. What is at issue is the prevalence of poverty in the world, and whether the globalized economies of the world ameliorate or perpetuate this poverty. 11 References. A. Siege
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