268 research outputs found
The Power of Ideas: Esotericism, Historicism, and the Limits of Discourse
No full textThis article is a response to the reviews by Giovanni Filoramo, Olav Hammer, Bernd-Christian Otto, Marco Pasi, and Michael Stausberg of Wouter J. Hanegraaff's book Esotericism and the Academy: Rejected Knowledge in Western Culture. The author attempts to clarify his view of the relation between history and theory, and between intellectual history and discourse theory in particular; he provides a summary of his motivations for writing the book and of its main argument; he concludes by addressing a number of theoretical issues raised by the respondents
Diagnosis and treatment of complicated and uncomplicated appendicitis
No full textAppendicitis is one of the most common causes of abdominal pain. Knowledge about appendicitis is already extensive. However, not too long ago a new theory emerged; two entities of appendicitis can be distinguished (complicated and uncomplicated). This provides new opportunities and challenges in the diagnosis and treatment of appendicitis. This thesis focuses on the treatment and diagnostics of complicated and uncomplicated appendicitis. This thesis contains several studies concerning the importance of differentiating between complicated and uncomplicated appendicitis, described the diagnostic capacity of imaging in discriminating complicated from uncomplicated appendicitis, involves the opinion of the average Dutch citizen concerning non-operative versus operative treatment for uncomplicated appendicitis and includes a study protocol which aims to externally validate and optimize a scoring system to rule out complicated appendicitis. The thesis also comprises a summary of the Dutch guideline for acute appendicitis
BOM@ERCIM - Towards an open access policy For ERCIM
No full textThis working paper presents collects background elements that have been discussed when designing the set of recommendations expressed in the BOM report. Such background elements highlight the key role current and future repositories may play in the open access arena
Een beeld van een kust: Inspiratie voor de Kustnota
No full textDe kust als spiegel / Maurits Groen De levende kust / Govert D. Geldof Integraal beleid : te kust en te keur? / Gerrit Hagelstein en Philip Idenburg De nieuwe kusten van Noordzee en IJsselmeer / Wouter van Dieren De kust als menselijke gradiënt / Reinier Jan Scheele Duinen in een levende kust / Helias Udo de Haas Het verlangen naar de kust : de kust als toeristisch-recreatief domein / Theo Beckers De kust over 25 jaar : een normatief gezichtspunt / Karel Soudijn Een beeld van kust / Anne van der Meidenkustnot
Centralized and decentralized control of structural vibration and sound radiation
No full textThis paper examines the performance of centralized and decentralized feedback controllers on a plate with multiple colocated velocity sensors and force actuators. The performance is measured by the reduction in either kinetic energy or sound radiation, when the plate is excited with a randomly distributed, white pressure field or colored noise. The trade-off between performance and control effort is examined for each case. The controllers examined are decentralized absolute velocity feedback, centralized absolute velocity feedback control and linear quadratic Gaussian (LQG) control. It is seen that, despite the fact that LQG control is a centralized, dynamic controller, there is little overall performance improvement in comparison to decentralized direct velocity feedback control if both are limited to the same control effort
Design of the European Lunar Penetrator (ELUPE) Descent Module Controller
No full textTo obtain unambiguous ground truth of water-ice residing in permanently shaded regions of the Moon and to characterise the local regolith, ESA considers a mission involving an instrumented penetrator implanted there by high-speed impact. Released into lunar orbit, the European Lunar Penetrator (ELUPE) Descent Module will autonomously traverse a controlled trajectory to its designated target. The associated attitude control problem involves highly nonlinear large-angle slew manoeuvres and unstable minor-axis spin manoeuvres. To establish a benchmark, a controller based on classical control techniques was designed, verified and tested in a simulation. Legacy control algorithms were implemented and extended. A thruster management function was developed to translate the control commands into thruster actions. For the simulator, accurate models of the descent module and its environment were created.A Monte Carlo simulation was run to determine the success rate of the ELUPE mission from a descent-and-landing perspective, and to assess the performance of the controller under off-nominal conditions. From the results, it was found that the success rate was 58.5% for a surface slope of 20°, and 74.2% for a slope of 10° or lower. Key factors affecting the success rate were identified to be the centre-of-mass offset and the solid rocket motor thrust misalignment angle. As further constraining these parameters would be unrealistic, it was recommended to modify the thrust curve of the solid rocket motor to improve the success rate.Analysis of the attack angle and the nutation angle just prior to impact, revealed their success criteria were met in 98.7% and 99.8% of all cases, respectively. These successful results confirmed the attitude control problem could be satisfactorily solved by a 'classical' controller. However, despite its good global performance, the proposed controller was found to also exhibit some serious shortcomings. For this reason, it was recommended to explore the possibilities for a different controller.To the best of the author's knowledge, this thesis represented the first known attempt at designing a comprehensive controller for a fully actuated, thruster-controlled penetrator mission targeted for an airless body. In addition, it was the first known study to provide insight into the feasibility and success rate of such a mission from a descent-and-landing perspective.Aerospace Engineerin
A Decentralized Recovery Method for Air Traffic Conflicts
No full textIn an effort to increase airspace capacity, new methods for the decentralization of air traffic control have been a topic for research since the early nineties. The Modified Voltage Potential is a method to provide decentralized conflict detection and resolution. Through this method, aircraft can fly direct routes while resolving conflicts in a distributed manner. Though successfully implemented in various studies, its behavior in conflicts where aircraft are flying near parallel tracks has raised concern. It was found that problems can arise during the recovery after the conflict resolution, the phase where an aircraft regards the conflict as resolved and reverts to its desired velocity. To improve the Modified Voltage Potential's behavior during recovery, a modification is proposed. Through the use of two criteria, aircraft evaluate whether a conflict is resolved and if they can revert to their initial or desired velocity. Through analysis of a state-based solution space and an experiment, this study finds that the proposed recovery method significantly improves the stability, efficiency, and safety of the MVP method.Aerospace Engineerin
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