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- Development of the First Force-Controlled Robot for Otoneurosurgery (2003)
- Objective: In some surgical specialties, e.g. orthopedics, robots are already used in the operating room for bony milling work. Oto- and otoneurosurgery may also greatly benefit by robotic enhanced precision. Study Design: Experimental study on robotic milling on oak wood and human temporal bone specimen. Methods: A standard industrial robot with a 6 degrees-of-freedom serial kinematics was used with force feedback to proportionally control the robot speed. Different milling modes and characteristic path parameters were evaluated to generate milling paths based on CAD geometry data of a cochlear implant and an implantable hearing system. Results: The best suited strategy proofed to be the spiral horizontal milling mode with the burr held perpendicularly to the temporal bone surface. In order to avoid high grooves, the distance in between paths should equal half the radius of the cutting burr head. Due to the vibration of the robot’s own motors, a rather high oscillation of the standard deviation of forces was encountered. This oscillation dropped drastically to nearly 0 N, when the burr head reached contact with the dura mater due to its damping characteristics. The cutting burr could be moved a long time on the dura without damaging it, because of its rather blunt head. The robot moved the burr very smoothly according to the encountered resistances. Conclusion: This is the first development of an functioning robotic milling procedure for otoneurosurgery with force-based speed control. It is planned to implement ultrasound-based local navigation and to perform robotic mastoidectomy.

- Akademisches Lehrmaterial online (2003)
- Kurzer Vortrag über den Dienst AKLEON. Es wird ein Überblick über die Nutzungsmöglichkeiten sowie die interne Realisierung des Dienstes gegeben.

- Embedding a Chained Lin-Kernighan Algorithm into a Distributed Algorithm (2004)
- The Chained Lin-Kernighan algorithm (CLK) is one of the best heuristics to solve Traveling Salesman Problems (TSP). In this paper a distributed algorithm is proposed, were nodes in a network locally optimize TSP instances by using the CLK algorithm. Within an Evolutionary Algorithm (EA) network-based framework the resulting tours are modified and exchanged with neighboring nodes. We show that the distributed variant finds better tours compared to the original CLK given the same amount of computation time. For instance fl3795, the original CLK got stuck in local optima in each of 10 runs, whereas the distributed algorithm found optimal tours in each run requiring less than 10 CPU minutes per node on average in an 8 node setup. For instance sw24978, the distributed algorithm had an average solution quality of 0.050% above the optimum, compared to CLK's average solution of 0.119% above the optimum given the same total CPU time (104 seconds). Considering the best tours of both variants for this instance, the distributed algorithm is 0.033% above the optimum and the CLK algorithm 0.099%.

- Relationship between Alternating omega-Automata and Symbolically Represented Nondeterministic omega-Automata (2005)
- There is a well known relationship between alternating automata on finite words and symbolically represented nondeterministic automata on finite words. This relationship is of practical relevance because it allows to combine the advantages of alternating and symbolically represented nondeterministic automata on finite words. However, for infinite words the situation is unclear. Therefore, this work investigates the relationship between alternating omega-automata and symbolically represented nondeterministic omega-automata. Thereby, we identify classes of alternating omega-automata that are as expressive as safety, liveness and deterministic prefix automata, respectively. Moreover, some very simple symbolic nondeterminisation procedures are developed for the classes corresponding to safety and liveness properties.

- Adding Position Structures to Katja (2005)
- This document introduces the extension of Katja to support position structures and explains the subtleties of their application as well as the design decisions made and problems solved with respect to their implementation. The Katja system was first introduced by Jan Schäfer in the context of his project work and is based on the MAX system developed by Arnd Poetzsch-Heffter.

- Evaluation eines Verschmelzungsalgorithmus für Lösungen des Handlungsreisendenproblems (2005)
- Das Handlungsreisendenproblem ist eines der bekanntesten NP-vollständigen kombinatorischen Optimierungsprobleme. Algorithmen mit unterschiedlichen Konzepten und Strategien wurden entwickelt, die sich in Lösungsqualität und Laufzeit unterscheiden. Ein vergleichsweise neuer Ansatz stellt jedoch das Kombinieren vorhandener Lösungen dar. Hier werden die Kantenmengen gegebener Handlungsreisendertouren als Ausgangsbasis für weitere Optimierungen verwendet. Erste Veröffentlichungen zu diesem Gebiet stellen bereits vielversprechende Ergebnisse vor, die nachfolgend vertieft evaluiert werden.

- Simple Loose Ownership Domains (2006)
- Ownership Domains generalize ownership types. They support programming patterns like iterators that are not possible with ordinary ownership types. However, they are still too restrictive for cases in which an object X wants to access the public domains of an arbitrary number of other objects, which often happens in observer scenarios. To overcome this restriction, we developed so-called loose domains which abstract over several precise domains. That is, similar to the relation between supertypes and subtypes we have a relation between loose and precise domains. In addition, we simplified ownership domains by reducing the number of domains per object to two and hard-wiring the access permissions between domains. We formalized the resulting type system for an OO core language and proved type soundness and a fundamental accessibility property.

- Formalisation of the UML Profile for SDL - A Case Study (2006)
- With the UML 2.0 standard, the Unified Modeling Language took a big step towards SDL, incorporating many features of the language. SDL is a mature and complete language with formal semantics. The Z.109 standard defines a UML Profile for SDL, mapping UML constructs to corresponding counterparts in SDL, giving them a precise semantics. In this report, we present a case study for the formalisation of the Z.109 standard. The formal definition makes the mapping precise and can be used to derive tool support.

- Redesign and Enhancement of the Katja System (2006)
- Katja is a tool generating order-sorted recursive data types as well as position types for Java, from specifications using an enhanced ML like notation. Katja’s main features are its conciseness of specifications, the rich interface provided by the generated code and the Java atypical immutability of types. After several stages of extending and maintaining the Katja project, it became apparent many changes had to be done. The original design of Katja wasn’t prepared for the introduction of several backends, the introduction of position sorts and constant feature enhancements and bug fixes. By supplying this report Katja reaches release status for the first time.