24 research outputs found
Bisimilarity of Pushdown Systems is Nonelementary
Given two pushdown systems, the bisimilarity problem asks whether they are
bisimilar. While this problem is known to be decidable our main result states
that it is nonelementary, improving EXPTIME-hardness, which was the previously
best known lower bound for this problem. Our lower bound result holds for
normed pushdown systems as well
Behavior-based Control for Service Robots inspired by Human Motion Patterns : a Robotic Shopping Assistant
Es wurde, unter Verwendung menschenĂ€hnlicher Bewegungsmuster und eines verhaltensbasierten Ansatzes, eine Steuerung fĂŒr mobile Serviceroboter entwickelt, die Aufgabenplanung, globale und lokale Navigation in dynamischen Umgebungen, sowie die gemeinsame AufgabenausfĂŒhrung mit einem Benutzer umfasst. Das Verhaltensnetzwerk besteht aus Modulen mit voneinander unabhĂ€ngigen Aufgaben. Das komplexe Gesamtverhalten des Systems ergibt sich durch die Vereinigung der Einzelverhalten (\u27Emergenz\u27)
Conceptual and procedural mathematical knowledge of beginning mathematics majors and preservice teachers
In light of known challenges in the transition from school to university in mathematics, we investigate differences in the (mathematical) prerequisites of mathematics majors and preservice mathematics teachers. Results show that although there are no significant differences in high school grade point average, mathematical prerequisites of mathematics majors are significantly better than those of preservice mathematics teachers. Differences are higher in conceptual than in procedural knowledge with medium effect sizes between mathematics majors and preservice higher secondary teachers and (very) large effect sizes between mathematics majors and preservice lower secondary or primary school teachers. These results are discussed regarding transition challenges and the fit of prerequisites and chosen study program
Reachability in Two-Dimensional Vector Addition Systems with States is PSPACE-complete
Determining the complexity of the reachability problem for vector addition
systems with states (VASS) is a long-standing open problem in computer science.
Long known to be decidable, the problem to this day lacks any complexity upper
bound whatsoever. In this paper, reachability for two-dimensional VASS is shown
PSPACE-complete. This improves on a previously known doubly exponential time
bound established by Howell, Rosier, Huynh and Yen in 1986. The coverability
and boundedness problems are also noted to be PSPACE-complete. In addition,
some complexity results are given for the reachability problem in
two-dimensional VASS and in integer VASS when numbers are encoded in unary.Comment: 27 pages, 8 figure
Gymnasiales Lehramt Mathematik studieren â eine Ăbersicht zur Studienorganisation in Deutschland
Das gymnasiale Lehramtsstudium der Mathematik ist an deutschen UniversitĂ€ten unterschiedlich organisiert. Traditionell wurden am Studienbeginn die Fachvorlesungen zur Analysis und Linearen Algebra gemeinsam mit Fachstudierenden gehört. In jĂŒngerer Zeit verbreiten sich alternative Modelle z. B. mit BrĂŒckenvorlesungen, die oft spezifisch fĂŒr das Gymnasiallehramt angeboten werden. Sie können gemeinsame Veranstaltungen mit Fachstudierenden ergĂ€nzen oder ersetzen. Dieser Beitrag zeigt auf, welche Modelle wie hĂ€ufig verbreitet sind, und spricht an, welche hochschuldidaktischen Fragen an der Studiengestaltung hĂ€ngen
The Role of Meson Retardation in the NN Interaction above Pion Threshold
A model is developed for the hadronic interaction in the two-nucleon system
above pion threshold which is based on meson, nucleon and degrees of
freedom and which includes full meson retardation in the exchange operators.
For technical reasons, the model allows maximal one meson to be present
explicitly. Thus the Hilbert space contains besides and also
configurations consisting of two nucleons and one meson. For this reason, only
two- and three-body unitarity is obeyed, and the model is suited for reactions
in the two nucleon sector only, where one pion is produced or absorbed.
Starting from a realistic pure nucleonic retarded potential, which had to be
renormalized because of the additional and degrees of freedom, a
reasonable fit to experimental -scattering data could be achieved.Comment: 30 pages revtex including 17 figures, outline of model and discussion
shortened, typos correcte
Bisimilarity of Pushdown Automata is nonelementary
Given two pushdown automata, the bisimilarity problem asks whether the infinite transition systems they induce are bisimilar. While this problem is known to be decidable our main result states that it is nonelementary, improving EXPTIME-hardness, which was the best previously known lower bound for this problem. Our lower bound result holds for normed pushdown automata as well
FlÀchendeckende Erfassung der Vegetation als Instrument der rÀumlichen Planung, dargestellt am Beispiel einer Vegetationstypenkarte
Nach einem kurzen Ăberblick ĂŒber die unterschiedlichen AnsĂ€tze flĂ€chendeckender Vegetationskartierungen in Japan und Deutschland wird die Vegetationstypenkarte DĂŒsseldorf als Fallbeispiel erlĂ€utert. Die Karte setzt die reale Vegetation ins VerhĂ€ltnis mit der FlĂ€chennutzung und der Baustruktur und aggregiert 37 Vegetationstypen aus den Haupttypen "Vegetation des bebauten Bereichs", "Ruderalvegetation", "Vegetation des landwirtschaftlich genutzten Bereichs", "Vegetation des forstwirtschaftlich genutzten Bereichs" und "GewĂ€sservegetation". Zu den einzelnen Typen werden Planungsziele vor allem aus Sicht des Biotop- und Artenschutzes formuliert.
Die Vegetationstypenkarte ist als ErgĂ€nzung zu den Karten der potentiell natĂŒrlichen Vegetation in der Stadtlandschaft und zu den meist selektiven Stadtbiotopkartierungen zu verstehen