On the max-algebraic core of a nonnegative matrix

The max-algebraic core of a nonnegative matrix is the intersection of column spans of all max-algebraic matrix powers. Here we investigate the action of a matrix on its core. Being closely related to ultimate periodicity of matrix powers, this study leads us to new modifications and geometric characterizations of robust, orbit periodic and weakly stable matrices.Comment: 27 page

The combination of spatial access methods and computational geometry in geographic database systems

Geographic database systems, known as geographic information systems (GISs) particularly among non-computer scientists, are one of the most important applications of the very active research area named spatial database systems. Consequently following the database approach, a GIS hag to be seamless, i.e. store the complete area of interest (e.g. the whole world) in one database map. For exhibiting acceptable performance a seamless GIS hag to use spatial access methods. Due to the complexity of query and analysis operations on geographic objects, state-of-the-art computational geomeny concepts have to be used in implementing these operations. In this paper, we present GIS operations based on the compuational geomeny technique plane sweep. Specifically, we show how the two ingredients spatial access methods and computational geomeny concepts can be combined für improving the performance of GIS operations. The fruitfulness of this combination is based on the fact that spatial access methods efficiently provide the data at the time when computational geomeny algorithms need it für processing. Additionally, this combination avoids page faults and facilitates the parallelization of the algorithms.

La reforma del federalismo en Alemania. Fines, negociaciones, resultados

L’objecte de l’article és l’estudi de la primera fase de reforma del federalisme,que va entrar en vigor l’1 de setembre de 2006, i que, partint de les nombroses reformes constitucionals empreses des de la creació de la República Federal d’Alemanya, ha portat a la reorganització del sistema de distribució de competències entre Bund i Länder. Després d’estudiar lescauses últimes de la reforma, l’autor analitza el procediment per dur-la a terme, els treballs de la Comissió sobre el federalisme i la culminació de lar eforma després de les eleccions generals. Després de considerar tant els assoliments com les qüestions no resoltes per la reforma, l’autor conclou que no es pot considerar que hi hagi hagut un guanyador clar com a conseqüència dels canvis introduïts, i es mostra crític amb alguns resultats de la reforma, especialment en l’àmbit competencial i, en particular, en relació amb la nova tècnica competencial que permet en certes matèries al Bund i als Länder dictar normes que substitueixin successivament les de l’altre ens.The object of the article is to study the first phase in the reform of federalism, which came into force on 1 Sept 2006 and that, based on the numerous constitutional reforms undertaken since the creation of the Federal Republic of Germany, has led to reorganization of the system to distribute competences between Bund and Länder. After studying the ultimate causes of there form, the author analyses the procedure to carry it out, the work by the Commission on federalism and the culmination of the reform after the general elections. After considering both the achievements as well as the matters not resolved by the reform, the author concludes that one may not consider a clear winner has appeared due to the changes enacted and he is also critical about some results of the reform, especially in the field of competences and, in particular, in relation to the new competence technique, that allows the Bund and Länder to issue regulations on certain matters that successively substitute those of the other body.El objeto del artículo es el estudio de la primera fase de reforma del federalismo, que entró en vigor el 1 de septiembre de 2006, y que, partiendo de las numerosas reformas constitucionales acometidas desde la creación de la República Federal de Alemania, ha llevado a la reorganización del sistema de distribución de competencias entre Bund y Länder. Tras estudiar las causas últimas de la reforma, el autor analiza el procedimiento para llevarla acabo, los trabajos de la Comisión sobre el federalismo y la culminación de la reforma tras las elecciones generales. Después de considerar tanto los logros como las cuestiones no resueltas por la reforma, el autor concluye que no puede considerarse que haya habido un ganador claro como consecuencia de los cambios introducidos, y se muestra crítico con algunos resultados de la reforma, especialmente en el ámbito competencial y, en particular, en relación con la nueva técnica competencial que permite en ciertas materias al Bund y a los Länder dictar normas que sustituyan sucesivamente a las del otro ente