Real-time output trajectory tracking neural sliding mode controller for induction motors

This paper deals with real-time discrete adaptive output trajectory tracking for induction motors in the presence of bounded disturbances. A recurrent high order neural network structure is used to design a nonlinear observer and based on this model, a discrete-time control law is derived, which combines discrete-time block control and sliding modes techniques. Applicability of the scheme is illustrated via experimental results in real-time for a three phase induction motor.     

Discrete-time modeling and control of a boost converter by means of a variational integrator and sliding modes

This work deals with the discrete-time modeling of a boost DC-to-DC power converter by means of a discrete Lagrangian formulation based on the midpoint rule integration method. Then in the basis of this model, a discrete-time sliding mode regulator is designed in order to force the boost circuit to track a DC-biased sinusoidal signal. Simulations and experimental tests are carried on where the great performance of the proposed methodology is verified.     

The skeleton in the closet: should historians of science care about the history of mathematics?

Up until the 1950s, the history of mathematics was an integral part of the history of science. To George Sarton and his contemporaries, mathematics was the rational skeleton that organized science and held it together, and its history was a fundamental component of the broader history of science. But when historians began focusing on the cultural roots of science rather than its rational structure, the study of mathematics was marginalized and ultimately excluded from the history of science. The alienation between the two fields is detrimental to both, and in recent years there has been a sustained effort to reestablish meaningful communication between the two. This time, however, mathematics is seen not as the static skeleton of science but, instead, as a dynamic and historically evolving field in its own right-just like science itself. The new approach allows for a culturally sensitive study of mathematics, as well as a new and fruitful relationship between the history of science and the history of mathematics. The essays in this Focus section offer a sampling of the new approaches, opening the way to a rapprochement between fields that have gone their separate ways but should by rights be closely interconnected.     

The superstar phenomenon in the knowledge management and intellectual capital academic discipline

This paper reports on the first documented attempt to investigate the presence of the superstar (or Matthew) effect in the knowledge management and intellectual capital (KM/IC) scholarly discipline. The Yule–Simon model and Lotka's square law were applied to the publication data obtained from 2175 articles from 11 KM/IC journals. Based on the findings, it was concluded that the KM/IC discipline represents a very young, attractive academic field that welcomes contributions from a variety of academics and practitioners. In their paper acceptance decisions, KM/IC journal editors are not biased towards a small group of highly productive researchers, which is a positive sign that the field has been progressing in the right direction. The discipline is driven more by academics than by practitioners, and the distribution of articles is more concentrated among a few academic but not practitioner institutions. It was also observed that the Yule–Simon model and Lotka's square law may produce different distributions with respect to institutions.     

Verteilte Metadatenverwaltung und Anfragebearbeitung für Internet-Datenquellen

Wir pr?sentieren in dieser Arbeit das ObjectGlobe-System, ein offenes und verteiltes Anfragebearbeitungssystem auf Internet-Datenquellen. ObjectGlobe erweitert die begrenzten F?higkeiten des Internets bezüglich Anfragebearbeitung, indem es einen offenen Marktplatz schafft, in dem eine Vielzahl von Anbietern Rechenzeit, Daten und Anfrageoperatoren bereitstellen. Den Schwerpunkt dieses Beitrags bildet die im Rahmen des ObjectGlobe-Projekts entwickelte Metadatenverwaltung MDV, ein verteiltes Metadaten-Management-System. Es besitzt eine 3-schichtige Architektur und unterstützt Caching und Replikation in der Mittelschicht, so dass Anfragen lokal ausgewertet werden k?nnen. Benutzer spezifizieren die Informationen, die sie ben?tigen und die repliziert werden, mit Hilfe einer besonderen Regelsprache. Um Replikate aktuell zu halten und die Replikation von neuen und relevanten Informationen anzusto?en, verwendet das MDV-System einen neuartigen Publish & Subscribe-Algorithmus. Wir beschreiben diesen Algorithmus im Detail und zeigen, wie er mit Hilfe eines normalen relationalen Datenbanksystems implementiert werden kann.