Numerical simulation of a regional train in cross-wind

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.In this work numerical investigations of regional trains were carried out studying the prediction accuracy of the aerodynamic load in cross-wind assessment of rail vehicles. The main focus is on 30° yaw angle. Two domain setups, one representing the wind tunnel setup and another more generic one, were investigated and validated against available measurements comparing load coefficients. Important aspects of a guideline assessing aerodynamic load coefficients with numerical simulation techniques are proposed. Based on practical considerations and on the presented results the use of a generic domain is suggested for virtual certification. Further improvement of the flow field prediction can be achieved using unsteady hybrid numerical techniques, such as detached eddy simulation. Load coefficient results of various unsteady approaches and comparisons of simulated and measured flow fields are shown. Hints about the usage of the employed hybrid method are given, and future investigations are proposed

On the Usefulness of Weight-Based Constraints in Frequent Subgraph Mining

Frequent subgraph mining is an important data-mining technique. In this paper we look at weighted graphs, which are ubiquitous in the real world. The analysis of weights in combination with mining for substructures might yield more precise results. In particular, we study frequent subgraph mining in the presence of weight-based constraints and explain how to integrate them into mining algorithms. While such constraints only yield approximate mining results in most cases, we demonstrate that such results are useful nevertheless and explain this effect. To do so, we both assess the completeness of the approximate result sets, and we carry out application-oriented studies with real-world data-analysis problems: software-defect localization, weighted graph classification and explorative mining in logistics. Our results are that the runtime can improve by a factor of up to 3.5 in defect localization and classification and 7 in explorative mining. At the same time, we obtain an even slightly increased defect-localization precision, stable classification precision and obtain good explorative mining results

Data-Mining Techniques for Call-Graph-Based Software-Defect Localisation

Defect localisation is an important problem in software engineering. This dissertation investigates call-graph-mining-based software defect localisation, which supports software developers by providing hints where defects might be located. It extends the state-of-the-art by proposing new graph representations and mining techniques for weighted graphs. This leads to a broader range of detectable defects, to an increased localisation precision and to enhanced scalability

A Time-Series Compression Technique and its Application to the Smart Grid

Time-series data is increasingly collected in many domains. One example is the smart electricity infrastructure, which generates huge volumes of such data from sources such as smart electricity meters. Although today this data is used for visualization and billing in mostly 15-min resolution, its original temporal resolution frequently is more fine-grained, e.g., seconds. This is useful for various analytical applications such as short-term forecasting, disaggregation and visualization. However, transmitting and storing huge amounts of such fine-grained data is prohibitively expensive in terms of storage space in many cases. In this article, we present a compression technique based on piecewise regression and two methods which describe the performance of the compression. Although our technique is a general approach for time-series compression, smart grids serve as our running example and as our evaluation scenario. Depending on the data and the use-case scenario, the technique compresses data by ratios of up to factor 5,000 while maintaining its usefulness for analytics. The proposed technique has outperformed related work and has been applied to three real-world energy datasets in different scenarios. Finally, we show that the proposed compression technique can be implemented in a state-of-the-art database management system

Wien und die jüdische Erfahrung 1900-1938

The growing integration and participation of the Jewish population in politics, society, culture arts and religion shaped these spheres in Vienna during the time of the First Republic. Social dynamics of the young democracy, interplay of the different Jewish milieus, immigration from Eastern and Southeastern Europe as well as the growing cultural links with Berlin, Budapest, Paris and Prague made Austrian-Jewish culture in all areas of the development of the city of Vienna highly influential. Antidemocratic tendencies, especially antisemitism, influenced both the discourses on current events and inner-Jewish debates such as the role of Jewish religion, acculturation and Zionism. The publication "Wien und die jüdische Erfahrung 1900 - 1938. Akkulturation - Antisemitismus, Zionismus" initiated by Univ.-Prof. Frank Stern and Mag. Barbara Eichinger from the Institute for Contemporary History, University of Vienna, shows the state of the art of research on this subject. The publications focus placed on the current interdisciplinary inclusion of Austrian-Jewish cultural history. The volume of approx. 400 pages presents up-to-date research papers by the contributors as well as an academic discourse among the authors. In order to make this discourse possible, the editors organised a four day international conference in March 2007, where academics presented their research in themed panels and discussed them in an interdisciplinary framework with other experts. The contributions to this volume present this research takting into consideration the discussions among the colleagues at the conference. Those authors who did not participate in the conference and are partly working at American universities (a.o. Harriet Pass Freidenreich, Sander Gilman) provide an insight into current US American research on the subject. The contributions in German and English by 29 authors are organized into the following subject areas: "Society and politics between acculturation and tradition" (Steven Beller, Eleonore Lappin, Klaus Hödl, Albert Lichtblau), "Music between concert hall and film: Viennese composers of Jewish descent" (Peter Dusek, Karin Wagner), "Zionism in Vienna: between coffee house, cultural and political movement" (Dieter Hecht, Armin Eidherr, Hanno Loewy), "Cultural transfer between Vienna and Palestine/Israel" (Klaus Davidowicz, Sandra Goldstein), "Viennese Jewish milieus 1900 - 1938" (Evelyn Adunka, Peter Landesmann, Marcus G. Patka, Karin Stögner), "Women´s movements in Vienna"(Harriet Pass Freidenreich, Elisabeth Malleier, Michaela Raggam-Blesch), "Identity crises and antisemitism" (Gabriele Anderl, Elisabeth Brainin and Samy Teicher, Sander Gilman, Siegfried Mattl, Michael Laurence Miller), "Literature and theater in interwar Vienna" (Brigitte Dallinger, Werner Hanak, Birgit Peter), "The Road into the open on stage and screen (Wolfgang Müller-Funk, Murray G. Hall, Bettina Riedmann). The authors come from research centres in Belgium, Germany, Israel, the USA and Hungary as well as all current research centres on Jewish history in Austria (a.o. Institute for Jewish Studies, Vienna; Institute for History, Salzburg; Center for Jewish Cultural History, Salzburg; Institutte for the History of the Jews in Austria, St. Pölten; Center for Jewish Studies, Graz; Institute of Contemporary History, Vienna; University of Performing Arts, Vienna; Institut for German Studies, Vienna; Institut for Theater, Film and Media Studies, Vienna; Jewish Museum of the City of Vienna). The volume will be published in the anniversary year 2008 with a preface by the rector of the University of Vienna, Univ.-Prof. Dr. Georg Winckler.Politik, Gesellschaft, Kultur, Kunst und Religion sind im Wien der Ersten Republik durch eine immense Zunahme der Integration und Partizipation der jüdischen Bevölkerung charakterisiert. Die innergesellschaftliche Dynamik der jungen Demokratie und die Wechselwirkung der verschiedenen jüdischen Milieus, die Zuwanderungen aus Ost- und Südosteuropa sowie die wachsende kulturelle Vernetzung mit Berlin, Budapest, Paris und Prag führten zu einflussreichen Ausprägungen der österreichisch-jüdischen Kultur in allen Bereichen der Entwicklung der Stadt Wien. Antidemokratische Tendenzen, insbesondere der Antisemitismus, beeinflussen sowohl die tagespolitische als auch die innerjüdischen Diskurse, etwa über die Rolle der jüdischen Religion, der Akkulturation und des Zionismus. Die Publikation "Wien und die jüdische Erfahrung 1900 - 1938. Akkulturation, Antisemitismus, Zionismus", initiiert von Univ.-Prof. Dr. Frank Stern und Mag. Barbara Eichinger am Institut für Zeitgeschichte, Universität Wien, zeigt den State-of-the-Art der Forschung zu diesem Thema. Wobei der Fokus auf der aktuellen interdisziplinären Einbeziehung österreichisch-jüdischer Kulturgeschichte liegt. Der ca. 400 Seiten umfassende Band präsentiert neben momentanen Forschungsarbeiten der Beitragenden einen gemeinsamen wissenschaftlichen Diskurs der AutorInnen untereinander. Um diesen zu ermöglichen, organisierten die HerausgeberInnen im März 2007 eine viertägige internationale Konferenz, auf der geladene WissenschafterInnen ihre Forschungsarbeiten in themenspezifischen Panels anderen ExpertInnen zur interdisziplinären Diskussion stellten. Die Präsentation ihrer fortgeschrittenen Forschungsarbeit unter Berücksichtigung der Diskussionen unter KollegInnen während der Konferenz in die Beiträge des vorliegenden Bandes integriert worden. Jene AutorInnen, die nicht an der Konferenz teilgenommen hatten und teilweise an amerikanischen Universitäten tätig sind (u.a. Harriet Pass-Freidenreich, Sander Gilman), zeigen mit ihren Essays ein Bild der gegenwärtigen US-amerikanischen Forschung zum Thema. Die in deutscher und englischer Sprache verfassten Beiträge der 30 AutorInnen finden sich in folgenden Themengebieten wieder: "Gesellschaft und Politik zwischen Akkulturation und Tradition" (Steven Beller, Eleonore Lappin, Klaus Hödl, Albert Lichtblau), "Musik zwischen Konzertsaal und Film: Wiener Komponisten jüdischer Herkunft (Peter Dusek, Karin Wagner), "Zionismus in Wien: Zwischen Kaffeehaus, kultureller und politischer Bewegung" (Dieter Hecht, Armin Eidherr, Hanno Loewy), "Kulturtransfer zwischen Wien und Palästina/Israel" (Klaus Davidowicz, Sandra Goldstein), "Wiener jüdische Milieus 1900 - 1938" (Evelyn Adunka, Peter Landesmann, Marcus G. Patka, Karin Stögner), "Frauenbewegungen in Wien" (Harriet Pass-Freidenreich, Elisabeth Malleier, Michaela Raggam-Blesch), "Identitätskrisen und Antisemitismus" (Gabriele Anderl, Elisabeth Brainin und Samy Teicher, Sander Gilman, Siegfried Mattl, Michael Laurence Miller), "Literatur und Theater im Wien der Zwischenkriegszeit" (Brigitte Dalinger, Werner Hanak, Birgit Peter), "Der Weg ins Freie auf Bühne und Leinwand" (Wolfgang Müller-Funk, Murray G. Hall, Bettina Riedmann). Mit den AutorInnen sind neben Forschungsstätten in Belgien, Deutschland, Israel den USA und Ungarn alle gegenwärtigen Forschungsstätten zur jüdischen Geschichte in Österreich (u.a. Institut für Judaistik Wien; Institut für Geschichte Salzburg; Zentrum für Jüdische Kulturgeschichte Salzburg; Institut für Geschichte der Juden in Österreich, St. Pölten; Zentrum für jüdische Studien, Graz; Institut für Zeitgeschichte Wien; Universität für darstellende Kunst Wien; Institut für Germanistik Wien; Institut für Theater-, Film- und Medienwissenschaft Wien; Jüdisches Museum der Stadt Wien) vertreten. Der Band soll mit einem Vorwort des Rektors der Universität Wien, Univ.-Prof. Dr. Georg Winckler, im Gedenkjahr 2008 erscheinen

Kombiniertes Mining von strukturellen und relationalen Daten

Data Mining Techniken wie Klassifikation, Regression und Clusteranalyse finden heutzutage eine weite Verbreitung. Entsprechende relationale Daten liegen in vielen Anwendungsdomänen vor, und effiziente Data Mining Algorithmen sind in kommerzielle Werkzeuge sowie in Datenbank Management Systeme integriert. In den letzten Jahren wurden aber auch verschiedene strukturelle Data Mining Techniken entwickelt, die z.~B.\ mit Graph-basierten Daten arbeiten. Solche Techniken erschließen neue Anwendungsgebiete, bieten aber auch das Potential, bisherige Techniken zu ergänzen. Oft können durch Kombination bisherige Ergebnisse verbessert werden. In diesem Beitrag präsentieren wir Arbeiten aus dem Bereich der Vorhersage von Kundenverhalten und der Fehlersuche in Software, in denen strukturelle und relationale Data Mining Techniken erfolgreich kombiniert wurden. Schließlich geben wir einen Ausblick auf weitere Anwendungsgebiete und zukünftige Herausforderungen

Localizing Defects in Multithreaded Programs by Mining Dynamic Call Graphs

Writing multithreaded software for multicore computers confronts many developers with the difficulty of finding parallel programming errors. In the past, most parallel debugging techniques have concentrated on finding race conditions due to wrong usage of synchronization constructs. A widely unexplored issue, however, is that a wrong usage of non-parallel programming constructs may also cause wrong parallel application behavior. This paper presents a novel defect-localization technique for multithreaded shared-memory programs that is based on analyzing execution anomalies. Compared to race detectors that report just on wrong synchronization, this method can detect a wider range of defects affecting parallel execution. It works on a condensed representation of the call graphs of multithreaded applications and employs data-mining techniques to locate a method containing a defect. Our results from controlled application experiments show that we found race conditions, but also other programming errors leading to incorrect parallel program behavior. On average, our approach reduced in our benchmark the amount of code to be inspected to just 7.1% of all methods

Mining Edge-Weighted Call Graphs to Localise Software Bugs

An important problem in software engineering is the automated discovery of noncrashing occasional bugs. In this work we address this problem and show that mining of weighted call graphs of program executions is a promising technique. We mine weighted graphs with a combination of structural and numerical techniques. More specifically, we propose a novel reduction technique for call graphs which introduces edge weights. Then we present an analysis technique for such weighted call graphs based on graph mining and on traditional feature selection schemes. The technique generalises previous graph mining approaches as it allows for an analysis of weights. Our evaluation shows that our approach finds bugs which previous approaches cannot detect so far. Our technique also doubles the precision of finding bugs which existing techniques can already localise in principle