TY - THES A1 - Leininger, Andreas T1 - New diagnosis and test methods with high compaction rates Y1 - 2006 SN - 3-86664-066-8 PB - Mensch & Buch Verl. CY - Berlin ER - TY - JOUR A1 - Anger, Christian A1 - Gebser, Martin A1 - Schaub, Torsten H. T1 - Approaching the core of unfounded sets Y1 - 2006 UR - http://www.cs.uni-potsdam.de/wv/pdfformat/angesc06a.pdf ER - TY - JOUR A1 - Shenoy, Pradeep A1 - Krauledat, Matthias A1 - Blankertz, Benjamin A1 - Rao, Rajesh P. N. A1 - Müller, Klaus-Robert T1 - Towards adaptive classification for BCI N2 - Non-stationarities are ubiquitous in EEG signals. They are especially apparent in the use of EEG-based brain- computer interfaces (BCIs): (a) in the differences between the initial calibration measurement and the online operation of a BCI, or (b) caused by changes in the subject's brain processes during an experiment (e.g. due to fatigue, change of task involvement, etc). In this paper, we quantify for the first time such systematic evidence of statistical differences in data recorded during offline and online sessions. Furthermore, we propose novel techniques of investigating and visualizing data distributions, which are particularly useful for the analysis of (non-) stationarities. Our study shows that the brain signals used for control can change substantially from the offline calibration sessions to online control, and also within a single session. In addition to this general characterization of the signals, we propose several adaptive classification schemes and study their performance on data recorded during online experiments. An encouraging result of our study is that surprisingly simple adaptive methods in combination with an offline feature selection scheme can significantly increase BCI performance Y1 - 2006 UR - http://iopscience.iop.org/1741-2552/3/1/R02/ U6 - https://doi.org/10.1088/1741-2560/3/1/R02 ER - TY - JOUR A1 - Bobda, Christophe T1 - Special issue on ReCoSoC 2007 : editorial Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/01419331 U6 - https://doi.org/10.1016/j.micpro.2009.01.001 SN - 0141-9331 ER - TY - JOUR A1 - Blankertz, Benjamin A1 - Dornhege, Guido A1 - Krauledat, Matthias A1 - Müller, Klaus-Robert A1 - Kunzmann, Volker A1 - Losch, Florian A1 - Curio, Gabriel T1 - The Berlin brain-computer interface : EEG-based communication without subject training N2 - The Berlin Brain-Computer Interface (BBCI) project develops a noninvasive BCI system whose key features are 1) the use of well-established motor competences as control paradigms, 2) high-dimensional features from 128-channel electroencephalogram (EEG), and 3) advanced machine learning techniques. As reported earlier, our experiments demonstrate that very high information transfer rates can be achieved using the readiness potential (RP) when predicting the laterality of upcoming left-versus right-hand movements in healthy subjects. A more recent study showed that the RP similarily accompanies phantom movements in arm amputees, but the signal strength decreases with longer loss of the limb. In a complementary approach, oscillatory features are used to discriminate imagined movements (left hand versus right hand versus foot). In a recent feedback study with six healthy subjects with no or very little experience with BCI control, three subjects achieved an information transfer rate above 35 bits per minute (bpm), and further two subjects above 24 and 15 bpm, while one subject could not achieve any BCI control. These results are encouraging for an EEG-based BCI system in untrained subjects that is independent of peripheral nervous system activity and does not rely on evoked potentials even when compared to results with very well-trained subjects operating other BCI systems Y1 - 2006 UR - http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=7333 U6 - https://doi.org/10.1109/Tnsre.2006.875557 SN - 1534-4320 ER - TY - THES A1 - Müller, Stephan Heinz T1 - Aggregates Caching for Enterprise Applications N2 - The introduction of columnar in-memory databases, along with hardware evolution, has made the execution of transactional and analytical enterprise application workloads on a single system both feasible and viable. Yet, we argue that executing analytical aggregate queries directly on the transactional data can decrease the overall system performance. Despite the aggregation capabilities of columnar in-memory databases, the direct access to records of a materialized aggregate is always more efficient than aggregating on the fly. The traditional approach to materialized aggregates, however, introduces significant overhead in terms of materialized view selection, maintenance, and exploitation. When this overhead is handled by the application, it increases the application complexity, and can slow down the transactional throughput of inserts, updates, and deletes. In this thesis, we motivate, propose, and evaluate the aggregate cache, a materialized aggregate engine in the main-delta architecture of a columnar in-memory database that provides efficient means to handle costly aggregate queries of enterprise applications. For our design, we leverage the specifics of the main-delta architecture that separates a table into a main and delta partition. The central concept is to only cache the partial aggregate query result as defined on the main partition of a table, because the main partition is relatively stable as records are only inserted into the delta partition. We contribute by proposing incremental aggregate maintenance and query compensation techniques for mixed workloads of enterprise applications. In addition, we introduce aggregate profit metrics that increase the likelihood of persisting the most profitable aggregates in the aggregate cache. Query compensation and maintenance of materialized aggregates based on joins of multiple tables is expensive due to the partitioned tables in the main-delta architecture. Our analysis of enterprise applications has revealed several data schema and workload patterns. This includes the observation that transactional data is persisted in header and item tables, whereas in many cases, the insertion of related header and item records is executed in a single database transaction. We contribute by proposing an approach to transport these application object semantics to the database system and optimize the query processing using the aggregate cache by applying partition pruning and predicate pushdown techniques. For the experimental evaluation, we propose the FICO benchmark that is based on data from a productive ERP system with extracted mixed workloads. Our evaluation reveals that the aggregate cache can accelerate the execution of aggregate queries up to a factor of 60 whereas the speedup highly depends on the number of aggregated records in the main and delta partitions. In mixed workloads, the proposed aggregate maintenance and query compensation techniques perform up to an order of magnitude better than traditional materialized aggregate maintenance approaches. The introduced aggregate profit metrics outperform existing costbased metrics by up to 20%. Lastly, the join pruning and predicate pushdown techniques can accelerate query execution in the aggregate cache in the presence of multiple partitioned tables by up to an order of magnitude. Y1 - 2016 ER - TY - THES A1 - Kilic, Mukayil T1 - Vernetztes Prüfen von elektronischen Komponenten über das Internet BT - Anwendungen bei der Einführung eines Carsharing-Systems Y1 - 2016 ER - TY - JOUR A1 - Willig, Andreas A1 - Mitschke, Robert T1 - Results of bit error measurements with sensor nodes and casuistic consequences for design of energy-efficient error control schemes N2 - For the proper design of energy-efficient error control schemes some insight into channel error patterns is needed. This paper presents bit error and packet loss measurements taken with sensor nodes running the popular RFM Y1 - 2006 SN - 978-3-540-32158-3 ER - TY - JOUR A1 - Rozinat, A A1 - Van der Aalst, Wil M. P. T1 - Conformance testing: Measuring the fit and appropriateness of event logs and process models N2 - Most information systems log events (e.g., transaction logs, audit traits) to audit and monitor the processes they support. At the same time, many of these processes have been explicitly modeled. For example, SAP R/3 logs events in transaction logs and there are EPCs (Event-driven Process Chains) describing the so-called reference models. These reference models describe how the system should be used. The coexistence of event logs and process models raises an interesting question: "Does the event log conform to the process model and vice versa?". This paper demonstrates that there is not a simple answer to this question. To tackle the problem, we distinguish two dimensions of conformance: fitness (the event log may be the result of the process modeled) and appropriateness (the model is a likely candidate from a structural and behavioral point of view). Different metrics have been defined and a Conformance Checker has been implemented within the ProM Framework Y1 - 2006 ER - TY - JOUR A1 - Gerbser, Martin A1 - Schaub, Torsten H. T1 - Tableau calculi for answer set programming Y1 - 2006 UR - http://www.cs.uni-potsdam.de/wv/pdfformat/gebsch06c.pdf U6 - https://doi.org/10.1007/11799573 SN - 0302-9743 ER -