University of Stuttgart

About: University of Stuttgart is a education organization based out in Stuttgart, Germany. It is known for research contribution in the topics: Laser & Finite element method. The organization has 27715 authors who have published 56370 publications receiving 1363382 citations. The organization is also known as: Universität Stuttgart.

Complex Event Processing

Abstract: Complex Event Processing (CEP) has evolved into the paradigm of choice for the development of monitoring and reactive applications. It also has a strong impact on future information systems and the way we subscribe to and consume information. Besides being a highly active research field, CEP already plays an important role in many application areas like logistics, energy management, finance, or manufacturing processes. Its importance for information systems is expected to grow further with the increasing number of decentralized information sources, such as blogs, and with the deployment of tagging and sensing technology as well as its integration in real-world objects. CEP addresses two crucial prerequisites to build highly scalable and dynamic systems. First, it decouples providers and receivers of information. Neither the providers need knowledge about the set of relevant receivers, nor do receivers need to know the set of relevant data or event sources. Second, CEP-systems do not only mediate information in form of events between providers and consumers, but support the detection of relationships among events, for instance, temporal relations that can be specified by definition of correlation rules (often called Event Patterns). Through aggregation and composition new complex events can be generated and used subsequently to derive more abstract events. CEP provides a natural decoupling between basic events with a strong relationship to the semantics of the underlying technology (e. g. sensor readings) and complex events closer to the semantics of the application. Therefore, it enables information systems to perform independent reconfigurations at the technical and application level. Furthermore, the stepwise correlation of events can help to reduce the message load and thus contributes towards a highly scalable information system. Business applications are increasingly interconnected and can impose a massive event load to be processed by current CEP systems. Moreover, the importance of sensing devices in applications is expected to grow. In the future, the Internet of Things may comprise billions of sensing devices. CEP will be a tool to derive understandable information on the basis of a large number of events. In this context it is important to support the distribution of event correlation in the presence of highly dynamic systems and support mechanisms for self-organization. Guaranteeing non-functional properties, such as, reliability, availability, performance, and security pose major challenges on the technical infrastructure, while expressiveness of event languages, event derivation and usability are challenges to make CEP accessible to a broader user community. This special issue intends to provide an insight on the applications and principles as well as the evolution of CEP. Moreover, we believe the selected articles from International and German researchers illustrate current trends and challenges in designing powerful, scalable as well as secure event processing systems. The group of Sharma Chakravarthy has a long experience in the field of Complex Event Processing and has designed one of the early and very influential event correlation languages, called Snoop. The work by Chakravarthy et al. gives a historical view on the development as well as the roots of Complex Event Processing. Furthermore, the authors point out important applications and challenges that go hand-in-hand with the development of CEP Systems. Distributed event-based systems are the key to increase the scalability of today’s information systems. Jacobsen et al. present the PADRES system which addresses the design of adaptive event-based systems. In their approach they show how content-based publish/subscribe systems can be extended to account also for composition of complex events as well as enable uniform query mechanisms for events in the future and the past. While in the past many efforts have focused on the design of efficient and expressive event-based systems, it is often hard to estimate the performance of eventbased systems in combination with QoS requirements of applications. The work by Kounev and Sachs bridges this gap by reviewing and proposing performance models that fit Distributed Event-Based Systems particularly well. Although the benefits of distributed event-based systems are often highlighted by researchers, so far most industrial solutions still rely on centralized event processing technology. Pletat et al. identify in their article one obstacle in deploying distributed event processing

Software visualization in software maintenance, reverse engineering, and re-engineering: a research survey

Abstract: Software visualization is concerned with the static visualization as well as the animation of software artifacts, such as source code, executable programs, and the data they manipulate, and their attributes, such as size, complexity, or dependencies. Software visualization techniques are widely used in the areas of software maintenance, reverse engineering, and re-engineering, where typically large amounts of complex data need to be understood and a high degree of interaction between software engineers and automatic analyses is required. This paper reports the results of a survey on the perspectives of 82 researchers in software maintenance, reverse engineering, and re-engineering on software visualization. It describes to which degree the researchers are involved in software visualization themselves, what is visualized and how, whether animation is frequently used, whether the researchers believe animation is useful at all, which automatic graph layouts are used if at all, whether the layout algorithms have deficiencies, and--last but not least--where the medium-term and long-term research in software visualization should be directed. The results of this survey help to ascertain the current role of software visualization in software engineering from the perspective of researchers in these domains and give hints on future research avenues.

Optical nanoantennas for multiband surface-enhanced infrared and raman spectroscopy

Abstract: In this article we show that linear nanoantennas can be used as shared substrates for surface-enhanced Raman and infrared spectroscopy (SERS and SEIRS, respectively). This is done by engineering the plasmonic properties of the nanoantennas, so to make them resonant in both the visible (transversal resonance) and the infrared (longitudinal resonance), and by rotating the excitation field polarization to selectively take advantage of each resonance and achieve SERS and SEIRS on the same nanoantennas. As a proof of concept, we have fabricated gold nanoantennas by electron beam lithography on calcium difluoride (1–2 μm long, 60 nm wide, 60 nm high) that exhibit a transverse plasmonic resonance in the visible (640 nm) and a particularly strong longitudinal dipolar resonance in the infrared (tunable in the 1280–3100 cm–1 energy range as a function of the length). SERS and SEIRS detection of methylene blue molecules adsorbed on the nanoantenna’s surface is accomplished, with signal enhancement factors of 5 × 102...

Identification of plasma-edge-related operational regime boundaries and the effect of edge instability on confinement in ASDEX Upgrade

Abstract: Local edge parameters on the ASDEX Upgrade tokamak are investigated at the L-mode to H-mode transition, during phases with various types of edge-localized modes (ELMs), and at the density limit. A scaling law for the boundary electron temperature, , is found which describes the H-mode threshold for deuterium-puffed discharges with favourable ion -drift direction. The region of stable operation is bounded by type I ELMs near the ideal ballooning limit and by a minimum temperature necessary to avoid thermal instability of the plasma edge. Stationary operation with type III ELMs imposes an upper limit on the edge temperature. Within the entire range of boundary densities investigated , both L-mode and H-mode are found to be accessible. During type I ELMy H-mode, a relation of global confinement with the edge pressure gradient is found which is connected with a loss of the favourable density dependence predicted by the ITER-92P and ITER-93H ELMy H-mode scalings. At high density, better confinement is achieved in H-modes with an edge pressure gradient below the ideal ballooning limit, e.g. during type III ELMy H-mode with impurity-seeded radiation.