Johannes Kepler University of Linz

About: Johannes Kepler University of Linz is a education organization based out in Linz, Oberösterreich, Austria. It is known for research contribution in the topics: Computer science & Thin film. The organization has 6605 authors who have published 19243 publications receiving 385667 citations.

On Schwarz-type Smoothers for Saddle Point Problems

Abstract: In this paper we consider additive Schwarz-type iteration methods for saddle point problems as smoothers in a multigrid method. Each iteration step of the additive Schwarz method requires the solutions of several small local saddle point problems. This method can be viewed as an additive version of a (multiplicative) Vanka-type iteration, well-known as a smoother for multigrid methods in computational fluid dynamics. It is shown that, under suitable conditions, the iteration can be interpreted as a symmetric inexact Uzawa method. In the case of symmetric saddle point problems the smoothing property, an important part in a multigrid convergence proof, is analyzed for symmetric inexact Uzawa methods including the special case of the additive Schwarz-type iterations. As an example the theory is applied to the Crouzeix-Raviart mixed finite element for the Stokes equations and some numerical experiments are presented.

Fourier synthesis of radiofrequency nanomechanical pulses with different shapes

Abstract: Four mechanical waveforms at the nanoscale have been electrically generated by Fourier synthesis of a monochromatic surface acoustic wave and three of its harmonics.

Entanglement Swapping with Photons Generated on Demand by a Quantum Dot.

Abstract: Photonic entanglement swapping, the procedure of entangling photons without any direct interaction, is a fundamental test of quantum mechanics and an essential resource to the realization of quantum networks. Probabilistic sources of nonclassical light were used for seminal demonstration of entanglement swapping, but applications in quantum technologies demand push-button operation requiring single quantum emitters. This, however, turned out to be an extraordinary challenge due to the stringent prerequisites on the efficiency and purity of the generation of entangled states. Here we show a proof-of-concept demonstration of all-photonic entanglement swapping with pairs of polarization-entangled photons generated on demand by a GaAs quantum dot without spectral and temporal filtering. Moreover, we develop a theoretical model that quantitatively reproduces the experimental data and provides insights on the critical figures of merit for the performance of the swapping operation. Our theoretical analysis also indicates how to improve state-of-the-art entangled-photon sources to meet the requirements needed for implementation of quantum dots in long-distance quantum communication protocols.

CE with MS detection: A rapidly developing hyphenated technique

Abstract: Thirty years of Electrophoresis – 22 years of CE-MS; what has happened to this hyphenated technique within the last decades? Was it able to develop from a scientifically interesting and promising but exotic technique, available exclusively to a restricted group of users with pronounced technical skills, to an almost routine technique (at least in some fields of application) performed on commercially available equipment? What might be the future of CE-MS with respect to technical developments or new fields of application? The present review paper will try to provide answers to some of these questions. Current progress as well as possible future directions in CE-MS will be displayed using the example of selected publications from several areas.

Large-Scale Weakly Labeled Semi-Supervised Sound Event Detection in Domestic Environments

Abstract: This paper presents DCASE 2018 task 4. The task evaluates systems for the large-scale detection of sound events using weakly labeled data (without time boundaries). The target of the systems is to provide not only the event class but also the event time boundaries given that multiple events can be present in an audio recording. Another challenge of the task is to explore the possibility to exploit a large amount of unbalanced and unlabeled training data together with a small weakly labeled training set to improve system performance. The data are Youtube video excerpts from domestic context which have many applications such as ambient assisted living. The domain was chosen due to the scientific challenges (wide variety of sounds, time-localized events.. .) and potential industrial applications .