Nano-photonics on luminescent molecular systems and metal particles in optical sub-wavelength microresonators

Mikroresonatoren, die für Licht im optischen Bereich entworfen sind, stellen nützliche Werkzeuge dar, um in die Licht-Materie-Wechselwirkung einzugreifen und sind deshalb oft verwendete Instrumente, um die spektralen und zeitlichen Eigenschaften nanoskopischer Objekte zu überwachen und zu beeinflussen. In dieser Arbeit wird die Lumineszenz von organischen Farbstoffmolekülen, energietransfergekoppelten Modellsystemen, photosynthetischen Komplexen und Metallnanopartikeln untersucht und durch den direkten Einfluss der photonischen und phononischen Umgebung kontrolliert. Die experimentellen Beobachtungen wurden durch konfokale Mikroskopie, in Kombination mit Spektroskopie und zeitkorrelliertem Einzelphotonenzählen, erzielt. Der photonische Einfluss wurde durch einen stimmbaren Fabry-Pérot Mikroresonator erreicht und der phononische Einfluss durch einen Helium-Bad-Kryostaten der das Experimentieren bei Temperaturen bis zu 1.6 K ermöglicht

The Economic Impact of Social Ties: Evidence from German Reunification

We use the fall of the Berlin Wall in 1989 to show that personal relationships which individuals maintain for non-economic reasons can be an important determinant of regional economic growth. We show that West German households who have social ties to East Germany in 1989 experience a persistent rise in their personal incomes after the fall of the Berlin Wall. Moreover, the presence of these households significantly affects economic performance at the regional level: it increases the returns to entrepreneurial activity, the share of households who become entrepreneurs, and the likelihood that firms based within a given West German region invest in East Germany. As a result, West German regions which (for idiosyncratic reasons) have a high concentration of households with social ties to the East exhibit substantially higher growth in income per capita in the early 1990s. A one standard deviation rise in the share of households with social ties to East Germany in 1989 is associated with a 4.6 percentage point rise in income per capita over six years. We interpret our findings as evidence of a causal link between social ties and regional economic development.

Evaluating Explanation Methods for Deep Learning in Security

Deep learning is increasingly used as a building block of security systems. Unfortunately, neural networks are hard to interpret and typically opaque to the practitioner. The machine learning community has started to address this problem by developing methods for explaining the predictions of neural networks. While several of these approaches have been successfully applied in the area of computer vision, their application in security has received little attention so far. It is an open question which explanation methods are appropriate for computer security and what requirements they need to satisfy. In this paper, we introduce criteria for comparing and evaluating explanation methods in the context of computer security. These cover general properties, such as the accuracy of explanations, as well as security-focused aspects, such as the completeness, efficiency, and robustness. Based on our criteria, we investigate six popular explanation methods and assess their utility in security systems for malware detection and vulnerability discovery. We observe significant differences between the methods and build on these to derive general recommendations for selecting and applying explanation methods in computer security.Comment: IEEE European Symposium on Security and Privacy, 202

Determination of Stator End Winding Inductance of Large Induction Machines: Comparison Between Analytics, Numerics, and Measurements

Knowledge of the end winding inductance of electrical machines is decisive for calculating their operating performance. In this article, two different approaches to analytically calculate the stator end winding inductance of large induction machines are discussed. The first method is based on the exact replication of the 3D conductor geometry using serially connected straight filaments, where the inductances are calculated by solving Neumann’s integral. In the second method, the end winding flux is resolved into components excited by the axial and circumferential end winding magnetomotive force, resulting in a far simpler geometrical model. In both cases, end face effects are taken into account by adopting the method of images. The analytical approaches are compared to the known analytical calculation method proposed by Alger [1]. In addition, the stator end winding inductance is computed by means of 3D finite-element analysis. Using experimental validation, it is shown that both the analytical and numerical results reasonably correlate with removed rotor inductance measurements taken for several induction machines with different rated powers and frame sizes, if the permeability of the laminated core is taken into consideration