A first proof of principle booster setup for the MADMAX dielectric haloscope

Axions and axion-like particles are excellent low-mass dark matter candidates. The MADMAX experiment aims to directly detect galactic axions with masses between $40\,\mu{\rm eV}$ and $400\,\mu{\rm eV}$ by using the axion-induced emission of electromagnetic waves from boundaries between materials of different dielectric constants under a strong magnetic field. Combining many such surfaces, this emission can be significantly enhanced (boosted) using constructive interference and resonances. We present a first proof of principle realization of such a booster system consisting of a copper mirror and up to five sapphire disks. The electromagnetic response of the system is investigated by reflectivity measurements. The mechanical accuracy, calibration process of unwanted reflections and the repeatability of a basic tuning algorithm to place the disks are investigated. We find that for the presented cases the electromagnetic response in terms of the group delay predicted by one-dimensional calculations is sufficiently realized in our setup. The repeatability of the tuning is at the percent level, and would have small impact on the sensitivity of such a booster.Comment: 10 pages, 12 figures; minor changes, introduction and references expanded, matches published versio

Casimir-Polder interaction of fullerene molecules with surfaces

We calculate the thermal Casimir--Polder potential of C60 and C70 fullerene molecules near gold and silicon nitride surfaces, motivated by their relevance for molecular matter wave interference experiments. We obtain the coefficients governing the asymptotic power laws of the interaction in the thermal, retarded and nonretarded distance regimes and evaluate the full potential numerically. The interaction is found to be dominated by electronic transitions, and hence independent of the internal temperature of the molecules. The contributions from phonon transitions, which are affected by the molecular temperature, give rise to only a small correction. Moreover, we find that the sizeable molecular line widths of thermal fullerenes may modify the nonretarded interaction, depending on the model used. Detailed measurements of the nonretarded potential of fullerene thus allow one to distinguish between different theories of incorporating damping.Comment: 9 pages, 8 figures, 9 table

Approach for Increasing the Resource Efficiency for the Production Process of Titanium Structural Components

Titanium structural components for the aircraft industry are usually manufactured from ingots of primary material. The process chain for the fabrication of these components consists of the production of titanium sponge, the melting process, the forging process and the milling process. High chip removal rates from up to 95% due to the milling process and a high energy demand in producing the titanium sponge of about 85% of the overall energy consumption characterize the process chain. This obviously leads to a high optimization potential under monetary and energetic aspects. Recycling titanium chips for the ingot production could help to dramatically improve the overall production process in terms of ecological aspects. However, process-induced contaminations of the chips prevent the use of high amounts of these in the melting procedure. Macroscopic impurities like residues of cooling lubricant can be removed in a complex cleaning process. Yet, contaminations like oxidization cannot be eliminated, hence only a small amount of titanium chips is usable in the melting process to achieve the required purity of the titanium alloy. This paper describes a novel method to decrease the energy consumption in fabricating titanium products. By reducing process-induced contaminations, the amount of titanium chips usable in the melting process can be significantly increased and consequently the necessary quantity of titanium sponge reduced. The described method contains the investigation of relevant influencing factors like the impact of tool and cooling concept on chip quality or manufacturing costs. The research of cause-effect relationships identifies the trade-off between ecological and economic targets. A mathematical description of this relationship is implemented within a simulation environment to find an optimum between ecological and economic targets. The paper describes this approach with samples of the titanium alloy Ti6Al4 V.BMWi/03ET1174

Data-Mining-Methoden zur frühzeitigen Erkennung bedrohlicher Situationen im Fahrzeug

Das autonome Fahren ist eines der großen Themen im Automobilbereich der Gegenwart. Umsatzstarke Soft­ware-Unternehmen gehen Kooperationen mit Unter­nehmen der Automobilbranche ein, um das automati­sierte Fahren schnellstmöglich voranzutreiben (Fuest 2015). Gleichzeitig forschen diverse Universitäten an dem Thema und zeigen bereits weitgehende Fortschrit­te. Exemplarisch ist die Universität Ulm zu nennen, die bereits Testfahrten im urbanen Gebiet erfolgreich absol­viert hat (Dietmayer 2014). Auch die Politik fördert den Forschungsschwerpunkt zunehmend. Als Beispiel ist das Förderprogramm »Elektroniksysteme für das vollauto­matisierte Fahren (ELEVATE)« zu nennen, welches vom Bundesministerium für Bildung und Forschung angebo­ten wird (Bundesministerium für Bildung und Forschung 2015). Diese intensive Forschung, die gleichzeitig von der Wirtschaft, der Wissenschaft und der Politik vorange­trieben wird, zeigt wie viel Potential das Thema besitzt. Auch dadurch stellen sich neue Herausforderungen an die Sensorik innerhalb der Fahrzeuge. Aktuell wird der Großteil der Sensordaten einmalig für den jeweiligen Zweck genutzt und anschließend verworfen. An diesen Punkt setzen das Vorhaben und der damit ver­bundene Einsatz von Data-Mining-Methoden an. Ziel ist die systematische Auswertung von Daten im Fahrzeug und von außerhalb (Car2X) in Echtzeit, um aktuelle Fahrsituationen mit einem digitalen Gedächtnis abzu­gleichen und somit einen kurzen Blick in die Zukunft abzuleiten. Hierbei werden Situationen durch Muster erkannt und Fahrzeug bzw. Fahrer konditioniert, um die Situation positiv zu beeinflussen. Das Vorhaben ist nicht ausschließlich auf das autonome Fahren ausgerichtet, sondern auch als Hilfe für fahrerge­lenkte Fahrzeuge konzipiert

Exchange-correlation functionals of i-DFT for asymmetrically coupled leads

A recently proposed density functional approach for steady-state transport through nanoscale systems (called i-DFT) is used to investigate junctions which are asymmetrically coupled to the leads and biased with asymmetric voltage drops. In the latter case, the system can simply be transformed to a physically equivalent one with symmetric voltage drop by a total energy shift of the entire system. For the former case, known exchange correlation gate and bias functionals have to be generalized to take into account the asymmetric coupling to the leads. We show how differential conductance spectra of the constant interaction model evolve with increasing asymmetry of both voltage drops and coupling to the leads.Comment: 8 pages; 8 figure

War and Veterans : An Introduction

acceptedVersio