4,925 research outputs found
Charting the Algorithmic Complexity of Waypoint Routing
Modern computer networks support interesting new routing models in which traffic flows from a source sto a destination t can be flexibly steered through a sequence of waypoints, such as (hardware) middleboxes or (virtualized) network functions (VNFs), to create innovative network services like service chains or segment routing. While the benefits and technological challenges of providing such routing models have been articulated and studied intensively over the last years, less is known about the underlying algorithmic traffic routing problems.
The goal of this paper is to provide the network community with an overview of algorithmic techniques for waypoint routing and also inform about limitations due to computational hardness. In particular, we put the waypoint routing problem into perspective with respect to classic graph theoretical problems. For example, we find that while computing a shortest path from a source s to a destination t is simple (e.g., using Dijkstra's algorithm), the problem of finding a shortest route from s to t via a single waypoint already features a deep combinatorial structure.</jats:p
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 and 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
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