Nonequilibrium phonon backaction on the current noise in atomic-sized junctions

We study backaction effects of phonon heating due to tunneling electrons on the current noise in atomic-sized junctions. Deriving a generalized kinetic approximation within the extended Keldysh Green's functions technique, we demonstrate the existence of a characteristic backaction contribution to the noise in case of low external phonon damping. We provide a physically intuitive interpretation of this contribution at large voltage in terms of slow fluctuations of the phonon occupation, and show that it generally gives a significant correction to the noise above the phonon emission threshold.Comment: v2 - update: 4 pages, 1 figure, minor changes in the main text nearly identical to the published version; the manuscript is supplemented by an updated Mathematica notebook and a new supplementary note in PDF, which are parts of the associated .zip bundl

Wave Propagation in the Ground and Isolation Measures

The first part of this report deals with wave propagation in the ground. Special attention is given to the radiation of waves from a source and on the effect of layering or continuous variation of the shear modulus in the soil on travelling waves. In the second part, vibration isolation measures are described, such as open or infilled trenches and rows of bore holes or piles. The results of different theoretical and experimental investigations are compared. Finally, recently developed isolation measures are presented

Searching for the Rail Bonus

The inherent superiority of rail-based public transport options over bus-based alternatives, all other things being equal, has been stipulated in the literature and in the public policy discussion for some time. The exact strength of any such rail bonus is important to a public transport operator which has to consider the replacement of rail-based services by bus services. The public transport operator of the city of Dresden (DVB), while generally upgrading its services, has to consider this option, in particular where the continuing tram operation would require a costly rehabilitation of the tracks. The measurement of any such systematic preference for rail-based modes is difficult, as is requires either a before-and-after study of such a switch, controlled for the other relevant service attributes, e.g. frequency, speed, reliability, price, route, etc., or a study of a network, in which rail- and road-based modes offer comparable types of services, with bus services inparticular not restricted to feeder services to rail/tram lines. Both are rare for obvious reasons. A recent service change of the DVB offered the opportunity to look at the issue in detail. A series of surveys were undertaken for this purpose before and after: A one-day travel diary (including a household questionnaire)  A survey of the image of the services A between-mode stated preference exercise focusing on the choice between public transport and private motorised transport where public transport was provided by either bus or tram (7 choice situations) A within-mode stated preference exercise looking at the trade-offs between public transport modes, in particular levels of comfort, travel times and transfers (7 choice situations). The paper reports detailed results from this study addressing the differences in preferences between the waves (effects of familiarity with an alternative) from both separate and joint stated preference and stated preference/revealed preference models. The modelling so far indicates a consistent, but weak preference for the rail option through a higher value-of-time for rail usage, higher valuation of new rail vehicles in comparison to new busses, although they are partially balanced by a higher transfer penalty. &nbsp

Die informations- und kommunikationstechnische Infrastruktur und ihre mittelfristige Entwicklung an den Hochschulen des Landes NRW

Dieser Bericht des Arbeitskreises der Leiter wissenschaftlicher Rechenzentren in NRW (ARNW) richtet sich an die Hochschulleitungen und die Verantwortlichen für Grundstrukturen in Information und Kommunikation (IuK). Er informiert über aktuelle wichtige Fragen, besonders über den Stand und Einsatz von IuK-Technologien. In Anbetracht der anhaltend schnellen Weiterentwicklung dieses Technologiefeldes, die sich auf alle Bereiche der Hochschulen auswirkt, halten wir das für wichtig, damit vermieden wird, dass wichtige Themen am Rande bleiben. Das neue Hochschulgesetz und der Qualitätspakt machen darüber hinaus eine Positionierung der Hochschulen in NRW zur IuK-Infrastruktur unabdingbar

Mechanism-controlled thermomechanical treatment of high manganese steels

Austenitic high manganese steels exhibit outstanding mechanical properties, such as high energy absorption, owing to various deformation-mechanisms such as dislocation slip, twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP). Here, we show a novel thermomechanical treatment to manufacture a high manganese steel Fe–18Mn-0.3C (wt.-%) with excellent mechanical performance by combining these three deformation-mechanisms. This process of mechanism-controlled rolling resulted in ultra-high tensile strength of the high manganese steel up to 1.6 GPa, simultaneously with uniform elongations up to 15%.A thermomechanical process was developed to establish this combination of properties. Warm rolling was conducted at 200 °C, to suppress TRIP and activate TWIP as deformation mechanism. Thus, a high density of deformation twins and dislocations was introduced to the microstructure, avoiding martensite formation. During a subsequent recovery annealing at 520 °C or 550 °C, the dislocation density was reduced, yet the high density of deformation twins was preserved. The combination of warm rolling and recovery annealing resulted in an ultrafine microstructure with a high density of twins and moderate density of dislocations. The TRIP effect is predominant during plastic deformation at ambient conditions in the highly twinned microstructure. The resulting steel exhibits an ultra-high yield strength and sufficient ductility, favorable properties for lightweight construction in automotive or aerospace industry

Stochastic optimization of a cold atom experiment using a genetic algorithm

We employ an evolutionary algorithm to automatically optimize different stages of a cold atom experiment without human intervention. This approach closes the loop between computer based experimental control systems and automatic real time analysis and can be applied to a wide range of experimental situations. The genetic algorithm quickly and reliably converges to the most performing parameter set independent of the starting population. Especially in many-dimensional or connected parameter spaces the automatic optimization outperforms a manual search.Comment: 4 pages, 3 figure

Handlungsempfehlungen für eine bessere Klimakoordination in Kommunen

Klimaschutz und Klimaanpassung sind in Deutschland bisher keine kommunalen Pflichtaufgaben. Die Dringlichkeit der Lage erfordert daher, dass Kommunen selbst aktiv werden. Ihnen bleibt nur noch wenig Zeit, eigene Lösungsansätze zum Umgang mit dem Klimawandel zu entwickeln und zu testen. „Hierfür fehlen Kommunen jedoch oft die personellen und finanziellen Ressourcen“, sagt der Stadtforscher Wolfgang Haupt von der Forschungsgruppe Urbane Nachhaltigkeitstransformationen des IRS. Vor diesem Hintergrund empfehlen die Autor*innen in ihrem neuen Policy Paper „Handlungsempfehlungen für eine bessere Klimakoordination in Kommunen“ den Fokus stärker auf den Transfer von bereits erprobten Maßnahmen aus anderen Städten zu legen. Ihre Handlungsempfehlungen richten sich an politische Verantwortliche in Kommunen und an Mitarbeitende von Stadtverwaltungen, die für die Koordination der Klimapolitik (Klimaschutz und/oder Klimaanpassung) innerhalb ihrer Stadt verantwortlich sind. Kern ihrer Handlungsempfehlungen sind drei erfolgreich erprobte Maßnahmen, die auf institutionelle Veränderungen innerhalb einer Stadtverwaltung abzielen. Konkret geht es um die die Einrichtung eines Klimarats (Potsdam), die Einführung eines Klima-Checks in der Bauleitplanung (Remscheid) und die Einrichtung einer Klima-Stabstelle (Würzburg). Diese Maßnahmen weisen ein hohes Transferpotenzial auf, da für deren Umsetzung keine besonderen Voraussetzungen innerhalb der Stadt nötig sind. Das Paper gibt Auskunft über die zentralen Erfolgsfaktoren der drei Maßnahmen