Indirect forces between impurities in one-dimensional quantum liquids

We investigate the indirect interaction between two isolated impurities in a Luttinger liquid described by a microscopic lattice model. To treat the electron-electron interaction U the functional renormalization group method is used. For comparison we also study the U=0 case. We find that for a wide range of impurity parameters the impurity interaction V_{12} as a function of their separation r oscillates with decaying amplitude between being attractive and repulsive. For half-filling of the band and in a crossover regime between weak and strong impurities the interaction becomes purely attractive. For U=0 and independent of the impurity strength the amplitude of the interaction energy falls off as 1/r. For U>0 the decay for small separations and weak to intermediate impurities is governed by a U dependent exponent larger than -1, which crosses over to -1 for large r. The crossover scale depends on the impurity strength and U. We present simple pictures which explain our results in the limits of weak and strong impurities. We finally also consider attractive interactions U<0.Comment: 8 pages, 9 figures include

Stochastic method for in-situ damage analysis

Based on the physics of stochastic processes we present a new approach for structural health monitoring. We show that the new method allows for an in-situ analysis of the elastic features of a mechanical structure even for realistic excitations with correlated noise as it appears in real-world situations. In particular an experimental set-up of undamaged and damaged beam structures was exposed to a noisy excitation under turbulent wind conditions. The method of reconstructing stochastic equations from measured data has been extended to realistic noisy excitations like those given here. In our analysis the deterministic part is separated from the stochastic dynamics of the system and we show that the slope of the deterministic part, which is linked to mechanical features of the material, changes sensitively with increasing damage. The results are more significant than corresponding changes in eigenfrequencies, as commonly used for structural health monitoring.Comment: This paper is accepted by European Physical Journal B on November 2. 2012. 5 pages, 5 figures, 1 tabl

Data management and GIS in the Center for Disaster Management and Risk Reduction Technology (CEDIM): from integrated spatial data to the mapping of risk

International audienceThe project "Risk Map Germany" of the Center for Disaster Management and Risk Reduction Technology (CEDIM) aims at the examination of existing and the development of new approaches for integrated risk assessment as well as the realisation of risk analyses for selected threats and regions. Hazard, vulnerability and risk maps display the results and provide valuable information for planning, insurances, emergency management, science and the public. This article describes the development of the basic information infrastructure for CEDIM and the "Risk Map Germany" providing components for the networking of participating institutions, for common data management, data dissemination and publication. While a web based project platform offers information and communication facilities for all the project members and also the presentation of CEDIM to the public, an integrated data base is prepared as foundation for cross-discipline but common risk assessment. It is made available by the spatial data service "CEDIM Data Center" which allows the project members to inform themselves about the characteristics of existing data and its applicability for their specific tasks by exploring GIS functionalities. Suitable data can be downloaded and further processed in their own work environment. The components' alignment with the principles of Spatial Data Infrastructures is required to accomplish the suppositions for long-term availability and accessibility of data, information and services

The fractal turbulent–non-turbulent interface in the atmosphere

With their constant increase in size, wind turbines are reaching unprecedented heights. Therefore, at these heights, they are influenced by wind conditions that have not yet been studied in detail. With increasing height, a transition to laminar conditions becomes more and more likely. In this paper, the presence of the turbulent–non-turbulent interface (TNTI) in the atmosphere is investigated. Three different on- and offshore locations are investigated. Our fractal scaling analysis leads to typical values known from ideal laboratory and numerical studies. The height distribution of the probability of the TNTI is determined and shows a frequent occurrence at the height of the rotor of future multi-megawatt turbines. The indicated universality of the fractality of the TNTI allows the use of simplified models in laboratory and numerical investigations.</p