Probing the nanoscale phase separation and photophysics properties of low-bandgap polymer:fullerene blend film by near-field spectroscopic mapping

The effect of the additive 1,8-octanedithiol (ODT) on the nanometer-scale morphology and local photophysical properties of low-bandgap polymer blends of poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b'] dithiophene)- alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT) and [6,6]-phenyl C(61) -butyric acid methyl ester (PCBM) is investigated. Phase separations of the PCPDTBT:PCBM blend film induced by ODT are visualized by the morphological changes from fibril-shaped features to spherical bumps, by the dramatically increased photoluminescence emission from PCPDTBT that was originally largely quenched, and by the fluctuations of spectral features at different locations of the sample surface. The correlations between the morphology and the local photophysical properties of the blend film with/without ODT at both the micrometer and nanometer scales are revealed by confocal and high-resolution near-field spectroscopic mapping techniques.     

Power comparator based on-site calibration of isolating current transformers

A portable system for on-site calibrations of isolating current transformers in stationary energy meter test systems is described. The uncertainties of the calibration system are in the order of 0.005 % for the ratio error and 0.01 crad for the phase displacement of the current transformer at power frequencies. The power comparator based measurements can be done at test currents from 50 mA to 120 A.     

Der Versuch einer großen Integration

The long established German Society for Internal Medicine (DGIM) profoundly incriminated itself through its actions and positions during the National Socialist era. The German clinical physician Paul Martini assumed the part of reorganizing the DGIM prior to its first post-war convention in 1948 in Karlsruhe. Martini, who himself had opposed the Nazi regime, adopted a course of comprehensive integration. He strived to incorporate both physicians who had been persecuted by the Nazi Regime as well as former moderate National Socialists into the DGIM. At the same time he campaigned to preserve the pan-German nature of the conferences and aimed rapidly to make the DGIM re-compatible with international research. However, this path led to an allegedly apolitical focus on science and decades of largely failing to confront its Nazi past.     

Numerical homogenization of heterogeneous and cellular materials utilizing the finite cell method

We present a new approach for the numerical homogenization of cellular and heterogeneous materials. The procedure is based on the finite cell method, which is applied to efficiently discretize representative volume elements for which effective material properties are computed. The starting point for our homogenization might be either a computer-aided design of a heterogeneous material or a three-dimensional computer tomography (CT-scan) of the specimen of interest. A fully automatic discretization in terms of finite cells, applying a hierarchic extension process to control the discretization error, is utilized to solve the corresponding boundary value problems arising during the homogenization. Special emphasis is placed on the numerical treatment of boundary conditions. To this end we apply the window method, which can be interpreted as a variant of the self-consistency method. Several numerical examples ranging from porous materials to fiber-reinforced composites will be presented, demonstrating the efficiency of our approach. The homogenization procedure will be also applied to a foam, a CT-scan of which is available.     

Temperature-enthalpy diagrams of different operating methods in blast-furnace processes

This report is concerned with the representation of temperature profiles for gas and solid in temperature-enthalpy-diagrams for the example of the blast-furnace process. Of particular interest is the point at which the gas and solid temperatures approach each other the most. For this, the temperature profiles for gas and solid are required, which can both be represented as a function of the specific enthalpy of the solid. With such diagrams we are able to judge the effects on process changes with reference to the position and the level of the minimum temperature difference between gas and solid, and to the level of the top-gas temperature and the caloric temperature dominating in front of the air-blast tuyères. In this context the influence of the coke ratio, of the furnace blast temperature, of the oxygen enrichment of the furnace blast, of the specific heat losses, as well as of the injected replacement fuels was studied for the example of pulverized coal and heavy oil. As a rule, the minimum temperature difference is to be found at the beginning of the smelting of the burden. Depending on the change of the process quantities the temperature difference can also arise at the top, as for example during oxygen enrichment.     

Simulation of the pressure distribution under a two-dimensional heap of polygonal particles

Granular heaps in two dimensions are studied using the molecular dynamics method with convex polygons. The angle of repose shows a dependence on the size dispersion of the particles. There is a pressure minimum under the apex of the heap which depends strongly on the way the heap is built. The results and the comparisons with the experiments suggest that there is not such a thing as a generic pressure distribution for granular heaps.     

Dynamic relations for sparsely sampled Gaussian processes

In longitudinal studies, it is common to observe repeated measurements data from a sample of subjects where noisy measurements are made at irregular times, with a random number of measurements per subject. Often a reasonable assumption is that the data are generated by the trajectories of a smooth underlying stochastic process. In some cases, one observes multivariate time courses generated by a multivariate stochastic process. To understand the nature of the underlying processes, it is then of interest to relate the values of a process at one time with the value it assumes at another time, and also to relate the values assumed by different components of a multivariate trajectory at the same time or at specific times selected for each trajectory. In addition, an assessment of these relationships will allow to predict future values of an individual’s trajectories.     

Predictive quality control of hybrid metal-CFRP components using information fusion

The paper presents an approach to determine the durability of hybrid metal-CFRP components combining the results of non-destructive testing (ndt) and finite element simulation The advantage of hybrid metal-CFRP components lies in the use of the properties of the materials used. CFRP parts with higher specific stiffness and strength are combined with metallic joining points, so that established joining processes for metal components can be applied to these lightweight components. In order to further promote the use of these hybrids in industry, it is necessary to guarantee a high level of component reliability through 100% quality control in order to avoid production-related defects. These defects such as delamination or fibre disorientation however vary in shape, size and position and lead to different effects on the part performance and reliability. Therefore the presented approach includes the application of non-destructive testing methods that are applied as in-line quality control measures in order to determine defect characteristics of the inspected parts. Due to the novelty of the component under test it is necessary to evaluate the individual criticality of detected defects and how they affect part performance during the testing procedure. Therefore the acquired ndt-data is used in finite element simulations where defect characteristics are added to the component model and whose effects on part reliability are evaluated. The generation of additional information combining non-destructive testing and simulation is referred to as data fusion. In order to evaluate the validity of the presented approach the determined part performances are compared to experimental mechanic tests.