Vergleich des Stofftransports von hängenden und akustisch levitierten Wassertropfen in CO2

High‐pressure acoustic levitation devices allows a contact‐free investigation of liquids. Here, acoustically levitated water droplets and pendant water droplets were examined in regards to the mass transfer coefficient in a static CO₂‐atmosphere under elevated pressures. Based on the droplet geometry and the decrease of the droplet volume over time, it was possible to calculate the mass transfer coefficient of water into CO₂ at any given time. Additionally, open questions regarding possible differences between pendant and acoustically levitated water droplets were discussed.     

Accurate junction detection and characterization in line-drawing images

In this paper, we present a new approach for junction detection and characterization in line-drawing images. We formulate this problem as searching for optimal meeting points of median lines. In this context, the main contribution of the proposed approach is three-fold. First, a new algorithm for the determination of the support region is presented using the linear least squares technique, making it robust to digitization effects. Second, an efficient algorithm is proposed to detect and conceptually remove all distorted zones, retaining reliable line segments only. These line segments are then locally characterized to form a local structure representation of each crossing zone. Finally, a novel optimization algorithm is presented to reconstruct the junctions. Junction characterization is then simply derived. The proposed approach is very highly robust to common geometry transformations and can resist a satisfactory level of noise/degradation. Furthermore, it works very efficiently in terms of time complexity and requires no prior knowledge of the document content. Extensive evaluations have been performed to validate the proposed approach using other baseline methods. An application of symbol spotting is also provided, demonstrating quite good results.     

Ester-functionalized poly(3-alkylthiophene) copolymers: Synthesis,physicochemical characterization and performance in bulk heterojunction organic solar cells

The introduction of functional moieties in the donor polymer (side chains) offers a potential pathway toward selective modification of the nanomorphology of conjugated polymer:fullerene active layer blends applied in bulk heterojunction organic photovoltaics, pursuing morphology control and solar cell stability. For this purpose, two types of poly(3-alkylthiophene) random copolymers, incorporating different amounts (10/30/50%) of ester-functionalized side chains, were efficiently synthesized using the Rieke method. The solar cell performance of the functionalized copolymers was evaluated and compared to the pristine P3HT:PCBM system. It was observed that the physicochemical and opto-electronic characteristics of the polythiophene donor material can be modified to a certain extent via copolymerization without (too much) jeopardizing the OPV efficiency, as far as the functionalized side chains are introduced in a moderate ratio (<30%) and that preference is given to side chains with a small molar volume. A range of complementary techniques – UV–Vis spectroscopy, (modulated temperature) differential scanning calorimetry, transmission electron microscopy and X-ray diffraction analysis – indicated that variations in polymer crystallinity, while maintaining a high level of regioregularity, are probably the main factor responsible for the observed differences.     

Thermal and aqueous stability improvement of graphene oxide enhanced diphenylalanine nanocomposites

Abstract

Nanocomposites of diphenylalanine (FF) and carbon based materials provide an opportunity to overcome drawbacks associated with using FF micro- and nanostructures in nanobiotechnology applications, in particular their poor structural stability in liquid solutions. In this study, FF/graphene oxide (GO) composites were found to self-assemble into layered micro- and nanostructures, which exhibited improved thermal and aqueous stability. Dependent on the FF/GO ratio, the solubility of these structures was reduced to 35.65% after 30 min as compared to 92.4% for pure FF samples. Such functional nanocomposites may extend the use of FF structures to e.g. biosensing, electrochemical, electromechanical or electronic applications.     

Self-healing through microencapsulated agents for protective coatings

The use of microcapsules containing healing agents, which can serve as source of self-healing for coatings, was investigated. The appropriate self-repairing coatings are designed to be used for heavy-duty corrosion protection or for the protection of moisture-sensitive substrates like wood. Microcapsules based on thermoset resins (urea–formaldehyde and melamine–formaldehyde) which contained components of different chemical natures (resins or inhibitors) were fabricated using emulsion techniques. The subsequent characterization included optical, fluorescence, and electron microscopy as well as adapted microindentation techniques to determine capsule break forces. Different model coatings were formulated making use of varying amounts of healing agent-charged microcapsules. The coated samples were then injured under controlled conditions (by Erichsen cupping in the case of steel, by simulated hail in the case of wood) and then subjected to salt spray testing (natural and accelerated), weathering, or even real-life exposure, always in comparison with a blank. The results obtained demonstrate the superiority of microcapsule-based self-healing coatings compared to classical protection formulations, and appropriate coating systems have in the meantime been successfully brought to the market.