Measurement of horizontal flow in a large scale furnace using acoustic vector tomography

Acoustic pyrometry is one of only a few techniques that can give information about temperature and flue gas velocity in a large scale furnace of a coal fired power station. The time of flight of acoustic signals through the furnace is influenced by both temperature and gas velocity. Here, the reconstruction of the velocity of gas from acoustic measurements via vector tomography is considered. A reconstruction algorithm based on a stable series expansion method for vorticity and a finite difference method for the nonrotational part of the vector field is presented. It is applied to realistic synthetic data and data measured at a large scale furnace.     

Early deuteration steps of Pd- and Ta/Pd- catalyzed Mg70Al30 thin films observed at room temperature

Deuterium absorption in Mg₇₀Al₃₀ thin films coated with a Pd layer and a Ta/Pd bilayer were investigated using in situ neutron reflectometry at room temperature and deuterium pressures up to 1.3 bar. The approach used provides a detailed profile, at the nanoscale, of the deuterium content inside the specific layers that constitute the films. It is found that Mg₇₀Al₃₀ can store up to 5 wt.% under these mild conditions following a two-step mechanism. The latter involves the deuteration of the top and bottom catalyst layers first, followed by the main Mg₇₀Al₃₀ layer. The presence of deuterium throughout the films in the early absorption stages evidences atomic deuterium spillover from the catalyst layers. The addition of a Ta layer between the Pd and Mg₇₀Al₃₀ was found to allow observable absorption at a pressure 10 times lower than on the Ta-free sample, without affecting the storage capacity. Our measurements imply that this improvement in kinetics is due to a lowering of the nucleation barrier for the formation of the hydride phase in the Mg₇₀Al₃₀ layer.     

Silica-Functionalized Nanolimes for the Conservation of Stone Heritage

The relatively recent development of nanolimes (i.e., alcoholic dispersions of Ca(OH)₂ nanoparticles) has paved the way for new approaches to the conservation of important art works. Despite their many benefits, nanolimes have shown limited reactivity, back-migration, poor penetration, and lack of proper bonding to silicate substrates. In this work a novel solvothermal synthesis process is presented by which extremely reactive nanostructured Ca(OH)₂ particles are obtained using calcium ethoxide as the main precursor species. Moreover, it is demonstrated that this material can be easily functionalized with silica-gel derivatives under mild synthesis conditions, thereby preventing particle growth, increasing total specific surface area, enhancing reactivity, modifying colloidal behavior, and functioning as self-integrated coupling agents. Additionally, the formation of calcium silicate hydrate (CSH) nanocement is promoted by the presence of water, resulting in optimal bonding when applied to silicate substrates, as evidenced by the higher reinforcement effect produced on treated Prague sandstone specimens as compared to those consolidated with nonfunctionalized commercial nanolime. The functionalization of nanolimes is not only a promising strategy for the design of optimized consolidation treatments for the cultural heritage, but may also have important implications for the development of advanced nanomaterials for building, environmental, or biomedical applications.     

On the Temperature-Induced Equilibration of Phase Distribution and Microstructure in a Gas-Atomized Titanium Aluminide Powder

Powder production by gas atomization of γ-TiAl based alloys typically yields a highly nonequilibrium material regarding the occurring phases and their microstructural appearance. In particular, the equilibration of the powder and the associated phase transformations during heating are of great importance for the subsequently applied densification techniques. The present work employs in situ high-energy X-ray diffraction to investigate how this thermodynamic equilibration manifests itself in the resulting phase distribution, the ordering behavior of the disordered α and β phase, both evidenced in the powder, and the change of the γ lattice parameters during heating of a Ti–46.3Al–2.2W–0.2B (at%) powder up to 850 °C. Complementary microstructural characterization of the gas-atomized powder and the heat-treated material condition reveals that the temperature exposure predominately affects the dendritic parts of the microstructure, especially when the α phase is transformed into γ phase with small embedded grains of α₂ and β_o.     

Characterization of Extracellular Vesicles from Preconditioned Human Adipose-Derived Stromal/Stem Cells

Cell-free therapy using extracellular vesicles (EVs) from adipose-derived mesenchymal stromal/stem cells (ASCs) seems to be a safe and effective therapeutic option to support tissue and organ regeneration. The application of EVs requires particles with a maximum regenerative capability and hypoxic culture conditions as an in vitro preconditioning regimen has been shown to alter the molecular composition of released EVs. Nevertheless, the EV cargo after hypoxic preconditioning has not yet been comprehensively examined. The aim of the present study was the characterization of EVs from hypoxic preconditioned ASCs. We investigated the EV proteome and their effects on renal tubular epithelial cells in vitro. While no effect of hypoxia was observed on the number of released EVs and their protein content, the cargo of the proteins was altered. Proteomic analysis showed 41 increased or decreased proteins, 11 in a statistically significant manner. Furthermore, the uptake of EVs in epithelial cells and a positive effect on oxidative stress in vitro were observed. In conclusion, culture of ASCs under hypoxic conditions was demonstrated to be a promising in vitro preconditioning regimen, which alters the protein cargo and increases the anti-oxidative potential of EVs. These properties may provide new potential therapeutic options for regenerative medicine.     

Processing Fiber-Reinforced Polymers: Specific Wear Phenomena Caused by Filler Materials

Fiber-reinforced polymers allow for the implementation of plastic materials in structural components. However, increasing incorporation of fibers up to 50 wt% causes accelerated component wear in injection molding machines. In particular, the barrel and screw in the compression zone suffer from increased wear. The abrasive fibers of the compacted polymer pellets in the solid bed protrude from the surfaces of the resin having an abrasive, brush-like behavior. A modified pin-on-disk testing system with specially designed polymer pins was used to emulate the described tribological system in laboratory scale. Through varying contact pressure, temperature, and surface modifications of the counterparts (blank or coated powder-metallurgical steel), abrasive wear as observed in industrial-sized extruder screws could be successfully simulated on a laboratory-scale testing system. Detailed investigations of the pins and disks highlighted that the glass fibers plow and cut the surface leading to abrasion as observed in the real field application. Temperature has been proven to be the most decisive driving force. Surface modifications such as protective physical vapor-deposited CrN coatings are effective against abrasive wear, clearly outperforming untreated steels. The presented pin-on-disk-test setup will improve screening of materials for extruders, thus enhancing the durability of injection molding machines. POLYM. ENG. SCI., 60:78–85, 2020. © 2019 Society of Plastics Engineers     

Erkenntnisse aus dem Pilotprojekt Bad Deutsch-Altenburg an der Donau für Schifffahrt, Ökologie und Wasserbau

This paper summarizes the knowledge increase based on the results of the pilot project Bad Deutsch-Altenburg (BDA) for navigation, ecology and hydraulic engineering in the Austrian Danube River. Concerning the various stakeholders and thematic fields it could be shown that the pilot project led to several changes, additionally to a significant knowledge gain: Navigation is confronted with intensified sedimentation in the ford section BDA but also with positive effects like decreased flow velocities along the groyne heads and a slightly increased fairway width. The ecological conditions improved by a restoration of river banks and rheophilisation of river shoreline zones (bank-near habitats) and the Johler sidearm. Positive effects were found regarding an expansion of biota indicating dynamic and riverine conditions (e.g. diatoms and pioneer vegetation) and regarding a major increase of young-of-the-year fish in reconstructed areas. Regarding hydraulic engineering, measures could be optimised that contribute to river bed stabilisation (granulometric bed improvement and groyne reshaping). Water levels at low flow conditions were slightly increased by means of the measures (also based on the aggradation within the area), having positive ecological effects for the National Park Donauauen. At the same time high water levels were slightly decreased, improving the situation during floods. A combination of optimized hydraulic engineering structures and bedload management based on the results of the pilot project should allow a sustainable improvement for navigation conditions, a stop or minimisation of river bed degradation and an improvement of the ecological situation. By integrating abiotic and biotic investigations the effects of river engineering measures can be better analysed and the gained knowledge forms the basis for future planning.