Synthesis of Tribologically Favorable Coatings for Hot Extrusion Tools by Suspension Plasma Spraying

Up to now, no coating systems have been marketed in the field of direct hot extrusion, which provide both surface protection of the parts in contact with the billet (i.e., container and die) as well as a significant reduction of the frictional losses induced by the billet passing over the container walls. To dispense with the use of lubricants and to enhance the usable forming capacity and therefore the efficiency of the process, different oxide ceramics were prepared in one suspension and plasma sprayed to produce coatings. The aim was to reach a sufficient level of feedstock mixing to obtain deterministic solid solutions of the oxide phases in coatings resulting in a reduction of their coefficient of friction under dry sliding conditions. To achieve this objective, the high specific surface area of nanosized feedstock with primary particle sizes below 100?nm was used. By means of x-ray diffraction it could be proven, that the desired phases could be synthesized to varying ratios regarding the different coating systems considered here. Besides the experimental work, the fundamentals of the mixing process of different oxides are discussed with regard to the crystallographic aspects.     

Antennas for next generation mobile communications

In future mobile communications many antennas will coexist on the device. This creates a number of problems related to bandwidth, efficiency, and correlation. Remedies are discussed in the paper, and attention is called to the promising area of adaptive matching, which also can solve problems related to the user.     

Enhancing the efficiency of alternating current driven organic light-emitting devices by optimizing the operation frequency

We report efficient and bright organic light-emitting devices operated by capacitive energy coupling. In this approach, the organic layers are enclosed between sputter-deposited hafnium dioxide layers to prevent charge carrier injection. When a sinusoidal voltage signal is applied to the electrodes, the devices emit bright green light whereas no detectable emission is generated upon application of a constant voltage. The efficiency of the process depends heavily on the frequency of the applied voltage signal. By optimizing the driving scheme, a record luminous efficacy for AC driven OLEDs of 2.7 lm/W at 500 cd/m² is achieved.     

Capillary self-alignment of polygonal chips: a generalization for the shift-restoring force

Capillary-driven self-alignment using droplets is currently extensively investigated for self-assembly and microassembly technology. In this technique, surface tension forces associated to capillary pinning create restoring forces and torques that tend to bring the moving part into the alignment. So far, most studies have addressed the problem of square chip alignment on a dedicated patch of a wafer, aiming to achieve 3D microelectronics. In this study, we investigate the shift-restoring forces for more complex moving parts such as regular—convex and non-convex—polygons and regular polygons with regular polygonal cavities. A closed-form approximate expression is derived for each of these polygonal geometries; this expression agrees with the numerical results obtained with the Surface Evolver software. For small shifts, it is found that the restoring force does not depend on the shift direction or on the polygonal shape. In order to tackle the problem of microsystem packaging, an extension of the theory is done for polygonal shapes pierced with connection vias (channels), and a closed form of the shift-restoring force is derived for these geometries and again checked against the numerical model. In this case, the restoring force depends on the shift direction. Finally, a non-dimensional number, the shift number, is proposed that indicates the isotropic or anisotropic behavior of the chip according to the shift direction.     

Experiences in building a Grid-based platform to serve Earth observation training activities

Earth observation data processing and storing can be done nowadays only using distributed systems. Experiments dealing with a large amount of data are possible within the timeframe of a lesson and can give trainees the freedom to innovate. Following these trends and ideas, we have built a proof-of-the-concept platform, named GiSHEO, for Earth observation educational tasks. It uses Grid computing technologies to analyze and store remote sensing data, and combines them with eLearning facilities. This paper provides an overview of the GiSHEO's platform architecture and of its technical and innovative solutions.     

Geometric adaption of biodegradable magnesium alloy scaffolds to stabilise biological myocardial grafts. Part I

Synthetic patch materials currently in use have major limitations, such as high susceptibility to infections and lack of contractility. Biological grafts are a novel approach to overcome these limitations, but do not always offer sufficient mechanical durability in early stages after implantation. Therefore, a stabilising structure based on resorbable magnesium alloys could support the biological graft until its physiologic remodelling. To prevent early breakage in vivo due to stress of non-determined forming, these scaffolds should be preformed according to the geometry of the targeted myocardial region. Thus, the left ventricular geometry of 28 patients was assessed via standard cardiac magnetic resonance imaging (MRI). The resulting data served as a basis for a finite element simulation (FEM). Calculated stresses and strains of flat and preformed scaffolds were evaluated. Afterwards, the structures were manufactured by abrasive waterjet cutting and preformed according to the MRI data. Finally, the mechanical durability of the preformed and flat structures was compared in an in vitro test rig. The FEM predicted higher durability of the preformed scaffolds, which was proven in the in vitro test. In conclusion, preformed scaffolds provide extended durability and will facilitate more widespread use of regenerative biological grafts for surgical left ventricular reconstruction.     

Synergistic effect of organoclay fillers based on fluorinated surfmers for preparation of polystyrene nanocomposites

Novel fluorinated reactive surfactants were used for the organic modification of monmorillonite clays. These organoclays were used for the preparation of polystyrene?clay nanocomposites by in‐situ free radical polymerization. Reference systems based on hydrocarbon homologous surfmer and nonpolymerizable surfactants were also used to deduce the effect of the fluorine moiety and the polymerizable function on the morphology and thermal stability of the prepared nanocomposites. Different structural parameters of the surfactants were investigated and modulated for the clay modification including: the nature of surfactant (surfmer/classical surfactant, fluorinated, or hydrocarbonated), the length of the fluorinated chain as well as the length of the hydrocarbon spacers linking the ammonium head to the fluorine chain or the polymerizable acrylic function. Wide angle‐X‐ray scattering (WAXD), thermogravimetric analysis (TGA), and electronic microcopies (TEM and SEM) were used to establish a structure‐morphology, thermal properties relationships, and to highlight the key parameters governing the exfoliation process. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42347.     

Effects of antimicrobial agents on the thermal and mechanical properties of acrylate hydrogel matrices

Polymer materials with antimicrobial activity are prepared by UV polymerization of acrylate and methacrylate mixture at room temperature. The antimicrobials are silver acetate and copper (II) acetate, used without pretreatment. Their chemical stability in the acrylate matrix and their effect on the thermal and mechanical properties of the polymer matrix are investigated as a function of their concentration up to 15 wt %. Physico‐chemical, thermal, rheological, and morphological analyses as well as the surveillance of metal salts release in aqueous medium are conducted. A significant decrease in the thermal stability of the salts introduced into the acrylate matrix is observed after UV treatment. The metal salts also have significant effects on the properties of the matrix. A plasticization and densification of the material associated with an aggregation of salts up to the percolation at the highest concentration are highlighted. At equal concentrations, the effects are more pronounced in the presence of copper salts. The latter was released more slowly than silver salts from acrylate material. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43501.     

Efficient Engineering and Production Concepts for Products in Regulated Environments – Dream or Nightmare?

Manufacturing of chemical‐pharmaceutical products is moving increasingly fast on a global scale. Therefore, developing and starting up production facilities fast, with high quality, and at reasonable costs has become extremely challenging. Engineering concepts like modularization, standardization and simultaneous/parallel engineering are discussed as methods for speeding up process design and filing for regulatory approval. Transfer from batch to continuous operation mode of production is pointed out as the key‐issue in such strategies.