Design and configuration of neuro mechanical networks

Neuro mechanical network (NMN) is a new concept of adaptronic character. The governing idea is to include geometry, topology, load carrying, energy transfer, actuating, sensing and control of a machine in one single mathematical state model and, thereby, enable a formulation of the design and configuration problem as an optimization problem. We have focused our attention on a type of NMN consisting of what we call active trusses. For these, we have established a state model and given a design optimization problem from which we have obtained numerical solutions. These solutions show that the approach has the possibility to suggest new families of designs that are superior to those of classical passive trusses. We also indicate how activation may result in singularities, the treatment of which is, so far, essentially an open problem.     

On the preparation methods for carbon nanofiber-supported Pt catalysts

A study of the suitability of different methods for preparing highly loaded, well dispersed carbon nanofiber (CNF) supported Pt catalysts intended for application in fuel cells is reported. Preparation routes that are successfully applied on conventional carbon supports are hampered by the lower surface area and number of surface groups on CNFs. Ion exchange, homogeneous deposition precipitation and impregnation are all techniques that are limited to low metal loading on this CNF support. The most promising methods are the colloidal methods. By the modified polyol method, a Pt-content of 24 wt% with a particle size of 2–4 nm was achieved. CNFs could also be completely covered by 2–3 nm Pt oxide particles by using the metal–oxide colloid route, reaching a Pt-content of 17 wt%. The merits that make these methods more suitable than the other methods and the mechanism for deposition of Pt particles on CNFs are discussed.     

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Ohne Zusammenfassung VDI     

Fabrication of transparent yttria by HIP and the glass-encapsulation method

This method consists of a combination of vacuum sintering at 1600 °C followed by hot isostatic pressing (HIP) at 1500 °C of a highly agglomerated commercial powder. The use of evacuated glass capsules to perform HIP treatment allowed samples that showed open porosity after vacuum sintering to be sintered to transparency. The sintering response of the investigated powder was studied by careful microstructural observations using scanning electron microscopy and optical microscopy both in reflection and transmission. The successful key of this method was to keep porosity intergranular during pre-sintering, so that it can be removed subsequently by HIP treatment. It was found that agglomerates of closely packed particles are helpful to reach that purpose, since they densify fully and leave only intergranular porosity. However, performing HIP treatment at 1625 °C was found to result in opaque samples. This was attributed to the diffusion of argon inside the capsule. Contamination at different steps of processing was also investigated by inductively coupled plasma mass spectrometry (ICP-MS).     

Effects of information technology failures on the market value of firms

IT failures abound but little is known about the financial impact that these failures have on a firm’s market value. Using the resource-based view of the firm and event study methodology, this study analyzes how firms are penalized by the market when they experience unforeseen operating or implementation-related IT failures. Our sample consists of 213 newspaper reports of IT failures by publicly traded firms, which occurred during a 10-year period. The findings show that IT failures result in a 2% average cumulative abnormal drop in stock prices over a 2-day event window. The results also reveal that the market responds more negatively to implementation failures affecting new systems than to operating failures involving current systems. Further, the study demonstrates that more severe IT failures result in a greater decline in firm value and that firms with a history of IT failures suffer a greater negative impact. The implications of these findings for research and practice are discussed.     

Tension,compression and shear fatigue of a closed cell polymer foam

A closed cell foam of polymetacrylimide (Rohacell) with three different densities is studied. The foam is tested quasistatically in tension, compression and shear. The tensile properties scale very well with the relative density of the foam, but the compression and shear properties do not scale the same way. It is believed to be due to cell edge and cell wall buckling being the dominated deformation mechanism in compression and shear for lower densities that does not occur for higher densities. Fatigue testing is then performed in tension, compression and shear. It is seen that for all load cases and densities, the fatigue life can be plotted using Basquin’s law. The results also show that the different failure mechanisms found in the static tests are the same in fatigue. This means that the fatigue life for different load types exhibit different failure mechanisms. This shows not only as a clear difference in the stress levels for fatigue failure, but also on the slope in the fatigue life relation.     

Periodic Control for Improved Low-Temperature Catalytic Activity

The influence of transient changes in the gas composition on the low-temperature activity of a commercial three-way catalyst and a Pt/Al₂O₃ model catalyst has been studied. By introducing well-controlled periodic O₂ pulses to simple gas mixtures of CO or C₃H₆ (in N₂), a substantial improvement of the low temperature oxidation activity was observed for both catalysts. The reason for low activity at low temperatures is normally attributed to self-poisoning by CO or hydrocarbons. The improved catalytic performance observed here is suggested to origin from the transients causing a surface reactant composition that is favourable for the reaction rate.     

Mechanistic aspects of lean NO2 reduction by propane over HZSM-5

This study focuses on the mechanism of lean NO₂ reduction by propane. In particular the role of isocyanate- and amine species has been studied in transient experiments by in situ Fourier Transform Infrared (FTIR) spectroscopy. The results imply that these species are possible reaction intermediates over acidic HZSM-5.     

Quantitative Use of Paramagnetic Relaxation Enhancements for Determining Orientations and Insertion Depths of Peptides in Micelles

We describe the background and implementation of a method to determine, at atomic resolution, the insertion depths and orientations of peptides embedded in micelles. A nonperturbing paramagnetic agent—Gd(DTPA–BMA)—was used to induce paramagnetic relaxation enhancements (PREs) of peptide atoms inside the micelle. By calibrating these PREs it was possible to translate them into distance restraints that could be used for structure calculation. We demonstrate this here on the antimicrobial peptides novicidin and novispirin. Characterization of the interactions between antimicrobial peptides and membranes is important for understanding of their biological activities and functions, and a further development of tools to study these interactions is described.