Thermoelastic Characterization of Changing Phase Distribution in Hardened Steel by Laser Ultrasonics

The increase of hardness of steel during a heat treatment intended to give components more performance is a result of a drastic change in grain size and microstructure, which in turn can be analyzed via changes in acoustic wave scattering. The degree of scattering is related to the grain size, alloy phases, elastic anisotropy, and phonon spectra, which are connected with the structural heterogeneity. In this study, an axially oriented hardening profile in a steel rod was induced by a Jominy test. All-optical photoacoustic excitation and detection schemes were used to establish the relation between the hardness, the elastic modulus, the elastic scattering, and the thermal diffusivity on a series of eight samples cut out from the gradient part of the rod. For each sample, the scattering of the photoacoustically excited traveling surface acoustic waves detected in a heterodyne diffraction and beam deflection setup was extracted from their damping behavior at different wavelengths and frequencies. Also, the thermal diffusivity was determined by fitting the slow time evolution of the laser-induced photo-thermoelastic displacement signal, and was found to be decreasing with decreasing grain size and increasing hardness.     

Measurement and Analysis of Drapeability Effects of Warp-Knit NCF with a Standardised,Automated Testing Device

Characterising the drapeability of reinforcement fabrics, is one of the most sought after abilities of those designing composite processes and components. This is not surprising as composite processes are being considered in a greater range of fields and applications. Drapeability effects are formed by the irregular rearrangement of fibres. This displacement can occur within the textile plane and result in fibre disorientations, undulations and gaps or the fibres can be pushed into the third dimension - forming wrinkles or loops. To measure such effects in non-crimp fabrics, the Textechno Drapetest automatic drapeability tester was developed. To show its viability as a tool for composite engineering, a set of fabrics was chosen to show that the influence of textile design parameters on drapeability effects is now quantifiable. The Textechno Drapetest uses a sophisticated digital image analysis system to measure the position and direction of fibres and conclude from this information on the extent and intensity of drapeability effects in the textile surface. To measure effects outside the surface, i.e. wrinkles, a laser triangulation sensor is employed. The textiles were varied in the production parameters of stitch point distance in machine direction (MD) and cross direction (CD), the weight per area, and the stitch pattern (tricot and chain). The measurements showed that the new test method is capable of measuring the effects that were expected from classical test setups as well as a range of additional effects. From the results a significant influence of the stitch yarn on the formation of effects can be deduced. Especially the density of stitch points is a parameter that lets the textile producer control the behaviour of the textile when they are formed into a doubly curved three dimensional shape. To control the gap formation, however, the spacing of the stitch points in machine or in crosswise direction is also of importance with a shorter stitch length decreasing the forming of gaps more than a tighter stitch yarn pitch.     

Substitutes for procedural fairness: Prototypical leaders are endorsed whether they are fair or not.

This article extends research on leader procedural fairness as well as the social identity model of leadership effectiveness (SIMOL) by demonstrating that leader prototypicality can act as a substitute for procedural fairness. Although procedural fairness in general and voice in particular have been found to have a robust positive influence on leader endorsement, the authors showed in an experimental scenario study and a correlational field study that the influence of voice on leader endorsement is substantially reduced when leaders are perceived as prototypical for the group that they lead and followers are highly identified with their group. Additionally, supportive of predictions of the SIMOL, leader prototypicality interacted with follower identification in predicting leader endorsement, such that prototypicality had a positive effect on leader endorsement, which was enhanced among high identifiers. Overall, these results suggest that leaders who are attuned to their followers' group identity can afford to go it alone, for the better or the worse. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bio-inspired chemical hydrogen storage and discharge as a source of electrical energy

Reversible bio-inspired chemical hydrogen storage systems accumulate electrical energy in the form of electrons and proton ions located on biomolecules or bio-like storage molecules. Electro-active biomolecules (EAB) in Yeast media show such behavior: 2e⁻ + 2H⁺ + EAB_(aq)⁺ ⇆ EABH/H_(aq)⁺, also electro-active Methylene Blue (MB): 2e⁻ + 2H⁺ + MB_(aq)⁺ ⇆ MBH/H_(aq)⁺. The power characteristics of microbial fuel cell stacks equipped with such bio-inspired hydrogen storage systems were examined. E. coli cultures charged these bio-inspired separate chemical hydrogen storage units up to E = 0.50 ± 0.06 V; cell potentials increased proportionally in serial double, triple, and quadruple hydrogen storage stacks up to E _OCV = 1.98 V; the maximum power densities that were obtained improved proportionally with stack length by an increment of 1.4. The bio-inspired chemical hydrogen storage principle is of great interest for application in low-cost batteries that store renewable energy.     

Compact high-resolution spaceborne echelle grating spectrometer with acousto-optical tunable filter based order sorting for the infrared domain from 2.2 to 4.3 microm

A new compact spaceborne high-resolution spectrometer developed for the European Space Agency's Venus Express spacecraft is described. It operates in the IR wavelength range of 2.2 to 4.3 microm and measures absorption spectra of minor constituents in the Venusian atmosphere. It uses a novel echelle grating with a groove density of 4 lines/mm in a Littrow configuration in combination with an IR acousto-optic tunable filter for order sorting and an actively cooled HgCdTe focal plane array of 256 by 320 pixels. It is designed to obtain an instrument line profile of 0.2 cm(-1). First results on optical and spectral properties are reported.     

Sequence determinants of protein aggregation in human VH domains

Human antibody variable heavy (VH) domains tend to aggregate upon denaturation, for instance, by heat or acid. We have previously demonstrated that domains resisting protein aggregation can be selected from CDR-only repertoires by phage display. Here we analysed their sequences to identify determinants governing protein aggregation. We found that, while many different CDR sequences conferred aggregation-resistance, certain physico-chemical properties were strongly selected for. Thus, hydrophobicity and beta-sheet propensity were significantly lower among the selected domains, whereas net negative charge was increased. Our results provide guidelines for the design of human VH repertoires with reduced levels of protein aggregation.     

Potential of non‐GMO biofortified pearl millet (Pennisetum glaucum) for increasing iron and zinc content and their estimated bioavailability during abrasive decortication

Two non‐GMO biofortified and one traditional pearl millet varieties were compared in abrasive decortication studies to evaluate their potential for increasing iron and zinc content. The phytate‐to‐mineral ratios were used to estimate mineral bioavailability. Iron and zinc contents in the biofortified varieties Tabi and GB8735 were two to threefold higher than in the traditional variety. Iron content reached 7.2 and 6.7 mg per 100 g DM in the biofortified varieties, which corresponds to the target values of biofortification programs. Zinc content was, respectively, 5.6 and 4.1 mg per 100 g DM in the GB8735 and Tabi varieties. Because of the presence of phytate and other chelating factors that were only partially removed during decortication, there was no improvement in iron bioavailability in the biofortified varieties. But whatever extraction rate, phytate‐to‐zinc ratios ranged between 6 and 18; zinc absorption could be improved by using these biofortified varieties for food processing.     

Experimental investigation of leaky lamb modes by an optically induced grating

By removing the symmetry of a free plate configuration, fluid loading significantly modifies the nature of acoustic waves travelling along a plate, and it even gives existence to new acoustic modes. We present theoretical predictions for the existence, dispersive behavior, and spatial distribution of leaky Lamb waves in a fluid-loaded film. Although Lamb modes are often investigated by studying the radiated fluid waves resulting from their leakage, here their properties are assessed by detecting the wave displacements directly using laser beam deflection. By using crossed laser beam excitation, the detection and analysis of the different modes is done at a fixed wavelength, allowing one to verify the existence, the velocity, and the damping of each predicted mode in a simple and unambiguous way. Our theoretical predictions for the nature of the modes in a water-loaded Plexiglas film, including parts of looping modes, are experimentally confirmed.     

The effect of Ni additions on the oxidation behaviour of Co–Re–Cr high-temperature alloys

Abstract

The present study focused on the influence of Ni on the microstructure and oxidation behaviour of Co–Re–Cr-based alloys. Alloys with three different Ni contents were tested in laboratory air at 800–1100 °C. A refinement and a reduction of the σ phase volume fraction as well as a change in the matrix microstructure were observed. Thermogravimetric measurements showed that the alloys with higher Ni contents possess a better oxidation resistance when exposed to higher temperatures. All alloys suffered from continuous mass loss during oxidation at 800 °C due to the formation of porous oxides scales, consisting of Co₃O₄, Co(Ni)O and Ni-doped CoCr₂O₄, which allow the evaporation of Re-oxides. At 900–1100 °C, only the alloy with 25 at. % Ni showed parabolic oxidation kinetics after a short period of transient oxidation. This is a result of the fast formation of a protective Cr₂O₃ layer. It was also found that exposure to air at 1000 °C leads to a phase transformation of the bulk material; an oxidation-induced formation of fine hexagonal close-packed (hcp) grains was observed near the oxide scales. It is supposed that the improved oxidation resistance of Ni-containing Co–Re–Cr alloys is a result of enhanced Cr diffusion caused by the Ni addition. The extensive formation of the fcc phase in the alloy matrix had a detrimental effect on the oxidation behaviour of the Ni-containing Co–Re–Cr-based alloys.