Rietveld refinement and estimation of residual stress in GDC–LSCF oxygen transport membrane ceramic composites

The phase purity and crystal structure of dual-phase Ce_.9Gd_.1O_2–δ–La_.6Sr_.4Co_.2Fe_.8O_3–δ (GDC–LSCF) composites were refined using data obtained from X-ray diffraction (XRD) by employing the Rietveld method. Rietveld analysis indicated that the structures of GDC and LSCF phases are well crystallized as cubic Fm$\stackrel{?}{3}$m and rhombohedral R$\stackrel{?}{3}$c space groups, respectively. Scanning electron microscopy images showed smooth and dense structures, depicting a homogeneous crystalline structure of the samples. When the composites were cooled from their sintering temperature (1250?°C), compressive stresses were generated in the GDC and corresponding tensile stresses were generated in the LSCF due to differences in thermal expansion coefficients. The compressive residual stresses of the composites were investigated by high-angle XRD measurements using the well-known sin²ψ method. The average compressive residual stresses in GDC phase are estimated to be ??312 and ??290?MPa for 80 GDC–20 LSCF and 50 GDC–50 LSCF, respectively. The aim of this study is to provide a better understanding of the crystal structures and residual stresses in GDC–LSCF composites through XRD and the suitability of these composites for oxygen transport membranes.     

SAW diffraction using the thin-element decomposition method

We adapt the angular spectrum of plane waves (ASPW) decomposition to numerical simulations of the diffraction of surface-acoustic waves (SAWs) on anisotropic model substrate, such as YZ lithium niobate. We utilize the thin-element decomposition (TED) method, appropriately modified for an anisotropic substrate; we also introduce a novel "average-wavenumber" variation of this scheme; these are numerically found to be mutually consistent. We apply the TED method to simulate wave propagation both in infinite periodic structures of metallized gratings and also in finite gratings. We demonstrate that the ASPW provides a convenient and numerically fast tool for precise diffraction calculations in practical SAW devices which also display structural variations in the lateral direction, perpendicular to the principal direction of wave propagation. Additionally, we compare the present TED method to waveguide theory in an analysis of the role of SAW reflections from the electrodes.     

Effect of cognitive load on speech prosody in aviation: Evidence from military simulator flights

Mental overload directly affects safety in aviation and needs to be alleviated. Speech recordings are obtained non-invasively and as such are feasible for monitoring cognitive load. We recorded speech of 13 military pilots while they were performing a simulator task. Three types of cognitive load (load on situation awareness, information processing and decision making) were rated by a flight instructor separately for each flight phase and participant. As a function of increased cognitive load, the mean utterance-level fundamental frequency (F0) increased, on average, by 7 Hz and the mean vocal intensity increased by 1 dB. In the most intensive simulator flight phases, mean F0 increased by 12 Hz and mean intensity, by 1.5 dB. At the same time, the mean F0 range decreased by 5 Hz, on average. Our results showed that prosodic features of speech can be used to monitor speaker state and support pilot training in a simulator environment.     

Universal heritage value,community identities and world heritage: forms,functions, processes and context at a changing Mt Fuji

ABSTRACT

Numerous international documents underline the high identity value of cultural heritage for local communities and its potential for sustainable development. Simultaneously, the inclusion in UNESCO’s World Heritage List depends on the outstanding universal value that presumes a global community and prioritises global heritage value before the local ones. This setup holds potential tension.

This paper discusses how to define heritage communities and access their heritage identities, differentiating between landscape forms, functions, processes and context. The case study of Mt Fuji World Heritage is used to illustrate the model. While global and national communities emphasise the form of the heritage and policies target the preservation of the present visual shape, the local and religious communities identify with the functions and practices embodied by the sites. Not all communities identify with the proposed interpretative context for Mt Fuji heritage value. Additional tension arises from the Eurocentric mind-set behind world heritage expertise.     

Analysis of the factors affecting the inherent viscosity of oriented polylactides during hydrolytic degradation

This study focuses on analyzing the effects of several factors on the rate of decay of inherent viscosity (iv) during hydrolytic degradation. The analysis was made for oriented PLLA, 96L/4D PLA and 80L/20D,L PLA. The analyzed polymers were found to have identical rate of iv loss (P < 0.05), given that the materials have otherwise similar initial material properties. The effect of the post-processing residual monomer was dose dependent, i.e. the higher the monomer content the faster the degradation (P < 0.05). Samples with a smaller diameter (1.1 mm) were found to have a faster rate of iv loss than the samples with a larger diameter (4 mm) (P < 0.05). A multiple linear regression analysis was used to create a five-component linear model to predict changes in the materials’ inherent viscosity. This model yielded accurate predictions during the initial stages of the hydrolytic degradation process where the iv loss was virtually linear.     

Interfacial microstructure and shear strength of reactive air brazed oxygen transport membrane ceramic–metal alloy joints

To fabricate a multi-layered structure for maximizing oxygen production, oxygen transport membrane (OTM) ceramics need to be joined or sealed hermetically metal supports for interfacing with the peripheral components of the system. Therefore, in this study, Ag–10 wt% CuO was evaluated as an effective filler material for the reactive air brazing of dense Ce_0.9Gd_0.1O_2–δ–La_0.7Sr_0.3MnO_3±δ (GDC–LSM) OTM ceramics. Thermal decomposition in air and wetting behavior of the braze filler was performed. Reactive air brazing was performed at 1050 °C for 30 min in air to join GDC–LSM with four different commercially available high temperature-resistant metal alloys, such as Crofer 22 APU, Inconel 600, Fecralloy, and AISI 310S. The microstructure and elemental distribution of the ceramic-ceramic and ceramic-metal interfaces were examined from polished cross-sections. The mechanical shear strength at room temperature for the as-brazed and isothermally aged (800 °C for 24 h) joints of all the samples was compared. The results showed that the strength of the ceramic-ceramic joints was decreased marginally by aging; however, in the case of metal-ceramic joints, different decreases in strengths were observed according to the metal alloy used, which was explained based on the formation of different oxide layers at the interfaces.     

Textural changes in metallurgical coke prepared with polyethylene

The effect of high-density polyethylene （HDPE） on the textural features of experimental coke was investigated using polar- ized-light optical microscopy and wavelet-based image analysis. Metallurgical coke samples were prepared in a laboratory-scale furnace with 2.5%, 5.0%, 7.5%, 10.0%, and 12.5% HDPE by mass, and one sample was prepared by 100% coal. The amounts and distribution of textures （isotropic, mosaic and banded） and por~s were obtained. The calculations reveal that the addition of HDPE results in a decrease of mosaic texture and an increase of isotropic texture. Ethylene formed from the decomposition of HDPE is considered as a probable reason for the texture modifications. The approach used in this study can be applied to indirect evaluation for the reactivity and strength of coke.