Processing and mechanical behavior at elevated temperatures of directionally solidified proton conducting perovskites

High-temperature proton conducting perovskite oxides have been fabricated by directional solidification using a laser-heated floating zone (LHFZ) method. Several families of compositions were selected: SrCe_1−xY_xO_3−δ (with x = 0.1, 0.2), BaCe_1−xM_xO_3−δ (with M = Y, Yb and Ca; x = 0.05, 0.2), Sr₃Ca_1.18Nb_1.82O_9−δ, SrZr_0.8Y_0.2O_3−δ and SrTi_0.95Sc_0.05O_3−δ. The resulting microstructures were characterized by electron microscopy and X-ray diffraction. The compounds exhibit a singular microstructure consisting of strongly textured crystalline cells surrounded by an intercellular amorphous phase. Compressive mechanical tests were performed at elevated temperatures in air at constant strain rate to evaluate the creep resistance. The results are discussed in terms of ionic radius, degree of aliovalence and content of dopant cations.     

N-1-alkylitaconamic acids-co-styrene copolymers. Surface characterization

A serie of six N-1-alkylitaconamic acids-co-styrene copolymers with alkyl groups varying in side chain length from 3 to 12 was used in this study. The surface behaviour of the copolymers has been studied as function of the side chain length. Contact angle data for two of these copolymer surfaces were obtained in water and several liquids. From this information the surface energy was determined. Differences in the wettability of N-1-alkylitaconamic acid-co-styrene are found. The results are discussed in terms of hydrophobic and polar effect of the copolymers. Results on spread monolayers characteristics of these copolymers on water surfaces are also reported. Surface pressure-area (π-A) isotherms on a pure water subphase exhibit a transition region depending on the length of the alkyl side chain of the itaconamic acid moiety. It was also analyzed the phase transition in the monolayer at the air/water interface by brewster angle microscopy (BAM). Molecular mechanics approach was used to obtain predictions about the local interaction energies between segments. It was possible to conclude that the local interaction energies of propyl and decyl derivatives are quite similar while the hexyl derivative has higher interaction energy. The analysis of the coulombic energies together with the dispersion van der Waals energies (VDW) would be indicative, in first approximation, that carbonyl groups are more exposed in the case of propyl than in the other copolymers studied.     

Fisk: A FORTRAN program to estimate the mode of (hornblende-) biotite gneiss and amphibolite from chemical analyses

FISK is a FORTRAN program that calculates the mode of biotite gneiss and amphibolite using the chemical analyses and the estimated An-content of plagioclase. A correction for accessory minerals is included. The program prints out the chemical analysis and the chemical composition of the calculated minerals.     

Determination of the heat release rate inside operational road tunnels by comparison with CFD calculations

Usually, during a fire inside a tunnel, the average heat release rate (HRR) is estimated according to the type of vehicle. Frequently, the overall HRR is considered, however it is also necessary to know its time evolution to design real time systems, particularly ventilation, which respond to fire events or signals as fast as possible. Nowadays, there is not a well established and generally accepted procedure to know the power liberated at each instant of time inside an operational tunnel. That procedure could help in taking the correct actions to adapt the tunnel ventilation in order to diminish the effects of the fire and the smoke. This work shows a method to calculate the heat release rate using sensors that can be installed inside an operational road tunnel. Besides, the location of the fire could also be calculated accurately and quickly. To achieve the previous purposes, a stationary database that depends on HRR, its location, and the ventilation speed is calculated with CFD programs; the data are compared with temperatures measured by the sensors located inside the tunnel. The program used to generate the database is the simplified model UPMTUNNEL. The predictions of the model are compared with the results of calculations carried out using the general purpose code FLUENT, and with measurements done in a tunnel with a real fire, produced with a fuel tray.     

Valency configuration of transition metal impurities in ZnO

We use the self-interaction corrected local spin-density approximation to investigate the ground state valency configuration of transition metal (TM=Mn, Co) impurities in n- and p-type ZnO. We find that in pure Zn_1−xTM_xO, the localized TM²⁺ configuration is energetically favored over the itinerant d-electron configuration of the local spin density (LSD) picture. Our calculations indicate furthermore that the (+/0) donor level is situated in the ZnO gap. Consequently, for n-type conditions, with the Fermi energy ε_F close to the conduction band minimum, TM remains in the 2+ charge state, while for p-type conditions, with ε_F close to the valence band maximum, the 3+ charge state is energetically preferred. In the latter scenario, modeled here by co-doping with N, the additional delocalized d-electron charge transfers into the entire states at the top of the valence band, and hole carriers will only exist, if the N concentration exceeds the TM impurity concentration.     

Energy at your service: highlighting energy usage systems in the context of energy efficiency analysis

Increasing energy efficiency has for a long time been identified as an important means of mitigating climate change. However, the full potential for technical energy efficiency has seldom been fully exploited. The traditional approach in energy systems analysis and policy is still largely supply-orientated, i.e. focusing on the management of energy conversion, production and distribution, and final use of energy in the form of energy carriers. This paper contributes to previous discussions on how to highlight and explore the user side in the analysis of energy systems in an efficiency context. The energy usage systems approach, including end-use technologies and the production of service demanded by a human activity system, is used to promote a dynamic bottom-up perspective on energy. In determining the possible potential for change by increasing energy efficiency, the demand for energy should not be considered synonymous with the demand for neither energy carriers, nor the measurable service volumes (such as kilometres travelled, square metre conditioned space, etc.), without considering the sociocultural context in which the service is being used or called upon. In summary, the predominant paradigm dealing with the energy system as a technical system managing resources and providing energy carriers should thus be complemented with the view of a socio-technical system facilitating and/or managing the services.     

The contribution of civilian health and social workers in the districts of S?r-Varanger and Vads? during World War II]

The eastern part of the county of Finnmark in North-Norway played a prominent part in the German planning of the attack on Murmansk in 1941. The Norwegian civilian population suffered badly from the warfare. In the last phase of the war, the Germans burnt down and destroyed almost everything in the entire county, and a considerable part of the Norwegian population was forced to evacuate. This paper recounts some of the wartime episodes on the coast between the city of Vard? and the Nordkinn peninsula. Vard? with its hospital and a number of fishing harbours were completely destroyed. Attention is drawn to the excellent job done by the civilian Norwegian health and social workers during the terrible years of German occupation.