SU-57 – An aluminosilicogermanate with a DFT topology and variable composition

An aluminosilicogermanate with a DFT zeotype framework (denoted as SU-57) was synthesized for the first time by ethanol-assisted hydrothermal synthesis at 160 and 170 °C. The compound was characterized by single crystal and powder X-ray diffraction, scanning and transmission electron microscopy, energy dispersive spectroscopy (EDS), thermogravimetry (TG) and solid state nuclear magnetic resonance (NMR) spectroscopy. SU-57 crystallizes in space group P4₂/n with estimated a ≈ 10.38–10.46 Å, c ≈ 8.88–8.91 Å, V ≈ 957–975 Å³. It has variable Al–Si–Ge composition with an approximate formula |C₂H₁₀N₂| [Al(Si_xGe_1?x)O₄]₂ (x ≈ 0.3–0.9), which results in a super-structure originated from different cation occupancies of the two unique tetrahedral (T) sites. Single crystal X-ray structure refinements, together with results from X-ray powder diffraction (XRPD) and EDS analysis, showed that (i) the AlO₄ and (Si, Ge)O₄ tetrahedra are only partially ordered over the DFT framework and do not follow a strict alternating manner. (ii) Al resides predominantly on one T site and Si and Ge predominantly on the other. (iii) The Al cation concentration (Al/(Al + Si + Ge)) is nearly constant and slightly less than 50 at%, while the Si and Ge cation concentrations vary over a large range. (iv) Al and Ge occupy both T sites. The cation disorder was confirmed by ²⁷Al and ²⁹Si solid state NMR. TG analysis and in situ XRPD showed that SU-57 was stable up to 375 °C in N₂ atmosphere.     

Heating technology and energy use: a discrete/continuous choice approach to Norwegian household energy demand

The aim of this paper is to describe the structure of the household’s energy demand as a discrete/continuous choice and, on this basis, establish an econometric model suitable for the data available in the Norwegian Energy Surveys. The discrete appliance choice is specified as a multinomial logit model, with a mixture of appliance attributes (operating costs) and individual characteristics (income, housing unit characteristics, etc.) as explanatory variables. In the next step the continuous choice of energy use is modelled conditional on the appliance choice. The energy prices turn out to be significant both when estimating the appliance choice and the conditional energy demand. The estimated price elasticity for energy exceeds minus unity. The paper discusses how this relatively strong price response should be interpreted in the context of other econometric analysis with no explicit appliance dependence. Finally, the significance of the many household characteristics at both stages of the model signals a high degree of heterogeneity within the households, which justifies the use of detailed micro-data in the modelling of the energy demand.     

Processing of thin film ceramic membranes for oxygen separation

Processing of dense and thin ceramic membrane layers for high temperature selective oxygen separation is addressed in this study. Mixed oxygen-ionic and electronic conducting perovskite oxide system based on La_0.2Sr_0.8Fe_0.8Ta_0.2O_3−δ composition is employed for processing of structural and functional layers. Special focus is aimed at obtaining thin layer and final microstructure with particle size in the sub-micron range. Thin layer deposition is performed by dip coating technique using stable colloidal suspension of perovskite particles dispersed within ethanol media. Two polymer based surfactants were screened for their effect on particle agglomeration and rheological response. By using optimum quantity of 2.5 wt.% addition of selected surfactant it is possible to obtain dense 15-60 μm thick functional layers. The thermal cycle applied resulted in final particle sizes within sub-micron range. By employing suspension with pore former it was possible to significantly increase the surface area of the functional layer.     

Dislocation‐Free and Atomically Flat GaN Hexagonal Microprisms for Device Applications

III‐nitrides are considered the material of choice for light‐emitting diodes (LEDs) and lasers in the visible to ultraviolet spectral range. The development is hampered by lattice and thermal mismatch between the nitride layers and the growth substrate leading to high dislocation densities. In order to overcome the issue, efforts have gone into selected area growth of nanowires (NWs), using their small footprint in the substrate to grow virtually dislocation‐free material. Their geometry is defined by six tall side‐facets and a pointed tip which limits the design of optoelectronic devices. Growth of dislocation‐free and atomically smooth 3D hexagonal GaN micro‐prisms with a flat, micrometer‐sized top‐surface is presented. These self‐forming structures are suitable for optical devices such as low‐loss optical cavities for high‐efficiency LEDs. The structures are made by annealing GaN NWs with a thick radial shell, reforming them into hexagonal flat‐top prisms with six equivalents either m‐ or s‐facets depending on the initial heights of the top pyramid and m‐facets of the NWs. This shape is kinetically controlled and the reformation can be explained with a phenomenological model based on Wulff construction that have been developed. It is expected that the results will inspire further research into micron‐sized III‐nitride‐based devices.     

Analysis and characterization of complex reactor behaviour: A case study

This paper analyzes the steady state and dynamic behaviour of a reactor for production of silicon metal, a submerged arc furnace. The furnace behaviour has been analyzed through simulation studies using a detailed, industrially proven, mechanistic simulation model. The analysis reveals that the silicon furnace has changing and complex dynamic behaviour, including inverse responses and slow modes, especially close to optimality. The paper analyzes the causes of the changing dynamic behaviour. It also shows how the margins to optimality can be deduced from the dynamic response to changes in the carbon coverage input.     

Knobology in use: an experimental evaluation of ergonomics recommendations

The scientific basis for ergonomics recommendations for controls has usually not been related to active goal-directed use. The present experiment tests how different knob sizes and torques affect operator performance. The task employed is to control a pointer by the use of a control knob, and is as such an experimentally defined goal-directed task relevant to machine systems in general. Duration of use, error associated with use (overshooting of the goal area) and movement reproduction were used as performance measures. Significant differences between knob sizes were found for movement reproduction. High torques led to less overshooting as opposed to low torques. The results from duration of use showed a tendency that the differences between knob sizes were reduced from the first iteration to the second iteration. The present results indicate that the ergonomically recommended ranges of knob sizes might differently affect operator performance.     

Control situations in high-speed craft operation

The control situation framework presented by Petersen (Cogn Technol Work 6(4):266–274, 2004) is elaborated upon in the context of military high-speed craft navigation. An observational study was done on a military navigational exercise in Indre Folda, a stretch of particularly demanding confined waters in Norway. The concept of control strategies is presented as a term related to how navigators choose to take out the control possibilities present in the system. Control actions are viewed as actions that fix the control demands and control possibilities over longer time-scales. Control strategies are different from control actions in that they continuously alter the control demands and control possibilities through its execution.