Investigation into the role of sodium chloride deposited on oxide and metal substrates in the initiation of hot corrosion

Sodium chloride is deposited on the surface of alumina substrates and exposed to air containing 1% SO2 at temperatures between 500 C and 700 C. In all cases the sodium chloride was converted to sodium sulfate. The volatilization of sodium chloride from the original salt particles was responsible for the development of a uniform coating of sodium sulfate on the alumina substrate. At temperatures above 625 C, a liquid NaCl-Na2SO4 autectic was formed on the substrate. The mechanisms for these reactions are given. One of the main roles of NaCl in low temperature hot corrosion lies in enabling a corrosive liquid to form

Investigation into the role of NaCL deposited on oxide and metal substrates in the initiation of hot corrosion

The conversion to Na2SO4 of NaCl deposited on oxide substrates was studied as a function of temperature, in air with various SO2 and H2O partial pressures. The substrate was either a pure oxide or an oxide scale growing on a metal specimen. The progress of the reaction was observed using the SEM-EDAX technique to monitor morphological effects and, as far as possible, establish the rate of the process. The physical characteristics of the interaction between salt and substrate were also examined with particular reference to physical damage to the underlying oxide, especially when this is a scale on a metal specimen. An effort was also made to establish the conditions under which liquid phases may form and the mechanisms by which they form

Measurement of the dependence of the light yields of linear alkylbenzene-based and EJ-301 scintillators on electron energy

An experimental test of the electron energy scale linearities of SNO+ and EJ-301 scintillators was carried out using a Compton spectrometer with electrons in the energy range 0.09-3 MeV. The linearity of the apparatus was explicitly demonstrated. It was found that the response of both types of scintillators with respect to electrons becomes non-linear below ~0.4 MeV. An explanation is given in terms of Cherenkov light absorption and re-emission by the scintillators.Comment: 8 pages, 7 figure

Observations on the ecology of arctic foxes Alopex lagopus in Eqalummiut Nunaat, West Greenland

Information on diet, home range and activity of arctic foxes Alopex lagopus was collected by radio-tracking and faecal analysis in Eqalummiut Nunaat, West Greenland during spring and summer 1984. The study aimed to investigate the feeding ecology of foxes in an area where »traditional« prey such as lemmings Dicrostonyx groenlandicus and coastal food sources are absent. Foxes were found to be heavily dependent on abundant caribou Rangifer tarandus carrion, and invertebrates found in the layer of soil above the permafrost. Scat analysis and behavioural observations showed that foxes were quick to modify their foraging to exploit seasonal changes in food availability, and preyed heavily on nesting birds, mainly passerines, when these became available. Mean home range size of two radio-tagged female foxes was 11.7 km2. It was thought that fox density was unusually high due to the abundance of caribou carrion as a result of the exceptionally long preceding winter. The incidence of food caches was investigated and it was found that most were unearthed in June, after the thaw and just before passerine prey became abundant. White-fronted goose eggs and caribou carrion were the items most frequently found at unearthed caches. Observations and radio-tracking revealed that foxes predominated in lowland areas, generally avoiding plateau areas above 500 m, where passerines and caribou carrion were scarce. Foxes were found 10 be 50% more numerous on the study area in 1984 than in 1979, and this was felt to be related to differences in the availability of caribou carrion. Foxes were found to be major predators of the eggs of Greenland White-fronted geese

Towards the development of societal twins

A digital twin is a virtual data-driven replica of a real-world system. Recently, digital twins have become popular in engineering and infrastructure planning where they provide insights into complex physical systems or processes. Yet, to date, considerably less research has explored how digital replicas of social systems - representing the decisions, behaviors and interactions of individual people, and, in turn, their emergent outcomes - might be developed and integrated with those of physical systems. In this position paper we discuss the need for such societal twins, what they might look like, and set out key challenges that will need to be overcome if these benefits are to be realised

A Bayesian palaeoenvironmental transfer function model for acidified lakes

A Bayesian approach to palaeoecological environmental reconstruction deriving from the unimodal responses generally exhibited by organisms to an environmental gradient is described. The approach uses Bayesian model selection to calculate a collection of probability-weighted, species-specific response curves (SRCs) for each taxon within a training set, with an explicit treatment for zero abundances. These SRCs are used to reconstruct the environmental variable from sub-fossilised assemblages. The approach enables a substantial increase in computational efficiency (several orders of magnitude) over existing Bayesian methodologies. The model is developed from the Surface Water Acidification Programme (SWAP) training set and is demonstrated to exhibit comparable predictive power to existing Weighted Averaging and Maximum Likelihood methodologies, though with improvements in bias; the additional explanatory power of the Bayesian approach lies in an explicit calculation of uncertainty for each individual reconstruction. The model is applied to reconstruct the Holocene acidification history of the Round Loch of Glenhead, including a reconstruction of recent recovery derived from sediment trap data.The Bayesian reconstructions display similar trends to conventional (Weighted Averaging Partial Least Squares) reconstructions but provide a better reconstruction of extreme pH and are more sensitive to small changes in diatom assemblages. The validity of the posteriors as an apparently meaningful representation of assemblage-specific uncertainty and the high computational efficiency of the approach open up the possibility of highly constrained multiproxy reconstructions

Improved large-mode area endlessly single-mode photonic crystal fibers

We numerically study the possibilities for improved large-mode area endlessly single mode photonic crystal fibers for use in high-power delivery applications. By carefully choosing the optimal hole diameter we find that a triangular core formed by three missing neighboring air holes considerably improves the mode area and loss properties compared to the case with a core formed by one missing air hole. In a realized fiber we demonstrate an enhancement of the mode area by ~30 % without a corresponding increase in the attenuation.Comment: 3 pages including 3 eps-figures. Accepted for Optics Letter

Low-loss criterion and effective area considerations for photonic crystal fibers

We study the class of endlessly single-mode all-silica photonic crystal fibers with a triangular air-hole cladding. We consider the sensibility to longitudinal nonuniformities and the consequences and limitations for realizing low-loss large-mode area photonic crystal fibers. We also discuss the dominating scattering mechanism and experimentally we confirm that both macro and micro-bending can be the limiting factor.Comment: Accepted for Journal of Optics A - Pure and Applied Optic

Measurement of the quenching factor of Na recoils in NaI(Tl)

Measurements of the quenching factor for sodium recoils in a 5 cm diameter NaI(Tl) crystal at room temperature have been made at a dedicated neutron facility at the University of Sheffield. The crystal has been exposed to 2.45 MeV mono-energetic neutrons generated by a Sodern GENIE 16 neutron generator, yielding nuclear recoils of energies between 10 and 100 keVnr. A cylindrical BC501A detector has been used to tag neutrons that scatter off sodium nuclei in the crystal. Cuts on pulse shape and time of flight have been performed on pulses recorded by an Acqiris DC265 digitiser with a 2 ns sampling time. Measured quenching factors of Na nuclei range from 19% to 26% in good agreement with other experiments, and a value of 25.2 \pm 6.4% has been determined for 10 keV sodium recoils. From pulse shape analysis, the mean times of pulses from electron and nuclear recoils have been compared down to 2 keVee. The experimental results are compared to those predicted by Lindhard theory, simulated by the SRIM Monte Carlo code, and a preliminary curve calculated by Prof. Akira Hitachi.Comment: 21 pages, 13 figure

Press protest and publics: the agency of publics in newspaper campaigns

Campaign advocacy is a common but rarely researched practice in British tabloid journalism. Newspaper campaigns give an account of ‘public opinion’ to politicians, make explicit claims to speak for ‘the public’ and authentically represent them, and also address readers in an unconventional way in order to recruit their support. This article therefore examines the effect to which agency is attributed to readers and other publics in two such campaigns, and argues that publics were portrayed as active only in relation to the newspaper’s activity, and as primarily as reacting emotionally to the problem. The campaigning press promote themselves commercially and politically as quasi-representatives who challenge distant and ‘out of touch’ political representatives with the populist impulses of ‘public’ demands, but without enhancing the democratic process, or publics’ position within it