Scaling Behaviour of Si-alloyed Steel Slabs under Reheating Conditions

Reheating of steel slabs for further processing such as hot rolling usually takes place in gas-fired pusher furnaces. Temperatures well above 1000°C, combined with an atmosphere containing H2O, CO2, and O2, lead to substantial oxidation of most steel grades. Newly developed advanced steels often contain significant amounts of Si. This element plays a dominant role in the scaling behaviour near the steel-scale-interface, since fayalite (Fe2SiO4) forms a eutectic with wuestite (Fe1–xO) that melts as low as 1177°C.To better understand the high temperature oxidation behaviour, lab-scale trials were performed with different steel grades containing up to 3 wt.% Si. Possible interactions of Si with other alloying elements present in the samples such as Cr, Mn and Al were also of interest. The atmosphere contained 20% H2O, 7% CO2, and 3% O2, resembling reheating conditions in pusher furnaces, and temperatures ranged from 1100 to 1240°C. For metallographic investigation, the oxidised samples were cold mounted under vacuum using taper section angles. After preparation, the sections were examined through light microscopy, SEM/EDS, XRD, and TEM. The local distribution of the alloying elements could be mapped efficiently, and phase identification was successful in most parts. Under the applied experimental conditions, the elements of interest were present in their oxidic form either as pure or as mixed oxides. Higher Si-contents led to an increased build-up of eutectic melting phase at the steel-scale-interface at temperatures above 1177°C, which in turn further accelerated the oxidation.

Critical phenomena: Corrections to scaling behaviour

In preceding chapters, while deriving the scaling behaviour of correlation functions, we have always kept only the leading term in the critical region. We examine now the different corrections to the leading behaviour. For instance, when we have solved the renormalizaton group (RG) equations, so far, we have neglected the small deviation of the effective coupling constant from its fixed-point value. Moreover, to establish RG equations, we have neglected corrections subleading by powers of the cut-off, and effects of other couplings of higher canonical dimensions. Subleading terms related to the value of the effective coupling constant which give the leading corrections, at least near four dimensions, can easily be derived from the solutions of the renormalization group (RG) equations and are discussed first. The situations below and at four dimensions (the upper-critical dimension) have to be examined separately. The second type of corrections involves additional considerations and is examined in the second part of the chapter. The last section is devoted to one physics application, provided by systems with strong dipolar forces, which have 3 as upper-critical dimension.

An analysis of temporal scaling behaviour of extreme rainfall in Germany based on radar precipitation QPE data

We investigated the depth–duration relationship of maximum rainfall over all of Germany based on 16 years of radar-derived quantitative precipitation estimates (namely, RADKLIM-YW, German Meteorological Service) with a space–time resolution of 1 km2 and 5 min. Contrary to the long-term historic records that identified a smooth power law scaling behaviour between the maximum rainfall depth and duration, our analysis revealed three distinct scaling regimes of which boundaries are approximately 1 h and 1 d. A few extraordinary events dominated a wide range of durations and deviate to the usual power law. Furthermore, the shape of the depth–duration relationship varied with the sample size of randomly selected radar pixels. A smooth scaling behaviour was identified when the sample size was small (e.g. 10 to 100), but the original three distinct scaling regimes became more apparent as the sample size increases (e.g. 1000 to 10 000). Lastly, a pixel-wise classification of the depth–duration relationship of the maximum rainfall at all individual pixels in Germany revealed three distinguishable types of scaling behaviour, clearly determined by the temporal structure of the extreme rainfall events at a pixel. Thus, the relationship might change with longer time series and can be improved once available.

Recent advances in applied avalanche research in Norway

<div> <p>Snow avalanches are a significant natural hazard and common phenomenon in Norway. Applied research on avalanches and their societal impact has been conducted at the Norwegian Geotechnical Institute (NGI) for nearly half a century.</p> <p>Recent activities within the applied avalanche research group at NGI have focused on four areas: (1) Improved understanding of is sought through the application of simple probabilistic release models and local wind modelling. Encouraging results are obtained by analysing and refining publicly available climate time series for temperature, snow depth and precipitation on a 1 km² grid. A major remaining challenge in view of elaborating realistic large-area avalanche hazard indication maps is the a priori determination of the size of release areas as a function of return period. (2) Different aspects of are investigated by means of a wide array of experimental technologies at the Ryggfonn full-scale test site, application of aerial survey methods to derive snow distribution, and investigation of the scaling behaviour of avalanches with extreme runouts in many different paths. The results of all these analyses point towards the need for a departure from modelling avalanches with Voellmy-type models in favour of models encompassing multiple flow regimes, a more realistic rheology and entrainment as well as deposition. (3) To improve risk assessment and mitigation measures, with structures are studied by documenting destructive avalanche events, constructing vulnerability curves for persons inside buildings based on historic avalanche events, improving methods for evaluation of individual risks, and development of criteria for physical mitigation measures against powder-snow avalanches. (4) Current efforts in focus on the one hand on simple block models for studying scaling behaviour on idealised and natural slopes and on the other hand on an advanced multi-flow-regime model that also incorporates different effects of the snow cover. Ongoing work aims, among others, at an entrainment and deposition model that is dynamically consistent and only depends on measurable snow properties. This contribution will present an overview of recent activities and advancements in applied avalanche research in Norway. It is hoped that it will serve to facilitate future international collaborative efforts to address challenges in applied avalanche research.</p> </div>