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Abstract

The results of a statistical analysis of the influence of the Hansbreen surface ablation relative to selectedmeteorological parameters (air temperature andsunshine duration) are presentedhere. Over the period1989 –2001 the lowest summer balance on the surface ablation of Hansbreen was recorded in 1994 (–0.56 m water equivalent). Concurrently, both the air temperature (mean seasonal ~2.3 °C) and the sunshine duration (seasonal sum ~278.9 h)were at their lowest. Owing to the relatively high sunshine duration (676.5 h),the highest values were in 1998 (–1.71 m w.e.); likewise,in 2001 (–1.84 m w.e.) when a high air temperature (mean of 3.6 °C) occurred. The statistical models erected on the basis of these data allow us to estimate fairly reliably the seasonal ablation of Hansbreen. The basis of these is the reasonably reliable relationship determinable between the seasonal sum of PDD (positive degree days) and the ablation intensity changes in respect of altitude above sea level. Sunshine duration is regarded here as being of very little significance in terms of increasing the accuracy of the models. The errors inherent in this models varies from 28% to as little as 7%. Shown models may eventually find application as a method of calculating the amount of water resulting from the decay of tidewater glaciers.
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Abstract

Spitsbergen glaciers react rapidly to changes in the polar environment, which is expressed in differences in extent of their fronts and surface geometry. The Scott Glacier, which is situated in the NW part of Wedel Jarlsberg Land, is an example of the glacier that has undergone almost continuous recession since the Little Ice Age, interrupted by surges. The variations in recession are characterised based on multiannual data with particularly consideration of the period 1990–2005 and the season 2005/2006. Acceleration of front recession and lowering the surface was found only within the tongue up to a height of about 220 m a.s.l. Whereas, in the area situated in the zone of rock steps and above in the ablation zone, the change of glacier surface ablation (Dh) has been recorded compared to the mean annual recession for the period 1990–2005. Moreover, for the upper firn field, the positive surface ablation (DhS7 = +0.19 m) was observed. As the result of progressive reduction of the Scott Glacier mass, with the participation of other factors (bedrock relief among others), new surfaces of roche moutonnée are uncovering particularly in the tongue zone.
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Abstract

Ablation casting is a technological process in which the increased cooling rate causes microstructure refinement, resulting in improved mechanical properties of the final product. This technology is particularly suitable for the manufacture of castings with intricate shapes and thin walls. Currently, the ablation casting process is not used in the Polish industry. This article presents the results of strength tests carried out on moulding sands based on hydrated sodium silicate hardened in the Floster S technology, intended for ablation casting of the AlSi7Mg (AK7) aluminium alloy. When testing the bending and tensile strengths of sands, parameters such as binder and hardener content were taken into account. The sand mixtures were tested after 24h hardening at room temperature. The next stage of the study describes the course of the ablation casting process, starting with the manufacture of foundry mould from the selected moulding mixture and ending in tests carried out on the ready casting to check the surface quality, structure and mechanical properties. The results were compared with the parallel results obtained on a casting gravity poured into the sand mould and solidifying in a traditional way at ambient temperature.
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