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Number of results: 5
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Abstract

Determination of the physico-chemical interactions between liquid and solid substances is a key technological factor in many industrial processes in metallurgy, electronics or the aviation industry, where technological processes are based on soldering/brazing technologies. Understanding of the bonding process, reactions between materials and their dynamics enables to make research on new materials and joining technologies, as well as to optimise and compare the existing ones. The paper focuses on a wetting force measurement method and its practical implementation in a laboratory stand – an integrated platform for automatic wetting force measurement at high temperatures. As an example of using the laboratory stand, an analysis of Ag addition to Cu-based brazes, including measurement of the wetting force and the wetting angle, is presented.
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Abstract

104 algal taxa (31 blue-green algae, 48 diatoms and 25 green algae) were identified from 18 stands of tundra soils in the Kaffiöyra Plain (Oscar II Land, NW Spitsbergen). Basing on numerical analysis by the reciprocal averaging method and on hierarchic classification based on ."distinguishing species", two groups of stands were distinguished: moist and wet ones characterized by diatoms, and dry and drying ones characterized by blue-green algae.
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Abstract

In the paper, an attempt was made to evaluate the effect of preliminary wetting of high-silica base during preparation of moulding sands containing a selected grade of sodium water-glass, designed for hardening by traditional drying or by electromagnetic microwaves at 2.45 GHz. In the research, some water was dosed during stirring the sandmix before adding 1.5 wt% of the binder that was unmodified sodium water-glass grade 137, characterised by high molar module within 3.2 to 3.4. Scope of the examinations included determining the effect of wetting the base on mechanical parameters like compression, bending and tensile strength, as well as on technological parameters like permeability, abrasion resistance and apparent density. The research revealed a significant positive effect of adding water to wet surfaces of high-silica base grains on mechanical properties and quality of moulding sands hardened by physical methods, in particular by microwave heating
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Abstract

The work presents investigation on the water droplet impingement at a substrate with three different surface coating. The experiments are carried out for two temperatures of the surface: 23ºC (room temperature) and -10ºC. The water droplet contact is recorded via ultra-fast camera and simultaneously via fast thermographic camera. The wetting properties are changing for subzero temperatures of substrates.
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Abstract

Some materials-related microstructural problems calculated using the phase-field method are presented. It is well known that the phase field method requires mesh resolution of a diffuse interface. This makes the use of mesh adaptivity essential especially for fast evolving interfaces and other transient problems. Complex problems in 3D are also computationally challenging so that parallel computations are considered necessary. In this paper, a parallel adaptive finite element scheme is proposed. The scheme keeps the level of node and edge for 2D and level of node and face for 3D instead of the complete history of refinements to facilitate derefinement. The information is local and exchange of information is minimized and also less memory is used. The parallel adaptive algorithms that run on distributed memory machines are implemented in the numerical simulation of dendritic growth and capillary-driven flows.
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