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Abstract

In [4], Császár has introduced the notions of weak structures and the structures α(w), π(w), σ(w), β(w). The main aim of this paper is to introduce and study properties of the structures r(w), α(w), π(w), σ(w) and β(w).

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Abstract

We define weak structures and show that these structures can replace in many situations generalized topologies or minimal structures.

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Abstract  

The aim of the present work was to provide arguments to the almost ‘hystorical’ problem of what β-tungsten is. WO3was reduced in dry H2gas atmosphere in order to examine, whether β-tungsten formed in such a way contains oxygen as part of the lattice described as WxO (e.g. W20O) or is a pure metallic phase of tungsten. As a result of thermoanalytical measurements and of chemical analysis for oxygen, the assumption is supported that in the 600-800C temperature range of metal formation not the WxO (β-W)→W(α-W) transformation but the β-W→α-W structural rearrangement of materials with identical chemical composition is the most probable process. The earlier opinion that the formation of the β-W structure requires the presence of oxygen atoms was not verified by our results.

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H A→B = H A→M /J kg −1 11.5 × 10 4 Convective heat transfer coefficient α /W m −2

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associated with the reactions, which may be represented by the process A solid → B solid + C gas , its reaction rate dα/d t can be written as 1 where α = ( W 0 − W t )/( W 0 − W ∞ ) ( W 0 , W t , and W ∞ are the initial, actual, and final mass of

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Journal of Thermal Analysis and Calorimetry
Authors: A. Kyritsis, A. Spanoudaki, C. Pandis, L. Hartmann, R. Pelster, N. Shinyashiki, J. C. Rodríguez Hernández, J. L. Gómez Ribelles, M. Monleón Pradas, and P. Pissis

controlled relative humidity rh (water activity α w ) at room temperature (25 °C). rh was adjusted by using saturated aqueous salt solutions [ 5 , 7 ]. The water content h , defined as the ratio of the mass of water in the hydrogel to the mass of the dry

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; then its expression is 0.319 α + ( w/cm )/(1− V f ). The degree of hydration (α) was calculated as the ratio of heat evolved ( Q t ) at 12, 24, and 48 h ( Table 3 ) to the total (and theoretical) heat of hydration of the Portland cement Q ∞ (468 J

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−1 °C), k ( α ) is the thermal conductivity of hardening concrete at degree of hydration α (W m −1 °C), and k 0 is the thermal conductivity of hardened concrete (W m −1 °C). Coefficient of thermal expansion

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