AdMaS - dotace 12


Recent Submissions

Now showing 1 - 5 of 5
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    Development of microstructure of the fly ash aerated concrete in time
    (Elsevier, 2015-07-09) Drochytka, Rostislav; Helanová, Ester
    Calciumhydrosilicate components formed during autoclaving process are highly complex formations, which often blend together mutually and form a variety of intermediate products, from completely amorphous, to the good crystalline phases. For fly ash autoclaved aerated concrete is the situation even more complicated by the fact, that high temperature and fluidized fly ash, as basic silica ingredients, have high variability of the chemical and mineralogical composition. This paper presents the results of the microstructure monitoring and physical and mechanical tests on samples of the fly ash aerated concrete based on high temperature and fluidized fly ashes performed after 2 years of storage in laboratory conditions. The microstructure of aerated concrete is evaluated on the basis of SEM images and mineralogical composition according to X-ray analysis. The changes in compressive strength, density and coefficient of thermal conductivity of the fly ash aerated concrete in time are evaluated.
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    Determine the Compressive Strength of Calcium Silicate Bricks by Combined Non-Destructive Method
    (Hindawi, 2014-09-01) Brožovský, Jiří
    The paper deals with the application of combined non-destructive method for assessment of compressive strength of calcium silicate bricks. In this case it is a combination of the rebound hammer method and ultrasonic pulse method. Calibration relationships for determining compressive strength of calcium silicate bricks obtained from non-destructive parameter testing for the combined method as well as for the L-type Schmidt rebound hammer and ultrasonic pulse method are quoted here. Calibration relationships are known for their close correlation and are applicable in practice. The highest correlation between variables is obtained from measurements using the SonReb combined non-destructive method, thereby a higher accuracy of predicted compressive strengths. Combined non-destructive SonReb method was proved as applicable for determination of compressive strength of calcium-silicate bricks at checking tests in a production plant and for evaluation of bricks built in existing masonry structures.
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    Automorphisms of Ordinary Differential Equations
    (Hindawi Publishing Corporation, 2014-01-29) Tryhuk, Václav; Chrastinová, Veronika
    The paper deals with the local theory of internal symmetries of underdetermined systems of ordinary differential equations in full generality. The symmetries need not preserve the choice of the independent variable, the hierarchy of dependent variables, and the order of derivatives. Internal approach to the symmetries of one-dimensional constrained variational integrals is moreover proposed without the use of multipliers.
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    Explicit general solution of planar linear discrete systems with constant coefficients and weak delays
    (Springer Nature, 2013-03-06) Diblík, Josef; Halfarová, Hana
    In this paper, planar linear discrete systems with constant coefficients and two delays $$ x(k+1)=Ax(k)+Bx(k-m)+Cx(k-n) $$ are considered where $k\in\bZ_0^{\infty}:=\{0,1,\dots,\infty\}$, $x\colon \bZ_0^{\infty}\to\mathbb{R}^2$, $m>n>0$ are fixed integers and $A=(a_{ij})$, $B=(b_{ij})$ and $C=(c_{ij})$ are constant $2\times 2$ matrices. It is assumed that the system considered system is one with weak delays. The characteristic equations of such systems are identical with those for the same systems but without delayed terms. In this case, after several steps, the space of solutions with a given starting dimension $2(m+1)$ is pasted into a space with a dimension less than the starting one. In a sense, this situation is analogous to one known in the theory of linear differential systems with constant coefficients and weak delays when the initially infinite dimensional space of solutions on the initial interval turns (after several steps) into a finite dimensional set of solutions. For every possible case, explicit general solutions are constructed and, finally, results on the dimensionality of the space of solutions are obtained.
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    Discrete matrix delayed exponential for two delays and its property
    (Springer Nature, 2013-06-13) Diblík, Josef; Morávková, Blanka
    In recent papers, a discrete matrix delayed exponential for a single delay was defined and its main property connected with the solution of linear discrete systems with a single delay was proved. In the present paper, a generalization of the concept of discrete matrix delayed exponential is designed for two delays and its main property is proved as well.