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Plant transpiration and self-organization of hydrologic cycle
Šír, Miloslav ; Lichner, Ľ. ; Tesař, Miroslav
We quantified the influence of plant transpiration on the entropy production associated with the degradation of solar energy on the Earth’s surface covered by plants. Two surfaces were studied: (1) biotic surface – plant transpiration taken as equal to the potential one, (2) abiotic surface – plant transpiration taken as if equal to zero. Two sources of entropy were taken into account – the entropy production associated with the conversion of solar radiation into (1) the sensible heat, and (2) latent heat. Surface processes in hydrologic cycle were examined in the experimental watershed Liz located in the Bohemian Forest (Czech Republic). We found that in the growing season 1992 the entropy production in humid hydrologic cycle (the Earth’s surface is biotic) was considerably higher than in the arid one (in 39 % of days the Earth’s surface behaved as biotic, in 61 % of days behaved as abiotic). Considering that the biotic effect on the Earth’s functioning can be assessed using the entropy production, we can assume that the hypothesis that biota – represented as a biotic surface – regulates Earth’s environment is proved in the watershed scale.
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Impact damper with Hertz's dynamic contact
Půst, Ladislav
The paper contains results of analytical and numerical investigation of the oscillations of 2DOF system in which the amplitudes are limited by one- or two-sided stops. It is shown that the application of stops in absorber subsystem can get lower the amplitudes of basic external forced system approx to 50%. The efficiency of stops application on self-excited system is very low.
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Self excited two-mass system with soft impacts
Tondl, Aleš ; Kocanda, Lubomír
To a basic one-mass self-excited system a tuned absorber is attachedthe motion of which is influenced by soft impacts. The self-excitation is consideredas of van der Pol type one. The stops are symmetrically situated to the absorbermass equilibrium position. The results of numerical simulation are presented indiagrams showing the measure of extreme deflection of the basic system mass tothe amplitude of the basic system vibration without absorber in dependence on thetuning coefficient of the absorber.
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Self-excited oscilator with soft stops
Tondl, Aleš ; Kocanda, Lubomír
A self-excited system with one degree of freedom the motion of which is influenced by symmetrically situated soft stops in a certain distance from the equilibrium position is analysed. The stops are characterized by additional spring stiffness and stop deformation. The maximum deflection of the oscillator decreases with decreasing the stop distances and with increasing the stop stiffness and damping due to the stop deformation.
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Fabrication of periodic stripes based on self-organization of Ni and C60
Vacík, Jiří ; Naramoto, H.
Fabrication of the self-organized mesoscopic stripe system induced by co-deposition of C60 and Ni on the MgO(001) substrate is reported. It was found that a periodic array of stripe domains is formed if specific deposition kinetics is applied. As a possible mechanism of the stripe formation a step-wise relaxation of the internal stress accumulated in the hybrid composite of the immiscible Ni and C60 (a-C) phases is suggested.
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