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Singular cases of the planar parallel robot
Belda, Květoslav ; Stejskal, V.
Singular cases - singularities of the robot are defined as positions in which the robot loses kinematic definiteness. The loss appears in both direct and inverse kinematic transformation. Existence of the singularities in the robot workspace causes sharp changes in profiles of the velocities and accelerations and changes in force effects. The objective of this paper is to investigate singularities (singular positions) of one parallel robot structure and to simply classify such singular cases.
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Quantitative modelling of effect of transverse - axial tubular system on electrical activity of cardiac cells: Development of model II
Pásek, Michal ; Christé, G. ; Šimurda, J.
In this work, we present a new version of cardiac ventricular cell model incorporating the transverse - axial tubular system. The improvements include reformulated description of L-type Ca2+ channel, of Ca2+ induced Ca2+ release from sarcoplasmic reticulum, of intracellular Ca2+ buffering and incorporation of potassium currents Ito, IK(Na) and IK(ATP). In comparison with the previous model (Pásek et al., 2002), the steady state simulations revealed more profound changes of tubular ionic concentration (12.8 % for Ca2+ and 4.7 % for K+ at 1 Hz). The refined model will be used for more exact quantitative exploration of the effect of transverse - axial tubular system on cellular electrical activity and excitation - contraction coupling.
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