An analytical solution for nonlinear vibration of an initially stressed beam with elastic end restraints resting on two-parameter foundation is obtained. The mode functions for linear vibration of a beam with elastic end restraints resting on a linear elastic foundation are obtained first and used to solve the nonlinear vibration equation recalling elliptic integrals. The results obtained from the present solution are compared against those obtained from finite element method and found in close agreement. The effects of elastic support stiffnesses at the beam ends, foundation stiffness, initial axial load and vibration amplitude on the natural frequency are studied. and Obsahuje seznam literatury
In this paper we prove the existence of mild solutions and the controllability for semilinear differential inclusions with nonlocal conditions. Our results extend some recent theorems.
In this paper we consider the equation \[y^{\prime \prime \prime} + q(t){y^{\prime }}^{\alpha} + p(t) h(y) =0,\] where $p,q$ are real valued continuous functions on $[0,\infty)$ such that $q(t) \ge 0$, $p(t) \ge 0$ and $h(y)$ is continuous in $(-\infty ,\infty)$ such that $h(y)y>0$ for $y \ne 0$. We obtain sufficient conditions for solutions of the considered equation to be nonoscillatory. Furthermore, the asymptotic behaviour of these nonoscillatory solutions is studied.
This paper presents a relaxed scheme for controller synthesis of continuous-time systems in the Takagi-Sugeno form, based on non-quadratic Lyapunov functions and a non-PDC control law. The relaxations here provided allow state and input dependence of the membership functions' derivatives, as well as independence on initial conditions when input constraints are needed. Moreover, the controller synthesis is attainable via linear matrix inequalities, which are efficiently solved by commercially available software.
It is shown that gigantic nonresonance pararnetric arnplification of weak external signals is possible in neural networks. The mechanisrn of amplificatiori is determined by periodic rnodulation of neuron threshold or otlier parameters. Brain rhythms can play the role of periodic rnodulation. The paper develops Hopfield hypothesis abont the connection of some brain rhythms and signál amplification. In artificial networks a special centra! generátor for pararnetric rnodulation is necessary.
We examined the capacity for nonshivering thermogenesis in four rodent species residing in the Ordos Plateau of Inner Mongolia. Nonshivering thermogenesis (NST, maximum NST minus resting metabolic rate) was determined for northern three-toed jerboas (Dipus sagitta), midday gerbils (Meriones meridianus), desert hamsters (Phodopus roborovskii), and striped hamsters (Cricetulus barabensis) in spring (May), summer (July, and autumn (OCtober) captured in the Kubuqi desert in 1997. NST was induced by norepinephrine (NE) and measured by using the closed-circuit respirometer at 27 °C. Our results showed significant increases from summer to autumn in NST for the four species. NST capacities were 0.52±0.27 ml O2/g0.73.h (n = 7) in summer and 2.49±1.29 (n = 6) in autumn for jerboas, 1.61±0.74 (n = 6) in summer and 3.26±1.35 (n = 5) in autumn for gerbils, 3.62±0.75 (n = 5) in summer and 9.71±2.81 (n = 6) in autumn for desert hamsters, and 6.81±3.02 (n = 8) in summer and 11.23±2.77 (n = 8) in autumn for striped hamsters. These results suggest that small mammals living in the inland arid region on Ordos Plateau adapt to their extreme environment physiologically by adjusting their thermogenic capacities to cope with the dramatic seasonal temperature fluctuations.
We study the existence and multiplicity of positive nonsymmetric and sign-changing nonantisymmetric solutions of a nonlinear second order ordinary differential equation with symmetric nonlinear boundary conditions, where both of the nonlinearities are of power type. The given problem has already been studied by other authors, but the number of its positive nonsymmetric and sign-changing nonantisymmetric solutions has been determined only under some technical conditions. It was a long-standing open question whether or not these conditions can be omitted. In this article we provide the answer. Our main tool is the shooting method.
In the present paper we give general nonuniqueness results which cover most of the known nonuniqueness criteria. In particular, we obtain a generalization of the nonuniqueness theorem of Chr. Nowak, of Samimi’s nonuniqueness theorem and of Stettner’s nonuniqueness criterion.
Recent results of the authors have demonstrated that the elevation of extracellular adenosine induced by the combined administration of dipyridamole, a drug inhibiting the cellular uptake of adenosine, and adenosine monophosphate (AMP), a soluble adenosine prodrug, mediates radioprotective effects in mice. Furthermore, it has been shown that this action is induced by at least two mechanisms: (1) protection by hypoxia as a result of the effects of treatment on the cardiovascular system (bradycardia, vasodilation), and (2) an enhanced regeneration of the radiation-perturbed hematopoiesis. Here, it was ascertained that the joint use of an optimal dose of noradrenaline given with dipyridamole and AMP combination eliminates the hypothermic and hypoxic effects of the treatment, but preserves the radioprotective action of dipyridamole and AMP combination in terms of hematopoietic recovery and partially also survival enhancing effects of the drugs in gamma-irradiated mice. These findings might be of importance for attempts to obtain available and tolerable radioprotective pharmacological prescriptions for clinical use.