in this paper, sufficient conditions are investigated for the existence of periodic (not necessarily positive) solutions for nonlinear several time delay population system with feedback control. nonlinear system affected by an periodic external source is studied. existence of a control variable provides  the extension of  some previous results obtained in other studies. we give a illustrative e...

‎in this work we introduce and study discrete time periodically correlated stable‎ ‎processes and multivariate stationary stable processes related to periodic and cyclic‎ ‎flows‎. ‎our study involves producing a spectral representation and a‎ ‎spectral identification for such processes‎. ‎we show that the third‎ ‎component of a periodically correlated stable process has a component related to a...

kleine-levin syndrome (kls) is a rare syndrome characterized by periodic hypersomnia, hyperphagia, behavioral disturbances, and in some instances hypersexuality. this report depicts a17-year-old boy with kls. he has experienced long periods of hypersomnia, sometimes up to 40 days. during these periods he was impatient, aggressive, depersonalized, suffering from hyperphagia, and amnesia. he did ...

primary hypokalemic periodic paralysis is a familial channelopathy inherited as an autosomal dominant trait. the first attack of paralysis may be evolved at any age, but has been reported to be most common in the second decade, so that some authorities believe that an episodic weakness beginning after age 25 is almost never due to primary periodic paralysis. in this retrospective study, we revi...

different discrete models of population dynamics of certain insects have been investigated under various feasible conditions within the framework of nonlinear dynamics. evolutionary phenomena are discussed through bifurcation analysis leading to chaos. some tools of nonlinear dynamics, such as lyapunov characteristic exponents (lce), lyapunov numbers, correlation dimension, etc. are calculated ...

the quasi-periodic order is a type of geometrical order in universe which is observed in the structure of quasi-crystals. this order was first introduced in mathematics in 1973 by roger penrose and then discovered in quasi-crystals in 1984 while spreading in mathematics, chemistry and physics. the paper professor james lu et al published in science magazine in 2007 illustrated that iranians wer...

in this paper the periodic solutions of fourth order delay differential equation of the form $ddddot{x}(t)+adddot{x}(t)+f(ddot{x}(t-tau(t)))+g(dot{x}(t-tau(t)))+h({x}(t-tau(t)))=p(t)$  is investigated. some new positive periodic criteria are given.

since 2005 a new powerful invariant of an algebra has emerged using the earlier work of horvath, hethelyi, kulshammer and murray. the authors studied morita invariance of a sequence of ideals of the center of a nite dimensional algebra over a eld of nite characteristic. it was shown that the sequence of ideals is actually a derived invariant, and most recently a slightly modied version o...

duffing harmonic oscillator is a common model for nonlinear phenomena in science and engineering. this paper presents he´s energy balance method (ebm) for solving nonlinear differential equations. two strong nonlinear cases have been studied analytically. analytical results of the ebm are compared with the solutions obtained by using he´s frequency amplitude formulation (faf) and numerical solu...

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