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 paper, we study some existence and uniqueness results for systems of differential equations in which each the system involves a different Stieltjes derivative. Specifically, show that problems can only have one solution under Osgood condition, or even, Montel–Tonelli condition. We also explore guaranteeing these conditions. Along way, obtain interesting properties Lebesgue–Stieltjes int...

For the existence of a branched covering Σ̃→ Σ between closed surfaces there are easy necessary conditions in terms of χ(Σ̃), χ(Σ), orientability, the total degree, and the local degrees at the branching points. A classical problem dating back to Hurwitz asks whether these conditions are also sufficient. Thanks to the work of many authors, the problem remains open only when Σ is the sphere, in wh...

in some of the new economic growth models, we pay attention to the effects of financial development on economic growth. this research investigates the relationship between capital market and economic growth in macro level during 1991-2011. the research is organized as follows: the introduction comes as the first section. in section ii, we review the literature on the relationship between econom...