Prof. Ioannis Stavroulakis

Department of Mathematics, University of Ioannina, 451 10 Ioannina HELLAS (Greece)

Prof. Ioannis Stavroulakis

Department of Mathematics, University of Ioannina, 451 10 Ioannina HELLAS (Greece)

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Academic Career Length

23Years (2004-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 September 2016 in Applied Mathematics Letters

Journal Article

An oscillation criterion for delay differential equations with several non-monotone arguments

HAYDAR AKCA

George E Chatzarakis

Ioannis Stavroulakis

1 January 2019 in Opuscula Mathematica

Journal Article

Oscillatory results for second-order noncanonical delay differential equations

Jozef Džurina

Irena Jadlovská

Ioannis Stavroulakis

The main purpose of this paper is to improve recent oscillation results for the second-order half-linear delay differential equation \[\left(r(t)\left(y'(t)\right)^\gamma\right)'+q(t)y^\gamma(\tau(t))= 0, \quad t\geq t_0,\] under the condition \[\int_{t_0}^{\infty}\frac{\text{d} t}{r^{1/\gamma}(t)} \lt \infty.\] Our approach is essentially based on establishing sharper estimates for positive solutions of the studied equation than those used in known works. Two examples illustrating the results are given.

1 April 2004

Book

Partial Differential Equations

Ioannis Stavroulakis

Stepan A Tersian

4 April 2020 in Applied Mathematics Letters

Journal Article

Oscillation criteria for first order linear delay differential equations with several variable delays

Abel Garab

Ioannis Stavroulakis

Consider the first order linear differential equation with several variable delays of the form

x^{'} (t) + \sum_{i = 1}^{m} p_{i} (t) x (t - τ_{i} (t)) = 0, t \geq t_{0},

where

p_{i} : [t_{0}, \infty) \to [0, \infty)

and

τ_{i} : [t_{0}, \infty) \to (0, \infty)

are continuous functions, such that

t - τ_{i} (t) \to \infty

(as

t \to \infty

) for all

1 \leq i \leq m

. Sufficient conditions are established under which some “

lim inf

-type” conditions for oscillation of all solutions remain valid if one replaces the

lim inf

lim sup

. This improves and generalizes many existing results in the literature, which is illustrated via examples.

11 March 2018 in Georgian Mathematical Journal

Journal Article

Oscillation of first-order differential equations with several non-monotone retarded arguments

GÖ

Consider the first-order linear differential equation with several non-monotone retarded arguments x ′ ⁢ ( t ) + ∑ i = 1 m p i ⁢ ( t ) ⁢ x ⁢ ( τ i ⁢ ( t ) ) = 0 {x^{\prime}(t)+\sum_{i=1}^{m}p_{i}(t)x(\tau_{i}(t))=0} , t ≥ t 0 {t\geq t_{0}} , where the functions p i , τ i ∈ C ⁢ ( [ t 0 , ∞ ) , ℝ + ) {p_{i},\tau_{i}\in C([t_{0},\infty),\mathbb{R}^{+})} , for every i = 1 , 2 , … , m {i=1,2,\ldots,m} , τ i ⁢ ( t ) ≤ t {\tau_{i}(t)\leq t} for t ≥ t 0 {t\geq t_{0}} and lim t → ∞ ⁡ τ i ⁢ ( t ) = ∞ {\lim_{t\to\infty}\tau_{i}(t)=\infty} . New oscillation criteria which essentially improve the known results in the literature are established. An example illustrating the results is given.

2 May 2020 in Symmetry

Journal Article

Oscillation Criteria for First Order Differential Equations with Non-Monotone Delays

Emad Attia

Hassan El-Morshedy

Ioannis Stavroulakis

New sufficient criteria are obtained for the oscillation of a non-autonomous first order differential equation with non-monotone delays. Both recursive and lower-upper limit types criteria are given. The obtained results improve most recent published results. An example is given to illustrate the applicability and strength of our results.

About Me

Prof. Dr. Ioannis P. Stavroulakis is a Professor Emeritus at the University of Ioannina. He has also had the following positions: Visiting Assistant Professor, at Brown University, USA; Assistant Professor, at the University of Rhode Island, USA; Visiting Researcher, at Ibaraki University, Japan; Visiting Scholar, at the Flinders University of South Australia, Adelaide; Visiting Professor, Boston University, USA; Visiting Professor, Ankara University, Turkey; Visiting Professor, University of South Africa (UNISA), South Africa; Visiting Professor, Al-Farabi Kazakh National University, Almaty, Kazakhstan. He obtained his Master’s in Mathematics (1973) at the City University of New York; Ph.D. in Mathematics (1976) at the University of Ioannina and Doctor Honoris Causa (2012)---the 1st to be awarded an Honorary Doctorate---at the University of Gjirokastra. He was awarded the following awards/distinctions: Ampere Foundation Fellowship; and Canon Foundation in Europe Research Fellowship; Two Special Issues dedicated to him have been published: (1) Global and Stochastic Analysis 5 No.1, (2018) (www.mukpublications.com) and (2) Nonlinear Dynamics and Systems Theory 19 (1-SI) (2019) (www.e-ndst.kiev.ua). Certificate of OBADA-PRIZE 2019 (in the top 10 out of 370).

Prof. Ioannis Stavroulakis

Prof. Ioannis Stavroulakis

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