Stability Results for Neutral Integro-Differential Equations with Multiple Functional Delays Ernest Yankson Department of Mathematics and Statistics, University of Cape Coast, Cape Coast, Ghana. author text article 2017 eng Necessary and sufficient conditions for the zero solution of the nonlinear neutral integro-differential equation\begin{eqnarray*}&&\frac{d}{dt}\Big(r(t)\Big[x(t)+Q(t, x(t-g_1(t)),...,x(t-g_N(t)))\Big]\Big)\\ &&= -a(t)x(t)+ \sum^{N}_{i=1}\int^{t}_{t-g_i(t)}k_i(t,s)f_i(x(s))ds \end{eqnarray*} to be asymptotically stable are obtained. In the process we invert the integro-differential equation and obtain an equivalent integral equation. The contraction mapping principle is used as the main mathematical tool for establishing the necessary and sufficient conditions. Khayyam Journal of Mathematics Tusi Mathematical Research Group (TMRG) and Department of Pure Mathematics, Ferdowsi University of Mashhad (in cooperation with The Center of Excellence in Analysis on Algebraic Structures) 2423-4788 3 v. 1 no. 2017 1 11 http://www.kjm-math.org/article_43831_2161050be631ca19a702fe6a0bd6d1c3.pdf dx.doi.org/10.22034/kjm.2017.43831 Periodic Solutions for Third-Order Nonlinear Delay Differential Equations with Variable Coefficients Abdelouaheb Ardjouni Department of Mathematics and Informatics, University of Souk Ahras, P.O. Box 1553, Souk Ahras, 41000, Algeria. author Farid Nouioua Department of Mathematics and Informatics, University of Souk Ahras, P.O. Box 1553, Souk Ahras, 41000, Algeria. author Ahcene Djoudi Department of Mathematics, University of Annaba, P.O. Box 12, Annaba, 23000, Algeria. author text article 2017 eng In this paper, the following third-order nonlinear delay differential equationwith periodic coefficients%\begin{align*}& x^{\prime\prime\prime}(t)+p(t)x^{\prime\prime}(t)+q(t)x^{\prime}(t)+r(t)x(t)\\& =f\left( t,x\left( t\right) ,x(t-\tau(t))\right) +\frac{d}{dt}g\left(t,x\left( t-\tau\left( t\right) \right) \right) ,\end{align*}is considered. By employing Green's function, Krasnoselskii's fixed pointtheorem and the contraction mapping principle, we state and prove theexistence and uniqueness of periodic solutions to the third-order nonlineardelay differential equation. Khayyam Journal of Mathematics Tusi Mathematical Research Group (TMRG) and Department of Pure Mathematics, Ferdowsi University of Mashhad (in cooperation with The Center of Excellence in Analysis on Algebraic Structures) 2423-4788 3 v. 1 no. 2017 12 21 http://www.kjm-math.org/article_44493_fca28ec0388a064bcfebffd47c16b12f.pdf dx.doi.org/10.22034/kjm.2017.44493 Operators Reversing Orthogonality and Characterization of Inner Product Spaces Paweł Wójcik Institute of Mathematics, Pedagogical University of Cracow, Podchorążych 2, 30-084 Kraków, Poland. author text article 2017 eng In this short paper we answer a question posed by Chmieliński in [Adv. Oper. Theory, 1 (2016), no. 1, 8-14]. Namely, we prove that among normed spaces of dimension greater than two,only inner product spaces admit nonzero linear operators which reverse the Birkhoff orthogonality. Khayyam Journal of Mathematics Tusi Mathematical Research Group (TMRG) and Department of Pure Mathematics, Ferdowsi University of Mashhad (in cooperation with The Center of Excellence in Analysis on Algebraic Structures) 2423-4788 3 v. 1 no. 2017 22 24 http://www.kjm-math.org/article_44746_9f829bbb7fc2df9483fd2622f9084732.pdf dx.doi.org/10.22034/kjm.2017.44746 Certain Properties of a Subclass of Univalent Functions With Finitely Many Fixed Coefficients S.Sunil Varma Department of Mathematics, Madras Christian College, Tambaram, Chennai-600059, Tamil Nadu, India author Thomas Rosy Department of Mathematics, Madras Christian College, Tambaram, Chennai-600059, Tamil Nadu, India author text article 2017 eng In this paper a new class of analytic, univalent and normalized functions with finitely many fixed coefficients is defined. Properties like coefficient condition, radii of starlikeness and convexity, extreme points and integral operators applied to functions in the class are investigated. Khayyam Journal of Mathematics Tusi Mathematical Research Group (TMRG) and Department of Pure Mathematics, Ferdowsi University of Mashhad (in cooperation with The Center of Excellence in Analysis on Algebraic Structures) 2423-4788 3 v. 1 no. 2017 25 32 http://www.kjm-math.org/article_44920_245bef22255f8b0b38f19d4c0c83a25b.pdf dx.doi.org/10.22034/kjm.2017.44920 On Para-Sasakian Manifolds Satisfying Certain Curvature Conditions with Canonical Paracontact Connection Selcen Yüksel Perktaş Faculty of Arts and Science, Department of Mathematics, Adıyaman University, Adıyaman, Turkey author text article 2017 eng In this article, the aim is to introduce a para-Sasakian manifold with acanonical paracontact connection. It is shown that $\varphi$-conharmonically flat, $\varphi$-$W_{2}$ flat and $\varphi$-pseudo projectively flat para-Sasakian manifolds with respect to canonical paracontact connection are all $\eta$-Einsteinmanifolds. Also, we prove that quasi-pseudo projectively flatpara-Sasakian manifolds are of constant scalar curvatures. Khayyam Journal of Mathematics Tusi Mathematical Research Group (TMRG) and Department of Pure Mathematics, Ferdowsi University of Mashhad (in cooperation with The Center of Excellence in Analysis on Algebraic Structures) 2423-4788 3 v. 1 no. 2017 33 43 http://www.kjm-math.org/article_45190_7d44a17d67db3000195bfd95cc73a650.pdf dx.doi.org/10.22034/kjm.2017.45190 Approximation for a Summation-Integral Type Link Operators Arun Kajla Department of Mathematics, Central University of Haryana, Haryana-123031, India. author text article 2017 eng The present article deals with the general family of summation-integral type operators. Here, we propose the Durrmeyer variant of the generalized Lupaş operators considered by Abel and Ivan (General Math. 15 (1) (2007) 21-34) and study local approximation, Voronovskaja type formula, global approximation, Lipchitz type space and weighted approximation results. Also, we discuss the rate of convergence for absolutely continuous functions having a derivative equivalent with a function of bounded variation. Khayyam Journal of Mathematics Tusi Mathematical Research Group (TMRG) and Department of Pure Mathematics, Ferdowsi University of Mashhad (in cooperation with The Center of Excellence in Analysis on Algebraic Structures) 2423-4788 3 v. 1 no. 2017 44 60 http://www.kjm-math.org/article_45322_725917aec0e6b1c459fe81fc2e4d7411.pdf dx.doi.org/10.22034/kjm.2017.45322 Ostrowski's Inequality for Functions whose First Derivatives are $s$-Preinvex in the Second Sense Badreddine Meftah Laboratoire des t&#039;el&#039;ecommunications, Facult&#039;e des Sciences et de la Technologie, University of 8 May 1945 Guelma, P.O. Box 401, 24000 Guelma, Algeria. author text article 2017 eng In this paper, we establish some new Ostrowski type inequalities forfunctions whose first derivatives are $s$-preinvex in the second sense. Khayyam Journal of Mathematics Tusi Mathematical Research Group (TMRG) and Department of Pure Mathematics, Ferdowsi University of Mashhad (in cooperation with The Center of Excellence in Analysis on Algebraic Structures) 2423-4788 3 v. 1 no. 2017 61 80 http://www.kjm-math.org/article_46863_69c7dd0b531fa53298dd16c90cd3a0f8.pdf dx.doi.org/10.22034/kjm.2017.46863 Proximal Point Algorithms for Numerical Reckoning Fixed Points of Hybrid-Type Multivalued Mappings in Hilbert Spaces Kritsada Lerkchaiyaphum Department of Mathematics, Faculty of Science and Technology, Nakhon Pathom Rajabhat University, Nakhon Pathom 73000, Thailand. author Withun Phuengrattana Research Center for Pure and Applied Mathematics, Research and Development Institute, Nakhon Pathom Rajabhat University, Nakhon Pathom 73000, Thailand. author text article 2017 eng In this paper, we propose a new iteration process to approximateminimizers of proper convex and lower semi-continuous functions andfixed points of $\lambda$-hybrid multivalued mappings in Hilbertspaces. We also provide an example to illustrate the convergencebehavior of the proposed iteration process and numerically comparethe convergence of the proposed iteration scheme with the existingschemes. Khayyam Journal of Mathematics Tusi Mathematical Research Group (TMRG) and Department of Pure Mathematics, Ferdowsi University of Mashhad (in cooperation with The Center of Excellence in Analysis on Algebraic Structures) 2423-4788 3 v. 1 no. 2017 81 89 http://www.kjm-math.org/article_46951_9c228d2ed70ca44facd3ac48e7b8797e.pdf dx.doi.org/10.22034/kjm.2017.46951