ORIGINAL_ARTICLE Stability Results for Neutral Integro-Differential Equations with Multiple Functional Delays 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. http://www.kjm-math.org/article_43831_2161050be631ca19a702fe6a0bd6d1c3.pdf 2017-01-01T11:23:20 2019-10-22T11:23:20 1 11 10.22034/kjm.2017.43831 Stability integro-differential equation functional delay Ernest Yankson ernestoyank@gmail.com true 1 Department of Mathematics and Statistics, University of Cape Coast, Cape Coast, Ghana. Department of Mathematics and Statistics, University of Cape Coast, Cape Coast, Ghana. Department of Mathematics and Statistics, University of Cape Coast, Cape Coast, Ghana. LEAD_AUTHOR
ORIGINAL_ARTICLE Periodic Solutions for Third-Order Nonlinear Delay Differential Equations with Variable Coefficients 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. http://www.kjm-math.org/article_44493_fca28ec0388a064bcfebffd47c16b12f.pdf 2017-01-01T11:23:20 2019-10-22T11:23:20 12 21 10.22034/kjm.2017.44493 fixed point periodic solutions third-order nonlinear delay differential equations Abdelouaheb Ardjouni abd_ardjouni@yahoo.fr true 1 Department of Mathematics and Informatics, University of Souk Ahras, P.O. Box 1553, Souk Ahras, 41000, Algeria. Department of Mathematics and Informatics, University of Souk Ahras, P.O. Box 1553, Souk Ahras, 41000, Algeria. Department of Mathematics and Informatics, University of Souk Ahras, P.O. Box 1553, Souk Ahras, 41000, Algeria. LEAD_AUTHOR Farid Nouioua fnouioua@gmail.com true 2 Department of Mathematics and Informatics, University of Souk Ahras, P.O. Box 1553, Souk Ahras, 41000, Algeria. Department of Mathematics and Informatics, University of Souk Ahras, P.O. Box 1553, Souk Ahras, 41000, Algeria. Department of Mathematics and Informatics, University of Souk Ahras, P.O. Box 1553, Souk Ahras, 41000, Algeria. AUTHOR Ahcene Djoudi adjoudi@yahoo.com true 3 Department of Mathematics, University of Annaba, P.O. Box 12, Annaba, 23000, Algeria. Department of Mathematics, University of Annaba, P.O. Box 12, Annaba, 23000, Algeria. Department of Mathematics, University of Annaba, P.O. Box 12, Annaba, 23000, Algeria. AUTHOR
ORIGINAL_ARTICLE Operators Reversing Orthogonality and Characterization of Inner Product Spaces 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. http://www.kjm-math.org/article_44746_9f829bbb7fc2df9483fd2622f9084732.pdf 2017-01-01T11:23:20 2019-10-22T11:23:20 22 24 10.22034/kjm.2017.44746 Birkhoff orthogonality orthogonality reversing mappings characterizations of inner product spaces Paweł Wójcik pwojcik@up.krakow.pl true 1 Institute of Mathematics, Pedagogical University of Cracow, Podchorążych 2, 30-084 Kraków, Poland. Institute of Mathematics, Pedagogical University of Cracow, Podchorążych 2, 30-084 Kraków, Poland. Institute of Mathematics, Pedagogical University of Cracow, Podchorążych 2, 30-084 Kraków, Poland. LEAD_AUTHOR
ORIGINAL_ARTICLE On Para-Sasakian Manifolds Satisfying Certain Curvature Conditions with Canonical Paracontact Connection 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. http://www.kjm-math.org/article_45190_7d44a17d67db3000195bfd95cc73a650.pdf 2017-01-01T11:23:20 2019-10-22T11:23:20 33 43 10.22034/kjm.2017.45190 Canonical connection paracontact metric structure normal structure Selcen Yüksel Perktaş sperktas@adiyaman.edu.tr true 1 Faculty of Arts and Science, Department of Mathematics, Adıyaman University, Adıyaman, Turkey Faculty of Arts and Science, Department of Mathematics, Adıyaman University, Adıyaman, Turkey Faculty of Arts and Science, Department of Mathematics, Adıyaman University, Adıyaman, Turkey LEAD_AUTHOR
ORIGINAL_ARTICLE Ostrowski's Inequality for Functions whose First Derivatives are $s$-Preinvex in the Second Sense In this paper, we establish some new Ostrowski type inequalities forfunctions whose first derivatives are $s$-preinvex in the second sense. http://www.kjm-math.org/article_46863_69c7dd0b531fa53298dd16c90cd3a0f8.pdf 2017-01-01T11:23:20 2019-10-22T11:23:20 61 80 10.22034/kjm.2017.46863 Ostrowski inequality midpoint inequality H"{o}lder inequality power mean inequality preinvex functions $s$-preinvex functions Badreddine Meftah badrimeftah@yahoo.fr true 1 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. 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. 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. LEAD_AUTHOR
ORIGINAL_ARTICLE Proximal Point Algorithms for Numerical Reckoning Fixed Points of Hybrid-Type Multivalued Mappings in Hilbert Spaces 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. http://www.kjm-math.org/article_46951_9c228d2ed70ca44facd3ac48e7b8797e.pdf 2017-01-01T11:23:20 2019-10-22T11:23:20 81 89 10.22034/kjm.2017.46951 Proximal point algorithm hybrid multivalued mapping Ishikawa iteration S-iteration Hilbert spaces Kritsada Lerkchaiyaphum a_krit2@hotmail.com true 1 Department of Mathematics, Faculty of Science and Technology, Nakhon Pathom Rajabhat University, Nakhon Pathom 73000, Thailand. Department of Mathematics, Faculty of Science and Technology, Nakhon Pathom Rajabhat University, Nakhon Pathom 73000, Thailand. Department of Mathematics, Faculty of Science and Technology, Nakhon Pathom Rajabhat University, Nakhon Pathom 73000, Thailand. AUTHOR Withun Phuengrattana withun_ph@yahoo.com true 2 Research Center for Pure and Applied Mathematics, Research and Development Institute, Nakhon Pathom Rajabhat University, Nakhon Pathom 73000, Thailand. Research Center for Pure and Applied Mathematics, Research and Development Institute, Nakhon Pathom Rajabhat University, Nakhon Pathom 73000, Thailand. Research Center for Pure and Applied Mathematics, Research and Development Institute, Nakhon Pathom Rajabhat University, Nakhon Pathom 73000, Thailand. LEAD_AUTHOR