http://journals.math.tku.edu.tw/index.php/TKJM/issue/feedTamkang Journal of Mathematics2017-05-16T10:11:52+08:00Editorial Officeeo-tkjm@mail2.tku.edu.twOpen Journal Systems<h2>Welcome to Tamkang Journal of Mathematics</h2><strong>Aims and Scope</strong><br /><div>To promote research interactions between local and overseas researchers, the Department has been publishing an international mathematics journal, the Tamkang Journal of Mathematics. The journal started as a biannual journal in 1970 and is devoted to high-quality original research papers in pure and applied mathematics. In 1985 it has become a quarterly journal.</div>http://journals.math.tku.edu.tw/index.php/TKJM/article/view/2200Helicoidal Surfaces in the three dimensional simply isotropic space I₃¹2017-05-16T10:11:51+08:00Murat Kemal Karacanmurat.karacan@usak.edu.trDae Won Yoondwyoon@gnu.ac.krSezai Kiziltugskiziltug@erzincan.edu.trIn this paper, we classify helicoidal surfaces in the three dimensional simply isotropic space I₃¹ satisfying some algebraic equations in terms of the coordinate functions and the Laplacian operators with respect to the first, the second and the third fundamental form of the surface. We also give explicit forms of these surfaces.2017-06-30T00:00:00+08:00http://journals.math.tku.edu.tw/index.php/TKJM/article/view/2240Signed strong Roman domination in graphs2017-05-16T10:11:51+08:00Seyed Mahmoud Sheikholeslamis.m.sheikholeslami@azaruniv.eduRana Khoeilarkhoeilar@azaruniv.eduLeila Asgharsharghil.sharghi@azaruniv.eduLet $G=(V,E)$ be a finite and simple graph of order $n$ and maximum degree $\Delta$. A signed strong Roman dominating function (abbreviated SStRDF) on a graph $G$ is a function $f:V\to \{-1,1,2,\ldots,\lceil\frac{\Delta}{2}\rceil+1\}$ satisfying the conditions that (i) for every vertex $v$ of $G$, $\sum_{u\in N[v]} f(u)\ge 1$, where $N[v]$ is the closed neighborhood of $v$ and (ii) every vertex $v$ for which $f(v)=-1$ is adjacent to at least one vertex $u$ for which $f(u)\ge 1+\lceil\frac{1}{2}|N(u)\cap V_{-1}|\rceil$, where $V_{-1}=\{v\in V \mid f(v)=-1\}$. The minimum of the values $\sum_{v\in V} f(v)$, taken over all signed strong Roman dominating functions $f$ of $G$, is called the signed strong Roman domination number of $G$ and is denoted by $\gamma_{ssR}(G)$. In this paper we initiate the study of the signed strong Roman domination in graphs and present some (sharp) bounds for this parameter.2017-06-30T00:00:00+08:00http://journals.math.tku.edu.tw/index.php/TKJM/article/view/2295On global dominating -X-coloring of graphs2017-05-16T10:11:52+08:00Rajeswari Malairajrajimaths11@gmail.comSahul Hamid Isnailsahulmat@yahoo.co.inLet $G$ be a graph. Among all $\chi$-colorings of $G$, a coloring with the maximum number of color classes that are global dominating sets in $G$ is called a global dominating-$\chi$-coloring of $G$. The number of color classes that are global dominating sets in a global dominating-$\chi$-coloring of $G$ is defined to be the global dominating -$\chi$- color number of $G$, denoted by $gd_{\chi}(G)$. This concept was introduced in \cite{a78}. This paper extends the study of this notion.2017-06-30T00:00:00+08:00http://journals.math.tku.edu.tw/index.php/TKJM/article/view/2299Strong convergence theorems for equilibrium problems involving Bregman functions in Banach spaces2017-05-16T10:11:52+08:00Eskandar Naraghiradeskandarrad@gmail.comSara Timnakstimnak@gmail.comIn this paper, using Bregman functions, we introduce new Halpern-type iterative algorithms for finding a solution of an equilibrium problem in Banach spaces. We prove the strong convergence of a modified Halpern-type scheme to an element of the set of solution of an equilibrium problem in a reflexive Banach space. This scheme has an advantage that we do not use any Bregman projection of a point on the intersection of closed and convex sets in a practical calculation of the iterative sequence. Finally, some application of our results to the problem of finding a minimizer of a continuously Fr\'{e}chet differentiable and convex function in a Banach space is presented. Our results improve and generalize many known results in the current literature.2017-06-30T00:00:00+08:00http://journals.math.tku.edu.tw/index.php/TKJM/article/view/2326Generalized k–uniformly convex harmonic functions with negative coefficients2017-05-16T10:11:52+08:00Shuhai Lilishms66@163.comHuo Tangthth2009@163.comLina Mamalina00@163.comAo Encfxyaoen@sina.comIn the present paper, we introduce some generalized $k$-uniformly convex harmonic functions with negative coefficients. Sufficient coefficient conditions, distortion bounds, extreme points, Hadamard product and partial sum for functions of these classes are obtained.2017-06-30T00:00:00+08:00http://journals.math.tku.edu.tw/index.php/TKJM/article/view/2359On inequalities of Hermite-Hadamard type for stochastic processes whose third derivative absolute values are quasi-convex2017-05-16T10:11:52+08:00Jesus Enrique Materanomateranojesus@gmail.comNelson Merentesnmerucv@gmail.comMaira Lopez-Valeraavalera7@gmail.comIn this paper we give some estimates of the right-hand side inequality of Hermite-Hadamad type for stochastic processes whose third derivatives in absolute values are quasi-convex.2017-06-30T00:00:00+08:00http://journals.math.tku.edu.tw/index.php/TKJM/article/view/2382Rectifying curves and geodesics on a cone in the Euclidean 3-space2017-05-16T10:11:52+08:00Bang-Yen Chenbychen@math.msu.eduA twisted curve in the Euclidean 3-space $\mathbb E^3$ is called a rectifying curve if its position vector field always lie in its rectifying plane. In this article we study geodesics on an arbitrary cone in $\mathbb E^3$, not necessary a circular one, via rectifying curves. Our main result states that a curve on a cone in $\mathbb E^3$ is a geodesic if and only if it is either a rectifying curve or an open portion of a ruling. As an application we show that the only planar geodesics in a cone in $\mathbb E^3$ are portions of rulings.2017-06-30T00:00:00+08:00http://journals.math.tku.edu.tw/index.php/TKJM/article/view/2442Entire solution originating from three fronts for a discrete diffusive equation2017-05-16T10:11:52+08:00Yan Yu Chenchenyanyu24@gmail.comIn this paper, we study a discrete diffusive equation with a bistable nonlinearity. For this equation, there are three types of traveling fronts. By constructing some suitable pairs of super-sub-solutions, we show that there are only two types of entire solutions originating from three fronts of this equation. These results show us some new dynamics of this discrete diffusive equation.2017-06-30T00:00:00+08:00