Journal of Discrete Mathematics The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. On the Barycentric Labeling of Certain Graphs Sun, 16 Nov 2014 12:44:52 +0000 Let be an abelian group. A graph is called -magic if there exists edge labeling such that the induced vertex set labeling , defined by , where the sum is over all edges in , is a constant map. A graph is -barycentric-magic (or has -barycentric labeling) if is -magic and also satisfies for all and for some vertex adjacent to . In this paper we consider some graphs and characterize all for which is -barycentric-magic. Saeid Alikhani and Zeynab Amirzadeh Copyright © 2014 Saeid Alikhani and Zeynab Amirzadeh. All rights reserved. Hermitian Self-Orthogonal Constacyclic Codes over Finite Fields Wed, 12 Nov 2014 07:07:21 +0000 Necessary and sufficient conditions for the existence of Hermitian self-orthogonal constacyclic codes of length over a finite field , coprime to , are found. The defining sets and corresponding generator polynomials of these codes are also characterised. A formula for the number of Hermitian self-orthogonal constacyclic codes of length over a finite field is obtained. Conditions for the existence of numerous MDS Hermitian self-orthogonal constacyclic codes are obtained. The defining set and the number of such MDS codes are also found. Amita Sahni and Poonam Trama Sehgal Copyright © 2014 Amita Sahni and Poonam Trama Sehgal. All rights reserved. Smarandache Curves according to Curves on a Spacelike Surface in Minkowski 3-Space Thu, 16 Oct 2014 09:20:29 +0000 We introduce Smarandache curves according to the Lorentzian Darboux frame of a curve on spacelike surface in Minkowski 3-space . Also, we obtain the Sabban frame and the geodesic curvature of the Smarandache curves and give some characterizations on the curves when the curve α is an asymptotic curve or a principal curve. And we give an example to illustrate these curves. Ufuk Ozturk and Esra Betul Koc Ozturk Copyright © 2014 Ufuk Ozturk and Esra Betul Koc Ozturk. All rights reserved. Counting Irreducible Polynomials of Degree over and Generating Goppa Codes Using the Lattice of Subfields of Thu, 18 Sep 2014 00:00:00 +0000 The problem of finding the number of irreducible monic polynomials of degree over is considered in this paper. By considering the fact that an irreducible polynomial of degree over has a root in a subfield of if and only if , we show that Gauss’s formula for the number of monic irreducible polynomials can be derived by merely considering the lattice of subfields of . We also use the lattice of subfields of to determine if it is possible to generate a Goppa code using an element lying in a proper subfield of . Kondwani Magamba and John A. Ryan Copyright © 2014 Kondwani Magamba and John A. Ryan. All rights reserved. Vague Filters of Residuated Lattices Wed, 10 Sep 2014 05:28:00 +0000 Notions of vague filters, subpositive implicative vague filters, and Boolean vague filters of a residuated lattice are introduced and some related properties are investigated. The characterizations of (subpositive implicative, Boolean) vague filters is obtained. We prove that the set of all vague filters of a residuated lattice forms a complete lattice and we find its distributive sublattices. The relation among subpositive implicative vague filters and Boolean vague filters are obtained and it is proved that subpositive implicative vague filters are equivalent to Boolean vague filters. Shokoofeh Ghorbani Copyright © 2014 Shokoofeh Ghorbani. All rights reserved. Modularity in the Semilattice of ω-Words Thu, 15 May 2014 11:29:53 +0000 A partial ordering of ω-words can be introduced with regard to whether an ω-word can be transformed into another by a Mealy machine. It is known that the poset of ω-words that is introduced by this ordering is a join-semilattice. The width of this join-semilattice has the power of continuum while the depth is at least . We have created a technique for proving that power-characteristic ω-words are incomparable. We use this technique to show that this join-semilattice is not modular. Jānis Buls and Edmunds Cers Copyright © 2014 Jānis Buls and Edmunds Cers. All rights reserved. -Approximation: A New Approach to Algebraic Approximation Mon, 28 Apr 2014 14:04:33 +0000 We intend to study a new class of algebraic approximations, called -approximations, and their properties. We have shown that -approximations can be used for applied problems which cannot be modeled by inclusion based approximations. Also, in this work, we studied a subclass of -approximations, called -approximations, and showed that this subclass preserves most of the properties of inclusion based approximations but is not necessarily inclusionbased. The paper concludes by studying some basic operations on -approximations and counting the number of -min functions. M. R. Hooshmandasl, A. Shakiba, A. K. Goharshady, and A. Karimi Copyright © 2014 M. R. Hooshmandasl et al. All rights reserved. Chaotification for Partial Difference Equations via Controllers Thu, 13 Mar 2014 12:25:46 +0000 Chaotification problems of partial difference equations are studied. Two chaotification schemes are established by utilizing the snap-back repeller theory of general discrete dynamical systems, and all the systems are proved to be chaotic in the sense of both Li-Yorke and Devaney. An example is provided to illustrate the theoretical results with computer simulations. Wei Liang, Yuming Shi, and Zongcheng Li Copyright © 2014 Wei Liang et al. All rights reserved. On Some Numbers Related to Extremal Combinatorial Sum Problems Mon, 03 Mar 2014 15:53:13 +0000 Let n, d, and r be three integers such that . Chiaselotti (2002) defined as the minimum number of the nonnegative partial sums with d summands of a sum , where are n real numbers arbitrarily chosen in such a way that r of them are nonnegative and the remaining are negative. Chiaselotti (2002) and Chiaselotti et al. (2008) determine the values of for particular infinite ranges of the integer parameters n, d, and r. In this paper we continue their approach on this problem and we prove the following results: (i) for all values of n, d, and r such that ; (ii) D. Petrassi Copyright © 2014 D. Petrassi. All rights reserved. The Concept of -Cycle and Applications Wed, 26 Feb 2014 12:54:51 +0000 The concept of -cycle is investigated for its properties and applications. Connections with irreducible polynomials over a finite field are established with emphases on the notions of order and degree. The results are applied to deduce new results about primitive and self-reciprocal polynomials. Umarin Pintoptang, Suton Tadee, and Vichian Laohakosol Copyright © 2014 Umarin Pintoptang et al. All rights reserved. A Characterization of 2-Tree Proper Interval 3-Graphs Sun, 23 Feb 2014 07:37:03 +0000 An interval p-graph is the intersection graph of a collection of intervals which have been colored with p different colors with edges corresponding to nonempty intersection of intervals from different color classes. We characterize the class of 2-trees which are interval 3-graphs via a list of three graphs and three infinite families of forbidden induced subgraphs. David E. Brown and Breeann M. Flesch Copyright © 2014 David E. Brown and Breeann M. Flesch. All rights reserved. Counting Extended Irreducible Goppa Codes Wed, 12 Feb 2014 12:33:16 +0000 We produce an upper bound on the number of extended irreducible Goppa codes over any finite field. John A. Ryan Copyright © 2014 John A. Ryan. All rights reserved. The Coarse Structure of the Representation Algebra of a Finite Monoid Thu, 30 Jan 2014 07:07:35 +0000 Let be a monoid, and let be a commutative idempotent submonoid. We show that we can find a complete set of orthogonal idempotents of the monoid algebra of such that there is a basis of adapted to this set of idempotents which is in one-to-one correspondence with elements of the monoid. The basis graph describing the Peirce decomposition with respect to gives a coarse structure of the algebra, of which any complete set of primitive idempotents gives a refinement, and we give some criterion for this coarse structure to actually be a fine structure, which means that the nonzero elements of the monoid are in one-to-one correspondence with the vertices and arrows of the basis graph with respect to a set of primitive idempotents, with this basis graph being a canonical object. Mary Schaps Copyright © 2014 Mary Schaps. All rights reserved. Noncrossing Monochromatic Subtrees and Staircases in 0-1 Matrices Thu, 23 Jan 2014 16:22:51 +0000 The following question is asked by the senior author (Gyárfás (2011)). What is the order of the largest monochromatic noncrossing subtree (caterpillar) that exists in every 2-coloring of the edges of a simple geometric ? We solve one particular problem asked by Gyárfás (2011): separate the Ramsey number of noncrossing trees from the Ramsey number of noncrossing double stars. We also reformulate the question as a Ramsey-type problem for 0-1 matrices and pose the following conjecture. Every 0-1 matrix contains zeros or ones, forming a staircase: a sequence which goes right in rows and down in columns, possibly skipping elements, but not at turning points. We prove this conjecture in some special cases and put forward some related problems as well. Siyuan Cai, Gillian Grindstaff, András Gyárfás, and Warren Shull Copyright © 2014 Siyuan Cai et al. All rights reserved. Combinatorial Interpretation of General Eulerian Numbers Thu, 02 Jan 2014 12:54:24 +0000 Since the 1950s, mathematicians have successfully interpreted the traditional Eulerian numbers and -Eulerian numbers combinatorially. In this paper, the authors give a combinatorial interpretation to the general Eulerian numbers defined on general arithmetic progressions . Tingyao Xiong, Jonathan I. Hall, and Hung-Ping Tsao Copyright © 2014 Tingyao Xiong et al. All rights reserved. A Theory of Cartesian Product and Factorization of Circulant Graphs Thu, 26 Dec 2013 18:06:55 +0000 We determine when the Cartesian product of two circulant graphs is also a circulant graph. This leads to a theory of factorization of circulant graphs. V. Vilfred Copyright © 2013 V. Vilfred. All rights reserved. Classification of Boolean Functions Where Affine Functions Are Uniformly Distributed Thu, 31 Oct 2013 15:18:06 +0000 The present paper on classification of -variable Boolean functions highlights the process of classification in a coherent way such that each class contains a single affine Boolean function. Two unique and different methods have been devised for this classification. The first one is a recursive procedure that uses the Cartesian product of sets starting from the set of one variable Boolean functions. In the second method, the classification is done by changing some predefined bit positions with respect to the affine function belonging to that class. The bit positions which are changing also provide us information concerning the size and symmetry properties of the classes/subclasses in such a way that the members of classes/subclasses satisfy certain similar properties. Ranjeet Kumar Rout, Pabitra Pal Choudhury, and Sudhakar Sahoo Copyright © 2013 Ranjeet Kumar Rout et al. All rights reserved. On a Property of a Three-Dimensional Matrix Wed, 30 Oct 2013 12:01:07 +0000 Let be the symmetrical group acting on the set and . Consider the set The main result of this paper is the following theorem. If the number of set entries is more than , then there exist entries such that , , and . The application of this theorem to the three-dimensional assignment problem is considered. David Blokh Copyright © 2013 David Blokh. All rights reserved. -Analogues of Symbolic Operators Sun, 14 Jul 2013 09:34:08 +0000 Here presented are -extensions of several linear operators including a novel -analogue of the derivative operator . Some -analogues of the symbolic substitution rules given by He et al., 2007, are obtained. As sample applications, we show how these -substitution rules may be used to construct symbolic summation and series transformation formulas, including -analogues of the classical Euler transformations for accelerating the convergence of alternating series. Michael J. Dancs and Tian-Xiao He Copyright © 2013 Michael J. Dancs and Tian-Xiao He. All rights reserved. Terminal Hosoya Polynomial of Line Graphs Thu, 13 Jun 2013 09:28:16 +0000 The terminal Hosoya polynomial of a graph is defined as , where is the number of pairs of pendant vertices of that are at distance . In this paper we obtain terminal Hosoya polynomial of line graphs. H. S. Ramane, A. B. Ganagi, K. P. Narayankar, and S. S. Shirkol Copyright © 2013 H. S. Ramane et al. All rights reserved. Equivalence of Right Infinite Words Mon, 15 Apr 2013 14:17:01 +0000 Closure properties of some classes of right infinite words have been studied extensively; we are interested in the general algebraic structure of right infinite words. We investigate preorder of morphism invariant classes and show that it is not a semilattice. Liga Kulesa Copyright © 2013 Liga Kulesa. All rights reserved. Decomposition of Graphs into Paths and Cycles Sun, 14 Apr 2013 08:45:07 +0000 A decomposition of a graph is a collection of edge-disjoint subgraphs of such that every edge of belongs to exactly one . If each is a path or a cycle in , then is called a path decomposition of . If each is a path in , then is called an acyclic path decomposition of . The minimum cardinality of a path decomposition (acyclic path decomposition) of is called the path decomposition number (acyclic path decomposition number) of and is denoted by () (()). In this paper we initiate a study of the parameter and determine the value of for some standard graphs. Further, we obtain some bounds for and characterize graphs attaining the bounds. We also prove that the difference between the parameters and can be made arbitrarily large. S. Arumugam, I. Sahul Hamid, and V. M. Abraham Copyright © 2013 S. Arumugam et al. All rights reserved. A Note on the Adversary Degree Associated Reconstruction Number of Graphs Sun, 31 Mar 2013 13:56:48 +0000 A vertex-deleted subgraph of a graph is called a card of . A card of with which the degree of the deleted vertex is also given is called a degree associated card (or dacard) of . The degree associated reconstruction number drn () of a graph is the size of the smallest collection of dacards of that uniquely determines . The adversary degree associated reconstruction number of a graph , adrn(), is the minimum number such that every collection of dacards of that uniquely determines . In this paper, we show that adrn of wheels and complete bipartite graphs on at least 4 vertices is 2 or 3. S. Monikandan, S. Sundar Raj, C. Jayasekaran, and A. P. Santhakumaran Copyright © 2013 S. Monikandan et al. All rights reserved. Efficient Prime Counting and the Chebyshev Primes Mon, 25 Mar 2013 08:24:56 +0000 The function where is the logarithm integral and the number of primes up to is well known to be positive up to the (very large) Skewes' number. Likewise, according to Robin's work, the functions and , where and are Chebyshev summatory functions, are positive if and only if Riemann hypothesis (RH) holds. One introduces the jump function at primes and one investigates , , and . In particular, , and for . Besides, for any odd , an infinite set of the so-called Chebyshev primes. In the context of RH, we introduce the so-called Riemann primes as champions of the function (or of the function ). Finally, we find a good prime counting function , that is found to be much better than the standard Riemann prime counting function. Michel Planat and Patrick Solé Copyright © 2013 Michel Planat and Patrick Solé. All rights reserved. -Pascal and -Wronskian Matrices with Implications to -Appell Polynomials Wed, 20 Mar 2013 18:22:29 +0000 We introduce a -deformation of the Yang and Youn matrix approach for Appell polynomials. This will lead to a powerful machinery for producing new and old formulas for -Appell polynomials, and in particular for -Bernoulli and -Euler polynomials. Furthermore, the --polynomial, anticipated by Ward, can be expressed as a sum of products of -Bernoulli and -Euler polynomials. The pseudo -Appell polynomials, which are first presented in this paper, enable multiple -analogues of the Yang and Youn formulas. The generalized -Pascal functional matrix, the -Wronskian vector of a function, and the vector of -Appell polynomials together with the -deformed matrix multiplication from the authors recent article are the main ingredients in the process. Beyond these results, we give a characterization of -Appell numbers, improving on Al-Salam 1967. Finally, we find a -difference equation for the -Appell polynomial of degree . Thomas Ernst Copyright © 2013 Thomas Ernst. All rights reserved. Determinant Representations of Polynomial Sequences of Riordan Type Wed, 20 Mar 2013 14:11:40 +0000 In this paper, using the production matrix of a Riordan array, we obtain a recurrence relation for polynomial sequence associated with the Riordan array, and we also show that the general term for the sequence can be expressed as the characteristic polynomial of the principal submatrix of the production matrix. As applications, a unified determinant expression for the four kinds of Chebyshev polynomials is given. Sheng-liang Yang and Sai-nan Zheng Copyright © 2013 Sheng-liang Yang and Sai-nan Zheng. All rights reserved. Construction of Dominating Sets of Certain Graphs Wed, 20 Mar 2013 08:35:05 +0000 Let be a simple graph. A set is a dominating set of , if every vertex in is adjacent to at least one vertex in . We denote the family of dominating sets of a graph with cardinality by . In this paper we introduce graphs with specific constructions, which are denoted by . We construct the dominating sets of by dominating sets of graphs , , and . As an example of , we consider . As a consequence, we obtain the recursive formula for the number of dominating sets of . Saeid Alikhani and Yee-Hock Peng Copyright © 2013 Saeid Alikhani and Yee-Hock Peng. All rights reserved. Improved Bounds on   Wed, 13 Mar 2013 10:25:07 +0000 An ()-arc is a set of n points of a projective plane such that some r, but no of them, are collinear. The maximum size of an ()-arc in PG(2, q) is denoted by (2, q). In this paper, a new (286, 16)-arc in PG(2,19), a new (341, 15)-arc, and a (388, 17)-arc in PG(2,25) are constructed, as well as a (394, 16)-arc, a (501, 20)-arc, and a (532, 21)-arc in PG(2,27). Tables with lower and upper bounds on (2, 25) and (2, 27) are presented as well. The results are obtained by nonexhaustive local computer search. Rumen Daskalov and Elena Metodieva Copyright © 2013 Rumen Daskalov and Elena Metodieva. All rights reserved. On Connected m-HPK-Residual Graphs Tue, 12 Mar 2013 08:01:30 +0000 We define m-HPK-residual graphs in which HPK is a hyperplane complete graph. We extend P. Erdös, F. Harary, and M. Klawe's definition of plane complete residual graph to hyperplane and obtain the hyperplane complete residual graph. Further, we obtain the minimum order of HPK-residual graphs and m-HPK-residual graphs. In addition, we obtain a unique minimal HPK-residual graphs and a unique minimal m-HPK-residual graphs. Huiming Duan and Yonghong Li Copyright © 2013 Huiming Duan and Yonghong Li. All rights reserved. Finite Iterative Algorithm for Solving a Complex of Conjugate and Transpose Matrix Equation Mon, 25 Feb 2013 10:11:21 +0000 We consider an iterative algorithm for solving a complex matrix equation with conjugate and transpose of two unknowns of the form: + . With the iterative algorithm, the existence of a solution of this matrix equation can be determined automatically. When this matrix equation is consistent, for any initial matrices , the solutions can be obtained by iterative algorithm within finite iterative steps in the absence of round-off errors. Some lemmas and theorems are stated and proved where the iterative solutions are obtained. A numerical example is given to illustrate the effectiveness of the proposed method and to support the theoretical results of this paper. Mohamed A. Ramadan, Talaat S. El-Danaf, and Ahmed M. E. Bayoumi Copyright © 2013 Mohamed A. Ramadan et al. All rights reserved.