Journal of Discrete Mathematics
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© 2014 , Hindawi Publishing Corporation . All rights reserved.

Modularity in the Semilattice of ωWords
Thu, 15 May 2014 11:29:53 +0000
http://www.hindawi.com/journals/jdm/2014/891760/
A partial ordering of ωwords can be introduced with regard to whether an ωword can be transformed into another by a Mealy machine. It is known that the poset of ωwords that is introduced by this ordering is a joinsemilattice. The width of this joinsemilattice has the power of continuum while the depth is at least . We have created a technique for proving that powercharacteristic ωwords are incomparable. We use this technique to show that this joinsemilattice 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
http://www.hindawi.com/journals/jdm/2014/909684/
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
http://www.hindawi.com/journals/jdm/2014/538423/
Chaotification problems
of partial difference equations are studied. Two chaotification
schemes are established by utilizing the snapback repeller theory
of general discrete dynamical systems, and all the systems are
proved to be chaotic in the sense of both LiYorke 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
http://www.hindawi.com/journals/jdm/2014/979171/
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
http://www.hindawi.com/journals/jdm/2014/823567/
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 selfreciprocal polynomials.
Umarin Pintoptang, Suton Tadee, and Vichian Laohakosol
Copyright © 2014 Umarin Pintoptang et al. All rights reserved.

A Characterization of 2Tree Proper Interval 3Graphs
Sun, 23 Feb 2014 07:37:03 +0000
http://www.hindawi.com/journals/jdm/2014/143809/
An interval pgraph 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 2trees which are interval 3graphs 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
http://www.hindawi.com/journals/jdm/2014/871871/
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
http://www.hindawi.com/journals/jdm/2014/529804/
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 onetoone 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 onetoone 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 01 Matrices
Thu, 23 Jan 2014 16:22:51 +0000
http://www.hindawi.com/journals/jdm/2014/731519/
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 2coloring 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 Ramseytype problem for 01 matrices and pose the following conjecture. Every 01 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
http://www.hindawi.com/journals/jdm/2014/870596/
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 HungPing 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
http://www.hindawi.com/journals/jdm/2013/163740/
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
http://www.hindawi.com/journals/jdm/2013/270424/
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 ThreeDimensional Matrix
Wed, 30 Oct 2013 12:01:07 +0000
http://www.hindawi.com/journals/jdm/2013/797249/
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 threedimensional 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
http://www.hindawi.com/journals/jdm/2013/487546/
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 TianXiao He
Copyright © 2013 Michael J. Dancs and TianXiao He. All rights reserved.

Terminal Hosoya Polynomial of Line Graphs
Thu, 13 Jun 2013 09:28:16 +0000
http://www.hindawi.com/journals/jdm/2013/857908/
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
http://www.hindawi.com/journals/jdm/2013/219291/
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
http://www.hindawi.com/journals/jdm/2013/721051/
A decomposition of a graph is a collection of edgedisjoint 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
http://www.hindawi.com/journals/jdm/2013/808105/
A vertexdeleted 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
http://www.hindawi.com/journals/jdm/2013/491627/
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 socalled Chebyshev primes. In the context of RH, we introduce the socalled 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
http://www.hindawi.com/journals/jdm/2013/450481/
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 AlSalam 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
http://www.hindawi.com/journals/jdm/2013/734836/
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.
Shengliang Yang and Sainan Zheng
Copyright © 2013 Shengliang Yang and Sainan Zheng. All rights reserved.

Construction of Dominating Sets of Certain Graphs
Wed, 20 Mar 2013 08:35:05 +0000
http://www.hindawi.com/journals/jdm/2013/587196/
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 YeeHock Peng
Copyright © 2013 Saeid Alikhani and YeeHock Peng. All rights reserved.

Improved Bounds on
Wed, 13 Mar 2013 10:25:07 +0000
http://www.hindawi.com/journals/jdm/2013/628952/
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 mHPKResidual Graphs
Tue, 12 Mar 2013 08:01:30 +0000
http://www.hindawi.com/journals/jdm/2013/983830/
We define mHPKresidual 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 HPKresidual graphs and mHPKresidual graphs. In addition, we obtain a unique minimal HPKresidual graphs and a unique minimal mHPKresidual 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
http://www.hindawi.com/journals/jdm/2013/170263/
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 roundoff 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. ElDanaf, and Ahmed M. E. Bayoumi
Copyright © 2013 Mohamed A. Ramadan et al. All rights reserved.

Induced Graphoidal Decompositions in Product Graphs
Wed, 20 Feb 2013 08:09:44 +0000
http://www.hindawi.com/journals/jdm/2013/892839/
Let be a nontrivial, simple, finite, connected, and undirected graph. A graphoidal decomposition (GD) of is a collection of nontrivial paths and cycles in that are internally disjoint such that every edge of lies in exactly one member of . By restricting the members of a GD to be induced, the concept of induced graphoidal decomposition (IGD) of a graph has been defined. The minimum cardinality of an IGD of a graph is called the induced graphoidal decomposition number and is denoted by (). An IGD of without any cycles is called an induced acyclic graphoidal decomposition (IAGD) of , and the minimum cardinality of an
IAGD of is called the induced acyclic graphoidal decomposition number of , denoted by (). In this paper we determine the value of ()
and () when is a product graph, the factors being paths/cycles.
Mayamma Joseph and I. Sahul Hamid
Copyright © 2013 Mayamma Joseph and I. Sahul Hamid. All rights reserved.

On Maximum Lee Distance Codes
Thu, 07 Feb 2013 12:28:55 +0000
http://www.hindawi.com/journals/jdm/2013/625912/
Singletontype upper bounds on the minimum Lee distance of general
(not necessarily linear) Lee codes over are discussed. Two bounds known for linear codes are shown to also hold in the general case, and several new bounds are established. Codes meeting these bounds are investigated and in some cases characterised.
Tim L. Alderson and Svenja Huntemann
Copyright © 2013 Tim L. Alderson and Svenja Huntemann. All rights reserved.

Sums of Products of Cauchy Numbers, Including PolyCauchy Numbers
Wed, 30 Jan 2013 11:45:18 +0000
http://www.hindawi.com/journals/jdm/2013/373927/
We investigate sums of products of Cauchy numbers including polyCauchy numbers: . A relation among these sums shown in the paper and explicit expressions of sums of two and three products (the case of and that of described in the paper) are given. We also study the other three types of sums of products related to the Cauchy numbers of both kinds and the polyCauchy numbers of both kinds.
Takao Komatsu
Copyright © 2013 Takao Komatsu. All rights reserved.

(0, 2)Graphs and Root Systems
Thu, 10 Jan 2013 18:03:28 +0000
http://www.hindawi.com/journals/jdm/2013/140537/
We construct (0, 2)graphs from root systems with simply laced diagram and study their properties.
Andries E. Brouwer and Leonard Chastkofsky
Copyright © 2013 Andries E. Brouwer and Leonard Chastkofsky. All rights reserved.

Another Note on Dilworth's Decomposition Theorem
Thu, 10 Jan 2013 14:44:09 +0000
http://www.hindawi.com/journals/jdm/2013/692645/
This paper proposes a new proof of Dilworth's theorem. The proof is based upon the minflow/maxcut property in flow networks. In relation to this proof, a new method to find both a Dilworth decomposition and a maximal antichain is presented.
Wim Pijls and Rob Potharst
Copyright © 2013 Wim Pijls and Rob Potharst. All rights reserved.