Utilitas Algorithmica (UA)
ISSN: xxxx-xxxx (print)
Utilitas Algorithmica (UA) is a premier, open-access international journal dedicated to advancing algorithmic research and its applications. Launched to drive innovation in computer science, UA publishes high-impact theoretical and experimental papers addressing real-world computational challenges. The journal underscores the vital role of efficient algorithm design in navigating the growing complexity of modern applications. Spanning domains such as parallel computing, computational geometry, artificial intelligence, and data structures, UA is a leading venue for groundbreaking algorithmic studies.
- Research article
- Full Text
- Ars Combinatoria
- Volume 032
- Pages: 57-64
- Published: 31/12/1991
- Research article
- Full Text
- Ars Combinatoria
- Volume 032
- Pages: 33-55
- Published: 31/12/1991
Golomb and Taylor (joined later by Etzion) have modified the notion of a complete Latin square to that of a Tuscan-\(k\) square. A Tuscan-\(k\) square is a row Latin square with the further property that for any two symbols \(a\) and \(b\) of the square, and for each \(m\) from \(1\) to \(k\), there is at most one row in which \(b\) is the \(m^{th}\) symbol to the right of \(a\). One question unresolved by a series of papers of the authors mentioned was whether or not \(n \times n\) Tuscan-\(2\) squares exist for infinitely many composite values of \(n+1\). It is shown here that if \(p\) is a prime and \(p \equiv 7 \pmod{12}\) or \(p \equiv 5 \pmod{24}\), then Tuscan-\(2\) squares of side \(2p\) exist. If \(p \equiv 7 \pmod{12}\), clearly \(2p + 1\) is always composite and if \(p \equiv 5 \pmod{24}\), \(2p+1\) is composite infinitely often. The squares constructed are in fact Latin squares that have the Tuscan-\(2\) property in both dimensions.
- Research article
- Full Text
- Ars Combinatoria
- Volume 032
- Pages: 17-31
- Published: 31/12/1991
It is shown that if \([n] = X_1 \cup X_2 \cup \cdots \cup X_l\) is a partition of \([n]\) and if \(S_t\) is a family of \(t\)-valued functions intersecting on at least one element of \(k\) (circularly) consecutive blocks, then \(|S_t| < t^{n-k}\). If given \(a_1 < a_2 < \cdots < a_y \leq l \), \(\acute{S}_t\) is a family of \(t\)-valued functions intersecting on at least one element of \(X_{a_{1}+m}, X_{a_{2}+m}, \ldots, X_{a_{k}+m}\) for some \(m\) with \(1-a_1 \leq m \leq n – a_k\), then \(|\acute{S}_t| \leq t^{n-k}\). Both these results were conjectured by Faudree, Schelp, and Sós [FSS]. The main idea of our proofs is that of anticlusters introduced by Griggs and Walker [GW] which we discuss in some detail. We also discuss several related intersection theorems about sets, \(2\)-valued functions, and \(t\)-valued functions.
- Research article
- Full Text
- Ars Combinatoria
- Volume 032
- Pages: 13-16
- Published: 31/12/1991
Let the edges of the complete graph \(K_n\) be \(2\)-colored. A Simple Hamiltonian Cycle is a Hamiltonian cycle in \(K_n\) that is either monochromatic or is a union of two monochromatic paths. The main result of this paper is that if \(n\) is an even integer greater than \(4\), then for every \(2\)-coloring of the edges of \(K_n\), there is a Simple Hamiltonian Cycle in \(K_n\) which is either monochromatic, or is a union of two monochromatic paths, where each path is of even length.
- Research article
- Full Text
- Ars Combinatoria
- Volume 032
- Pages: 3-11
- Published: 31/12/1991
Uniquely pseudointersectable graphs are defined; this is closely related to the uniquely intersectable graphs introduced by Alter and Wang [1]. The S-property is necessary but not sufficient for a graph to be uniquely pseudointersectable. This condition is also sufficient for graphs with unique minimum cover. Finally, we show that for supercompact graphs, unique pseudointersectability and unique intersectability are equivalent. Thus we generalize some of the results in [1] to a wider class of graphs.
- Research article
- Full Text
- Journal of Combinatorial Mathematics and Combinatorial Computing
- Volume 010
- Pages: 217-221
- Published: 31/10/1991
A connected graph \(G\) is unicentered if \(G\) has exactly one central vertex. It is proved that for integers \(r\) and \(d\) with \(1 \leq r < d \leq 2r\), there exists a unicentered graph \(G\) such that rad\((G) = r\) and diam\((G) = d\). Also, it is shown that for any two graphs \(F\) and \(G\) with rad\((F) = n \geq 4\) and a positive integer \(d\) (\(4 \leq d \leq n\)), there exists a connected graph \(H\) with diam\((H) = d\) such that the periphery and the center of \(H\) are isomorphic to \(F\) and \(G\), respectively.
- Research article
- Full Text
- Journal of Combinatorial Mathematics and Combinatorial Computing
- Volume 010
- Pages: 213-216
- Published: 31/10/1991
In this paper we obtain some inequalities on the existence of balanced arrays (\(B\)-arrays) of strength four in terms of its parameter by using Minkowski’s inequality.
- Research article
- Full Text
- Journal of Combinatorial Mathematics and Combinatorial Computing
- Volume 010
- Pages: 205-212
- Published: 31/10/1991
Let \(q\) be a prime power, \({F}_{q^2}\) the finite field with \(q^2\) elements, \(U_n({F}_{q^2})\) the finite unitary group of degree \(n\) over \({F}_{q^2}\), and \(UV_n({F}_{q^2})\) the \(n\)-dimensional unitary geometry over \({F}_{q^2}\). It is proven that the subgroup consisting of the elements of \(U_n({F}_{q^2})\) which fix a given \((m, s)\)-type subspace of \(UV_n({F}_{q^2})\), acts transitively on some subsets of subspaces of \(UV_n({F}_{q^2})\). This observation gives rise to a number of Partially Balanced Incomplete Block Designs (PBIBD’s).
- Research article
- Full Text
- Journal of Combinatorial Mathematics and Combinatorial Computing
- Volume 010
- Pages: 201-204
- Published: 31/10/1991
There are two criteria for optimality of weighing designs. One, which has been widely studied, is that the determinant of \(XX^T\) should be maximal, where \({X}\) is the weighing matrix. The other is that the trace of \((XX^T)^{-1}\) should be minimal. We examine the second criterion. It is shown that Hadamard matrices, when they exist, are optimal with regard to the second criterion, just as they are for the first one.
- Research article
- Full Text
- Journal of Combinatorial Mathematics and Combinatorial Computing
- Volume 010
- Pages: 193-200
- Published: 31/10/1991
In 1988, Sarvate and Seberry introduced a new method of construction for the family of weighing matrices \(W(n^2(n-1), n^2)\), where \(n\) is a prime power. We generalize this result, replacing the condition on \(n\) with the weaker assumption that a generalized Hadamard matrix \(GH(n; G)\) exists with \(|G| = n\), and give conditions under which an analogous construction works for \(|G| < n\). We generalize a related construction for a \(W(13, 9)\), also given by Sarvate and Seberry, producing a whole new class. We build further on these ideas to construct several other classes of weighing matrices.




