Given positive integers a, b and c to compute a generating system for the numerical semigroup whose elements are all positive integer solutions of the inequality axmod b ≤ cx is equivalent to computing a Bézout sequence connecting two reduced fractions. We prove that a proper Bézout sequence is completely determined by its ends and we give an algorithm to compute the unique proper Bézout sequen...

The Wiener index is one of the main descriptors that correlate a chemical compound’s molecular graph with experimentally gathered data regarding the compound’s characteristics. A long standing conjecture on the Wiener index ([4], [5]) states that for any positive integer n (except numbers from a given 49 element set), one can find a tree with Wiener index n. In this paper, we prove that every i...

Finding differentially regulated subgraphs in a biochemical network is an important problem in bioinformatics. We present a new model for finding such subgraphs which takes the polarity of the edges (activating or inhibiting) into account, leading to the problem of finding a connected subgraph induced by k vertices with maximum weight. We present several algorithms for this problem, including d...

In this paper, we extend the notion of tree language quotients to bottom-up quotients. Instead of computing the residual of a tree language from top to bottom and producing a list of tree languages, we show how to compute a set of k-ary trees, where k is an arbitrary integer. We define the quotient formula for different combinations of tree languages: union, symbol products, compositions, itera...

In this paper, we study the problem of computing a minimum cost Steiner tree subject to a weight constraint in a Halin graph where each edge has a nonnegative integer cost and a nonnegative integer weight. We prove the NP-hardness of this problem and present a fully polynomial time approximation scheme for this NP-hard problem.

Suppose G is a tree. Graham’s “Tree Reconstruction Conjecture” states that G is uniquely determined by the integer sequence |G|, |L(G)|, |L(L(G))|, |L(L(L(G)))|, . . ., where L(H) denotes the line graph of the graph H . Little is known about this question apart from a few simple observations. We show that the number of trees on n vertices which can be distinguished by their associated integer s...

The problem of annual production scheduling in surface mining consists of determining an optimal sequence of extracting the mineralized material from the ground. The main objective of the optimization process is usually to maximize the total Net Present Value of the operation. Production scheduling is typically a mixed integer programming (MIP) type problem. However, the large number of integer...

This paper studies the algorithms for coding and decoding Prufer codes of a labeled tree. The algorithms for coding and decoding Prufer codes of a labeled tree in the literatures require time usually. Although there exist linear time algorithms for Prufer-like codes [1,2,3], the algorithms utilize the integer sorting algorithms. The special range of the integers to be sorted is utilized to obta...

This paper presents a new algorithm for solving mixed integer nonlinear programming problems. The algorithm uses a branch and bound strategy where a nonlinear programming problem is solved in each integer node of the tree. The nonlinear programming problems, at each integer node of the tree, are not solved to optimality, rather one iteration step is taken at each node and then linearizations of...

We present a stochastic model for capacity-expansion planning of electricity distribution networks subject to uncertain demand (CEP). We formulate CEP as a multistage stochastic mixed-integer program with a scenario-tree representation of uncertainty. At each node of the scenario-tree, the model determines capacity-expansions, operating con guration, and power ows. A “super-arc” representation ...