Minimal graphs for hamiltonian extension

ODAM-Vol. 3 (2020), Issue 1, pp. 25 – 27 Open Access Full-Text PDF
Christophe Picouleau
Abstract: For every \(n\ge 3\), we determine the minimum number of edges of graph with \(n\) vertices such that for any non edge \(xy\) there exits a hamiltonian cycle containing \(xy\).
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Solving some variants of vehicle routing problem with Branch-and-cut and Column generation algorithms

OMS-Vol. 4 (2020), Issue 1, pp. 63 – 73 Open Access Full-Text PDF
Abdullahi Ibrahim, Jeremiah Ishaya, Rabiat Abdulaziz, Sowole Samuel
Abstract: In this research work, we applied some solving techniques on Travelling salesman problem (TSP) and Capaciated Vehicle routing problem (CVRP) which are some of the variants of vehicle routing problem. For each of the considered problem, Branch-and-cut was applied on TSP and Column generation technique was used on CVRP. We obtained optimal solution and tour. Hence, these methods can be used to solve similar problem for optimal solution.
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On Backlund transformation of Riccati equation method and its application to nonlinear partial differential equations and differential-difference equations

OMS-Vol. 4 (2020), Issue 1, pp. 56 – 62 Open Access Full-Text PDF
Reham Hassan, Mustafa El-Agamy, Mohamed Soror Abdel Latif, Hamed Nour
Abstract: In this paper, we investigate the equivalence between the Backlund transformation of Riccati equation method and the extended tanh-function method. It is proved that the two methods are equivalent when applying them to partial differential equations and differential-difference equations. Two examples are introduced to justify our results.
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On algebraic properties of fundamental group of intuitionistic fuzzy topological spaces (IFTSs)

OMS-Vol. 4 (2020), Issue 1, pp. 34 – 47 Open Access Full-Text PDF
Laaro Abdullateef
Abstract: In this paper, the notion of some algebraic properties of fundamental group of intuitionistic fuzzy topological spaces (IFTSs) are introduced. We give a necessary and sufficient condition for a fundamental group of IFTSs to be abelian, a necessary and sufficient conditions for a subset of fundamental group of IFTSs to be subgroup, a necessary and sufficient condition for a subgroup of fundamental group of IFTSs to be normal and a necessary and sufficient condition for an element to be in a center of fundamental group of IFTSs. We also describe the set of centralizers of an element in a fundamental group of IFTSs and the quotient fundamental group of IFTSs.
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A coupled fixed point theorem for maps satisfying rational type contractive condition in dislocated quasi b-metric space

OMS-Vol. 4 (2020), Issue 1, pp. 27 – 33 Open Access Full-Text PDF
Mesaud Tesfaye, Kidane Koyas, Solomon Gebregiorgis
Abstract: In this paper, a coupled fixed point theorem for maps satisfying rational type contractive condition in the perspective of dislocated quasi b-metric space have been formed and the existence and uniqueness of a couple fixed point have been proved. Our result improves and generalizes comparable results in the literature.
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Effect of salinity on the structural strengths of conventional concrete

EASL-Vol. 3 (2020), Issue 1, pp. 21 – 34 Open Access Full-Text PDF
E. E. Ikponmwosa, S. O. Ehikhuenmen, G. M. Sobamowo, E. Ambrose
Abstract: This research focuses on the effect salinity on the structural strengths of conventional concrete. The unreinforced beam, cylinder and cube specimens produced were cured up to 120 days in different curing medium and tested at varying predetermined curing age. The physio-chemical properties of Unilag tap and lagoon water, physical properties, workability, compressive, split tensile and flexural strengths were determined. Two curing media (salt water I & salt water II) having five times (5\(\times\)) and ten times (10\(\times\)) the chloride content of lagoon water were simulated. The results revealed that the structural strengths of concrete samples cured in lagoon water recorded lower strengths when compared to samples cured in salt water I but higher in strength development than samples cured in salt water II. The percentage decrease in structural strengths increased from lagoon water to salt water II which recorded the highest value of 29.35%, 17.67% and 33.65% at 28-day for compressive, tensile and flexural strengths respectively. The mathematical models developed using Modified Regression Approach to predict the structural strengths were in good agreement with the experimental data. This research reveals that the salt water solution simulation in the laboratory does not fully replicate the aggressiveness of actual marine water (environment).
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One method towards the trisection of the angle

OMS-Vol. 4 (2020), Issue 1, pp. 23 – 26 Open Access Full-Text PDF
Gerasimos T. Soldatos
Abstract: This article maintains that the impossibility of trisection is based on a cubic polynomial whose trigonometric content is not clear; or, the impossibility may be referring to one particular trisection method even if the cubic equation does constitute the equation of trisection. It next proceeds to trisection “indirectly” by attempting bto construct one of the two trisectors on the basis of reductio ad absurdum.
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The Hadamard product and recursively defined sequences

ODAM-Vol. 3 (2020), Issue 1, pp. 20 – 24 Open Access Full-Text PDF
Sergei Dmitrievich Kazenas
Abstract: In this paper, the approach to obtaining nontrivial formulas for some recursively defined sequences is illustrated. The most interesting result in the paper is the formula for the solution of quadratic map-like recurrence. Also, some formulas for the solutions of linear difference equations with variable coefficients are obtained. At the end of the paper, some integer sequences associated with a quadratic map are considered.
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