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Non-cancellation Phenomena in the Class Of Finitely Generated Groups with Finite Commutator Subgroups
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Habtay GhebrewoldWe observe some non-cancellation phenomena arising from recent studies of the non-cancellation set χ (G) of a certain group G. Here χ (G) denotes the set of all isomorphism classes of groups H such that H × Z G ×... -
Gorenstein injective envelopes and covers over n-perfect rings
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: EdgarE. Enochs J.A. López-RamosWe prove the existence of Gorenstein injective envelopes and covers over n-perfect rings for some classes of modules associated with a dualizing bimodule. -
Abelian Groups with a Minimal Generating Set
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Pavel Růžčka --- Department of Algebra, Sokolovská, Czech RepublicWe study the existence of minimal generating sets in Abelian groups. We prove that Abelian groups with minimal generating sets are not closed under quotients, nor under subgroups, nor under in.nite products. We give necessary and su.cient conditions for existence... -
The relationship between torsional rigidity and bending strength characteristics of SA pine
Item type: Journal Article • Journal: The Southern African Forestry Journal • Authors: W. M. G. Burdzik [d849458e21] P. D. Nkwera --- Department of Civil Engineering,The modulus of rigidity, G, and bending moment ofelasticity, MOE, of SA pine are evaluated from a direct torsion test and bending tests. Specimens were subjected to a series of tests with the view to determining direct torsional rigidity, apparent... -
Flat model structures under excellent extensions
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Wei Ren --- , ChinaWe prove that the weak equivalences, cofibrations and fibrations in Gillespie’s flat model structure are invariant under excellent extensions of rings. As applications, the flat and cotorsion dimensions of unbounded complexes along excellent extensions are investigated, and moreover, some homological... -
Curvature properties of metric and semi-symmetric linear connections
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Miloš Z. Petrović --- , Serbia Nenad O. Vesić --- , Serbia Milan Lj. Zlatanović --- , SerbiaConsidering a non-symmetric linear connection and its dual one appear 6 independent curvature tensors [15]. In the present paper we study properties of curvature tensors of semi-symmetric metric connections on a generalized Riemannian manifold. -
The significance of the contributions of congruences to the theory of connectednesses and disconnectednesses for topological spaces and graphs
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Stefan Veldsman --- Nelson Mandela University, South AfricaThis is a survey of some of the consequences of the recently introduced congruences on the theory of connectednesses (radical classes) and disconnectednesses (semisimple classes) of graphs and topological spaces. In particular, it is shown that the connectednesses and disconnectednesses... -
On elliptic curves assigned to a pair of right triangles with an equal hypotenuse
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Arman Shamsi Zargar --- University of Mohaghegh Ardabili, Iran Seiji Tomita --- Tokyo Software Company (Inc.), JapanConsider a pair of right triangles with an equal hypotenuse. This turns out to solve the diophantine system of equations a 2 + b 2 = c 2 + d 2 = e 2 in integers. To this system we...