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Publisher: Springer-Verlag (Total: 2352 journals)

 Afrika Matematika   [SJR: 0.248]   [H-I: 6]   [1 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1012-9405 - ISSN (Online) 2190-7668    Published by Springer-Verlag  [2352 journals]
• On the m -step two-parameter generalized Hermitian and skew-Hermitian
splitting preconditioning method
• Authors: Mehdi Bastani; Davod Khojasteh Salkuyeh
Pages: 999 - 1010
Abstract: In this paper, the non-Hermitian positive definite linear systems are solved via preconditioned Krylov subspace methods such as the generalized minimal residual (GMRES) method. To do so, the two-parameter generalized Hermitian and skew-Hermitian splitting (TGHSS) iteration method is applied to establish an m-step polynomial preconditioner. Some theoretical results are also given to investigate the convergence properties of the preconditioned method. Three numerical examples are presented to demonstrate the performance of the new method and to compare it with a recently proposed method.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0489-5
Issue No: Vol. 28, No. 7-8 (2017)

• On two groups of the form $$2^{8}{:}A_{9}$$ 2 8 : A 9
• Authors: Ayoub B. M. Basheer; Jamshid Moori
Pages: 1011 - 1032
Abstract: This paper is dealing with two split extensions of the form $$2^{8}{:}A_{9}.$$ We refer to these two groups by $$\overline{G}_{1}$$ and $$\overline{G}_{2}.$$ For $$\overline{G}_{1},$$ the 8-dimensional GF(2)-module is in fact the deleted permutation module for $$A_{9}.$$ We firstly determine the conjugacy classes of $$\overline{G}_{1}$$ and $$\overline{G}_{2}$$ using the coset analysis technique. The structures of inertia factor groups were determined for the two extensions. The inertia factor groups of $$\overline{G}_{1}$$ are $$A_{9},\,A_{8},\, S_{7},\,(A_{6} \times 3){:}2$$ and $$(A_{5} \times A_{4}){:}2,$$ while the inertia factor groups of $$\overline{G}_{2}$$ are $$A_{9},\, PSL(2,8){:}3$$ and $$2^{3}{:}GL(3,2).$$ We then determine the Fischer matrices for these two groups and apply the Clifford–Fischer theory to compute the ordinary character tables of $$\overline{G}_{1}$$ and $$\overline{G}_{2}.$$ The Fischer matrices of $$\overline{G}_{1}$$ and $$\overline{G}_{2}$$ are all integer valued, with sizes ranging from 1 to 9 and from 1 to 4 respectively. The full character tables of $$\overline{G}_{1}$$ and $$\overline{G}_{2}$$ are $$84 \times 84$$ and $$40 \times 40$$ complex valued matrices respectively.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0500-1
Issue No: Vol. 28, No. 7-8 (2017)

• $$({\alpha ,\beta })$$ ( α , β ) -Intuitionistic fuzzy bi-ideals of
semigroups
• Authors: Saleem Abdullah; Shah Hussain
Pages: 1033 - 1059
Abstract: In this article, a new generalization of intuitionsitic fuzzy bi-ideals of a semigroup considered so called $$(\alpha ,\beta )$$ -intuitionistic fuzzy bi-ideals, (1, 2)-ideals in a semigroup. We combine the notion of intuitionsitic fuzzy point and intuitionistic fuzzy sets to defined different types of intuitionsitic fuzzy bi-ideals of a semigroups. We investigate different properties of these notions and their relationships, particularly, we define $$(\in ,\in \vee q)$$ -intuitionistic fuzzy bi-ideals and (1, 2) ideals in semigroups.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0501-0
Issue No: Vol. 28, No. 7-8 (2017)

• Ricci solitons in Sasakian manifold
• Authors: Kanak Kanti Baishya
Pages: 1061 - 1066
Abstract: Recently the present author introduced the notion of generalized quasi-conformal curvature tensor which bridges conformal curvature tensor, concircular curvature tensor, projective curvature tensor and conharmonic curvature tensor. The object of the present paper is to find out curvature conditions for which Ricci solitons in Sasakian manifolds are sometimes shrinking and some other time remain expanding.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0502-z
Issue No: Vol. 28, No. 7-8 (2017)

• Leaf number and Hamiltonian $$C_4$$ C 4 -free graphs
• Authors: P. Mafuta
Pages: 1067 - 1074
Abstract: Let G be a simple 2-connected, $$C_4$$ -free graph with minimum degree $$\delta (G)\ge 4$$ and leaf number L(G) such that $$\delta (G)\ge \displaystyle \frac{1}{2}L(G)$$ . We show that G is Hamiltonian. In addition, we provide family of graphs to show that the results are best possible for aforementioned class of graphs. The results, apart from supporting the conjecture (Graffiti.pc 190) of the computer program Graffiti.pc, instructed by DeLaVi $${\tilde{n}}$$ a, provide a new sufficient condition for Hamiltonicity in $$C_4$$ -free graphs.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0503-y
Issue No: Vol. 28, No. 7-8 (2017)

• On optimal control of forward–backward stochastic differential
equations
• Authors: F. Baghery; N. Khelfallah; B. Mezerdi; I. Turpin
Pages: 1075 - 1092
Abstract: We consider a control problem where the system is driven by a decoupled as well as a coupled forward–backward stochastic differential equation. We prove the existence of an optimal control in the class of relaxed controls, which are measure-valued processes, generalizing the usual strict controls. The proof is based on some tightness properties and weak convergence on the space $$\mathcal {D}$$ of càdlàg functions, endowed with the Jakubowsky S-topology. Moreover, under some convexity assumptions, we show that the relaxed optimal control is realized by a strict control.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0504-x
Issue No: Vol. 28, No. 7-8 (2017)

• Studies on Cauchy problems for impulsive differential models involving
higher order Riemann–Liouville fractional derivatives
• Authors: Yuji Liu
Pages: 1093 - 1113
Abstract: In this article, existence results of solutions of a class of boundary value problems of nonlinear singular multi-term fractional differential models with impulses on half line involving higher order Riemann–Liouville fractional derivatives are established. Our analysis rely on a well known fixed point theorems. Examples are presented to illustrate the main theorems.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0505-9
Issue No: Vol. 28, No. 7-8 (2017)

• Krasnosel’skii type fixed point theorems in ordered Banach spaces
• Authors: Amina Boucenna; Smaïl Djebali; Toufik Moussaoui
Pages: 1115 - 1129
Abstract: The aim of this work is to present new abstract fixed point theorems in ordered Banach spaces and on Banach algebras. The main existence results generalize Krasnosel’skii’s fixed point theorem of compression and expansion to a class of $$\alpha$$ -homogeneous operators and monotone operators. Two applications to nonlinear Hammerstein integral equations, one of which is of fractional order, are provided together with a numerical example.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0506-8
Issue No: Vol. 28, No. 7-8 (2017)

• Some new explicit values of Ramanujan–Selberg continued fraction
• Authors: Nipen Saikia; Chayanika Boruah
Pages: 1131 - 1141
Abstract: We use Ramanujan’s mixed modular equations to evaluate some new values of the parameter $$J_n$$ involving Ramanujan’s theta-function $$f(-q)$$ . The values $$J_n$$ are then used to evaluate new explicit values of the Ramanujan–Selberg continued fraction.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0507-7
Issue No: Vol. 28, No. 7-8 (2017)

• Gorenstein FI -flat dimension and relative homology
• Authors: B. Vasudevan; R. Udhayakumar; C. Selvaraj
Pages: 1143 - 1156
Abstract: In this paper, we study some properties and behavior of finite Gorenstein FI-flat dimension through the methods of relative homological algebra.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0508-6
Issue No: Vol. 28, No. 7-8 (2017)

• Fourier-Bessel Dini Lipschitz functions in the space $$L_{\alpha ,n}^{2}$$
L α , n 2
• Authors: S. El Ouadih; R. Daher
Pages: 1157 - 1165
Abstract: In this paper, using a generalized translation operator, we obtain an analog of Younis’s Theorem 5.2 in Younis (Int J Math Math Sci 9:301–312, 1986) for the generalized Fourier-Bessel transform for functions satisfying the Fourier-Bessel Dini Lipschitz condition in the space $$L_{\alpha ,n}^{2}$$ .
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0509-5
Issue No: Vol. 28, No. 7-8 (2017)

• The partial r -Bell polynomials
• Authors: Miloud Mihoubi; Mourad Rahmani
Pages: 1167 - 1183
Abstract: In this paper, we show that the r-Stirling numbers of both kinds, the r-Whitney numbers of both kinds, the r-Lah numbers and the r-Whitney-Lah numbers form particular cases of a family of polynomials forming a generalization of the partial Bell polynomials. We deduce the generating functions of several restrictions of these numbers. In addition, a new combinatorial interpretations is presented for the r-Whitney numbers and the r-Whitney-Lah numbers.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0510-z
Issue No: Vol. 28, No. 7-8 (2017)

• A note on the lattice of fuzzy hyperideals of a hyperring
• Authors: D. Bayrak; S. Yamak
Pages: 1185 - 1192
Abstract: Many studies have investigated lattices of fuzzy algebraic systems. One of them belongs to Borzooei et al. (Soft Comput 12:739–749, 2008) who found some properties of lattices of fuzzy algebraic structures. In this study, we solve the problem of finding necessary and sufficient conditions for distributivity and modularity of lattice of fuzzy hyperideals of a hyperring which was one of the open problems in Borzooei’s paper.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0511-y
Issue No: Vol. 28, No. 7-8 (2017)

• Well-posedness and energy decay for Timoshenko systems with discrete time

• Authors: Aissa Guesmia
Pages: 1253 - 1284
Abstract: In this paper, we consider a vibrating system of Timoshenko-type in a bounded one-dimensional domain with discrete time delay and complementary frictional damping and infinite memory controls all acting on the transversal displacement. We show that the system is well-posed in the sens of semigroup and that, under appropriate assumptions on the weights of the delay and the history data, the stability of the system holds in case of the equal-speed propagation as well as in the opposite case in spite of the presence of a discrete time delay, where the decay rate of solutions is given in terms of the smoothness of the initial data and the growth of the relaxation kernel at infinity. The results of this paper extend the ones obtained by the present author and Messaoudi in (Acta Math Sci 36:1–33, 2016) to the case of presence of discrete delay.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0514-8
Issue No: Vol. 28, No. 7-8 (2017)

• Weakly invo-clean unital rings
• Authors: Peter V. Danchev
Pages: 1285 - 1295
Abstract: We define and completely describe the structure of weakly invo-clean rings possessing identity. We show that these rings are clean but neither weakly nil-clean nor invo-clean, and thus they have some new exotic properties different to those established by Breaz et al. (J Algebra Appl 15, 2016) and Danchev (Commun Korean Math Soc 32:19–27, 2017), respectively.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0515-7
Issue No: Vol. 28, No. 7-8 (2017)

• Hom-alternative modules and Hom–Poisson comodules
• Authors: Ibrahima Bakayoko; Bakary Manga
Pages: 1297 - 1311
Abstract: In this paper we introduce modules over both left and right Hom-alternative algebras. We give some constructions of left and right Hom-alternative modules and give various properties of both, as well as examples. Then, we prove that morphisms of left alternative algebras extend to morphisms of left Hom-alternative algebras. Next, we introduce comodules over Hom–Poisson coalgebras and show that we may obtain a structure map of a comodule over a Hom–Poisson coalgebra from a given one.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0516-6
Issue No: Vol. 28, No. 7-8 (2017)

• Authors: Pierre Kouadjo Brou; Youssouf M. Diagana
Pages: 1313 - 1325
Abstract: Let R be a ring and A a subring of R. Let $$h=\left( \mathcal {M} _{n}\right) _{n\in \mathbb {Z}\cup \left\{ +\infty \right\} }$$ be a family of subgroups of an R-module $$\mathcal {M}$$ . We say that h is an A-quasi-graduation of $$\mathcal {M}$$ if for every $$p\in \mathbb {N}, \mathcal {M}_{p}$$ is a sub-A-module of R with $$\mathcal {M}_{\infty }=(0)$$ . We present weak notions of J-independence for different extensions of the analytic spread. We show that under some conditions they coincide with $$\lim \nolimits _{n \rightarrow +\infty }\ell _{J}(h^{(n!)},A,k)$$ , where, for all integers $$p, h^{(p)} = (\mathcal {M}_{pn})_{n\in \mathbb {Z}\cup \left\{ +\infty \right\} }$$ and where $$\ell _J (h^{(p)}, A, k)$$ is the maximum number of elements of J which are J-independent of order k with respect to the A-quasi-graduation $$h^{(p)}$$ of the R-module $$\mathcal {M}$$ .
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0517-5
Issue No: Vol. 28, No. 7-8 (2017)

• Asymptotic property of the time-dependent solution of the M/G/1 queueing
model with single working vacation and vacation interruption
• Authors: Ehmet Kasim; Geni Gupur
Pages: 1327 - 1348
Abstract: In this paper we consider an M/G/1 queueing model with single working vacation and vacation interruption. By studying the spectral properties of the corresponding operator we obtain that the time-dependent solution of the model strongly converges to its steady-state solution.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0518-4
Issue No: Vol. 28, No. 7-8 (2017)

• On special type-2 Bishop motion and Bishop Darboux rotation axes of the
space curve
• Authors: Ayşe Zeynep Azak; Melek Masal
Pages: 1349 - 1355
Abstract: We have given a generalization of one parameter special Frenet motion to type-2 Bishop motion in Euclidean 3-space $$E^3$$ . Type-2 Bishop motion have been defined for space curve $$\beta$$ and then type-2 Bishop Darboux vector of this motion has been calculated for fixed and moving spaces in $$E^3$$ . Also, we have showed that type-2 Bishop rotation for space curves is decomposed into two simultaneous rotations. One of the axes of this simultaneous rotations is a parallel of the binormal vector of the curve, the other is the direction of the type-2 Bishop Darboux vector of the curve.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0519-3
Issue No: Vol. 28, No. 7-8 (2017)

• Subclasses of starlike and convex functions involving Poisson distribution
series
• Authors: G. Murugusundaramoorthy
Pages: 1357 - 1366
Abstract: The purpose of the present paper is to establish connections between various subclasses of analytic univalent functions by applying certain convolution operator involving Poisson distribution series. To be more precise,we investigate such connections with the classes of analytic univalent functions of $$\beta$$ -starlike and $$\beta$$ -uniformly convex functions of order $$\alpha$$ in the open unit disk $${\mathbb {U}}$$ . Further we point out some consequences of our main results.
PubDate: 2017-12-01
DOI: 10.1007/s13370-017-0520-x
Issue No: Vol. 28, No. 7-8 (2017)

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