WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7150

Browse

Filters

2001 - 200932010 - 2019112020 - 20212

Settings

Department: search.filters.department.İzmir Institute of Technology. MathematicsPublisher: search.filters.publisher.Taylor and Francis Ltd.

Search Results

Now showing 1 - 10 of 16
  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    On simple-direct modules
    (Taylor and Francis Ltd., 2021) Büyükaşık, Engin; Demir, Özlem; Diril, Müge
    Recently, in a series of papers “simple” versions of direct-injective and direct-projective modules have been investigated. These modules are termed as “simple-direct-injective” and “simple-direct-projective,” respectively. In this paper, we give a complete characterization of the aforementioned modules over the ring of integers and over semilocal rings. The ring is semilocal if and only if every right module with zero Jacobson radical is simple-direct-projective. The rings whose simple-direct-injective right modules are simple-direct-projective are fully characterized. These are exactly the left perfect right H-rings. The rings whose simple-direct-projective right modules are simple-direct-injective are right max-rings. For a commutative Noetherian ring, we prove that simple-direct-projective modules are simple-direct-injective if and only if simple-direct-injective modules are simple-direct-projective if and only if the ring is Artinian. Various closure properties and some classes of modules that are simple-direct-injective (resp. projective) are given. © 2020 Taylor & Francis Group, LLC.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Integrally Closed Rings Which Are Prufer
    (Taylor and Francis Ltd., 2019) Ay Saylam, Başak
    Let R be a commutative ring with zero divisors. It is well known that if R is integrally closed, then R is a Prufer domain if and only if there is an integer n > 1 such that, for all . We soften this result for commutative rings with zero divisors by proving that this integer n does not have to work for all a, b is an element of R.
  • Article
    Citation - WoS: 6
    Citation - Scopus: 6
    Exponential Stability for the Nonlinear Schrodinger Equation With Locally Distributed Damping
    (Taylor and Francis Ltd., 2020) Cavalcanti, Marcelo M.; Correa, Wellington J.; Özsarı, Türker; Sepulveda, Mauricio; Vejar-Aseme, Rodrigo
    In this paper, we study the defocusing nonlinear Schrodinger equation with a locally distributed damping on a smooth bounded domain as well as on the whole space and on an exterior domain. We first construct approximate solutions using the theory of monotone operators. We show that approximate solutions decay exponentially fast in the L-2-sense by using the multiplier technique and a unique continuation property. Then, we prove the global existence as well as the L-2-decay of solutions for the original model by passing to the limit and using a weak lower semicontinuity argument, respectively. The distinctive feature of the paper is the monotonicity approach, which makes the analysis independent from the commonly used Strichartz estimates and allows us to work without artificial smoothing terms inserted into the main equation. We in addition implement a precise and efficient algorithm for studying the exponential decay established in the first part of the paper numerically. Our simulations illustrate the efficacy of the proposed control design.
  • Article
    Citation - WoS: 12
    Citation - Scopus: 11
    Rugged Modules: the Opposite of Flatness
    (Taylor and Francis Ltd., 2018) Büyükaşık, Engin; Enochs, Edgar; Rozas, J. R. García; Kafkas Demirci, Gizem; López-Permouth, Sergio; Oyonarte, Luis
    Relative notions of flatness are introduced as a mean to gauge the extent of the flatness of any given module. Every module is thus endowed with a flatness domain and, for every ring, the collection of flatness domains of all of its modules is a lattice with respect to class inclusion. This lattice, the flatness profile of the ring, allows us, in particular, to focus on modules which have a smallest flatness domain (namely, one consisting of all regular modules.) We establish that such modules exist over arbitrary rings and we call them Rugged Modules. Rings all of whose (cyclic) modules are rugged are shown to be precisely the von Neumann regular rings. We consider rings without a flatness middle class (i.e., rings for which modules must be either flat or rugged.) We obtain that, over a right Noetherian ring every left module is rugged or flat if and only if every right module is poor or injective if and only if R = S×T, where S is semisimple Artinian and T is either Morita equivalent to a right PCI-domain, or T is right Artinian whose Jacobson radical properly contains no nonzero ideals. Character modules serve to bridge results about flatness and injectivity profiles; in particular, connections between rugged and poor modules are explored. If R is a ring whose regular left modules are semisimple, then a right module M is rugged if and only if its character left module M+ is poor. Rugged Abelian groups are fully characterized and shown to coincide precisely with injectively poor and projectively poor Abelian groups. Also, in order to get a feel for the class of rugged modules over an arbitrary ring, we consider the homological ubiquity of rugged modules in the category of all modules in terms of the feasibility of rugged precovers and covers for arbitrary modules.
  • Article
    Citation - WoS: 7
    Citation - Scopus: 7
    Boosting the Decay of Solutions of the Linearised Korteweg-De Vries–burgers Equation To a Predetermined Rate From the Boundary
    (Taylor and Francis Ltd., 2019) Özsarı, Türker; Arabacı, Eda
    The aim of this article is to extend recent results on the boundary feedback controllability of the Korteweg-de Vries equation to the Korteweg-de Vries–Burgers equation which is posed on a bounded domain. In the first part of the paper, it is proven that all the sufficiently small solutions can be steered to zero at any desired exponential rate by means of a suitably constructed boundary feedback controller. In the second part, an observer is proposed when a type of boundary measurement is available while there is no full access to the medium.
  • Article
    Citation - WoS: 13
    Citation - Scopus: 14
    Poor and Pi-Poor Abelian Groups
    (Taylor and Francis Ltd., 2017) Alizade, Rafail; Büyükaşık, Engin
    In this paper, poor abelian groups are characterized. It is proved that an abelian group is poor if and only if its torsion part contains a direct summand isomorphic to (Formula presented.) , where P is the set of prime integers. We also prove that pi-poor abelian groups exist. Namely, it is proved that the direct sum of U(ℕ), where U ranges over all nonisomorphic uniform abelian groups, is pi-poor. Moreover, for a pi-poor abelian group M, it is shown that M can not be torsion, and each p-primary component of M is unbounded. Finally, we show that there are pi-poor groups which are not poor, and vise versa.
  • Article
    Citation - WoS: 11
    Citation - Scopus: 11
    Neat-Flat Modules
    (Taylor and Francis Ltd., 2016) Büyükaşık, Engin; Durğun, Yılmaz
    Let R be a ring. A right R-module M is said to be neat-flat if the kernel of any epimorphism Y → M is neat in Y, i.e., the induced map Hom(S, Y) → Hom(S, M) is surjective for any simple right R-module S. Neat-flat right R-modules are projective if and only if R is a right (Formula presented.) -CS ring. Every cyclic neat-flat right R-module is projective if and only if R is right CS and right C-ring. It is shown that, over a commutative Noetherian ring R, (1) every neat-flat module is flat if and only if every absolutely coneat module is injective if and only if R ≅ A × B, wherein A is a QF-ring and B is hereditary, and (2) every neat-flat module is absolutely coneat if and only if every absolutely coneat module is neat-flat if and only if R ≅ A × B, wherein A is a QF-ring and B is Artinian with J 2(B) = 0.
  • Article
    Citation - WoS: 7
    Citation - Scopus: 7
    The Proper Class Generated by Weak Supplements
    (Taylor and Francis Ltd., 2014) Alizade, Rafail; Demirci, Yılmaz Mehmet; Durğun, Yılmaz; Pusat, Dilek
    We show that, for hereditary rings, the smallest proper classes containing respectively the classes of short exact sequences determined by small submodules, submodules that have supplements and weak supplement submodules coincide. Moreover, we show that this class can be obtained as a natural extension of the class determined by small submodules. We also study injective, projective, coinjective and coprojective objects of this class. We prove that it is coinjectively generated and its global dimension is at most 1. Finally, we describe this class for Dedekind domains in terms of supplement submodules.
  • Article
    Citation - WoS: 13
    Citation - Scopus: 13
    Absolutely S-Pure Modules and Neat-Flat Modules
    (Taylor and Francis Ltd., 2015) Büyükaşık, Engin; Durğun, Yılmaz
    Let R be a ring with an identity element. We prove that R is right Kasch if and only if injective hull of every simple right R-modules is neat-flat if and only if every absolutely pure right R-module is neat-flat. A commutative ring R is hereditary and noetherian if and only if every absolutely s-pure R-module is injective and R is nonsingular. If every simple right R-module is finitely presented, then (1)R R is absolutely s-pure if and only if R is right Kasch and (2) R is a right (Formula presented.) -CS ring if and only if every pure injective neat-flat right R-module is projective if and only if every absolutely s-pure left R-module is injective and R is right perfect. We also study enveloping and covering properties of absolutely s-pure and neat-flat modules. The rings over which every simple module has an injective cover are characterized. © 2015 Taylor & Francis Group, LLC.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    A Biomathematical Model for Phoma Tracheiphila Citrus Resistance Screening
    (Taylor and Francis Ltd., 2012) Khanchouch, Khaled; Hajlaoui, Mohamed Rabeh; Kutucu, Hakan
    The causal agent of Mal Secco, Phoma tracheiphila, is responsible for many important losses in the Citrus crop worldwide. The resistance enhancement of Citrus susceptible to the pathogen infection depends on the availability of a valid test for disease assessment. However, the resistance analysis tests used give controversial results. In this paper, we propose a new mathematical model to conduct a rapid and efficient resistance screening test. This model has the advantage to give a strict evaluation of the resistance and not a relative estimation as in the usual tests. The results obtained by this model are in concordance with those observed in the orchards.