فهرست مطالب

Sahand Communications in Mathematical Analysis - Volume:17 Issue: 3, 2020
  • Volume:17 Issue: 3, 2020
  • تاریخ انتشار: 1399/05/13
  • تعداد عناوین: 12
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  • Atefeh Foroozandeh, Ataollah Askari Hemmat *, Hossein Rabbani Pages 1-31
    Despite the growing growth of technology, handwritten signature has been selected as the first option between biometrics by users. In this paper, a new methodology for offline handwritten signature verification and recognition based on the Shearlet transform and transfer learning is proposed. Since, a large percentage of handwritten signatures are composed of curves and the performance of a signature verification/recognition system is directly related to the edge structures, subbands of shearlet transform of signature images are good candidates for input information to the system. Furthermore, by using transfer learning of some pre-trained models, appropriate features would be extracted. In this study, four pre-trained models have been used: SigNet and SigNet-F (trained on offline signature datasets), VGG16 and VGG19 (trained on ImageNet dataset). Experiments have been conducted using three datasets: UTSig, FUM-PHSD and MCYT-75. Obtained experimental results, in comparison with the literature, verify the effectiveness of the presented method in both signature verification and signature recognition.
    Keywords: Offline handwritten signature, Signature verification, Signature recognition, Shearlet transform, Transfer learning
  • Reyhaneh Bagheri, Davood Alimohammadi * Pages 33-70
    ‎In this paper, we provide a complete description of weighted composition operators between extended Lipschitz algebras on compact metric spaces. We give necessary and sufficient conditions for the injectivity and the sujectivity of these operators. We also obtain some sufficient conditions and some necessary conditions for a weighted composition operator between these spaces to be compact.
    Keywords: Compact operator, Extended Lipschitz algebra, Lipschitz mapping, Supercontactive mapping, Weighted composition operator
  • Rasoul Jahed, Hamid Vaezi *, Hossein Piri Pages 71-80
    In this paper, we study the iterations of quasi $phi$-nonexpansive mappings and its applications in Banach spaces. At the first, we prove strong convergence of the sequence generated by the hybrid proximal point method to a common fixed point of a family of quasi $phi$-nonexpansive mappings.  Then, we give  applications of our main results in equilibrium problems.
    Keywords: Demiclosed‎, ‎equilibrium problem‎, ‎fixed point‎, ‎hybrid projection‎, ‎quasi nonexpansive mapping‎, Resolvent
  • Ali Ghaffari *, Samaneh Javadi, Ebrahim Tamimi Pages 81-91
    Let  $left{a_alpharight}_{alphain I}$ be a bounded net in a Banach algebra $A$ and $varphi$ a nonzero multiplicative linear functional on $A$. In this paper, we deal with the problem of when $|aa_alpha-varphi(a)a_alpha|to0$ uniformly for all $a$ in weakly compact subsets of $A$. We show that Banach algebras associated to locally compact groups such  as Segal algebras and $L^1$-algebras are responsive to this concept. It is also shown that $Wap(A)$ has a left invariant $varphi$-mean if and only if there exists a bounded net $left{a_alpharight}_{alphain I}$ in $left{ain A; varphi(a)=1right}$ such that $|aa_alpha-varphi(a)a_alpha|_{Wap(A)}to0$ uniformly for all $a$ in weakly compact subsets of $A$. Other results in this direction are also obtained.
    Keywords: Banach algebra, $varphi$-amenability, $varphi$-means, Weak almost periodic, Weak$^*$ topology
  • Atefe Razghandi, AliAkbar Arefijamaal * Pages 93-106

    In this paper we consider  (extended) metaplectic representation of the  semidirect product  $G_{mathbb{J}}=mathbb{R}^{2d}timesmathbb{J}$  where $mathbb{J}$ is a closed subgroup of $Sp(d,mathbb{R})$, the symplectic group. We will investigate continuous representation frame on $G_{mathbb{J}}$. We also discuss the existence of duals for such frames and give several characterization for them. Finally, we rewrite the dual conditions, by using the Wigner distribution and obtain more reconstruction formulas.

    Keywords: Representation frames, Dilation groups, Dual frames, Continuous frames
  • Mansooreh Moosapoor *, Mohammad Shahriari Pages 107-116
    In this paper, we introduce subspace-frequently hypercyclic operators. We show that these operators are subspace-hypercyclic and there are subspace-hypercyclic  operators that are not subspace-frequently hypercyclic. There is a criterion like to subspace-hypercyclicity criterion that implies subspace-frequent hypercyclicity and if an operator $T$ satisfies this criterion, then $Toplus T$ is subspace-frequently hypercyclic. Additionally, operators on finite spaces can not  be subspace-frequently hypercyclic.
    Keywords: Subspace-frequently hypercyclic operators, Subspace-hypercyclic operators, Frequently hypercyclic operators, Hypercyclic operators
  • Sinan Ercan * Pages 117-130
    The aim of the present work is to introduce the concept of $lambda _{r}$-almost convergence of sequences. We define the spaces $fleft( lambda _{r}right) $ and $f_{0}left( lambda _{r}right) $ of $ lambda _{r}$-almost convergent and $lambda _{r}$-almost null sequences. We investigate some inclusion relations concerning those spaces with examples and we determine the $beta $- and $gamma $-duals of the space $fleft( lambda _{r}right) $. Finally, we give the characterization of some matrix classes.
    Keywords: Almost convergence, Matrix domain, $beta $-, $gamma $-duals, Matrix transformations
  • Nasrin Ebrahimi Hoseinzadeh, Abasalt Bodaghi *, MohammadReza Mardanbeigi Pages 131-143

    The aim of this paper is to introduce $n$-variables mappings which are cubic in each variable and to apply a fixed point theorem for the Hyers-Ulam stability of such mapping in non-Archimedean normed spaces. Moreover, a few corollaries corresponding to some known stability and hyperstability outcomes are presented.

    Keywords: Multi-cubic mapping, Hyers-Ulam stability, Fixed point, non-Archimedean normed space
  • Gholamreza Rahimlou, Reza Ahmadi *, MohammadAli Jafarizadeh, Susan Nami Pages 145-160

    The notion of $k$-frames was recently introduced by Gu avruc ta in Hilbert  spaces to study atomic systems with respect to a bounded linear operator. A continuous frame is a family of vectors in a Hilbert space which allows reproductions of arbitrary elements by continuous super positions. In this manuscript, we construct a continuous $k$-frame, so called c$k$-frame along with an atomic system for this version of frames. Also we introduce a new method for obtaining the dual of a c$k$-frame and prove some new results about it.

    Keywords: c-frame, $K$-frame, c$K$-frame, c$k$-atom, c$k$-dual
  • Sedigheh Barootkoob * Pages 161-173
    In this paper, we define a new concept of factorization for a bounded bilinear mapping $f:Xtimes Yto Z$, depended on  a natural number $n$ and a cardinal number $kappa$; which is called $n$-factorization property of level $kappa$. Then we study the relation between $n$-factorization property of  level $kappa$ for $X^*$ with respect to $f$ and automatically boundedness and $w^*$-$w^*$-continuity and also strong Arens irregularity. These results may help us to prove some previous  problems related to strong Arens irregularity more easier than old. These include some results proved by Neufang in ~cite{neu1} and ~cite{neu}.  Some applications to certain bilinear mappings on convolution algebras, on a locally compact group, are also included. Finally, some solutions related to  the Ghahramani-Lau conjecture is raised.
    Keywords: Bilinear map, Factorization property, Strongly Arens irregular, Automatically bounded, $w^*$-$w^*$-continuous
  • Hamideh Mohammadzadehkan *, Ali Ebadian, Kazem Haghnejad Azar Pages 175-188
    In this paper, we discuss some properties of joint spectral {radius(jsr)} and  generalized spectral radius(gsr)  for a finite set of upper triangular matrices with entries in a Banach algebra and represent relation between geometric and joint/generalized spectral radius. Some of these are in scalar matrices, but  some are different. For example for a bounded set of scalar matrices,$Sigma$, $r_*left(Sigmaright)= hat{r}left(Sigmaright)$, but for a bounded set of  upper triangular matrices with entries in a Banach algebra($Sigma$), $r_*left(Sigmaright)neqhat{r}left(Sigmaright)$. We  investigate when the set is  defective or not and equivalent properties for having a norm equal to jsr, too.
    Keywords: Banach algebra, Upper Triangular Matrix, Generalized Spectral Radius, Joint Spectral Radius, Geometric Joint Spectral Radius
  • Tesfalem Hadush Meche, Habtu Zegeye * Pages 189-217
    In this article, we introduced an iterative scheme for finding a common element of the set of fixed points of a multi-valued hemicontractive-type mapping, the set of common solutions of a finite family of split equilibrium problems and the set of common solutions of a finite family of variational inequality problems in real Hilbert spaces. Moreover, the sequence generated by the proposed algorithm is proved to be strongly convergent to a common solution of these three problems under mild conditions on parameters. Our results improve and generalize many well-known recent results existing in the literature in this field of research.
    Keywords: Fixed point, multi-valued, hemicontractive-type, variational inequality, split equilibrium problems, strong convergence, Monotone mapping