Publication Date: 2012
Statistical Papers (09325026)53(3)pp. 685-696
Skew-symmetric distributions of various types have been the center of attraction by many researchers in the literature. In this article, we shall introduce another more general class of skew distributions, specially related to the Laplace distribution. This new class contains some previously known skew distributions. We shall investigate different characteristics of members of this class such as its moments, thus generalizing a result of Umbach (Stat Probab Lett 76:507-512, 2006), limiting behavior, moment generating function, unimodality and reveal its natural occurrence as the distribution of some order statistics. In addition, we will generalize a result of Aryal and Rao (Nonlinear Anal 63:639-646, 2005) in connection with truncated skew-Laplace distribution and study its certain stochastic orderings. Some illustrative examples are also provided. © 2011 Springer-Verlag.
Publication Date: 2023
Miskolc Mathematical Notes (17872405)24(3)pp. 1117-1126
In this paper, we obtain a generalization of a fixed point theorem given by Popescu [O. Popescu, Comput. Math. Appl., vol. 62, no. 10, pp. 3912–3919, 2011]. An example is also given to support our main result. © (2023) Miskolc University Press
Publication Date: 2013
Communications in Statistics - Theory and Methods (1532415X)42(13)pp. 2324-2334
Skew-symmetric distributions of various types have been the center of attraction by many researchers in the literature. In this article, we will introduce a uni/bimodal generalization of the Azzalini's skew-normal distribution which is indeed an extension of the skew-generalized normal distribution obtained by Arellano-Valle et al. (2004). Our new distribution contains more parameters and thus it is more flexible in data modeling. Indeed, certain univariate case of the so called flexible skew-symmetric distribution of Ma and Genton (2004) is also a particular case of our proposed model. We will first study some basic distributional properties of the new extension, such as its distribution function, limiting behavior and moments. Then, we will investigate some useful results regarding its relation with other known distributions, such as student's t and skew-Cauchy distributions. In addition, we will present certain methods to generate the new distribution and, finally, we shall apply the model to a real data set to illustrate its behavior comparing to some rival models. © Taylor and Francis Group, LLC.
Publication Date: 2017
Canadian Mathematical Bulletin (14964287)60(1)pp. 122-130
We characterize two important notions of amenability and compactness of a locally compact quantum group G in terms of certain homological properties. For this, we show that G is character amenable if and only if it is both amenable and co-amenable. We finally apply our results to Arens regularity problems of the quantum group algebra L1(G). In particular, we improve an interesting result by Hu, Neufang, and Ruan. © 2016 Canadian Mathematical Society.
Publication Date: 2011
Utilitas Mathematica (03153681)84pp. 105-117
The multiplicative Wiener index, π (G) , is equal to the product of distances between all pairs of vertexes of a (molecular) graph G. In this paper we compute this index for some nanotubes and nanotori by consider them as cartesian product of paths and cycles. Also we compute this index for some composite graphs.
Publication Date: 2025
Journal of Statistical Theory and Practice (15598616)19(2)
In this paper, another motivation for the well-known quadratic transmuted family of distributions is pointed out and a new relation for the expected value of this family in terms of the Gini index is presented. A bug of the generalized transmuted-G family of distributions Nofal et al. (Commun Stat Theory Methods 46:4119–4136, 2016) is illustrated. In that work, the necessary conditions for the density and distribution functions are not satisfied, for some parameter values. Moreover, a new flexible family of distributions is introduced from a fresh perspective, and their key properties are studied in general forms. As an example, a new high flexible distribution is introduced and some of its important futures such as the moment generating function, moments, order statistics and the stress-strength parameter are investigated. In addition, the parameters of the proposed new distribution are estimated using the maximum likelihood method, and three real data sets are scrutinized to assess the distribution’s adequacy in providing satisfactory fits. © Grace Scientific Publishing 2025.
Publication Date: 2015
Journal of Applied Statistics (02664763)42(12)pp. 2654-2670
In this paper, a discrete counterpart of the general class of continuous beta-G distributions is introduced. A discrete analog of the beta generalized exponential distribution of Barreto-Souza et al. [2], as an important special case of the proposed class, is studied. This new distribution contains some previously known discrete distributions as well as two new models. The hazard rate function of the new model can be increasing, decreasing, bathtub-shaped and upside-down bathtub. Some distributional and moment properties of the new distribution as well as its order statistics are discussed. Estimation of the parameters is illustrated using the maximum likelihood method and, finally, the model with a real data set is examined. © 2015 Taylor & Francis.
Publication Date: 2017
Communications in Statistics - Theory and Methods (1532415X)46(9)pp. 4296-4310
In this paper, the researchers attempt to introduce a new generalization of the Weibull-geometric distribution. The failure rate function of the new model is found to be increasing, decreasing, upside-down bathtub, and bathtub-shaped. The researchers obtained the new model by compounding Weibull distribution and discrete generalized exponential distribution of a second type, which is a generalization of the geometric distribution. The new introduced model contains some previously known lifetime distributions as well as a new one. Some basic distributional properties and moments of the new model are discussed. Estimation of the parameters is illustrated and the model with two known real data sets is examined. © 2017 Taylor & Francis Group, LLC.
Publication Date: 2016
Communications in Statistics - Theory and Methods (1532415X)45(5)pp. 1575-1575
Publication Date: 2017
RAIRO - Operations Research (28047303)51(4)pp. 921-930
Various reward-risk performance measures and ratios have been considered in reward-risk portfolio selection problems. This paper investigates the optimal portfolio corresponding to the CVaR (STARR) ratio. Considering the LP solvability of CVaR, a method is proposed for detecting the optimal portfolio by using the corresponding Mean-CVaR optimization problem. By applying LP tools, a method is suggested for producing the optimal portfolio as a by-product during the procedure of computing the efficient frontier of the Mean-CVaR problem. © EDP Sciences, ROADEF, SMAI 2017.
Publication Date: 2015
Journal of Algebra and its Applications (17936829)14(3)
Let λ be an artin algebra. By letting the Nakayama functor act degree-wise, we define a translation ? in the category of complexes of finitely generated λ-modules, C(mod λ). Then we investigate the existence of almost split sequences in the category C(mod λ). As an application of our results, we see that the full subcategory of D(mod λ) consisting of complexes isomorphic to perfect complexes admits almost split sequences. © World Scientific Publishing Company.
Publication Date: 2007
AIP Conference Proceedings (0094243X)971pp. 105-111
In this paper we extend the 2-D directed graphical representation for DNA sequences. The main purpose is to making a directed graph corresponding to a DNA sequence which hasn't any complete coincidence of the edges. To prevent repetition of the edge e we define e→1 by using the outer product of two vectors and some mathematical concepts. Moreover, we have applied this method for some DNA sequences to show the advantage of this method over the some other methods. © 2008 American Institute of Physics.
Publication Date: 2014
Journal Of Medical Signals And Sensors (22287477)4(1)pp. 72-83
Improving the quality of medical images at pre- and post-surgery operations are necessary for beginning and speeding up the recovery process. Partial differential equations-based models have become a powerful and well-known tool in different areas of image processing such as denoising, multiscale image analysis, edge detection and other fields of image processing and computer vision. In this paper, an algorithm for medical image denoising using anisotropic diffusion filter with a convenient stopping criterion is presented. In this regard, the current paper introduces two strategies: utilizing the efficient explicit method due to its advantages with presenting impressive software technique to effectively solve the anisotropic diffusion filter which is mathematically unstable, proposing an automatic stopping criterion, that takes into consideration just input image, as opposed to other stopping criteria, besides the quality of denoised image, easiness and time. Various medical images are examined to confirm the claim.
Publication Date: 2021
Numerical Algorithms (10171398)88(1)pp. 67-91
This paper introduces an adaptive collocation method to solve retarded and neutral delay differential equations (RDDEs and NDDEs) with constant or time-dependent delays. The delays are allowed to be small or become vanishing during the integration. We determine the convergence properties of the proposed method for neutral equations with solutions in appropriate Sobolev spaces. It is shown that the proposed scheme enjoys the spectral accuracy. Numerical results show that the proposed method can be implemented in an efficient and accurate manner for a wide range of RDDE and NDDE model problems. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.
Publication Date: 2024
Journal Of The Iranian Statistical Society (17264057)23(1)pp. 99-115
This paper examines a novel extension of the geometric distribution characterized by two parameters, that is not created based on discretizing existing continuous models. This model, due to its analytical form of the cumulative distribution function and simple structure, can be of interest from mathematical perspectives, particularly in cases where the analysis of stochastic orders is desired. In addition, it is a suitable candidate for analyzing monotone hazard rate discrete data, in view of the fact that its hazard rate function exhibits monotonicity in both increasing and decreasing directions. Additionally, the behavior of the survival function of residual lifetime is briefly addressed. The parameters of the distribution are estimated using the maximum likelihood method, and a real-world data set is scrutinized to assess the distribution's adequacy in providing satisfactory fits. © (2024), (Iranian Statistical Society). All rights reserved.
Tavassoli kajani m., ,
Vahdati, S.,
Abbas, Z.,
Maleki, M. Publication Date: 2012
Journal Of Applied Mathematics (16870042)2012
Rational Chebyshev bases and Galerkin method are used to obtain the approximate solution of a system of high-order integro-differential equations on the interval [0,∞). This method is based on replacement of the unknown functions by their truncated series of rational Chebyshev expansion. Test examples are considered to show the high accuracy, simplicity, and efficiency of this method. © 2012 M. Tavassoli Kajani et al.
Publication Date: 2018
Journal of Mathematical Analysis and Applications (10960813)467(2)pp. 1168-1173
In this paper, we define the class of (α,β)-nonexpansive mappings which is properly larger than the class of α-nonexpansive mappings and prove that every (α,β)-nonexpansive mapping T:C→C has an approximate fixed point sequence, where C is a nonempty bounded subset of a Banach space X, α>0 and β≥0. This, in particular, gives an affirmative answer to the open question posed by Ariza-Ruiz and et al. concerning the existence of an approximate fixed point sequence for α-nonexpansive mappings, Ariza-Ruiz et al. (2016) [4]. © 2018 Elsevier Inc.
Publication Date: 2025
Journal of Mathematical Analysis and Applications (10960813)551(1)
In this paper, we introduce a new concept of asymptotic function to derive the Weierstrass theorem for transfer weakly lower continuous functions without coercivity condition in dual spaces that are endowed with the weak⁎ topology. Moreover, by this asymptotic function we establish a necessary and sufficient condition for a minimization problem within the framework of transfer weakly lower continuous and quasiconvex functions in dual spaces. © 2025 Elsevier Inc.
Publication Date: 2017
Far East Journal of Mathematical Sciences (09720871)102(1)pp. 111-119
Although in classical theory of time series analysis, it is customary to consider white noise processes as the error term, in functional time series analysis, this assumption can be put in abeyance. An approach to weaken this assumption is to consider the notion of weakly dependent functional processes. In this paper, we study the periodograms and their asymptotic properties in L2 -m -approximable processes that constitute a special class of weakly dependent functional processes. © 2017 Pushpa Publishing House, Allahabad, India.
Publication Date: 2020
Kyoto Journal of Mathematics (21543321)60(1)pp. 61-91
According to Auslander's formula, one way of studying an abelian category C is to study mod-C, which has nicer homological properties than C, and then translate the results back to C. Recently, Krause gave a derived version of this formula and thus renewed the subject. This paper contains a detailed study of various versions of Auslander's formula, including the versions for all modules and for unbounded derived categories. We also include some results concerning recollements of triangulated categories. © 2020 by Kyoto University.
Publication Date: 2007
Journal of Computational and Theoretical Nanoscience (15461955)4(6)pp. 1174-1178
Topological indices of nanotubes are numerical descriptors that are derived from graph of chemical compounds. Such indices based on the distances in graph are widely used for establishing relationships between the structure of nanotubes and their physico-chemical properties. The Balaban index of a molecular graph calculates the average distance sum connectivity index. Balaban index measures the ramification and it tends to increase with molecular ramification. In this paper we derive the exact expressions for Balaban index of zigzag polyhex nanotorus. Copyright © 2007 American Scientific Publishers. All rights reserved.
Publication Date: 2017
Statistics (02331888)51(5)pp. 1143-1158
In this paper, we develop a bivariate discrete generalized exponential distribution, whose marginals are discrete generalized exponential distribution as proposed by Nekoukhou, Alamatsaz and Bidram [Discrete generalized exponential distribution of a second type. Statistics. 2013;47:876–887]. It is observed that the proposed bivariate distribution is a very flexible distribution and the bivariate geometric distribution can be obtained as a special case of this distribution. The proposed distribution can be seen as a natural discrete analogue of the bivariate generalized exponential distribution proposed by Kundu and Gupta [Bivariate generalized exponential distribution. J Multivariate Anal. 2009;100:581–593]. We study different properties of this distribution and explore its dependence structures. We propose a new EM algorithm to compute the maximum-likelihood estimators of the unknown parameters which can be implemented very efficiently, and discuss some inferential issues also. The analysis of one data set has been performed to show the effectiveness of the proposed model. Finally, we propose some open problems and conclude the paper. © 2017 Informa UK Limited, trading as Taylor & Francis Group.
Publication Date: 2015
Canadian Journal of Mathematics (0008414X)67(1)pp. 28-54
We study bounded derived categories of the category of representations of infinite quivers over a ring R. In case R is a commutative noetherian ring with a dualising complex, we investigate an equivalence similar to Grothendieck duality for these categories, while a notion of dualising complex does not apply to them. The quivers we consider are left (resp. right) rooted quivers that are either noetherian or their opposite are noetherian. We also consider reflection functor and generalize a result of Happel to noetherian rings of finite global dimension, instead of fields.
Publication Date: 2010
Discrete Applied Mathematics (0166218X)158(6)pp. 659-665
In this paper, we investigate the best pixel expansion of various models of visual cryptography schemes. In this regard, we consider visual cryptography schemes introduced by Tzeng and Hu (2002) [13]. In such a model, only minimal qualified sets can recover the secret image and the recovered secret image can be darker or lighter than the background. Blundo et al. (2006) [4] introduced a lower bound for the best pixel expansion of this scheme in terms of minimal qualified sets. We present another lower bound for the best pixel expansion of the scheme. As a corollary, we introduce a lower bound, based on an induced matching of hypergraph of qualified sets, for the best pixel expansion of the aforementioned model and the traditional model of visual cryptography scheme realized by basis matrices. Finally, we study access structures based on graphs and we present an upper bound for the smallest pixel expansion in terms of strong chromatic index. © 2009 Elsevier B.V. All rights reserved.
Publication Date: 2013
Match (03406253)69(3)pp. 765-773
Let G = (V, E) be a simple graph with n = |V | vertices and m = |E| edges. The first and the second Zagreb indices of G are defined as M1(G) = Σ uεV du2 = Σ uvεE[du + dv] and M2(G) = Σ uvεE du dv, respectively, where du denotes the degree of vertex u. We compare the multiplicative versions of these indices.
Publication Date: 2012
Canadian Mathematical Bulletin (14964287)55(3)pp. 449-461
We study the complementation of the spaceW(X,Y) of weakly compact operators, the space K(X,Y) of compact operators, the space U(X,Y) of unconditionally converging operators, and the space CC(X,Y) of completely continuous operators in the space L(X,Y) of bounded linear operators from X to Y. Feder proved that if X is infinite-dimensional and c 0 → Y, then K(X,Y) is uncomplemented in L(X,Y). Emmanuele and John showed that if c 0 → K(X,Y), then K(X,Y) is uncomplemented in L(X,Y). Bator and Lewis showed that if X is not a Grothendieck space and c 0 → Y, then W(X,Y) is uncomplemented in L(X,Y). In this paper, classical results of Kalton and separably determined operator ideals with property (*) are used to obtain complementation results that yield these theorems as corollaries. © Canadian Mathematical Society 2011.
