WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/20.500.14365/5

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Now showing 1 - 20 of 280

Citation - WoS: 12
Citation - Scopus: 10
An Advanced Method With Convergence Analysis for Solving Space-Time Fractional Partial Differential Equations With Multi Delays
(Springer Heidelberg, 2019) Kürkçü, ÖmÜr Kıvanç; Aslan, Ersin; Sezer, Mehmet
This study considers the space-time fractional partial differential equations with multi delays under a unique formulation, proposing a numerical method involving advanced matrix system. This matrix system is made up of the matching polynomial of complete graph together with fractional Caputo and Jumarie derivative types. Also, the derivative types are scrutinized to determine which of them is more proper for the method. Convergence analysis of the method is established via an average value of residual function using double integrals. The obtained solutions are improved with the aid of a residual error estimation. A general computer program module, which contains few steps, is developed. Tables and figures prove the efficiency and simplicity of the method. Eventually, an algorithm is given to illustrate the basis of the method.
Citation - WoS: 11
Citation - Scopus: 17
An Aggregated Fuzzy Naive Bayes Data Classifier
(Elsevier Science Bv, 2015) Tütüncü, Gözde Yazgı; Kayaalp, Necla
In this study, an Aggregated. Fuzzy Naive Bayes Classifier is proposed for decision-making problems where both linguistic and numerical information are available. In the solution process of such problems, all attributes are considered as fuzzy numbers and a procedure based on 2-tuple fuzzy linguistic representation model is generated for combining them. This procedure and subsequent Fuzzy Naive Bayes classification are performed based on arithmetic operations defined by Chen's function principle. The proposed method was demonstrated on 2 well-known examples from the literature in which both numerical and linguistic attributes were considered. The results show that the proposed Aggregated Fuzzy Naive Bayes Classifier is notably efficient in decision-making where the attributes are in more realistic forms. (C) 2015 Elsevier B.V. All rights reserved.
Citation - WoS: 5
Citation - Scopus: 4
Almost Automorphic Solutions of Delayed Neutral Dynamic Systems on Hybrid Domains
(Univ Belgrade, Fac Electrical Engineering, 2016) Adıvar, Murat; Koyuncuoglu, Halis Can; Raffoul, Youssef N.
We study the existence of almost automorphic solutions of the delayed neutral dynamic system on hybrid domains that are additively periodic. We use exponential dichotomy and prove the uniqueness of projector of exponential dichotomy to obtain some limit results leading to sufficient conditions for existence of almost automorphic solutions to neutral system. Unlike the existing literature we prove our existence results without assuming boundedness of the coefficient matrices in the system. Hence, we significantly improve the results in the existing literature. Finally, we also provide an existence result for almost periodic solutions of the system.
Citation - WoS: 15
Citation - Scopus: 13
Almost Automorphic Solutions of Discrete Delayed Neutral System
(Academic Press Inc Elsevier Science, 2016) Adıvar, Murat; Koyuncuoglu, Halis Can
We study almost automorphic solutions of the discrete delayed neutral dynamic system x(t + 1) = A(t)x(r) + Delta Q(t, x(t - g(t)) + G(t, x(t), x(t - g(t)) by means of a fixed point theorem due to Krasnoselskii. Using discrete variant of exponential dichotomy and proving uniqueness of projector of discrete exponential dichotomy we invert the equation and obtain some limit results leading to sufficient conditions for the existence of almost automorphic solutions of the neutral system. Unlike the existing literature we prove our existence results without assuming boundedness of inverse matrix A (t)(-1). Hence, we significantly improve the results in the existing literature. We provide two examples to illustrate effectiveness of our results. Finally, we also provide an existence result for almost periodic solutions of the system. (C) 2015 Elsevier Inc. All rights reserved.
Citation - WoS: 1
Citation - Scopus: 1
Analysis for the Identification of an Unknown Diffusion Coefficient Via Semigroup Approach
(Wiley, 2009) Demir, Ali; Özbilge Kahveci, Ebru
This paper presents a semigroup approach for the mathematical analysis of the inverse coefficient problems of identifying the unknown coefficient k(u(x)) in the inhomogenenous quasi-linear parabolic equation u(t)(x, t) = (k(u(x))u(x)(x, t))(x) + F(u) with the Dirichlet boundary conditions u(0, t)=psi(0),u(1, t)=psi(1) and source function F(u). The main purpose of this paper is to investigate the distinguishability of the input-output mappings Phi[.] : K -> C-1[0, T], psi[.]: K -> C-1[0,T] via sernigroup theory. Copyright (C) 2009 John Wiley & Sons, Ltd.
Citation - WoS: 12
Citation - Scopus: 14
Analysis of a Semigroup Approach in the Inverse Problem of Identifying an Unknown Coefficient
(John Wiley & Sons Ltd, 2008) Demir, Ali; Özbilge Kahveci, Ebru
This article presents a semigroup approach to the mathematical analysis of the inverse coefficient problems of identifying file Unknown coefficient k(u(x)) in file quasi-linear parabolic equation u(t)(x,t) = (k(u(x))u(x)(x,t))(x) +F(x,t), with Dirichlet boundary conditions u(0,t)=psi(0), u(l,t) = psi(1) and funclion F(x,t). The main purpose of this paper is to investigate the distinguishability of the input-out mappings phi[center dot]:k -> C-1[0,T], psi[center dot]:K -> C-1[0,T] via semigroup theory. Copyright (C) 2008 John Wiley & Sons, Ltd.
Citation - WoS: 4
Citation - Scopus: 4
Analysis of a Semigroup Approach in the Inverse Problem of Identifying an Unknown Parameters
(Elsevier Science Inc, 2011) Özbilge Kahveci, Ebru; Demir, Ali
This article presents a semigroup approach to the mathematical analysis of the inverse parameter problems of identifying the unknown parameters p(t) and q in the linear parabolic equation u(t)(x, t) = u(xx) + qu(x)(x, t) + p(t)u(x, t), with Dirichlet boundary conditions u(0, t) = psi(0), u(1, t) = psi(1). The main purpose of this paper is to investigate the distinguishability of the input-output mapping Phi[.] : P -> H-1,H- 2 [0, T], via semigroup theory. In this paper, it is shown that if the nullspace of the semigroup T(t) consists of only zero function, then the input-output mapping Phi[.] has the distinguishability property. It is also shown that the types of the boundary conditions and the region on which the problem is defined play an important role in the distinguishability property of the mapping. Moreover, under the light of the measured output data u(x)(0, t) = f(t) the unknown parameter p(t) at (x, t) = (0, 0) and the unknown coefficient q are determined via the input data. Furthermore, it is shown that measured output data f(t) can be determined analytically by an integral representation. Hence the input-output mapping Phi[.] : P -> H-1,H-2 [0, T] is given explicitly interms of the semigroup. (C) 2011 Elsevier Inc. All rights reserved.
An Analysis of Conservative Finite Difference Schemes for Differential Equations With Discontinuous Coefficients
(Elsevier Science Inc, 2007) Özbilge Kahveci, Ebru
A class of monotone conservative schemes is derived for the boundary value problem related to the Sturm-Liouville operator Au : = -(k(x)u'(x))' + q(x)u(x), with discontinuous coefficient k = k(x). The discrete analogous of the law of conservation are compared for the finite element and finite difference approaches. In the class of discontinuous coefficients, the necessary condition for conservativeness of the finite difference scheme is derived. The obtained one parametric family of conservative schemes permits one to construct new conservative schemes. The examples, presented for different discontinuous coefficients, and results show how the conservativeness conditions need to be taken into account in numerical solving boundary value problems. (c) 2007 Elsevier Inc. All rights reserved.
Citation - WoS: 1
Analysis of Joint Reliability Importance in Linear M-Consecutive L-Out System
(Ankara Univ, Fac Sci, 2020) Kan, Cihangir; Ozkut, Murat
Combinatorial techniques have an important role to compute the joint reliability importance (JRI) of some coherent systems. We obtain combi- natorial formula for calculation of the JRI of two components in a generalised version of consecutive type systems consisting of n linearly ordered components such that system fails if and only if (i§) there are at least m l-overlapping runs of k consecutive failed components (n m(k l) + l; l < k). Overlapping runs mean having common elements which is denoted by l: We concentrate on both s-independent & identical components and exchangeable components. Explicit combinatorial formulae are provided for computing the JRI of the above mentioned cases. For both cases, we also compare the results with lin- ear m-consecutive-k-out-of-n:F system (nonoverlapping case when l = 0). In addition, some numerical and illustrative examples are presented.
Citation - WoS: 11
Citation - Scopus: 10
Analysis of the Inverse Problem in a Time Fractional Parabolic Equation With Mixed Boundary Conditions
(Springer, 2014) Özbilge Kahveci, Ebru; Demir, Ali
This article deals with the mathematical analysis of the inverse coefficient problem of identifying the unknown coefficient k(x) in the linear time fractional parabolic equation D-t(alpha) u(x, t) = (k(x)u(x))(x), 0 < alpha <= 1, with mixed boundary conditions u(0, t) = psi(0)(t), u(x)(1, t) = psi(1)(t). By defining the input-output mappings Phi[.] : kappa -> C-1[0, T] and psi[.] : kappa -> C[0, T], the inverse problem is reduced to the problem of their invertibility. Hence the main purpose of this study is to investigate the distinguishability of the input-output mappings Phi[.] and Phi[.]. This work shows that the input-output mappings Phi[.] and Phi[.] have the distinguishability property. Moreover, the value k(0) of the unknown diffusion coefficient k(x) at x = 0 can be determined explicitly by making use of measured output data (boundary observation) k(0) ux(0, t) = f (t), which brings greater restriction on the set of admissible coefficients. It is also shown that the measured output data f (t) and h(t) can be determined analytically by a series representation, which implies that the input-output mappings Phi[.] : kappa -> C1[0, T] and Phi[.] : kappa -> C[0, T] can be described explicitly.
Citation - WoS: 4
Citation - Scopus: 4
Analyzing Component Failures in Series-Parallel Systems With Dependent Components
(Elsevier Ltd, 2024) Torrado, N.; Ozkut, M.
This paper investigates a series-parallel system comprising N independent subsystems with interchangeable dependent components, a prevalent reliability structure in engineering and network design. The primary aim of this research is to derive the joint probability distribution of the number of failed components within these configurations, considering component dependence and varying distributions across subsystems. This approach reflects a more realistic scenario than previously explored in the literature. Initially, the analysis is conducted for systems with two subsystems and subsequently extended to encompass configurations with N subsystems. The study also evaluates key reliability metrics including the average number of failed components and the mean time to failure (MTTF) of the entire system, theoretically proving that the system's MTTF increases with the number of components under certain sufficient conditions. In addition to probabilistic analysis, an optimization problem is addressed to determine the optimal allocation of components within each subsystem. The objective is to minimize the average cost associated with corrective maintenance, thereby enhancing the cost-effectiveness of system operation. © 2024 The Authors
Citation - WoS: 3
Citation - Scopus: 3
Analyzing the Multi-State System Under a Run Shock Model
(Cambrıdge Unıv Press, 2024) Özkut, Cemal Murat; Kan, Cihangir; Franko, Ceki; Ozkut, Murat
A system experiences random shocks over time, with two critical levels, d1 and d2, where $d_{1} \lt d_{2}$. k consecutive shocks with magnitudes between d1 and d2 partially damaging the system, causing it to transition to a lower, partially working state. Shocks with magnitudes above d2 have a catastrophic effect, resulting in complete failure. This theoretical framework gives rise to a multi-state system characterized by an indeterminate quantity of states. When the time between successive shocks follows a phase-type distribution, a detailed analysis of the system's dynamic reliability properties such as the lifetime of the system, the time it spends in perfect functioning, as well as the total time it spends in partially working states are discussed.
Association Analysis Between Endoplasmic Reticulum Aminopeptidase 1 (erap1) Polymorphism With Ankylosing Spondylitis Disease Risk in Turkish Population
(Wiley-Blackwell, 2015) Akbulut, E.; Erdemir, A.; Ozgen, M.; Baskin, Y.; Yalçin, Femin; Balik, D. Turgut
[Abstract Not Available]
Citation - WoS: 2
Asymptotic Constancy for Solutions of Abstract Non-Linear Fractional Equations With Delay and Generalized Hilfer ( A, B, A )- Derivatives
(Pergamon-elsevier Science Ltd, 2025) Kostic, Marko; Koyuncuoglu, Halis Can; Katican, Tugce
In this paper, we investigate the asymptotic constancy for solutions of abstract non-linear fractional differential (difference) equations with delay and generalized Hilfer ( a, b, a )- derivatives. Our results are applicable to the abstract fractional functional equations with the usually considered Riemann-Liouville, Caputo, Hilfer and Prabhakar derivatives.
Asymptotic Properties of Mth Spacings Based on Records
(Elsevier B.V., 2024) Bayramoglu, I.; Stepanov, A.
In this work, the mth spacings based on record values obtained from continuous distributions are discussed. We first present distributional results for such spacings, and then, by making use of classification of distribution tails, derive asymptotic results for the mth record spacings. We also obtain strong limit results for them and illustrate our theoretical results by examples. Finally, we support our findings by data obtained from simulation experiments. © 2024
Citation - WoS: 20
Citation - Scopus: 20
Awareness, Treatment, Control of Hypertension, and Associated Factors: Results From a Turkish National Study
(Taylor & Francis Inc, 2018) Dastan, Ilker; Erem, Ayşegül; Cetinkaya, Volkan
Objective: Despite the fact that hypertension (HT) can be diagnosed and easily treated, it is frequently not handled well throughout the world, and as a developing country in Turkey. The objective of this study was to assess the factors associated with the awareness, treatment, and control of HT in Turkey. Methods: Data came from Chronic Diseases and Risk Factors Survey, comprising a nationally representative sample of 12,971 individuals, conducted by the Turkish Ministry of Health in 2011. HT was defined as having systolic/diastolic blood pressure (BP) at least 140/90 mmHg, usage of HT medicines, or having a previous diagnosis. Awareness, treated, and controlled HT were determined by questionnaires/BP measurements. Stepwise multiple logistic regression analysis was used to estimate associated factors. Results: The prevalence of HT was found to be 24.8%. Awareness, treatment, and control rates were 65%, 59%, and 30%, respectively. The risk factors for lack of awareness or treatment of HT were male gender, young age, rural residency, lower education, being employed, sedentary lifestyle, and less physical activity for women, unhealthy dietary habits for men, and modifiable risk factors, including smoking and drinking for men. Increasing age, low education for women, marital status subgroups within gender ( being single for men and being married for women), smoking and alcohol use for men, and diseases such as diabetes and obesity were also correlated with poor control of HT. Conclusion: This study recognized associated risk factors that may guide policies and interventions to enhance awareness, treatment, and control of HT in Turkey.
Citation - WoS: 9
Citation - Scopus: 10
Baker-Lin Type Bivariate Distributions Based on Order Statistics
(Taylor & Francis Inc, 2014) Bayramoglu, K.; Bayramoglu (Bairamov), I.
Baker (2008) introduced a new class of bivariate distributions based on distributions of order statistics from two independent samples of size n. Lin and Huang (2010) discovered an important property of Baker's distribution and showed that the Pearson's correlation coefficient for this distribution converges to maximum attainable value, i.e., the correlation coefficient of the Frechet upper bound, as n increases to infinity. Bairamov and Bayramoglu (2013) investigated a new class of bivariate distributions constructed by using Baker's model and distributions of order statistics from dependent random variables, allowing higher correlation than that of Baker's distribution. In this article, a new class of Baker's type bivariate distributions with high correlation are constructed based on distributions of order statistics by using an arbitrary continuous copula instead of the product copula.
Citation - WoS: 5
Citation - Scopus: 5
Bi-Hamiltonian Structures for Integrable Systems on Regular Time Scales
(Amer Inst Physics, 2009) Szablikowski, Blazej M.; Blaszak, Maciej; Silindir, Burcu
A construction of the bi-Hamiltonian structures for integrable systems on regular time scales is presented. The trace functional on an algebra of delta-pseudodifferential operators, valid on an arbitrary regular time scale, is introduced. The linear Poisson tensors and the related Hamiltonians are derived. The quadratic Poisson tensors are given by the use of the recursion operators of the Lax hierarchies. The theory is illustrated by Delta-differential counterparts of Ablowitz-Kaup-Newell-Segur and Kaup-Broer hierarchies.
Citation - WoS: 2
Citation - Scopus: 3
Bivariate and Multivariate Distributions With Bimodal Marginals
(Taylor & Francis Inc, 2020) Bayramoğlu, İsmihan
We consider simple variate distributions, which are the special cases of general elliptically contoured and Kotz type distributions. In particular, we analyze the distributions having joint probability density functions (pdf) defined as functions of allowing easy calculations of different probabilities when using transformations with spherical coordinates. In the case of we give the various examples of such pdfs whose graphs resemble a bell sunken from the middle. These distributions can be used for modelling data clustered in some areas between concentric circles or ellipses. The easy analytical form of considered distributions make it possible to use them in many applications which require simplicity of calculations. The example of probability density function allowing high correlation is also considered. We also discuss the multivariate conditional ordering of random vectors and compute the structure functions considered in the paper probability density functions. The distributions with bimodal marginals can be used in many areas, such as hydrology, biology, medicine, economics, ecology, physics, and astronomy.
Citation - WoS: 5
Bivariate General Random Threshold Models and Exceedance Statistics
(Inst Applied Mathematics, 2020) Erem, Aysegul; Bayramoglu Ismihan
This paper presents derivations of asymptotic and exact distributions of bivariate exceedance statistics defined for some general threshold models. The asymptotic distribution of exceedance statistics appear to be marginal free, depending only on copulas of underlying joint distributions. In particular cases, the exact formulas for these new distributions can be obtained. Applications in medicine and economics are also discussed.

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Browsing WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection by Department "İEÜ, Fen Edebiyat Fakültesi, Matematik Bölümü"