İşletme Fakültesi

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Citation Count: 1
Analysis of the Patients and Physicians Connection Network on an online Health Information Platform
(IOS Press, 2014) Aydın, Mehmet Nafiz; Perdahci, N. Ziya
Social network applications have gained popularity in the health domain as they bring health information seekers (patients and alike) and medication advice providers (physicians and other relevant actors) together. By employing a network science perspective this research is aimed to understand an information network establishing connections among and between information seekers and providers. We found that such a connection network surfaces most of the essential characteristics of a typical complex network. Furthermore a detailed structural analysis shows some intriguing relations and connection behaviours in the network. Implications of the findings are discussed from the perspectives of medical informatics and social network analysis.
Citation Count: 0
A characterization of totally umbilical hypersurfaces of a space form by geodesic mapping
(Springer, 2013) Canfes, Elif Ozkara; Özdeğer, Abdülkadir
The idea of considering the second fundamental form of a hypersurface as the first fundamental form of another hypersurface has found very useful applications in Riemannian and semi-Riemannian geometry especially when trying to characterize extrinsic hyperspheres and ovaloids. Recently T. Adachi and S. Maeda gave a characterization of totally umbilical hypersurfaces in a space form by circles. In our paper we give a characterization of totally umbilical hypersurfaces of a space form by means of geodesic mapping.
Citation Count: 1
Continuous dependence on data for a solution of the quasilinear parabolic equation with a periodic boundary condition
(Springer International Publishing Ag, 2013) Kanca, Fatma; Baglan, Irem Sakinc; Kanca, Fatma
In this paper we consider a parabolic equation with a periodic boundary condition and we prove the stability of a solution on the data. We give a numerical example for the stability of the solution on the data.
Citation Count: 6
Corporate Governance and Tunneling: Empirical Evidence from Turkey
(Economics Bulletin, 2018) Akben Selçuk, Elif; Sener, Pınar
This study investigates whether internal governance mechanisms affect tunneling through intercorporate loans for a sample of Turkish listed non-financial firms over the period 2006 to 2014. While the findings reveal a significant and positive relationship between state ownership and tunneling and a significant and negative relationship between foreign ownership and tunneling the relationship between family ownership and tunneling is non-linear. In addition while board size is negatively associated with tunneling independent directors do not prevent the embezzlement of resources. Furthermore the results indicate that while older firms firms with family chairman and higher growth opportunities are more likely to engage in tunneling activities firm size high cash holding leverage and financial distress do not affect tunneling.
Citation Count: 4
Development of a supervised classification method to construct 2D mineral maps on backscattered electron images
(Tubitak, 2020) Çavur, Mahmut; Çavur, Mahmut
The Mineral Liberation Analyzer (MLA) can be used to obtain mineral maps from backscattered electron (BSE) images of particles. This paper proposes an alternative methodology that includes random forest classification, a prospective machine learning algorithm, to develop mineral maps from BSE images. The results show that the overall accuracy and kappa statistic of the proposed method are 97% and 0.94, respectively, proving that random forest classification is accurate. The accuracy indicators also suggest that the proposed method may be applied to classify minerals with similar appearances under BSE imaging. Meanwhile, random forest predicts fewer middling particles with binary and ternary composition, but the MLA predicts more middling particles only with ternary composition. These discrepancies may arise because the MLA, unlike random forest, may also measure the elemental compositions of mineral surfaces below the polished section.
Citation Count: 7
Does financial flexibility enhance firm value? A comparative study between developed and emerging countries
(VGTU, 2020) Bilyay Erdoğan, Seda
This paper investigates the effect of financial flexibility on firm value, on a comparative basis between developed and emerging countries in Europe. Our dataset covers 4,334 companies from 15 developed and 1,436 companies from 6 emerging countries in Europe for the period between 2000 and 2016. First, depending on companies’ maintenance of leverage that is below-predicted levels for a successive number of years, I identify the financially flexible companies in the sample. Second, I examine whether financial flexibility affects firm value. Our results demonstrate that firms’ financial flexibility positively contributes to firm value in all estimations. Furthermore, this study presents unprecedented evidence that the effect of financial flexibility on firm value is more significant for emerging countries when compared to developed countries in Europe. Moreover, I demonstrate for the first time that firm characteristics, including firm size and age, which proxy for asymmetric information within a company, negatively moderate the relationship between flexibility and firm value. Managers, both in developed and in emerging countries, who aim to surge their firm value up, should give importance to the maintenance of financial flexibility in their capital structure decisions. Last, managers of relatively smaller and younger companies should put more emphasis on becoming financially flexible if they want to improve their firms’ value.
Citation Count: 2
Does governance affect corporate diversification behaviour in emerging markets?
(Routledge Journals, Taylor & Francıs Ltd, 2020) Sener, Pınar; Akben Selçuk, Elif
This paper investigates the role of firm-level and country-level governance on corporate diversification behaviour in emerging markets. The results show that firms with combined leadership structure are more diversified while firms with more independent directors are less diversified. There is a U-shaped relationship between ownership concentration and diversification. No significant association between country-level shareholder protection and diversification is demonstrated.
Citation Count: 0
Generalized and numerical solution for a quasilinear parabolic equation with nonlocal conditions
(Univ Babes-Bolyai, 2015) Kanca, Fatma; Baglan, Irem Sakinc
In this paper we study the one dimensional mixed problem with nonlocal boundary conditions for the quasilinear parabolic equation. We prove an existence uniqueness of the weak generalized solution and also continuous dependence upon the data of the solution are shown by using the generalized Fourier method. We construct an iteration algorithm for the numerical solution of this problem. We analyze computationally convergence of the iteration algorithm as well as on test example.
Citation Count: 5
Heuristic Methods for Postoutage Voltage Magnitude Calculations
(TUBITAK Scientific & Technical Research Council Turkey, 2016) Dağ, Hasan; Ceylan, Oğuzhan; Dağ, Hasan
Power systems play a significant role in every aspect of our daily lives. Hence their continuation without any interruption (or with the least duration of interruption due to faults or scheduled maintenances) is one of the key aims of electrical energy providers. As a result electrical energy providers need to check in great detail the integrity of their power systems by performing regular contingency studies of the equipment involved. Among others line and transformer outage simulations constitute an integral part of an electrical management system. Both accuracy and calculation speed depend on the branch outage model and/or the solution algorithms applied. In this paper the local constrained optimization problem of the single-branch outage problem is solved by intelligent methods: particle swarm optimization differential evolution and harmony search. Simulations of IEEE 14- 30- 118- and 300 -bus systems are computed both by intelligent methods and by AC load flow. The results of the intelligent method -based simulations and AC load flow -based simulations are compared in terms of accuracy and computation speed.
Citation Count: 8
The impact of text preprocessing on the prediction of review ratings
(Tubitak, 2020) Dağ, Hasan; Dağ, Hasan
With the increase of e-commerce platforms and online applications, businessmen are looking to have a rating and review system through which they can easily reveal the feelings of customers related to their products and services. It is undeniable from the statistics that online ratings and reviews attract new customers as well as increase sales by means of providing confidence, ratification, opinions, comparisons, merchant credibility, etc. Although considerable research has been devoted to the sentiment analysis for review classification, rather less attention has been paid to the text preprocessing which is a crucial step in opinion mining especially if convenient preprocessing strategies are found out to increase the classification accuracy. In this paper, we concentrate on the impact of simple text preprocessing decisions in order to predict fine-grained review rating stars whereas the majority of previous work focused on the binary distinction of positive vs. negative. Therefore, the aim of this research is to analyze preprocessing techniques and their influence, at the same time explain the interesting observations and results on the performance of a five-class-based review rating classifier.
Citation Count: 5
An inverse coefficient problem for a quasilinear parabolic equation with nonlocal boundary conditions
(Springer International Publishing Ag, 2013) Kanca, Fatma; Bağlan, İrem
In this paper the inverse problem of finding the time-dependent coefficient of heat capacity together with the nonlocal boundary conditions is considered. Under some natural regularity and consistency conditions on the input data, the existence, uniqueness and continuous dependence upon the data of the solution are shown. Some considerations on the numerical solution for this inverse problem are presented with an example.
Citation Count: 9
Inverse Coefficient Problem of the Parabolic Equation with Periodic Boundary and Integral Overdetermination Conditions
(Hindawi Publishing Corporation, 2013) Kanca, Fatma
This paper investigates the inverse problem of finding a time-dependent diffusion coefficient in a parabolic equation with the periodic boundary and integral overdetermination conditions. Under some assumption on the data the existence uniqueness and continuous dependence on the data of the solution are shown by using the generalized Fourier method. The accuracy and computational efficiency of the proposed method are verified with the help of the numerical examples.
Citation Count: 10
Numerical solution and distinguishability in time fractional parabolic equation
(Springer International Publishing Ag, 2015) Demir, Ali; Kanca, Fatma; Ozbilge, Ebru
This article deals with the mathematical analysis of the inverse problem of identifying the distinguishability of input-output mappings in the linear time fractional inhomogeneous parabolic equation D(t)(alpha)u(x t) = (k(x)u(x))(x) + r(t)F(x t) 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[center dot] : kappa -> C-1[0 T] and psi[center dot] : 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[center dot] and psi[center dot]. Moreover 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[center dot] : kappa -> C-1[0 T] and psi[center dot] : kappa -> C[0 T] can be described explicitly where Phi[r] = k(x)u(x)(x t
Citation Count: 5
Perceived Financial Needs, Income Sources, and Subjective Financial Well-Being in an Emerging Market
(Springer Publishing Co, 2019) Kiymaza, Halil; Öztürkkal, Belma
This study investigates perceived financial needs and subjective financial well-being using data from a national survey of 2,567 households in Turkey. Financial needs are measured by consumer perceived ability to meet current living expenses in the short-term as well as their assessment for the retirement security in the long-term. We also investigate how income sources are related to subjective financial well-being. Findings show that households' daily concerns including the inability to meet short-term expenses including healthcare, daily living expenses (food and utilities), and the inability to maintain the existing living standard are highly significant factors in explaining their subjective financial well-being. We also find that having enough income during retirement and ability to find a job in the future are positively related to subjective financial well-being. Finally, when households ' incomes are from work, rental properties, family, and pension, they feel more financially secure.
Citation Count: 4
Personality Motivation and Math Achievement Among Turkish Students: Evidence from PISA Data
(Sage Publications Inc, 2017) Akben Selçuk, Elif
Using the Turkish portion of the Programme for International Student Assessment dataset (N=4848
Citation Count: 4
Project Management Method Adoption: A Service Industry Case Study
(IGI Global, 2017) Dilan, Ebru; Aydın, Mehmet Nafiz
The purpose of this research is to understand what aspects of brand-named project management method (Project Management Institute - PMI) have been adopted in a service organization and how. The case context examined demonstrates how a weak-matrix organizational structure and agency interpretation along with project management maturity for IT outsourcing projects can affect adoption of a project management method. An interpretative case study is employed for examining the interplays among key notions underlying project management method adoption in IT outsourcing projects. The case study is framed with a research logic constituting the underlying notions of method adoption: the context the agency and the method and its fragments. It is found that the organization realizes 43 out of 47 processes proposed by PMI. It is also observed that the perceived project management maturity level is not aligned with the method fragments adopted. Among other discussion points the present findings contribute to the existing literature by emphasizing the effects of management control on PM method adoption in IT outsourcing. Furthermore this case allows us to argue that product-focused orientation in project management method adoption is evident and has several implications. The adoption and adaptation of processes in different types of projects is on the authors' future research agenda.
Citation Count: 0
A sparsity-preserving spectral preconditioner for power flow analysis
(TUBITAK Scientific & Technical Research Council Turkey, 2016) Yetkin, Emrullah Fatih; Dağ, Hasan
Due to the ever-increasing demand for more detailed and accurate power system simulations the dimensions of mathematical models increase. Although the traditional direct linear equation solvers based on LU factorization are robust they have limited scalability on the parallel platforms. On the other hand simulations of the power system events need to be performed at a reasonable time to assess the results of the unwanted events and to take the necessary remedial actions. Hence to obtain faster solutions for more detailed models parallel platforms should be used. To this end direct solvers can be replaced by Krylov subspace methods (conjugate gradient generalized minimal residuals etc.). Krylov subspace methods need some accelerators to achieve competitive performance. In this article a new preconditioner is proposed for Krylov subspace-based iterative methods. The proposed preconditioner is based on the spectral projectors. It is known that the computational complexity of the spectral projectors is quite high. Therefore we also suggest a new approximate computation technique for spectral projectors as appropriate eigenvalue-based accelerators for efficient computation of power flow problems. The convergence characteristics and sparsity structure of the preconditioners are compared to the well-known black-box preconditioners such as incomplete LU and the results are presented.
Citation Count: 0
Time Space and Closure in Karamanlidika Temasa-i Dunya ve Cefakar u Cefakes : Rewriting Polipathis
(Ahmet Yesevi University, 2018) Şişmanoğlu Şimşek, Şehnaz
This article criticises the argument that then arrative fiction called Temasa-i Dunya ve Cefakar u Cefakes (1871-1872) by Evangelinos Misailidis (1820-1890) an Ottoman Christian-Orthodox citizen is just a mere imitation of the Greek novel O Polipathis (1839). Using mainly Gerard Genette's the oretical framework and narratological concepts it can be said that Misailidis has significantly transformed Polipa this semantically especially in terms of time space and closure in then arrative. Hence this study also focuses on the problem of there writing of a text using varied writing strategies. Finally this article claims that as it contains various writing strategies as well as newnarrativepossibilities Dunya is an original novel that reveals the multilingual Ottoman world and Ottoman literature in then ineteenth century.

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