İşletme Fakültesi

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Citation Count: 11
Bivariate Pseudo-Gompertz distribution and concomitants of its order statistics
(Elsevier Science Bv, 2013) Gebizlioğlu, Ömer Lütfi; Gebizlioğlu, Ömer Lütfi
This paper presents a new bivariate Pseudo-Gompertz distribution that sprouts from the classical Gompertz distribution and possesses the features of pseudo-distribution functions. In addition to some standard properties of the proposed distribution distributions of order statistics and their concomitants for samples drawn from the new distribution are obtained. The survival and hazard functions of the concomitants are shown and their values are tabled. Interpretations of the results are given in connection with risk events and risk management. (C) 2013 Elsevier B.V. All rights reserved.
Citation Count: 3
Competition in Turkish Banking: Impacts of Restructuring and the Global Financial Crisis
(Wiley, 2014) Yıldırım, Canan
This paper investigates the evolution of competition in the Turkish banking industry by taking into account the transformation in the sector in the aftermath of the country's financial crisis of 2000 to 2001 and the global financial crisis. The results demonstrate that the level of competition in the system did not increase despite the restructuring that was undertaken and the increased foreign bank participation. In addition the level of competition in the sector deteriorated during the global crisis. There is also some evidence that the market power of banks with different ownership characteristics varied and did not converge over time.
Citation Count: 5
A Competitive Intelligence Practices Typology in an Airline Company in Turkey
(Springer, 2020) Şahin, Murat; Bisson, Christophe
Oil prices, political instabilities, travel legislations, and many other competitive factors make it essential for any international airline with the instinct to survive to be on constant watch in such a fiercely competitive environment. To meet this need, it is vital for international airline companies to integrate competitive intelligence (CI) into their strategy building process. In this study, we create for the first time a typology of competitive intelligence practices of an international airline company (in Turkey), based on the model developed by (Wright et al.Journal of Strategic Marketing, 20(1), 19-33,2012), and it is one of the very first to investigate Competitive intelligence in this sector. Furthermore, we made a two-step cluster analysis to uncover hidden clusters that change the way of thinking within the company. Our findings show where the company would need to make improvements on the 6 strands of the model which are attitude, gathering, use, location, technological support, and IT support. Yet, that could lead towards stronger business performance. It might also inspire other companies of the airline sector and beyond.
Citation Count: 4
Computing finite time non-ruin probability and some joint distributions in discrete time risk model with exchangeable claim occurrences
(Elsevier Science, 2017) Gebizlioğlu, Ömer Lütfi; Gebizlioğlu, Ömer Lütfi
In this paper we study a discrete time risk model based on exchangeable dependent claim occurrences. In particular we obtain expressions for the finite time non-ruin probability and the joint distribution of the time to ruin the surplus immediately before ruin and the deficit at ruin. An illustration of the results is given and some implications of the results are provided. Comparisons are made with the corresponding results for the classical compound binomial model of independent and identically distributed claim occurrences. (C) 2016 Elsevier E.V. All rights reserved.
Citation Count: 12
Corporate diversification and firm value: evidence from emerging markets
(Emerald Group Publishing Limited, 2015) Akben Selçuk, Elif
Purpose - The purpose of this paper is to investigate the impact of corporate diversification on firm value in a sample of nine emerging markets including Brazil Chile Indonesia Malaysia Philippines Poland South Africa Thailand and Turkey. For the purpose of this study a company is classified as diversified when it is operating in two or more lines of business defined by the two-digit SIC codes. Design/methodology/approach - Employing panel data from 1568 companies for the period 2005-2010 this paper estimates both a fixed effects model and a dynamic generalized method of moments model. Data are collected both at company level and segment level within each firm. Findings - Overall analysis results suggest that for the period from 2005 to 2010 diversified firms in emerging markets are valued more compared to single-segment firms operating in similar industries providing support for diversification premium. Originality/value - The effect of diversification on company value in emerging markets is an important managerial and public policy concern. Although the literature on developed country diversified firms is rich only a few studies have examined diversification-value relationship in the context of developing countries. Furthermore most previous research on the value effects of corporate diversification in emerging markets has taken the form of case studies within countries and concentrated on the 1990s. This paper tries to fill these gaps by using a larger sample and more recent data and methodology.
Citation Count: 5
Designing of multi-targeted molecules using combination of molecular screening and in silico drug cardiotoxicity prediction approaches
(Elsevier Science Inc, 2014) Buturak, Birce; Durdagi, Serdar; Noskov, Sergei Y.; Ildeniz, A. Tugba Ozal
We have previously investigated and reported a set of phenol- and indole-based derivatives at the binding pockets of carbonic anhydrase isoenzymes using in silico and in vitro analyses. In this study we extended our analysis to explore multi-targeted molecules from this set of compounds. Thus 26 ligands are screened at the binding sites of 229 proteins from 5 main enzyme family classes using molecular docking algorithms. Derived docking scores are compared with reported results of ligands at carbonic anhydrase I and II isoenzymes. Results showed potency of multi-targeted drugs of a few compounds from investigated ligand set. These promising ligands are then tested in silico for their cardiotoxicity risks. Results of this work can be used to improve the desired effects of these compounds by molecular engineering studies. In addition these results may lead to further investigation of studied molecules by medicinal chemists to explore different therapeutic aims. (C) 2014 Elsevier Inc. All rights reserved.
Citation Count: 2
Determination of a diffusion coefficient in a quasilinear parabolic equation
(De Gruyter Open Ltd, 2017) Kanca, Fatma
This paper investigates the inverse problem of finding the time-dependent diffusion coefficient in a quasilinear parabolic equation with the nonlocal boundary and integral overdetermination conditions. Under some natural regularity and consistency conditions on the input data the existence uniqueness and continuously dependence upon the data of the solution are shown. Finally some numerical experiments are presented.
Citation Count: 5
Determination of an Unknown Heat Source from Integral Overdetermination Condition
(Springer International Publishing, 2018) Baglan, İrem Sakınç; Kanca, Fatma; Mishra, Vishnu Narayan
In this research we consider a coefficient problem of an inverse problem of a quasilinear parabolic equation with periodic boundary and integral over determination conditions. We prove the existence uniqueness and continuously dependence upon the data of the solution by iteration method. Also we consider numerical solution for this inverse problem using linearization and finite difference method is proved.
Citation Count: 30
Factors Affecting Firm Competitiveness: Evidence from an Emerging Market
(MDPI, 2016) Akben Selçuk, Elif
The objective of this study is to investigate the factors affecting firm competitiveness in an emerging marketTurkey. In the paper competitiveness is proxied by a firm's financial performance. The empirical analysis is based on firms listed on Borsa Istanbul and covers the period between 2005 and 2014. Results from a firm-level panel data model indicate that return on assets is positively related to firm size international sales liquidity and growth and negatively related to leverage and R&D expenditures. On the other hand gross profit margin is positively related to size and international sales and negatively related to leverage and R&D expenditures. Finally results show that Tobin's Q ratio is higher for firms with higher levels of debt and higher liquidity levels.
Citation Count: 8
Family involvement, corporate governance and dividends in Turkey
(Emerald Group Publishing Limited, 2019) Sener, Pinar; Akben Selçuk, Elif
Purpose: The purpose of this paper is to investigate the relationship between dividends and family involvement as well as corporate governance characteristics among Turkish public firms. Design/methodology/approach: Using panel data on Turkish firms listed on the Borsa Istanbul 100 index for 2006–2014 three models are estimated. For the first two models where the dependent variables are the dividend payout ratio and dividend yield respectively tobit regressions are run. The last model which employs a dividend dummy as the dependent variable is estimated with logistic regression. Findings: There is a positive and concave relationship between family ownership and dividends. The existence of a family chairman reduces dividends. There is a positive association between board size and dividends and this relationship is weaker for firms with higher levels of family ownership. Finally the ratio of independent directors on the board is negatively associated with dividends. Practical implications: The findings imply that firms with substantial family ownership and active family participation in management are more likely to send a negative signal to minority shareholders by paying lower dividends. In addition minority shareholders should pay attention to the board structure of firms in which they invest. Originality/value: This study is one of the few to analyze the nonlinear relationship between family ownership and dividend payments as well as the role of family management in a developing country. Second it investigates the role of board characteristics in explaining dividend payment decisions. © 2019 Emerald Publishing Limited.
Citation Count: 12
Financial Literacy among Turkish College Students: The Role of Formal Education, Learning Approaches, and Parental Teaching
(Ammons Scientific Ltd, 2014) Akben Selçuk, Elif; Altıok-Yılmaz, Ayşe
This study assessed financial literacy and its correlates among Turkish college students with special emphasis on the role of formal education learning approaches and parental influences. Financial literacy was measured by the College Student Financial Literacy Survey which assesses knowledge in four areas: general financial management saving and borrowing insurance and investing. 853 Turkish university students were administered the survey (416 men 437 women ; M age = 20.3 yr. SD = 0.6). The mean percentage of correct responses was 45% (SD = 12.8%). Regression results showed that formal finance education in college a deep approach to learning and direct financial teaching by parents were significantly associated with higher financial literacy scores.
Citation Count: 2
Harmony Search Algorithm Based Management of Distributed Energy Resources and Storage Systems in Microgrids
(MDPI, 2020) Ceylan, Oğuzhan; Sezgin, Mustafa Erdem; Goel, Murat; Verga, Maurizio; Lazzari, Riccardo; Kwaye, Marcel Pendieu; Sandroni, Carlo
Microgrids are composed of distributed energy resources (DERs), storage devices, electric vehicles, flexible loads and so on. They may either operate connected to the main electricity grid (on-grid operation) or separated from the grid (islanded operation). The outputs of the renewable energy sources may fluctuate and thus can cause deviations in the voltage magnitudes especially at islanded mode. This may affect the stability of the microgrids. This paper proposes an optimization model to efficiently manage controllable devices in microgrids aiming to minimize the voltage deviations both in on-grid and islanded operation modes. RSE Distributed Energy Resources Test Facility (DER-TF), which is a low voltage microgrid system in Italy, is used to verify the algorithm. The test system's data is taken through an online software system (REDIS) and a harmony search based optimization algorithm is applied to control the device parameters. The experimental results show that the harmony search based optimization approach successfully finds the control parameters, and can help the system to obtain a better voltage profile.
Citation Count: 2
Informed trading, order flow shocks and the cross section of expected returns in Borsa Istanbul
(Routledge Journals, 2020) Tiniç, Murat; Salih, Aslihan
This paper examines the relationship between information asymmetry and stock returns in Borsa Istanbul. For all stocks that are traded in Borsa Istanbul between March 2005 and April 2017, we estimate the probability of informed trading (PIN) to proxy for information asymmetry.? Firm-level cross-sectional regressions indicate a statistically insignificant relationship between PIN estimates and future returns. Moreover, univariate and multivariate portfolio analyses assert that investors that hold stocks that have high information asymmetry do not obtain significant future returns. Consequently, our results suggest that information asymmetry proxied by PIN is a firm-specific risk and can be eliminated with portfolio diversification. Findings are robust to different factorizations in estimating PIN and free of any bias due to trade classification algorithms, boundary solutions, floating-point exceptions and symmetric?order flow shocks.
Citation Count: 14
An Inverse Boundary Value Problem for a Second Order Elliptic Equation in a Rectangle
(Vilnius Gediminas Tech Univ, 2014) Mehraliyev, Yashar T.; Kanca, Fatma
In this paper the inverse problem of finding a coefficient in a second order elliptic equation is investigated. The conditions for the existence and uniqueness of the classical solution of the problem under consideration are established. Numerical tests using the finite-difference scheme combined with an iteration method is presented and the sensitivity of this scheme with respect to noisy overdetermination data is illustrated.
Citation Count: 8
An inverse coefficient problem for a quasilinear parabolic equation with periodic boundary and integral overdetermination condition
(Wiley-Blackwell, 2015) Bağlan, İrem Sakınç; Kanca, Fatma
In this paper the inverse problem of finding the time-dependent coefficient of heat capacity together with the solution periodic boundary and integral overdetermination 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. Copyright (c) 2014 John Wiley & Sons Ltd.
Citation Count: 3
Inverse Coefficient Problem for a Second-Order Elliptic Equation with Nonlocal Boundary Conditions
(Wiley, 2016) Kanca, Fatma
In this research article the inverse problem of finding a time-dependent coefficient in a second-order elliptic equation is investigated. The existence and the uniqueness of the classical solution of the problem under consideration are established. Numerical tests using the finite-difference scheme combined with an iteration method are presented and the sensitivity of this scheme with respect to noisy over determination data is illustrated. Copyright (C) 2015 John Wiley & Sons Ltd.
Citation Count: 8
The inverse problem of the heat equation with periodic boundary and integral overdetermination conditions
(Springer International Publishing Ag, 2013) Kanca, Fatma
In this paper the inverse problem of finding the time-dependent coefficient of heat capacity together with the solution of a heat equation with periodic boundary and integral overdetermination conditions is considered. The conditions for the existence and uniqueness of a classical solution of the problem under consideration are established. A numerical example using the Crank-Nicolson finite-difference scheme combined with the iteration method is presented.
Citation Count: 0
The “karakoncolos/kalikancaros” belief in Turkish and Greek sources [Türkçe ve yunanca kaynaklarda karakoncolos/kalikancaros inancı]
(Milli Folklor Dergisi, 2018) Şişmanoğlu Şimşek, Şehnaz
The belief in “karakoncolos/kalikancaros” is seen in a wide geography spreading from Central Anatolia and Black Sea region in Turkey to Balkan Peninsula including Greece Bulgaria and Serbia. Though karakoncolos is defined under different names in Turkish sources the period it is depicted and its features are almost similar. According to this the karakoncolos believed to have emerged on the coldest days of the year is depicted as a creature that is often hairy resembling animal haunting people and disturbing them. One of the first written sources in Turkish that included the belief in karakoncolos is Evliya Çelebi’s Seyahatnâme. Today it is rarely a tradition in games such as “karakoncilo” in the Eastern Black Sea or a belief that has been almost forgotten or even unknown by the majority even though it continues to exist as a trivial image in Turkish literature and cinema. On the other hand this belief often referred to as kalikancaros in Greek was compiled by the folklorist Nikolaos Politis at an early date (1904). In this study first of all referring to the various beliefs concerning kalikancaros in the mentioned compilations of Politis the rewritings of them in the present Greek children’s literature by Filippos Mandilaras will be introduced. In today’s Greece it will be revealed that especially during the Christmas period it continues to exist as a popular figure of the musical performances in schools and in children’s books. When we have a look at the Turkish and Greek compilations of this belief in general which is spread over a wide geographical area we can see that the reviewed Turkish sources are mostly collected from the Eastern Black Sea region and rarely lived as an almost forgotten tradition. Today in Greece also due to the Velloudios’ paintings which still circulate today the mentioned belief continues to exist as a “national” and a popular element of the childrens’ literature. © 2019 Milli Folklor Dergisi. All rights reserved.
Citation Count: 1
A max–min model of random variables in bivariate random sequences
(Elsevier, 2021) Gebizlioğlu, Ömer Lütfi; Gebizlioğlu, Ömer Lütfi
We introduce a max–min model to bivariate random sequences and applying bivariate binomial distribution in fourfold scheme derive the distributions of associated order statistics in a new model. Some examples for special cases are presented and applications of the results in reliability analysis and actuarial sciences are discussed.
Citation Count: 1
Measurement of bivariate risks by the north-south quantile points approach
(Elsevier Science, 2014) Gebizlioğlu, Ömer Lütfi; Gebizlioğlu, Ömer Lütfi
This paper attempts to determine the Value at Risk (VaR) and Conditional Value at Risk (CVaR) measures for the sum of bivariate risks under dependence. The computation of these risk measures is performed by the north-south quantile points of bivariate distributions. The Farlie-Gumbel-Morgenstern (FGM) copula model is chosen to express dependence of bivariate risks. The behaviors of VaR and CVaR are examined by varying dependence parameter values of the copula model and probability levels of the risk measures. The findings are interpreted from the view point of portfolio risk management. (C) 2013 Elsevier B.V. All rights reserved.

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