İşletme Fakültesi

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Citation - WoS: 7
Citation - Scopus: 7
Anytime. Everywhere. Mobile Learning in Higher Education: Creating a Gis Course
(Springer-Verlag Berlin, 2012) Erkollar, Alptekin; Oberer, Birgit
The course concepts introduced in this contribution were implemented in 2011 in a university in Turkey and show an approach for integrating mobile learning modules in higher education. The results of the course show the advantages as well as potential for improvement of the system and the use of it in higher education.
Applications of Eigenvalue Counting and Inclusion Theorems in Model Order Reduction
(Springer-Verlag Berlin, 2010) Yetkin, E. Fatih; Dağ, Hasan
We suggest a simple and an efficient iterative method based on both the Gerschgorin eigenvalue inclusion theorem and the deflation methods to compute a Reduced Order Model (ROM) to lower greatly the order of a given state space system. This method is especially efficient in symmetric state-space systems but it works for the other cases with some modifications.
Citation - WoS: 7
Citation - Scopus: 12
Comparative Study of Active Power Curtailment Methods of Pvs for Preventing Overvoltage on Distribution Feeders
(IEEE, 2018) Paudyal, Sumit; Bhattarai, Bishnu P.; Tonkoski, Reinaldo; Dahal, Sudarshan; Ceylan, Oğuzhan
Overvoltage is one of the major issues on distribution grids with high penetration of photovoltaic (PV) generation. Overvoltage could be prevented through the control of active/reactive power of PVs. However given the high R/X ratio of low voltage feeders voltage control by using reactive power would not be as effective as using active power. Therefore active power curtailment (APC) of PVs though not desirable becomes necessary at times to prevent the overvoltage issues. Existing literature is rich in centralized and droop-based methods for APC and/or reactive power control of PVs to prevent overvoltage issues. In this context this paper revisits the most popular existing methods and evaluates the performance of droop-based and centralized methods using a typical North American 240 V low voltage feeder with 24 residential homes. In this work our key findings are: a) droop-based methods provided conservative solutions or did not eliminate the overvoltages completely b) power flow sensitivity based droop approach led to 13% more curtailment than the centralized approaches c) centralized approach had 40% less energy curtailed compared with standard droop while no overvoltages were observed and d) operating PVs at non-unity power factor in centralized approach led to 5% less energy curtailment.
Citation - Scopus: 2
A Comparative Study of Surrogate Based Learning Methods in Solving Power Flow Problem
(IEEE, 2020) Ceylan, Oğuzhan; Taşkın, Gülsen; Paudyal, Sumit
Due to increasing volume of measurements in smart grids, surrogate based learning approaches for modeling the power grids are becoming popular. This paper uses regression based models to find the unknown state variables on power systems. Generally, to determine these states, nonlinear systems of power flow equations are solved iteratively. This study considers that the power flow problem can be modeled as an data driven type of a model. Then, the state variables, i.e., voltage magnitudes and phase angles are obtained using machine learning based approaches, namely, Extreme Learning Machine (ELM), Gaussian Process Regression (GPR), and Support Vector Regression (SVR). Several simulations are performed on the IEEE 14 and 30-Bus test systems to validate surrogate based learning based models. Moreover, input data was modified with noise to simulate measurement errors. Numerical results showed that all three models can find state variables reasonably well even with measurement noise.
Citation - Scopus: 2
Complex Adaptive Systems Theory in the Context of Business Process Management
(Springer Verlag, 2014) Uluhan, Eray; Aydın, Mehmet Nafiz
Organizations require agility adaptiveness and flexibility to survive and to deal with complexity in business ecosystems and business processes are recognized as cornerstones of successful organizations. Paradigms underlying existing business process management (BPM) methods and solutions have been questioned for their ability to capture the complexity of business dynamics. The basic trust of this research is to search for an alternative approach to better understand underpinnings of business process management. In this paper we contend that Complex Adaptive Systems (CAS) theory can be an alternative approach to better examine underpinnings of the very notion of business process. In this regard we articulate the basic principles of CAS in the business process management context. It is this articulation that paves the way to establish an appropriate account for BPM. © Springer International Publishing Switzerland 2014.
Considerations and Confusions About Theregulatory Focus Theory and a Future Agendafor Researchers in Marketing
(Boğaziçi Üniversitesi, İktisadi ve İdari Bilimler Fakültesi, 2017) Merdin-Uygur, Ezgi
The regulatory focus theory is the mark of a paradigm shift away from a unidimensional hedonism towards a multiplicity of regulatory foci. It possesses great explanatory power; however a lot remains unresolved despite a promising body of empirical work. This paper highlights various considerations concerning the conceptual and comparative qualities of the regulatory focus theory. The discussion moves into the intersection of regulatory focus and consumer behavior literature, briefly summarizing the findings and followed by a number of propositions to be tested for future research.
Citation - WoS: 7
Citation - Scopus: 7
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 - Scopus: 9
Delineating the Concept of Corporate Social Innovation: Toward a Multidimensional Model
(Inderscience Publishers, 2019) Esen, Ayla; Maden-Eyiusta, Ceyda
Business organisations are facing increasing pressure over their role in society. Social innovation is a relatively new concept used to define efforts to develop novel and innovative solutions to social challenges. The aim of this study is to conceptualise a novel form of social innovation, namely, ‘corporate social innovation’, by focusing on social innovation efforts initiated by private sector organisations. This study also aims to provide insight into: 1) the definition of corporate social innovation; 2) the key dimensions underlying the social innovation capability of business organisations. Data were collected through semi-structured interviews with 20 experts who play an active role in various social innovation projects in their respective organisations and/or adopt social innovation as an academic field of interest. The interview results extend our conceptual understanding of the corporate social innovation phenomenon by providing a comprehensive definition of the concept and describing a six-factor model of corporate social innovation capability.
Citation - WoS: 5
Citation - Scopus: 6
Determinants of Corporate Cash Holdings: Firm Level Evidence From Emerging Markets
(Springer, 2017) Akben Selçuk, Elif; Altiok-Yilmaz, Ayse
The objective of this chapter is to investigate the factors affecting corporate cash holdings in five emerging markets namely Brazil Indonesia Mexico Russia and Turkey. The sample consists of 1991 firms listed on the major stock exchange of their countries and covers the period between 2009 and 2015. The model is estimated by Arellano–Bond dynamic generalized method of moments. Results show that firms which use higher leverage in their capital structure hold more cash. More profitable firms are shown to have higher levels of cash holdings. Another variable which has a positive effect on the level of cash holdings in any given period is the level of cash holdings in the previous period as shown by the positive and significant coefficient of the lagged dependent variable in the model. Liquidity and firm size have a negative and statistically significant impact on the level of corporate cash holdings. Firms with higher level of capital expenditures are also shown to hold less cash. Finally growth opportunities do not have a significant impact on the level of cash holdings for the firms in the emerging markets analyzed. © Springer International Publishing AG 2017.
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 - WoS: 4
Citation - Scopus: 4
A Novel Approach for Voltage Control in Electrical Power Distribution Systems
(IEEE, 2018) Ceylan, Oğuzhan; Dimitrovski, Aleksandar; Starke, Michael; Tomsovic, Kevin
This paper proposes a novel approach for voltage control in 3-phase unbalanced distribution systems. The approach is based on the change of the magnetizing reactances of the voltage regulators in the system. We used an augmented Lagrangian-based optimization model to determine the optimal settings on a modified IEEE 123 Bus Test System with large PV penetration. Simulations were performed on a minute-based resolution either by controlling regulators or by controlling the magnetizing reactances of the regulators only. The simulation results presented and their comparison show that the control of the magnetizing reactances of the regulators may improve the voltage profile and may be an addition or alternative to both traditional voltage control devices such as capacitors tap changers and newer devices such as smart inverters.
On the Selection of Interpolation Points for Rational Krylov Methods
(Springer-Verlag Berlin, 2012) Yetkin, E. Fatih; Dağ, Hasan
We suggest a simple and an efficient way of selecting a suitable set of interpolation points for the well-known rational Krylov based model order reduction techniques. To do this some sampling points from the frequency response of the transfer function are taken. These points correspond to the places where the sign of the numerical derivation of transfer function changes. The suggested method requires a set of linear system's solutions several times. But they can be computed concurrently by different processors in a parallel computing environment. Serial performance of the method is compared to the well-known H-2 optimal method for several benchmark examples. The method achieves acceptable accuracies (the same order of magnitude) compared to that of H-2 optimal methods and has a better performance than the common selection procedures such as linearly distributed points.
The Relationship Between Firm Size and Export Sales: Sector or Size What Matters?
(Physica-Verlag, 2017) Berk, Niyazi; Öztürkkal, Belma
This paper examines the performance of export focused companies listed on the Borsa Istanbul trading in the emerging market of Turkey. Using the panel data of stock market prices (1995–2011) we study the performance of companies in different sectors and their return performance in the volatile exchange rate environment and devaluation periods of 1996 1997 1998 1999 2001 and 2008. The paper investigates sales market capitalization or asset performances’ statistical significance level with regard to these companies’ export level. We review the performance of these operational measures in an environment of changing foreign exchange rates. Regression analysis is used to measure the effects of currency devaluation on the companies analyzed. Finally the study analyzes the export sales of companies by sector following a period of sharp devaluation. © Springer International Publishing AG 2017.
Citation - WoS: 1
Citation - Scopus: 1
Sparsity Preserving Computation for Spectral Projectors
(Amer Inst Physics, 2011) Yetkin, E. Fatih; Dağ, Hasan
Several areas of applications such as model order reduction preconditioner design and eigenvalue problems for spectral projectors can be found in the literature. In this paper a fast and sparsity preserving approach for computing the spectral projectors is proposed. The suggested approach can be used in both Newton iteration and integral representation based methods. A comparison of the original and the suggested approaches in terms of computation time sparsity preservation and accuracy is presented in this paper.
Citation - WoS: 1
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.
Citation - Scopus: 6
Trends in Social Media Application: the Potential of Google+ for Education Shown in the Example of a Bachelor's Degree Course on Marketing
(Springer, 2011) Erkollar, Alptekin; Oberer, Birgit
Google Plus has the potential to improve students' collaboration through circles conduct research for projects with sparks improve the student-instructor relationship by using this kind of social media to get in touch with each other and support blended learning with the hang out functionality. The course concept which is shown as an example offers a concrete approach for integrating Google Plus functionalities in education. The results of the forthcoming analysis of the concept in use will show advantages and potential for improvement both of the system and the use of it in education. © 2011 Springer-Verlag.

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