Yönetim Bilişim Sistemleri Bölümü Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12469/68

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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: 8
Citation - Scopus: 14
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: 3
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.
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.
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 - 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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