Yönetim Bilişim Sistemleri Bölümü Koleksiyonu

Permanent URI for this collectionhttps://gcris.khas.edu.tr/handle/20.500.12469/68

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Citation - Scopus: 15
Branch outage solution using particle swarm optimization
(2008) Ceylan, Oğuzhan; Ceylan, Oğuzhan; Ozdemir, Aydogan; Dağ, Hasan; Dağ, Hasan
For post outage MW line flows and voltage magnitude calculations most of the methods use linear methods because of their simplicity. Especially for reactive power flow calculations one can face high errors. In this paper we use a minimization method that minimizes the errors resulting from the linear system model implementation. We solve the optimization problem using particle swarm optimization. We give some outage examples using IEEE 14 bus IEEE 30 bus and IEEE 57 bus data and compare the results with full ac load flow calculation. © 2008 Australasian Universities Power Engineering Conference (AUPEC'08).
Citation - Scopus: 1
Heterosim: Heterogeneous Simulation Framework
(Association for Computing Machinery, 2009) Dursun, Taner; Dağ, Hasan; Dağ, Hasan
In order to arrange heterogeneous simulation executions it would be useful to have simulation tools that enable easy and fast creation of simulation sessions employing real-time software components beside simulation codes. Although there have been considerable amount of research activities in simulation community the current simulation tools are not sufficiently capable to support such a cooperation between components working in real-time and simulation-time. In this paper we propose a new approach for constructing hybrid simulations that leverages usage of simulation systems. We introduce HeteroSim a Java-based simulation system that can execute discrete event simulations by employing both simulation and real world software entities. This model is applicable to many software related areas such as scenario-based software testing and development of simulators. As a case study we are able to rely on this model in order to build simulations combining both the simulated elements of a High Performance Computing (HPC) system and already implemented elements of our Policy Based Management (PBM) framework so-called POLICE [1][2]. In this manner it may be possible to study the efficiency of POLICE on management of HPC systems.
Citation - Scopus: 12
Comparison of Post Outage Bus Voltage Magnitudes Estimated by Harmony Search and Differential Evolution Methods
(2009) Ceylan, Oğuzhan; Ceylan, Oğuzhan; Özdemir, Aydoğan; Dağ, Hasan; Dağ, Hasan; Özdemir, Serpil
Contingency studies are indispensable tools of both the power system planning and operational studies. Real time implementation of operational problems makes necessary the use of high speed computational methods while requiring reasonable accuracies. On the other hand, accuracy of the results and the speed of calculation depend on branch outage modeling as well as solution algorithm used. This paper presents a comparison of post outage bus voltage magnitudes calculated by two meta-heuristic approaches; namely differential evolution (DE) and harmony search (HS) methods. The methods are tested on IEEE 14, IEEE 30, IEEE 57, and IEEE 118 bus test systems and the results are compared both in terms of accuracy and calculation speed.
Citation - WoS: 0
Citation - Scopus: 0
Towards Faster Branch Outage Simulations Using Simulated Annealing and Parallel Programming
(IEEE, 2009) Ceylan, Oğuzhan; Dağ, Hasan; Özdemir, Aydoğan; Ceylan, Oğuzhan; Dağ, Hasan; Özdemir, Serpil
Contingency studies such as branch outage and generator outage are among important studies of energy management centers operations. Branch outage modeling on the other hand is one of the basic steps of post-outage state estimation of an electrical power system. Real time implementation of the problem brings the necessity of using high speed methods while providing a reasonable accuracy. This paper presents simulated annealing based solution of the branch outage event which is formulated as a local optimization problem. To speed up the solution procedure the distributed computing toolbox of Matlab is used as a parallel programming tool. The results of the proposed method are compared to those of full AC method and are discussed both from the point of accuracy and solution speed.
Citation - Scopus: 2
Parallel Implementation of Iterative Rational Krylov Methods for Model Order Reduction
(IEEE, 2009) Yetkin, Emrullah Fatih; Yetkin, Emrullah Fatih; Dağ, Hasan; Dağ, Hasan
Model order reduction (MOR) techniques are getting more important in large scale computational tasks like large scale electronic circuit simulations. In this paper we present some experimental work on multiprocessor systems for rational Krylov methods. These methods require huge memory and computational power especially in large scale simulations. Therefore these methods are fairly suitable for parallel computing. ©2009 IEEE.
Citation - WoS: 0
Citation - Scopus: 0
Dynamic Priority Packet Scheduler With Deadline Considerations (dpd)
(INT INST Informatics & Systemics, 2010) Dağ, Tamer; Dağ, Tamer
Providing quality of service (QoS) to applications with different traffic characteristics based on their needs is an important research area for today's and tomorrow's high speed networks. Various techniques have been proposed to achieve good QoS for diverse application types. Among these techniques packet scheduling algorithms decide on how to process packets at network nodes
Citation - WoS: 0
Parallel Implementation Of Iterative Rational Krylov Methods For Model Order Reduction
(IEEE, 2010) Yetkin, E. Fatih; Dağ, Hasan; Dağ, Hasan; Yetkin, Emrullah Fatih
Model order reduction (MOR) techniques are getting more important in large scale computational tasks like large scale electronic circuit simulations. In this paper we present some experimental work on multiprocessor systems for rational Krylov methods. These methods require huge memory and computational power especially in large scale simulations. Therefore these methods are fairly suitable for parallel computing.
Citation - WoS: 0
Citation - Scopus: 0
Comparison of Cost-Free Computational Tools for Teaching Physics
(IEEE, 2010) Er, Neslihan Fatma; Dağ, Hasan; Dağ, Hasan
It is widely accepted that it is quite difficult to engage today's students, from high schools to university, both in educational activities in class and "teaching" them physics due to their prejudices about the complexity of physics. The difficulty in capturing students' attention in class for a long time also plays a role in less effective teaching during learning activities. Research shows that students learn little from traditional lectures. According to constructivist learning theories, visual aids and hands-on activities play a major role in learning physics. In addition to laboratory work there are many computational tools for teaching physics, which help teachers and students in constructing a conceptual framework. With this in mind, this paper compares freeware and open source computational tools for teaching physics.
Citation - WoS: 1
Citation - Scopus: 1
A Critical Analysis of Current Legal Developments on the Political Participation of Minorities in Turkey
(2010) Akbulut, Olgun; Akbulut, Olgun
This is a follow-up article to the one published in the IJMGR half a decade ago (Vol. 12 2005). Although there have been domestic and international legal cases that are directly concerned with the political participation of minorities in Turkey few improvements have been made in law covering the subject. This encouraged this author to analyse and criticise the judgements of the European Court of Human Rights and the legal and political actors at domestic level. The aim of this article is to reflect upon how international human rights monitoring affects national laws in certain thorny issues such as the rights of minorities. Since the current and previous articles have a common theme and complement each other I strongly recommend reading both articles. © 2010 Martinus Nijhoff Publishers.
Citation - Scopus: 3
A Spectral Divide and Conquer Method Based Preconditioner Design for Power Flow Analysis
(2010) Dağ, Hasan; Yetkin, Emrullah Fatih; Yetkin, Emrullah Fatih; Dağ, Hasan
Power system simulations most of the time require solution of a large sparse linear system. Traditional methods such as LU decomposition based direct methods are not suitable for parallelization in general. Thus Krylov subspace based iterative methods (i.e. Conjugate Gradient Generalized Minimal Residuals (GMRES)) can be used as very good alternatives compared to direct methods. On the other hand Krylov based iterative solvers need a preconditioner to accelerate the convergence process. In this work we suggest a new preconditioner for GMRES which can be used in Newton iteration of power flow analysis. The new preconditioner employs the basic spectral divide and conquer methods and invariant subspaces for clustering the eigenvalues of the Jacobean matrix appears in Newton-Raphson steps of power flow simulation. ©2010 IEEE.
Citation - WoS: 0
Citation - Scopus: 0
Guidelines for It Change Management Shown on an Example in Turkey
(Int Business Information Management Assoc-IBIMA, 2010) Oberer, Birgit; Oberer, Bırgıt; Erkollar, Alptekin
In today's highly technology driven competitive global markets the ability to adopt is the only guarantee of survival. Businesses need to show ability to enable a competitive edge by taking their products or services to markets before the competitors. Today business have to take care that IT systems are able to adapt to the changes caused by our highly technology driven society and the influences of digitalization and globalization to support the needs of businesses quickly and efficiently. The following contribution gives an overview about a work in progress that is defining the guidelines for IT change management in Turkey.
Citation - WoS: 0
Citation - Scopus: 0
On-Line Transient Stability Assessment Using Matlab Parallel Programming Environment
(IEEE, 2010) Soykan, Gürkan; Dağ, Hasan; Dağ, Hasan
Transient Stability Assessment (TSA) is the major part of Dynamic Security Assessment (DSA) in an electric power system. On-line TSA has gained more importance for power system security in last two decades. The decreasing costs of hardware and advanced package programs and techniques encourage researchers to apply parallel programming to the problems that are either too much time consuming or impossible to solve using serial computers. The real-time evaluation of TSA is now almost possible thanks to such tools and techniques. We demonstrate the use of the parallel computing toolbox of Mat lab for TSA. In this regard IEEE 57 and 118 bus systems are tested with 57 and 56 contingencies respectively. Each contingency requires solution of a transient stability problem. The parallel performance of this implementation is expected to spur researchers to use parallel programming in Mat lab environment. It requires minimal knowledge regarding parallel programming.
Citation - Scopus: 25
Gravitational Search Algorithm for Post-Outage Bus Voltage Magnitude Calculations
(2010) Ceylan, Oğuzhan; Dağ, Hasan; Ozdemir, Aydogan; Ceylan, Oğuzhan; Dağ, Hasan
Branch outage problem is one of the key problems in power system security analysis. This paper solves branch outage problem using a bounded approach. Local constrained optimization problem in the bounded approach is solved by the gravitational search algorithm. Test results of IEEE 14 30 and 118 bus systems are compared to those of ac load flow method in terms of both accuracy and speed.
Citation - Scopus: 4
Harmony Search Method Based Parallel Contingency Analysis
(2010) Ceylan, Oğuzhan; Dağ, Hasan; Dağ, Hasan; Ceylan, Oğuzhan; Ozdemir, Aydogan
Power system security management is one of the key problems in power system analysis. Power system management center operators need to simulate contingencies as fast as possible and take the remedial actions in time. These contingency analyses comprise of the outages of the branches transformers and other power system components. This paper solves branch outage problem using a bounded approach. Harmony search method is used to solve the local constrained optimization problem of the bounded approach. Several outage simulations using IEEE 14 30 and 118 bus systems are performed and compared against AC power flow in terms of accuracy. In order to speed up the contingency simulation the problem is also solved in a parallel environment. Speed up results of the IEEE 118 and 300 bus test systems are given. ©2010 IEEE.
Citation - WoS: 0
Applications of Eigenvalue Counting and Inclusion Theorems in Model Order Reduction
(Springer-Verlag Berlin, 2010) Yetkin, E. Fatih; Dağ, Hasan; Dağ, Hasan; Yetkin, Emrullah Fatih
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: 0
Citation - Scopus: 1
Parallel Contingency Analysis Using Differential Evolution Based Solution for Branch Outage Problem
(IEEE, 2010) Ceylan, Oğuzhan; Dağ, Hasan; Dağ, Hasan; Ceylan, Oğuzhan; Özdemir, Aydoğan; Özdemir, Serpil
Contingency analysis is one of the most fundamental work an electricity management center operator has to perform regularly. If both bus voltage magnitudes and reactive power flowing on the branches during any type of outages are within the acceptable limits the system is called secure. In this paper we solve the contingency problem using a recently developed local constrained optimization based branch outage problem. The optimization problem resulted from the formulation of branch outage is solved by differential evolution method. Using Matlab's parallel computing toolbox contingency analysis for IEEE 300 test system is performed and the results are presented. The study shows that it is straight forward to implement contingency analysis on the Matlab's parallel environment and obtain near linear speedups.
Citation - WoS: 0
Citation - Scopus: 1
Distributed Memory Parallel Transient Stability Analysis on a Pc Cluster With Ethernet
(Praise Worthy Prize Srl, 2010) Soykan, Gürkan; Dağ, Hasan; Flueck, Alexander J.; Dağ, Hasan
On-line transient stability analysis is a necessity for real-time power system control and security. Parallel processing is a natural technology for achieving real-time solution performance. This paper presents a parallel-in-space algorithm based on a multi-level partitioning scheme in a distributed memory cluster environment. The main aim of the research is to decrease the wallclock time of transient stability analysis of large scale power systems by leveraging open source software and commodity off the shelf hardware of a Linux PC cluster. The proposed solution algorithm focuses on speeding up the transient stability simulation by partitioning via METIS the linearized update solution process of the Very Dishonest Newton Method for solving the differential-algebraic equation system. Results are presented for two power systems: I) 3493 buses 844 generators 6689 branches and 2) 7935 buses 2135 generators 13624 branches. The simulations were run on a small Linux-cluster with a 100 Mbit/s ethernet interconnect which is cheaper than any specially constructed parallel computer. By tuning vertex weights the performance of the partition strategy can be improved relative to the no-weight case. The proposed method easily can be adapted by commercial packages and used in various parallel environments including multicore architectures with non-uniform memory access. Copyright (C) 2010 Praise Worthy Prize S.r.l. - All rights reserved.
Citation - WoS: 0
Citation - Scopus: 1
National Electronic Government Strategies in Austria
(ACAD Conferences Ltd, 2011) Oberer, Birgit; Oberer, Bırgıt; Erkollar, Alptekin
One of the most emerging concepts of information technology is the one of electronic government. Electronic services that are made available by governments to citizens businesses and other governments (international) or governmental authorities (national) are general proof of the changes being made in the public sector. Intersecting the government citizen and business domain a business model can be defined considering the government-to-business government-to-citizen and government-to-government approaches. Governments around the world try to follow their most of the time ambitious strategies to become or stay competitive. In this study Austrian strategies and projects for electronic government as well as their implementation plans were analysed followed by an examination of the electronic services offered by the national governmental authorities in Austria one pioneer in electronic government in Europe leading in the European E-Government ranking 2010 and the declared 'European champion in eGovernment' for the fourth time in a row. The results revealed that Austria has developed hybrid electronic government strategies and has launched projects in that field in which national governmental authorities have to participate in order to offer electronic government services at a high level and in a competitive international environment. On a whole offering a one-stop shop gateway to governmental information and transactions generally offers higher attractiveness for conducting nationwide business and all incentives for electronic government focus on developing good practices in the area of efficient and effective electronic government. Nevertheless national strategies are transformed and implemented in different ways not always following the one-stop-shop approach and contributing to the development of isolated applications instead of integrated ones.
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, Bırgıt; 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.
Citation - Scopus: 5
Power Flow Using Thread Programming
(2011) Dağ, Hasan; Dağ, Hasan; Soykan, Gürkan
Power flow problem which is one of the most important applications in power system is solved using OpenMP Application Program Interface (API) a thread based programming technique for the shared memory programming environments. The parallel implementation of power flow is tested on a shared memory machine with cache-coherent non-uniform memory access (ccNUMA) architecture. Results are presented for various power test systems. The thread programming based power flow program decreases the runtime substantially. OpenMP lets a user concentrate on his/her own work rather than the parallel programming details. OpenMP is a set of compiler directives and requires minimal knowledge regarding parallel programming. It can easily be used not only on the shared memory systems but also on the systems with hyper threading and multi-core technologies as well. Thus speeding up any kind of power system related study is now viable without having to have expensive parallel computers and extensive experience on theirs programming. Since todays' and future personal computers and servers will mostly be based on the multi-core technologies the proposed method is an alternative to hard-coded parallel programming. © 2011 IEEE.

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