Now showing items 1-20 of 27

  • A country-specific analysis on internet interconnection ecosystems 

    Authors:Cakmak, Gorkem; Aydın, Mehmet Nafiz
    Publisher and Date:(IEEE, 2018)
    With the proliferating number of diverse participants and destinations to reach the Internet construct has become more intricate to assay. Today Internet Service Providers (ISPs) establish resilient networks from multiple providers and broaden the number of peering links-as financially as viable. However the complex structure of the global Internet ecosystem and entwined roles of Internet players simply prevent us from conducting generalized models for grasping interconnections which could be ...

  • A preconditioner for transient stability time domain simulation 

    Authors:Soykan, Gürkan; Flueck, Alexander J.; Daǧ, Hasan
    Publisher and Date:(2011)
    Transient Stability analysis which is one of the most important tasks of power system dynamic security analysis determines the dynamic behaviour of the power system after a large disturbance. Differential and algebraic equations (DAEs) model the nonlinear dynamic power system. The conventional time domain solution process uses a Newton method to simultaneously solve the differential equations discretized via an implicit integration method alongside the non-linear algebraic network equations. Direct ...

  • A spectral divide and conquer method based preconditioner design for power flow analysis 

    Authors:Daǧ, Hasan; Yetkin, Emrullah Fatih
    Publisher and Date:(2010)
    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 ...

  • Attitudes towards knowledge management in Turkish companies 

    Authors:Üçdal, Erol; Güzey, Yildiz Y.
    Publisher and Date:(2002)
    Attitudes towards knowledge management in Turkish companies are discussed. More and more companies in Turkish economy are allocating responsibility and a budget for knowledge management. Analysis show that the acts of successful knowledge management strategies brings new types of working giving people the chance to invest in knowledge maintaining the culture change and rewarding employees with new incentive schemes.

  • Branch outage solution using particle swarm optimization 

    Authors:Ceylan, Oǧuzhan; Ozdemir, Aydogan; Daǧ, Hasan
    Publisher and Date:(2008)
    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 ...

  • Comparison of feature selection algorithms for medical data 

    Data mining application areas widen day by day. Among those areas medical area has been receiving quite a big attention. However working with very large data sets with many attributes is hard. Experts in this field use heavily advanced statistical analysis. The use of data mining techniques is fairly new. This paper compares three feature selection algorithms on medical data sets and comments on the importance of discretization of attributes. © 2012 IEEE.

  • Complex Adaptive Systems Theory in the Context of Business Process Management 

    Authors:Uluhan, Eray; Aydın, Mehmet Nafiz
    Publisher and Date:(Springer Verlag, 2014)
    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 ...

  • Google plus in the higher education space. Are educators ready for social media learning in schools? 

    Social Media have an increasing influence on higher education. In the past mainly privacy issues discouraged educators from using social media in teaching but with Google Plus a new way of communicating is promised. Apart from the possibility to post information for students use a videoconferencing tool or a tool to get updated on selected topics instructors can also use Google Plus as a tool for cross-course communication. In general nearly all web services can be adapted for educational use. It ...

  • Gravitational search algorithm for post-outage bus voltage magnitude calculations 

    Authors:Ceylan, Oǧuzhan; Ozdemir, Aydogan; Daǧ, Hasan
    Publisher and Date:(2010)
    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.

  • Guidelines for IT change management shown on an example in Turkey 

    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 ...

  • Harmony search method based parallel contingency analysis 

    Authors:Ceylan, Oǧuzhan; Daǧ, Hasan; Ozdemir, Aydogan
    Publisher and Date:(2010)
    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. ...

  • HeteroSim: Heterogeneous simulation framework 

    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 ...

  • Implementation of a SDN (Software defined network) 

    Improving resource efficiency enhancing network security and achieving simpler network management have become the main goals for networking in the previous years. To accomplish these ideas an efficient routing traffic monitoring access control and server load balancing systems need to be designed. However these objectives make the optimization and management of networks rather difficult. In this paper Software Defined Networks (SDN) an alternative way for creating an optimized network by taking ...

  • Management Information Systems: The Virtual Team Scorecard (VTS) 

    Authors:Oberer, Birgit; Erkollar, Alptekin
    Publisher and Date:(2013)
    Organizations resisting changes are missing opportunities to grow or to become or remain competitive. Management Information Systems (MIS) used as decision support systems may support organizations in making use of changes in environmental conditions. Nevertheless innovative structures are needed to motivate organizations contributing in change projects. Tn this study a virtual team scorecard which can be used as a management information system enabling requirements analyses for managing virtual ...

  • On-line transient stability assessment using Matlab parallel programming environment 

    Authors:Soykan, Gürkan; Daǧ, Hasan
    Publisher and Date:(IEEE, 2009)
    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 ...

  • Parallel contingency analysis using differential evolution based solution for branch outage problem 

    Authors:Ceylan, Oǧuzhan; Daǧ, Hasan; Ozdemir, Aydogan
    Publisher and Date:(IEEE, 2009)
    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 ...

  • Parallel implementation of iterative rational Krylov methods for model order reduction 

    Authors:Yetkin, Emrullah Fatih; Daǧ, Hasan
    Publisher and Date:(IEEE, 2009)
    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.

  • Parallel-in-space implementation of transient stability analysis on a Linux cluster with infiniband 

    Authors:Soykan, Gürkan; Flueck, Alexander J.; Daǧ, Hasan
    Publisher and Date:(IEEE, 2012)
    On-line transient stability analysis is an inevitable way to provide real time power system security and control. Parallel computing is one of the most viable ways to perform on-line transient stability analysis. This paper presents the performance results of a parallel-in-space algorithm based on a multilevel partitioning scheme on an Infiniband cluster system. The algorithm decreases the transient stability simulation time using METIS for partitioning in conjunction with the linearized update ...

  • Post outage bus voltage calculations for double branch outages 

    Authors:Ceylan, Oǧuzhan; Ozdemir, Aydogan; Daǧ, Hasan
    Publisher and Date:(IEEE, 2012)
    Secure operation of electrical power systems is vital hence fast and accurate post-outage state calculations are important for contingency analysis. Contingency analysis includes simulations of both the single and double branch outages. This paper presents constrained optimization problem of a recently developed double branch outage model. Harmony search algorithm is used as an optimization tool. IEEE 30 Bus Test system simulation results are given and compared with those of the AC load flow in ...

  • Post-outage state estimations for outage management 

    Authors:Ceylan, Oǧuzhan; Ozdemir, Aydogan; Daǧ, Hasan
    Publisher and Date:(IFAC Secretariat, 2011)
    Real time outage information is required to the utility operators for outage management process. In addition to some basic information regarding the outage post-outage system status will help to improve the response to outages and management of system reliability. This paper presents particle swarm optimization based reactive power estimations for branch outages. Post outage voltage magnitudes and reactive power flows results for IEEE 14 and IEEE 30 bus systems are given. Simulation results show ...