Enformasyon Teknolojileri Bölümü Koleksiyonu

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    Bayesian and Graph Theory Approaches to Develop Strategic Early Warning Systems for the Milk Market
    (Springer-Verlag Berlin, 2015) Gürpınar, Furkan; Bisson, Christophe; Diner, Öznur Yaşar
    This paper presents frameworks for developing a Strategic Early Warning System allowing the estimatation of the future state of the milk market. Thus this research is in line with the recent call from the EU commission for tools which help to better address such a highly volatile market. We applied different multivariate time series regression and Bayesian networks on a pre-determined map of relations between macro economic indicators. The evaluation of our findings with root mean square error (RMSE) performance score enhances the robustness of the prediction model constructed. Finally we construct a graph to represent the major factors that effect the milk industry and their relationships. We use graph theoretical analysis to give several network measures for this social network
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    Citation Count: 5
    Double branch outage modeling and its solution using differential evolution method
    (2011) Dağ, Hasan; Ceylan, Oğuzhan; Dağ, Hasan
    Power system operators need to check the system security by contingency analysis which requires power flow solutions repeatedly. AC power flow is computationally slow even for a moderately sized system. Thus fast and accurate outage models and approximated solutions have been developed. This paper adopts a single branch outage model to a double branch outage one. The final constrained optimization problem resulted from modeling is then solved by using differential evolution method. Simulation results for IEEE 30 and 118 bus test systems are presented and compared to those of full AC load flow in terms of solution accuracy. © 2011 IEEE.
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    Electromagnetic interactions of heavy ions at small impact parameters and lepton pair productions
    (Institute of Physics Publishing, 2011) Güçlü, Mehmet Cem; Yılmaz Şengül, Melek
    In peripheral collisions the strong electromagnetic fields are produced since the fully stripped heavy ions moves at ultra-relativistic velocities. Lepton pairs especially the electron-positron pairs are the result of this collisions. At the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) virtual photons produce many particles such as electron-positron pairs heavy lepton (muons and tauons) pairs magnetic monopoles W-pairs b-quark pairs and possibly the Higgs. At small impact parameters the colliding nuclei make peripheral collisions photon fluxes are very large and these are responsible for the multiple photonuclear interactions. Free pair productions bound free pair productions and nuclear Coulomb excitations are important examples of such interactions and these processes play important roles in the beam luminosity at RHIC and LHC. Here we obtained bound free electron-positron pair production with nuclear breakup for heavy ion collisions at RHIC and LHC.
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    On the inverse point-source problem of the poisson equation
    (Istanbul University, 2005) Yılmaz, Melek; Şengül, Metin Y.; Geçkinli, Melih
    In this work a basic inverse heat conduction problem of a simple 2-D model with steady state heat source is taken into view. The physical problem is for a square region with uniform thermophysical properties and a point heat source of unit magnitude. To obtain boundary data temperature probes are placed at the midpoints of the sides of the square domain. The objective of the inverse problem is to estimate the coordinates of the point source with the least amount of data. Initially the inverse problem is analyzed to determine the main causes that render the problem ill conditioned. As for the solution among the methods that has been tried so far the best results are obtained from a backpropagating ANN with four-probe data. When white Gaussian noise is added to the measurements no catastrophic failure has been observed.