Ankara, Turkey
Ankara, Turkey

Atılım University is a private university founded in 1996. It is located in Ankara, the capital of Turkey. The language of instruction for most courses is English. Education programs are at international standards .The University of the Incarnate Word in San Antonio, Texas is the sister university of Atılım, and 6 European universities in France, the Netherlands, Poland and Spain in accordance with the student exchange program. Also, it is among the Erasmus University Charter universities. Wikipedia.


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A criterion for the global asymptotic stability of fixed-point state-space digital filters using two's complement arithmetic is presented. The criterion is a modified form of a well-known criterion due to Mills, Mullis, and Roberts. The criterion is in the form of linear matrix inequality and, hence, computationally tractable. An example shows the effectiveness of the modified criterion. © 2009 Elsevier Ltd. All rights reserved.


Eryilmaz S.,Atilim University
IEEE Transactions on Reliability | Year: 2013

A κ - out - of - ν : G system consists of n components, and operates if at least κ of its components operate. Its reliability properties have been widely studied in the literature from different perspectives. This paper is concerned with the reliability analysis of a κ - out - of - ν : G system equipped with a single warm standby unit. We obtain an explicit expression for the reliability function of the system for arbitrary lifetime distributions. Two different mean residual life functions are also studied for the system. © 2012 IEEE.


Sulfonated polyphenyl sulfone/phosphotungstic acid/silica (sPPS/PWA/silica) hybrid membranes were prepared and characterized as alternative materials for PEMFC operation at high temperature and low humidity conditions. Polyphenyl sulfone polymer (PPS) was sulfonated with trimethylsilyl chlorosulfonate in 1,2 dichloroethane at ambient temperatures. The degree of sulfonation was determined by 1H-NMR analysis. Sulfonation levels from 25 to 45% were easily achieved by varying the content of the sulfonation agent. The hybrid membrane was composed of the mixture of sPPS solution, PWA/silica particles. The structures of the membranes were investigated by Scanning Electron Microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and by thermogravimetric analysis (TGA). The composite membranes gained good thermal resistance with insertion of PWA/silica. SEM results have proven the uniform and homogeneous distribution of PWA/silica in hybrid membrane. The existence PWA/silica has improved the water uptake, proton conductivity and oxidative stability of hybrid membrane. Gas diffusion electrodes (GDE) were fabricated by ultrasonic coating technique. Catalyst loading was 0.4 mg Pt/cm2 for both anode and cathode sides. The membranes were tested in a single cell with a 5 cm2 active area operating at the temperature range of 70 to 120°C and 100 and 30% relative humidity conditions. Single PEMFC tests performed at different operating temperatures indicated that sPPS/PWA/silica hybrid membrane was more stable and also performed better than pristine sPPS membrane. At the overall, the sPPS/PWA/silica hybrid membrane seems to be a promising alternative membrane for the possible utilization in PEMFC. © 2014 Elsevier Ltd. All rights reserved.


Melikoglu M.,Atilim University
Renewable and Sustainable Energy Reviews | Year: 2013

Turkey imports most of its energy. However, according to the recently avowed Vision 2023 agenda the country also plans to produce 30% of its electricity demand from renewable energy sources by 2023. Meanwhile, each year around 25 million tonnes of municipal solid waste (MSW) is generated nationwide. Not only MSW pollutes the environment handling, processing and storage requires precious labour and capital. In that context, a synergistic solution can be created between MSW management and energy supply. In this study, economics and environmental impacts of electricity generation from MSW via (i) direct combustion and (ii) biogas harnessing in 81 cities of Turkey is analysed in detail for a period between 2012 and 2023. Firstly, it is estimated that nationwide 8500 GWh of electricity could have been generated by direct combustion of MSW in 2012. This is predicted to rise 9700 GWh in 2023. It is calculated that 3100 million m3 of methane would be emitted from the landfills of Turkey in 2012. If no action taken this would rise to 3600 million m3 in 2023. Furthermore, it is estimated that by capturing 25% of this methane via landfill bioreactors 2900 GWh or 0.5% of Turkey's annual electricity demand could be supplied in 2023. Simulations also showed that by realizing apposite landfill investments by 2023 annual energy savings worth 200-900 million € could be generated from MSW. Consequently, this could lead to greenhouse gas emission savings up to 11.0 million tonnes of CO 2 per annum. © 2012 Elsevier Ltd.


An LMI-based criterion for the global asymptotic stability of 2-D state-space digital filters described by the Roesser model employing two's complement overflow arithmetic is presented. Under a certain assumption, the criterion turns out to be an improvement over a criterion due to El-Agizi and Fahmy pertaining to two's complement arithmetic and has a form similar to a criterion due to Xiao and Hill pertaining to saturation arithmetic. Examples show the effectiveness of the new criterion. © 2012 Elsevier Inc. All rights reserved.


A novel criterion for the global asymptotic stability of discrete-time systems in a statespace realization using saturation arithmetic was previously given by Liu and Michel. In their approach, as in most (or probably all) existing approaches, the matrix P is assumed to be symmetric. In this communique, it is shown that their approach is such as to be extended to allow the use of an unsymmetric matrix P. Taking note of this, a more general form of their criterion is presented. A modified form of the criterion is also presented. Examples show the effectiveness of the generalized approach. To the best of author's knowledge, this communique is the first report of exploiting an unsymmetric P to obtain a stability condition with reduced conservatism. © 2011 Elsevier Ltd. All rights reserved.


Melikoglu M.,Atilim University
Renewable and Sustainable Energy Reviews | Year: 2013

Natural gas is the primary source for electricity production in Turkey. However, Turkey does not have indigenous resources and imports more than 98.0% of the natural gas it consumes. In 2011, more than 20.0% of Turkey's annual trade deficit was due to imported natural gas, estimated at US$ 20.0 billion. Turkish government has very ambitious targets for the country's energy sector in the next decade according to the Vision 2023 agenda. Previously, we have estimated that Turkey's annual electricity demand would be 530,000 GWh at the year 2023. Considering current energy market dynamics it is almost evident that a substantial amount of this demand would be supplied from natural gas. However, meticulous analysis of the Vision 2023 goals clearly showed that the information about the natural gas sector is scarce. Most importantly there is no demand forecast for natural gas in the Vision 2023 agenda. Therefore, in this study the aim was to generate accurate forecasts for Turkey's natural gas demand between 2013 and 2030. For this purpose, two semi-empirical models based on econometrics, gross domestic product (GDP) at purchasing power parity (PPP) per capita, and demographics, population change, were developed. The logistic equation, which can be used for long term natural gas demand forecasting, and the linear equation, which can be used for medium term demand forecasting, fitted to the timeline series almost seamlessly. In addition, these two models provided reasonable fits according to the mean absolute percentage error, MAPE %, criteria. Turkey's natural gas demand at the year 2030 was calculated as 76.8 billion m3 using the linear model and 83.8 billion m3 based on the logistic model. Consequently, found to be in better agreement with the official Turkish petroleum pipeline corporation (BOTAS) forecast, 76.4 billion m3, than results published in the literature. © 2013 Published by Elsevier Ltd.


Melikoglu M.,Atilim University
Renewable and Sustainable Energy Reviews | Year: 2013

Turkey is a recently developed country, a regional power in the Middle East and an economic powerhouse of the region. Turkey's electricity demand is continuously increasing due to fast economic growth coupled with the country's vibrant young population. It is envisaged that this demand would keep on increasing almost exponentially in the next decade according to the recently avowed Vision 2023 agenda. According to which, the Turkish government ambitiously wants to provide 30.0% of the country's electricity demand from renewable energy sources by 2023. Turkey has vast renewable energy potential including hydro, geothermal, solar and wind. However, historically there is only one playmaker that is hydropower. Thus a detailed review of the current status and future prospects of Turkish hydropower market is urgently needed to generate a roadmap for the Vision 2023 agenda. This paper was intended to provide that vital information. Currently, more than 25.0% or 57.5 TWh of the country's electricity demand is supplied from hydropower. According to official projections this would increase to approximately 116.0 TWh in 2023. In this study, hydropower's supply rate of Turkey's annual electricity demand was assessed based on the official projections and a forecast was generated. Results showed that between 22.0% and 27.0% of Turkey's annual electricity demand should be supplied from hydropower in 2023. Therefore, between 22.5 TWh and 45.0 TWh of electricity should be generated from renewable energy sources other than hydropower to provide a total of 30.0% renewable energy based electricity generation in 2023. © 2013 Elsevier Ltd.


Karapinar E.,Atilim University
Computers and Mathematics with Applications | Year: 2010

The notion of coupled fixed point is introduced by Bhaskar and Lakshmikantham (2006) in [13]. In this manuscript, some results of Lakshmikantham and Ćirić (2009) in [5] are extended to the class of cone metric spaces. © 2010 Elsevier Ltd. All rights reserved.


Singh V.,Atilim University
Signal Processing | Year: 2012

A new criterion for the global asymptotic stability of 2-D discrete systems described by the Roesser model using saturation arithmetic is presented. The criterion is a generalization over an earlier criterion due to Liu and Michel. The generalized criterion has the feature that Lyapunov matrix P is not restricted to be symmetric, i.e., P can be even unsymmetric. A modified form of the criterion is also presented. Two examples showing the effectiveness of the generalized approach to yield new 2-D stability results are provided. To the best of authors knowledge, the use of unsymmetric P to obtain new 2-D stability conditions (i.e., conditions which are outside the scope of symmetric P) is demonstrated, for first time, in this paper. © 2011 Elsevier B.V.

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