Cilt:61 Sayı:01 (2019)

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https://dspace.ankara.edu.tr/handle/20.500.12575/76507

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Browsing Cilt:61 Sayı:01 (2019) by Author "Other"

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    A Comparatıve Study: Voltage Multıplıers For RF Energy Harvestıng System
    (Ankara Üniversitesi Mühendislik Fakültesi, 2019-06-30) Sarı, Filiz; Uzun, Yunus; Other; Other
    Voltage multipliers are widely used for energy harvesting processes to convert the received AC signal to DC signal, also enhanced the low level received signal. In this study, Villard, Dickson and Greinacher type voltage multipliers are analyzed without impedance matching and substrate materials to decide the effective voltage multiplier type depend on the inputs of the harvester. So, load resistance, input power and input frequencies’ effects are analyzed and compared with each other. Agilent Advanced Design System (ADS) is used for simulations. HSMS 2852 Schottky diode and capacitors are used for these voltage multipliers. Results show that, determining load resistance is important for evaluating high efficiency, e.g. efficiency differences are reached 33% between 2kΩ and 20 kΩ for Dickson voltage multiplier at 100 MHz input frequency. Furthermore, the best efficiency is obtained by Greinacher voltage multiplier for low input frequencies which is lower than 1 GHz but there are no significant differences are observed for high frequencies. This study shows that load resistance, input frequency and input power are important parameters for voltage multiplier selection and Greinacher voltage multiplier is the best choice to obtain high efficiency for low frequency application of RF harvesting.
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    Efficient Chebyshev Economization for Elementary Functions
    (Ankara Üniversitesi Fen Fakültesi, 2019-06-30) Bekir, Esmat; Other; Other
    This paper presents economized power series for trigonometric and hyperbolic functions. It determines the smallest range over which a function need to be computed and scales the Chebyshev polynomials accordingly. Thus reduced degree polynomials (and hence reduced computations) can be obtained while maintaining the same accuracy as those unscaled higher degree polynomials.
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    Quality of Software Projects – A Case Study
    (Ankara Üniversitesi Fen Fakültesi, 2019-06-30) Ayyıldız, Tülin Erçelebi; Kıral, Alper; Other; Other
    In software projects, many points that are overlooked such as time constraints and human factors are causing great problems in the future. By measuring the quality of software projects, problems that may arise in important parameters such as maintenance-repair, functionality and reliability can be eliminated. In this study, metrics that can be used for measuring maintainability quality attribute within the scope of ISO 9126 Quality Standard are examined. In order to perform the study, 40 open source object-oriented software was selected and code complexity analysis was performed. Values of metric sets such as Chidamber and Kemerer (CK), Lorenz and Kidd (LK) and McCabe's complex Suite were determined by the Understand Code Analysis tool. It was determined whether the obtained values exceeded the threshold values indicated in the literature. Frequencies of metrics passing threshold values were determined for 40 open source object-oriented software projects, and the consistency among the metrics was evaluated using WEKA Machine Learning Software and EXCEL Data Analysis Tool. When the results were evaluated, it was observed that in addition to CK metrics such as WMC, CBO, and RFC, which measure the maintainability quality attribute, NOC (CK), NIM (LK), and the ratio of comment/code metrics have been observed to yield significant measurement results.