Cilt:61 Sayı:01 (2019)
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Item A Comparatıve Study: Voltage Multıplıers For RF Energy Harvestıng System(Ankara Üniversitesi Mühendislik Fakültesi, 2019-06-30) Sarı, Filiz; Uzun, Yunus; Other; OtherVoltage 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.Item Desıgning a Secure Blockchain-Based Trading Platform for Internet of Things(Ankara Üniversitesi Fen Fakültesi, 2019-06-30) Osmanoğlu, Murat; Elbuz, Aydın; Tanrıöver, Ömer Özgür; Bilgisayar Mühendisliği; Mühendislik FakültesiBlockchain, a distributed database technology attracts intensive attention recently. It was first described in 1991 by Stuart Haber and W. Scott Stornetta, in order to prevent tampering for document timestamps. After that, Satoshi Nakamoto conceptualized this technology with his work, a peer-to-peer electronic cash system named as Bitcoin. Due to its authenticity, user anonymity and data immutability; this technology has also been applied to different areas ranging from finance, supply-chain managements to social services. In this paper, we propose a blockchain based application for trading data, collected from IoT devices. Our application enables the sellers to commercialize their data in exchange of the currency produced by the application. The application also utilizes smart contracts to establish trust between both sides of the exchange. Furthermore, we discuss the security and reliability of the system componentsItem Efficient Chebyshev Economization for Elementary Functions(Ankara Üniversitesi Fen Fakültesi, 2019-06-30) Bekir, Esmat; Other; OtherThis 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.Item Estimating co2 Emissions By Using Energy Intensıty Data of Oecd Countries(Ankara Üniversitesi Fen Fakültesi, 2019-06-30) Gunduç, Semra; Eryiğit, Recep; Bilgisayar Mühendisliği; Mühendislik FakültesiIt is discussed that economic development has an essential effect on the country’s CO2 emission which plays an important role in global warming. In this research well-known machine learning algorithm Extreme Learning Machine, ELM, is used to investigate the relationship between CO2 emission and energy intensity for countries in OECD. The results indicate a strong correlation and the method perform well for estimation.Item Focusing, Imaging and Fourier Transforming With a Large Numerical Aperture, Dielectric Flat Photonic Crystal Lens in Metamaterial Regime(Ankara Üniversitesi Fen Fakültesi, 2019-06-30) Çolak, Evrim; Çakmak, Atilla Özgür; Elektrik-Elektronik Mühendisliği; Mühendislik FakültesiAn untraditional Gradient Index Photonic Crystal (GRIN PC) is employed within the long wavelength regime to exhibit focusing, imaging and Fourier Transforming. A very large numerical aperture is aimed by breaking the paraxial wave approximation and the slowly changing refractive index assumption. This untraditional GRIN PC is shown to exhibit very similar lensing characteristics as its analytically solvable counterparts demonstrate. The results suggest that Fourier Transforming together with Fractional Fourier Transforms can be obtained from the present design. The performance of the GRIN PC lens is very much dependent on the excitation source as it is expected from GRIN optics and adiffractional propagating beams over large distances can be obtained.Item Investigating Doubly Charged Leptons at Future Energy Frontier Muon-Proton Colliders(Ankara Üniversitesi Fen Fakültesi, 2019-06-30) Ozansoy, Aysuhan; Fizik; Fen FakültesiWe study the doubly charged leptons considered in extended isospin models at muon-proton colliders. We respect the lepton flavor conservation and take into consideration the single production of the doubly charged leptons related to second generation. We give the effective lagrangian describing the doubly charged lepton gauge interactions. We calculate the signal and corresponding background cross sections and analyze the kinematical distributions to obtain the suitable cuts for the discovery. We choose the W-boson hadronic decay channel to get the accessible mass limits and couplings of doubly charged leptons for various muon-proton colliders.Item Prıvacy-Preservıng K-Nearest Neıghbour Interpolatıon Method ın an Outsourced Envıronment(Ankara Üniversitesi Mühendislik Fakültesi, 2019-06-30) KALIDEEN, Muhammad Rifthy; Osmanoğlu, Murat; Tuğrul, Bülent; Bilgisayar Mühendisliği; Mühendislik FakültesiOne of the most emerging computer technologies of this decade is cloud computing that allows data owners to outsource their storage and computing requirements. It enables data owners to avoid the costs of building and maintaining a private storage infrastructure. While outsourcing data to cloud promises significant benefits, it possesses substantial security and privacy concerns, especially when data stored in the cloud is sensitive and confidential, like a business plan. Encrypting the data before outsourcing can ensure privacy. However, it will be very difficult to process the cipher text created by the traditional encryption method. Considering this fact, we propose an efficient protocol that allows a query owner to retrieve the interpolation of the top k records from two different databases that are closest to a query point. Note that the databases are stored in two different cloud service providers in encrypted form. We also show that the proposed protocol ensures the privacy and the security of the data and the query point.Item Quality of Software Projects – A Case Study(Ankara Üniversitesi Fen Fakültesi, 2019-06-30) Ayyıldız, Tülin Erçelebi; Kıral, Alper; Other; OtherIn 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.Item Synaptıc Transmıssıon: A Model on the Formatıon Of End-Plate Potentıal and a Study on Sımulatıon(Ankara Üniversitesi Fen Fakültesi, 2019-06-30) Özbek, Levent; Temuçin, Çağrı; Cengiz, Bülent; Öztürk, Fikri; İstatistik; Fen FakültesiIn this study, the emergences of postsynaptic action potentials are investigated using simulation study which is depended on the statistical model of acetylcholine (Ach) quantal release theory at motor end-plate. It is supposed that the end-plate potentials (EPP) are sum of miniature end-plate potentials (MEPP) which are released as quantal and random in number (N). By the hypothesis that N number has a Poisson and MEPPs have a Gaussian distribution, EPPs are obtained by simulating distributions parameters. Our study suggests that the simulation of the EPPs are a convenient tool in understanding both physiological process of synaptic transmission and pathological process of neuromuscular junction.