Cilt:62 Sayı:02 (2020)

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https://dspace.ankara.edu.tr/handle/20.500.12575/76533

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Browsing Cilt:62 Sayı:02 (2020) by Author "Other"

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    Analyzıng The Performance Of Pure Lateratıon In Indoor Envıronments Wıth Varıous Performance Metrıcs
    (Ankara Üniversitesi Fen Fakültesi, 2020-12-31) Cengiz, Korhan; Other; Other
    Nowadays, determining the location of the users and devices in indoor buildings is promising research topic. Accurate position determination of the users for indoor environments is used for numerous applications such as public safety, supermarkets, health care applications, travelling, social networks and tourism. However, global positioning systems created for outdoor localizations cannot be used for indoor positioning systems (IPS) because detecting the exact position of a target is an issue for IPS. For indoor environments, there are several positioning algorithms such as lateration, fingerprinting, dead reckoning etc. Lateration is low cost and easy to deploy when compared to other existing algorithms. Therefore, in this study, received signal strength based pure lateration that uses synthetic data generated from MATLAB is proposed. The performance of pure lateration is investigated in terms of several performance metrics such as effect of varying number of the access points (AP), varying dimensions of the measurement area, varying Gaussian Noise power and varying number of test points in the field. The simulation of the pure lateration algorithm is conducted in MATLAB. The effect of the performance metrics are investigated and discussed in details. According to the results, accuracy performance of lateration is increased when the number of APs increase in the area, however this will bring some hardware costs. In addition, when the number of test points increases in the field, in other words the step size between two test points decreases in the field the error performance of lateration is also enhanced however, this will also cause to computational costs. Finally, enlarging the measurement area causes to decrease the accuracy performance of lateration as expected. The main purpose of this study is to obtain the optimum conditions for lateration to provide a solution for real time applications. For future work, the real time implementations of this study are performed and to improve the accuracy performance, it is aimed to use a curve fitting idea to the measured values.
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    Lpı Radar Waveform Classıfıcatıon Usıng Bınary Svm And Multı-Class Svm Based On Prıncıpal Components Of Tfı
    (Ankara Üniversitesi Fen Fakültesi, 2020-12-31) Bektaş, Almıla; Ergezer, Halit; Other; Other
    Since cognition has become an important topic in Electronic Warfare (EW) systems, Electronic Support Measures (ESM) are used to monitor, intercept and analyse radar signals. Low Probability of Intercept (LPI) radars is preferred to be able to detect targets without being detected by ES systems. Because of their properties as low power, variable frequency, wide bandwidth, LPI Radar waveforms are difficult to intercept with ESM systems. In addition to intercepting, the determination of the waveform types used by the LPI Radars is also very important for applying counter-measures against these radars. In this study, a solution for the LPI Radar waveform recognition is proposed. The solution is based on the training of Support Vector Machine (SVM) after applying Principal Component Analysis (PCA) to the data obtained by Time-Frequency Images (TFI). TFIs are generated using Choi-Williams Distribution. High energy regions on these images are cropped automatically and then resized to obtain uniform data set. To obtain the best result in SVM, the SVM Hyper-Parameters are also optimized. Results are obtained by using one-against-all and one-against-one methods. Better classification performance than those given in the literature have been obtained especially for lower Signal to Noise Ratio (SNR) values. The cross-validated results obtained are compared with the best results in the literature.
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    Towards Real Tıme Image Dehazıng On Androıd Operatıng System
    (Ankara Üniversitesi Fen Fakültesi, 2020-07-01) Cimtay, Yücel; Other; Other
    Sis, görüntü ve videonun kalitesini düşüren en önemli etkilerden biridir. Bu, kontrastı azaltır ve görsel verimliliği azaltır. Sis giderme için genellikle Atmosferik ışık saçılım modeli (AISM) kullanılır. Bu modelde ölçülecek iki bilinmeyen vardır: atmosferik ışık ve iletim. Bu tür hesaplamalar kolay değildir ve atmosferik ışığın hesaplanması çok zaman alır. Bu durum, gerçek zamanlı olarak sisin çözülmesini zorlaştırır. Sis giderme uygulamaları uzun süredir yaygın olarak uygulanmasına rağmen, bu çalışma android işletim sistemi üzerinde gerçek zamanlı sis gidermnin ilk denemelerinden biridir. Bu, gerçek zamanlı sis gidermeyi bir mobil uygulama veya araca dönüştürmek açısından çok önemlidir.