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    Amplitude and frequency detection of power system signals with chaotic distortions using independent component analysis
    (ELSEVIER SCIENCE SA, 2014) Ugur, M.; Cekli, S.; Uzunoglu, C. P.
    In this paper independent component analysis (ICA) method for amplitude and frequency estimation of highly distorted power system signals is presented. In a power system the accuracy of amplitude and frequency detection is strictly related to distortion strength of the system signal. Distorted system signal may contain chaotic (ferroresonance) and non-chaotic (white, pulse, harmonic etc.) noise. In this study, chaotic distortions are used to contaminate system signal, which is the worst case scenario for a power system. The proposed method is employed to eliminate the noise and hence to improve the efficiency of the estimation. To simulate chaotic distortions Duffing Oscillator solutions are used. Computer simulations have been carried out for the performance analysis of the proposed method and the comparison of the results of the proposed method with the conventional filters are presented. (C) 2013 Elsevier B.V. All rights reserved.
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    Amplitude and frequency estimation of power system signals using independent component analysis [Bagimsiz bilesen analizi ile enerji sistemleri isaretlerinin genlik ve frekans kestirimi]
    (2013) Uzunoglu, C.P.; Ugur, M.; Turan, F.; Cekli, S.
    In this paper independent component analysis (ICA) method for amplitude and frequency estimation of distorted power system signals is proposed. In order to protect system and keep it in safe operation mode the amplitude and frequency estimation should be conducted accurately. Transient disturbances of the power system may reduce estimation performance due to the distortion strength. In this study white noise and pulse noise which are very common for power systems, are used to contaminate power system signal. Thus, the proposed method is employed to decompose noise from system signal and hence to improve the efficiency of the estimation. Computer simulations have been carried out for the performance analysis of the ICA method and the comparison of the results of the proposed method with the conventional filters are displayed by using mean square error (MSE) values. © 2013 IEEE.
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    Evaluation of ultrasound-guided bilateral low thoracic erector spinae plane block for postoperative analgesia in cesarean delivery patients: a prospective, randomized, controlled clinical trial
    (Elsevier Editora Ltda, 2022) Aygun, H.; Ozturk, N.K.; Ugur, M.; Aydin, Y.; Celik, G.I.; Thomas, D.T.; Tulgar, S.
    Background: Erector spinae plane block (ESPB) is a recently described block. In many reports, ESPB has been reported to provide effective postoperative analgesia in patients undergoing cesarean delivery (CD). Herein, we compared the effectiveness of ESPB and control group in postoperative analgesia in patients undergoing CD under spinal anesthesia. Methods: This assessor-blinded, prospective, randomized, efficiency study was conducted in the postoperative recovery room and ward at a tertiary university hospital. Eighty-six patients ASA II–III were recruited. Following exclusion, 80 patients were randomized into two equal groups (block and control group). Standard multimodal analgesia was performed in the control group while ESPB block was performed in the intervention (ESPB) group. Opioid consumption was measured and pain intensity between groups was compared using Numeric Rating Scores (NRS). Results: NRS was lower in Group ESPB at 3rd and 6th hours. There was no difference between NRS scores at other hours. Opioid consumption was lower in Group ESPB. Conclusion: When added to multimodal analgesia, bilateral ultrasound guided low thoracic ESPB leads to improve the quality of analgesia in the first 24 hours in patients undergoing CD. © 2021 Sociedade Brasileira de Anestesiologia
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    Modelling of chaotic surface tracking on the polymeric insulators with Hidden Markov Models
    (IEEE Computer Society, 2014) Uzunoğlu, C.P.; Cekli, S.; Ugur, M.
    In this study, chaotic surface tracking patterns observed on polymeric high voltage (HV) outdoor insulation materials were investigated and simulated. The polymeric samples are tested according to the IEC 587 Inclined Plane Tracking Test Standard. Since the chaotic surface tracking patterns manifests smutty and disordered images, they are preprocessed and purified by image processing tools. Internal and external effects may severely decrease insulation performance. In order to examine external effects, samples are subjected to moisture and vibration effect. Polymer samples are investigated by their fractal dimension which is a prominent tool for analyzing chaotic images. To simulate these chaotic surface tracking patterns Hidden Markov Models (HMM) are used. © 2014 IEEE.
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    Wavelet analysis of a memristor emulated model proposed for compact fluorescent lamp operated systems
    (ELSEVIER SCIENCE SA, 2018) Babacan, Y.; Uzunoglu, C. P.; Cekli, S.; Kacar, F.; Ugur, M.
    Compact fluorescent lamps (CFLs) are widely employed in lighting systems thanks to their energy efficient characteristics. In contrast to incandescent lamps, CFLs have highly non-linear current-voltage characteristics and exhibit harmonic distortions during their operation. Although nonlinearity and accelerated harmonic effects may cause disturbance in power networks, CFLs are frequently preferred due to their low energy consumption. In this study a test set-up is operated for investigating non-linear characteristics of commercially available CFLs. During these tests non-linear current and voltage waveforms of CFLs are analyzed via oscilloscope and compared with the proposed memristor emulator circuit output waveforms. The non-linear characteristics of CFLs are accurately modelled by proposed memristor emulator circuit, which has a tunable threshold property. To obtain proper comparison wavelet analysis is conducted for current waveforms of CFLs and memristor emulator circuit. The wavelet analysis is an efficient tool for processing non-linear signals, which are prone to display high frequency distortions. In addition to wavelet analysis, the Fourier Transform (FFT) characteristics and total harmonic distortion (THD) levels are also analyzed for correlation of CFLs and proposed memristor. (C) 2018 Elsevier B.V. All rights reserved.