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Öğe A new approach based on 2D wavelet transform in the analysis of wettability behavior and evaporation rate for the surface of PTFE dielectric material used in high voltage applications(Elsevier B.V., 2024) Karhan, Mustafa; Arslan, ÖzkanIn this study, a new approach based on 2D wavelet transform is proposed for the analysis of wettability behavior and evaporation rate. Droplet images were taken from the PTFE dielectric sample surface at 30th, 270th, 510th, 750th, 990th, 1230th, 1470th, and 1710th seconds. The droplet images were decomposed into sub-bands using functions from six different wavelet families. The energy, entropy, mean, standard deviation, skewness, and kurtosis measures were calculated using wavelet coefficients for each sub-band image. Linear, exponential, and polynomial fitting methods were used to estimate the contact angle of the droplet images. The energy and standard deviation values, which are the selected optimal measures, were used as input in the fitting methods, and the regression coefficient (R2) and Root Mean Square Error (RMSE) values of the fitting methods were calculated. Thus, a high-performing contact angle prediction model with 2nd level sub-band image wavelet coefficients has been obtained. © 2024Öğe Effect of electric field on contact angle and droplet shape in XLPE dielectric materials(Gazi Univ, Fac Engineering Architecture, 2021) Karhan, Mustafa; Çakır, Musa Faruk; Arslan, Özkan; Issi, Fatih; Eyupoglu, VolkanXLPE dielectric materials have an important place in electricity transmission and distribution. The aging of XLPE dielectric materials during the service period is inevitable. The surface properties of XLPE dielectric materials play an active role in the determination and evaluation of their service life. Properties such as hydrophobicity and hydrophilicity are the methods used in the analysis of the surface properties of materials. Within the scope of this project, contact angle measurements were carried out under the electric field for evaluation and determination on the wettability behavior of the XLPE material, which plays an important role in electrical insulation, which is widely used in electrical energy transmission and distribution. In the contact angle measurement platform manufactured using the 3D printer, XLPE insulator was placed between the aluminum plane electrodes and exposed to an electric field. A high voltage source of 0-10kV was used as a high voltage generator during the experiments. Snapshots of the 1.8M saltwater droplet dropped on the XLPE insulator surface under the electric field were taken. In the image processing part of the study, images taken with a digital microscope were processed using the image processing techniques with the help of a graphical user interface (GUI) prepared on the MATLAB platform. Contact angle values were obtained as output. Contact angles obtained from XLPE surfaces under the electric field will allow an evaluation of the service life of XLPE dielectric materials. An approach based on the contact angle for evaluation and determination of the wettability of XLPE dielectric materials is presented. As a result, the correlation between the electric field, wettability, and contact angle was observed.Öğe Effect of Hilbert-Huang transform on classification of PCG signals using machine learning(King Saud bin Abdulaziz University, 2022) Arslan, Özkan; Karhan, MustafaHeartbeat sounds are biological signals used in the early diagnosis of cardiovascular diseases. Digital heartbeat sound recordings, called phonocardiogram (PCG), are used in the determination and automatic classification of possible heart diseases. Healthy and pathological PCG signals are non-stationary signals and conventional feature extraction methods are insufficient in classifying these signals. In this study, PCG signals in healthy and four pathological categories are decomposed into intrinsic mode functions (IMFs) by Hilbert-Huang transform. Mel-frequency cepstral coefficient (MFCC) features were extracted from each mode to investigate the effect of the modes obtained by Hilbert-Huang transform on the classification of PCG signals. Genetic algorithm was used as feature selection method and k-nearest neighbor (KNN), multilayer perceptron (MLP), support vector machine (SVM) and deep neural network (DNN) machine learning methods were used as classifier. We have implemented multi classifications of five PCG classes (healthy, aortic stenosis, mitral stenosis, mitral regurgitation and mitral valve prolapse) by using 5-fold cross validation and 10 × 5-fold cross validation Data Analysis Protocol (DAP) framework. The results show that the DNN model provides the highest classification performance with 98.9% precision, 98.7% recall, 98.8% F1-score and 98.9% accuracy using 5-fold cross validation, and Matthews correlation coefficient of 0.981 using the DAP method. © 2021 The AuthorsÖğe İmge işleme yöntemleri ile kayısılarda yaprak delen hastalığı sonucu oluşan lekelerin tespiti(Namık Kemal Üniversitesi, 2011) Karhan, MustafaBu tezde, görüntü bölütleme algoritmaları ile kayısılarda Yaprak Delen (Çil) Hastalığı sonucu meyve üzerinde oluşan lekeler (çiller) tespit edilmiş ve kayısıdaki kaliteyi yorumlamaya yönelik görüntü işleme teknikleri kullanılmıştır. Görüntü işleme tabanlı gerçek zamanlı çalışan bir sınıflandırma sistemi uygulanmıştır. Görüntü işleme kısmında, görüntü iyileştirme yöntemleri ve renk tabanlı bir bölütleme işlemi yapılmıştır. Bu tezde geliştirilen görüntü işleme yöntemi ile kayısının leke olmayan, olgunlaşmasından veya diğer sebeplerden dolayı oluşan kırmızılıkların, ikili görüntüde oluşturduğu yanılsama lekeler morfolojik işlemlerle en aza indirgenerek, morfolojik süzgeç çıkışındaki görüntüde daha yüksek doğrulukta tespit gözlemlenmiştir. Bilinen temel bir bölütleme yöntemi ile sonuçlar karşılaştırılmış ve daha iyi sonuçlar elde edilmiştir. Kayısıda yaprak delen hastalığı sebebiyle kayısı üzerinde oluşan lekeler (çiller) kayısı kalitesinde önemli bir yer tutmaktadır. Bu tezde geliştirilen yöntem ile lekelerin tespiti ve kayısı yüzeyinde kapladığı alan sonucu kayısıda kalite sınıflandırması yapılabilir ve daha doğru fiyatlandırma belirlenebilir.Öğe Investigation of the effect of roughness value on the wettability behavior under electric field in XLPE materials used in medium and high voltage applications(Springer Science and Business Media Deutschland GmbH, 2021) Karhan, Mustafa; Çakır, Musa Faruk; Arslan, ÖzkanXLPE material, which is widely used as a polymeric insulator in medium and high voltage applications, plays an active and important role in electricity transmission and distribution. The aging of XLPE materials due to various factors is inevitable. It is observed that fault and troubleshooting increase with the aging of materials. Wettability behavior is one of the fundamental surface properties of materials. Surface properties also play an important role in the determination and estimation of the service life of the materials. By performing contact angle measurements for XLPE material surfaces, determinations and evaluations about the wettability behavior (hydrophobicity and hydrophilicity) of the materials can be made. In this study, contact angle measurements of XLPE materials with different roughness values were carried out under the electric field. With the help of the experimental setup designed and implemented, XLPE samples were placed between the aluminum plane electrodes and exposed to the electric field. 10 kV HVDC high-voltage generator was used when performing the measurements. 1.8 M (molarity) saltwater in the volume of 20 µl was dropped on the XLPE sample surface with a syringe and the droplet snapshots were taken with a digital microscope for contact angle measurement under the electric field. The acquired images were processed using basic image processing techniques with the help of a GUI developed on the MATLAB software platform. Contact angle values were obtained for 50 XLPE-A (Ra = 0.469 µm) and 50 XLPE-B (Ra = 5.456 µm) sample surfaces. Contact angles obtained from rough XLPE surfaces under the electric field allow for evaluation of the service life of XLPE materials. While determining and evaluating the wettability behavior of XLPE materials, an approach based on the contact angle is presented. As a result, the correlation between the electric field, surface roughness, wettability, and contact angle was observed. When the results were evaluated, it was observed that the contact angle values close to the hydrophobic surface value approached the hydrophilic values as a result of the increase in surface roughness and/or exposure to the electric field. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
