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      • Crack detection in folded plates with back-propagated artificial neural network

        Oguzhan Das,Can Gonenli,Duygu Bagci Das 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.46 No.3

        Localizing damages is an essential task to monitor the health of the structures since they may not be able to operate anymore. Among the damage detection techniques, non-destructive methods are considerably more preferred than destructive methods since damage can be located without affecting the structural integrity. However, these methods have several drawbacks in terms of detecting abilities, time consumption, cost, and hardware or software requirements. Employing artificial intelligence techniques could overcome such issues and could provide a powerful damage detection model if the technique is utilized correctly. In this study, the crack localization in flat and folded plate structures has been conducted by employing a Backpropagated Artificial Neural Network (BPANN). For this purpose, cracks with 18 different dimensions in thin, flat, and folded structures having 150 , 300 , 450 , and 600 folding angle have been modeled and subjected to free vibration analysis by employing the Classical Plate Theory with Finite Element Method. A Four-nodded quadrilateral element having six degrees of freedom has been considered to represent those structures mathematically. The first ten natural frequencies have been obtained regarding healthy and cracked structures. To localize the crack, the ratios of the frequencies of the cracked flat and folded structures to those of healthy ones have been taken into account. Those ratios have been given to BPANN as the input variables, while the crack locations have been considered as the output variables. A total of 500 crack locations have been regarded within the dataset obtained from the results of the free vibration analysis. To build the best intelligent model, a feature search has been conducted for BAPNN regarding activation function, the number of hidden layers, and the number of hidden neurons. Regarding the analysis results, it is concluded that the BPANN is able to localize the cracks with an average accuracy of 95.12%.

      • KCI등재

        Finite element vibration analysis of laminated composite parabolic thick plate frames

        Oguzhan Das,Hasan Ozturk,Can Gonenli 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.1

        In this study, free vibration analysis of laminated composite parabolic thick plate frames by using finite element method is introduced. Governing equations of an eigenvalue problem are obtained from First Order Shear Deformation Theory (FSDT). Finite element method is employed to obtain natural frequency values from the governing differential equations. The frames consist of two flat square plates and one singly curved plate. Parameters like radii of curvature, aspect ratio, ply orientation and boundary conditions are investigated to understand their effect on dynamic behavior of such a structure. In addition, multi-bay structures of such geometry with different stacking order are also taken into account. The composite frame structures are also modeled and simulated via ANSYS to verify the accuracy of the present study.

      • Free vibration and buckling analyses of curved plate frames using finite element method

        Oguzhan Das,Hasan Ozturk,Can Gonenli 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.86 No.6

        This study investigates the free vibration and buckling analyses of isotropic curved plate structures fixed at all ends. The Kirchhoff-Love Plate Theory (KLPT) and Finite Element Method (FEM) are employed to model the curved structure. In order to perform the finite element analysis, a four-node quadrilateral element with 5 degrees of freedom (DOF) at each node is utilized. Additionally, the drilling effect (θz) is considered as minimal to satisfy the DOF of the structure. Lagrange's equation of motion is used in order to obtain the first ten natural frequencies and the critical buckling values of the structure. The effects of various radii of curvatures and aspect ratio on the natural frequency and critical buckling load values for the single-bay and twobay curved frames are investigated within this scope. A computer code based on finite element analysis is developed to perform free vibration and buckling analysis of curved plate frames. The natural frequency and critical buckling load values of the present study are compared with ANSYS R18.2 results. It has been concluded that the results of the present study are in good agreement with ANSYS results for different radii of curvatures and aspect ratio values of both single-bay and two-bay structures.

      • SCIESCOPUSKCI등재

        A Lower Serum Gamma-Glutamyltransferase Level Does Not Predict a Sustained Virological Response in Patients with Chronic Hepatitis C Genotype1

        ( Fatih Guzelbulut ),( Mesut Sezikli ),( Zuleyha Akkan Cetinkaya ),( Selvinaz Ozkara ),( Can Gonen ),( Ayse Oya Kurdas Ovunc ) 대한소화기학회 2013 Gut and Liver Vol.7 No.1

        Background/Aims: Low gamma-glutamyltransferase (GGT) level was shown to be an independent predictor of a sustained virological response (SVR) in chronic hepatitis C. We aimed to determine factors associated with high GGT level, and to evaluate whether low GGT level is an independent predictor of a SVR in chronic hepatitis C genotype 1. Methods: We retrospectively reviewed our data of patients with chronic hepatitis C genotype 1 treated with pegylated interferon-α and ribavirin. Baseline features were compared between patients with normal and high GGT levels. Factors associated with high GGT level and those associated with a SVR were determined by univariate and multivariate analysis. Results: This study included 57 patients. Mean age was 52.28±9.35 years. GGT levels was elevated in 27 patients (47.4%). GGT levels were normal in 63.3% of the patients who achieved a SVR and in 40.7% of those who did not achieve a SVR (p>0.05). By multivariate logistic regression analysis, the presence of cirrhosis (odds ratio [OR], 9.41; 95% confidence interval [CI], 1.08 to 102.61) and female gender (OR, 6.77; 95% CI, 1.23 to 37.20) were significantly associated with high GGT level, and only rapid virological response was associated with a SVR (OR, 8.369; 95% CI, 1.82 to 38.48). Conclusions: Low GGT level does not predict a SVR; however, it may be a predictor of high fibrosis scores. (Gut Liver 2013;7:74-81)

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