yıldırım özüpak

Dr. yıldırım özüpak


Research Focus & Metrics

Academic Career Length

8Years (2019-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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14 May 2025 in Water, Air, & Soil Pollution
Verified
Journal Article
Open access
PDF file
YÖyıldırım özüpak
yıldırım özüpak
YIYıldırım
Yıldırım
FAFeyyaz ALPSALAZ
Feyyaz ALPSALAZ
EAEmrah ASLAN
Emrah ASLAN
Air pollution poses a critical challenge to environmental sustainability, public health, and urban planning. Accurate air quality prediction is essential for devising effective management strategies and early warning systems. This study utilized a dataset comprising hourly measurements of pollutants such as PM2.5, NOx, CO, and benzene, sourced from five metal oxide sensors and a certified analyzer in a polluted urban area, totaling 9,357 records collected over one year (March 2004–February 2005) from the Kaggle Air Quality Data Set. A comprehensive comparison of ten machine learning regression models XGBoost, LightGBM, Random Forest, Gradient Boosting, CatBoost, Support Vector Regression (SVR) with Bayesian Optimization, Decision Tree, K-Nearest Neighbors (KNN), Elastic Net, and Bayesian Ridge was conducted. Model performance was enhanced through Bayesian optimization and randomized cross-validation, with stacking employed to leverage the strengths of base models. Experimental results showed that hyperparameter optimization and ensemble strategies significantly improved accuracy, with the SVR model optimized via Bayesian optimization achieving the highest performance: an R2 score of 99.94%, MAE of 0.0120, and MSE of 0.0005. These findings underscore the methodology’s efficacy in precisely capturing the spatial and temporal dynamics of air pollution.

8 December 2025 in Scientific Reports
Verified
Journal Article
Open access
PDF file
HUHasan Uzel
Hasan Uzel
YÖyıldırım özüpak
yıldırım özüpak
FAFeyyaz Alpsalaz
Feyyaz Alpsalaz
EAEmrah Aslan
Emrah Aslan
This study proposes a hybrid machine learning approach that integrates Artificial Neural Networks (ANN) and Random Forest (RF) classifiers, enhanced by Optuna hyperparameter optimization, for fault detection and classification in power transmission networks. The model is trained on a synthetic dataset generated from MATLAB/Simulink simulations of an 11 kV multi-generator system, incorporating three-phase current (Ia, Ib, Ic) and voltage (Va, Vb, Vc) signals under fault scenarios such as line-to-ground (LG), double line-to-ground (LLG), and three-phase symmetrical (LLLG) faults. To address class imbalance, the Synthetic Minority Oversampling Technique (SMOTE) is applied, ensuring balanced representation of rare fault categories. The ANN-RF model achieves superior performance, with 99.8% accuracy, 99.5% precision, and 99.4% recall, consistently outperforming traditional classifiers including K-Nearest Neighbors, Bagging, AdaBoost, and Gradient Boosting. Its effectiveness arises from ANN’s non-linear feature extraction, RF’s ensemble robustness, and Optuna’s hyperparameter tuning, with SMOTE improving detection of rare fault types. Compared with advanced models such as Modified InceptionV3 (98.93% accuracy) and Extreme Learning Machines (99.60% accuracy), the proposed approach provides a balanced trade-off between sensitivity and specificity, offering a reliable solution for fault identification. Nonetheless, challenges in computational efficiency and reliance on simulated data highlight the need for validation with real-world measurements and further optimization for real-time smart grid applications.

18 June 2025 in New Zealand Journal of Crop and Horticultural Science
Verified
Journal Article
Closed access
YÖyıldırım özüpak
yıldırım özüpak
FAFeyyaz Alpsalaz
Feyyaz Alpsalaz
EAEmrah Aslan
Emrah Aslan
HUHasan Uzel
Hasan Uzel
This study presents a hybrid learning model that integrates MobileNetV2 and Vision Transformer (ViT) with a stacking model to classify maize leaf diseases, addressing the critical need for early detection to improve agricultural productivity and sustainability. Utilising the ‘Corn or Maize Leaf Disease Dataset’ from Kaggle, comprising 4,062 high‐resolution images across five classes (Common Rust, Grey Leaf Spot, Healthy, Northern Leaf Blight, Not Maize Leaf), the model achieves an impressive accuracy of 96.73%. Transfer learning from ImageNet, coupled with data augmentation (rotation, flipping, scaling, brightness adjustment), enhances generalisation, while a 20% dropout rate mitigates overfitting. The key advantage of the hybrid model lies in its ability to combine the strengths of MobileNetV2's localised feature extraction and ViT's global context understanding, enhanced by the stacking model's ability to reduce the weaknesses of either model. Explainable AI techniques, including SHapley Additive exPlanations (SHAP), Local Interpretable Model‐agnostic Explanations (LIME), and Grad‐CAM, provide transparent insights into model decisions, fostering trust among agricultural stakeholders. Comparative analysis demonstrates the model’s superiority over prior works, with F1‐scores ranging from 0.9276 to 1.0000. Despite minor misclassifications due to visual similarities, the model offers a robust, interpretable solution for precision agriculture.

27 June 2025 in IEEE Access
Verified
Journal Article
Open access
EAEmrah ASLAN
Emrah ASLAN
YÖyıldırım özüpak
yıldırım özüpak
FAFeyyaz ALPSALAZ
Feyyaz ALPSALAZ
Zakaria M.S ElbarbaryZakaria M.S Elbarbary
Zakaria M.S Elbarbary
Power transformers are critical components in ensuring the continuous and stable operation of power systems. Failures in these units can lead to significant power outages and costly downtime. Existing maintenance strategies often fail to accurately predict such failures, highlighting the need for novel predictive approaches. This study aims to improve the reliability of power systems by predicting transformer failures through the integration of IoT technologies and advanced machine learning techniques. The proposed hybrid model combines the LightGBM algorithm with GridSearch optimization to achieve both high predictive accuracy and computational efficiency. In addition, the model enhances interpretability by incorporating SHapley Additive exPlanations (SHAP) and Local Interpretable Model-Agnostic Explanations (LIME) for transparent decision making. The study presents a detailed comparison of different classification algorithms and evaluates their performance using metrics such as accuracy, recall, and F1 score. The results show that the hybrid model outperforms other methods, achieving an accuracy of 99.91%. The SHAP and LIME analyses provide engineers and researchers with valuable insights by highlighting the most influential features in failure prediction. In addition, the model’s ability to efficiently handle large data sets enhances its practicality in real-world power systems. By proposing an innovative approach to failure prediction, this research contributes to both the theoretical foundation and practical advancement of sustainable and reliable energy infrastructures.

28 November 2025 in Scientific Reports
Verified
Journal Article
Open access
PDF file
SASüheyla Demirtaş Alpsalaz
Süheyla Demirtaş Alpsalaz
EAEmrah ASLAN
Emrah ASLAN
YÖyıldırım özüpak
yıldırım özüpak
FAFeyyaz ALPSALAZ
Feyyaz ALPSALAZ
HUHasan Uzel
Hasan Uzel
VBViktoriia Bereznychenko
Viktoriia Bereznychenko
This study introduces a hybrid deep learning model integrating EfficientNet-B3 and Vision Transformer with an Attention Fusion mechanism for automated colon cancer detection using the Kvasir endoscopic dataset. The model leverages EfficientNet-B3’s strength in capturing fine-grained local textures and Vision Transformer’s ability to model global contextual relationships. A multi-head attention-based fusion block harmonizes these features, achieving comprehensive representations and enhanced classification stability. Model optimization was guided by the Matthews Correlation Coefficient (MCC), alongside evaluations of accuracy, F1-score, and Brier Score. Experimental results demonstrate a 96.2% accuracy and an MCC of 0.961, surpassing standalone baselines and existing benchmark architectures. Cross-validation confirmed robust generalization, while Grad-CAM analyses improved interpretability by visualizing salient histopathological regions influencing predictions. Despite slight overfitting tendencies, the model maintained strong performance across all eight image classes. These findings highlight the model’s ability to address limitations of single-architecture approaches by combining local and global feature extraction, offering rapid, objective, and reliable diagnostic support. The proposed framework shows significant promise for integration into computer-aided colonoscopy systems, paving the way for enhanced clinical diagnostics and reduced pathologist workload through AI-driven precision medicine.

1 January 2025 in International Transactions on Electrical Energy Systems
Verified
Journal Article
Open access
BSBenkaihoul Said
Benkaihoul Said
FBFarouk Ibrahim Bouguenna
Farouk Ibrahim Bouguenna
AZAyyoub Zeghlache
Ayyoub Zeghlache
MAMustafa Abdullah
Mustafa Abdullah
YÖyıldırım özüpak
yıldırım özüpak
Ievgen ZaitsevIevgen Zaitsev
Ievgen Zaitsev
This study proposes an advanced hybrid fault‐tolerant control (FTC) architecture for permanent magnet synchronous motors (PMSMs) operating under speed sensor faults (SSFs), integrating model predictive control (MPC), third‐order sliding mode control (TOR‐SMC), and a model reference adaptive system (MRAS). The key innovation lies in the synergistic combination of MPC’s predictive optimization with the robustness of TOR‐SMC and the real‐time adaptive estimation capability of MRAS, enabling reliable operation in the presence of sensor degradation or failure. A residual‐based fault detection mechanism is embedded to monitor discrepancies between actual and estimated rotor speeds, enabling rapid fault identification and seamless transition to observer‐based control. The proposed hybrid control system is designed within a hierarchical architecture, wherein MPC optimizes inverter switching actions, TOR‐SMC ensures robust disturbance rejection and chattering suppression, and MRAS delivers high‐fidelity speed estimation. Simulation studies under various operating scenarios—encompassing step changes in speed, variable torque loads, and fault scenarios—demonstrate that the system achieves a maximum speed estimation error of 1.8%, speed tracking accuracy of 97.6%, and a fault detection time of less than 2.5 ms, which is 41.3% faster than extended Kalman filter (EKF)–based schemes. Quantitatively, the proposed method reduces torque ripples by 32.5%, current overshoot by 35.7%, and transient response time by 27%, while improving overall fault tolerance by 63% compared to conventional FTC approaches. The TOR‐SMC module contributes to a 78% reduction in chattering and ensures stable electromagnetic torque behavior even under dynamic torque disturbances. In parallel, MRAS offers faster convergence (2.5 ms) and smoother transitions compared to SMO and EKF observers, maintaining control integrity despite sensor anomalies. This comprehensive and modular FTC approach addresses a critical vulnerability in PMSM drive systems and is particularly well‐suited for deployment in electric vehicles, aerospace systems, and renewable energy platforms, where high reliability, real‐time responsiveness, and robustness to sensor degradation are paramount. The results confirm the proposed hybrid MPC–TOR‐SMC–MRAS framework as a scalable and high‐performance solution for next‐generation motor control systems under fault‐prone environments.