Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 1Citation - Scopus: 1Completeness of Energy Eigenfunctions for the Reflectionless Potential in Quantum Mechanics(Aip Publishing, 2024) Erman, Fatih; Turgut, O. TeomanThere are a few exactly solvable potentials in quantum mechanics for which the completeness relation of the energy eigenstates can be explicitly verified. In this article, we give an elementary proof that the set of bound (discrete) states together with the scattering (continuum) states of the reflectionless potential form a complete set. We also review a direct and elegant derivation of the energy eigenstates with proper normalization by introducing an analog of the creation and annihilation operators of the harmonic oscillator problem. We further show that, in the case of a single bound state, the corresponding wave function can be found from the knowledge of continuum eigenstates of the system. Finally, completeness is shown by using the even/odd parity eigenstates of the Hamiltonian, which provides another explicit demonstration of a fundamental property of quantum mechanical Hamiltonians.Article Machinability Investigation on Cnc Milling of Recycled Short Carbon Fiber Reinforced Magnesium Matrix Composites(Iop Publishing Ltd, 2024) Atasoy, Sahin; Kandemir, SinanThis study investigates the machinability of magnesium matrix composites reinforced with short carbon fibers, which represent novel materials in the field. AZ91 alloy and its composites containing 2.5 and 5 wt% recycled carbon fiber (rCF) reinforcements were used as workpieces. Face milling was conducted using uncoated carbide cutting tools under dry cutting conditions with varied cutting speeds (480-560-640 m min(-1)) and feed rates (0.65-0.8-0.95 mm min(-1)). The experimental design was based on the Taguchi L-9 (3(3)) orthogonal array. Analysis included cutting forces, surface roughness, wear on cutting inserts, and chip morphology to assess machinability. Taguchi, analysis of variance, and regression methods were employed to analyze cutting force and surface roughness results. Findings indicated satisfactory machinability for AZ91 alloy and comparatively poorer performance for the 5 wt% rCF reinforced composite, with increased reinforcement content correlating with higher cutting force and surface roughness. SEM and EDX analyses revealed significant built-up layer formation on cutting inserts, with predominantly spiral-shaped continuous chips observed in the experiments. Overall, the study affirmed the machinability of the composites and identified suitable cutting parameters for further investigations.Article Citation - WoS: 4Citation - Scopus: 5Diffusion-Based Data Augmentation Methodology for Improved Performance in Ocular Disease Diagnosis Using Retinography Images(Springer Heidelberg, 2024) Aktas, Burak; Ates, Doga Deniz; Duzyel, Okan; Gumus, AbdurrahmanDeep learning models, integral components of contemporary technological landscapes, exhibit enhanced learning capabilities with larger datasets. Traditional data augmentation techniques, while effective in generating new data, have limitations, especially in fields like ocular disease diagnosis. In response, alternative augmentation approaches, including the utilization of generative AI, have emerged. In our study, we employed a diffusion-based model (Stable Diffusion) to synthesize data by faithfully recreating crucial vascular structures in the retina, vital for detecting eye diseases by using the Ocular Disease Intelligent Recognition dataset. Our goal was to augment retinography images for ocular disease diagnosis using diffusion-based models, optimizing the outputs of the fine-tuned Stable Diffusion model, and ensuring the generated data closely resembles real-world scenarios. This strategic approach resulted in improved performance in classification models and augmentation outperformed traditional methods, exhibiting high precision rates ranging from 85% to 76.2% and recall values of 86%, and 75% for 5 classes. Beyond performance enhancement, we demonstrated that the inclusion of synthetic data, coupled with data reduction using the t-SNE method, effectively addressed dataset imbalance. As a result of synthetic data addition, notable increases of 3.4% in the precision metric and 12.8% in the recall metric were observed in the 7-class case. Strategically synthesizing data addressed underrepresented classes, creating a balanced dataset for comprehensive model learning. Surpassing performance improvements, this approach underscores synthetic data's ability to overcome the limitations of traditional methods, particularly in sensitive medical domains like ocular disease diagnosis, ensuring accurate classification. The codes of the study will be shared on GitHub in a way that benefits everyone interested: https://github.com/miralab-ai/generative-data-augmentation.Article Citation - WoS: 2Citation - Scopus: 2Exploring the Use of Water-Extracted Flaxseed Hydrocolloids in Three-Dimensional Cell Culture(Mary Ann Liebert, inc, 2024) Yildirim-Semerci, Ozum; Bilginer-Kartal, Rumeysa; Arslan-Yildiz, AhuPlant-derived hydrocolloids offer promising prospects in biomedical applications. Among these, Flaxseed hydrocolloid (FSH) can form a soft, elastic, and biocompatible hydrocolloid with tunable viscosity and superior swelling capacity, making it an attractive scaffold. This study introduces a green extraction method for FSH, employing a single-step aqueous extraction process and fabrication of FSH scaffold. Despite growing interest, the pristine form of FSH has not been investigated for sustainable long-term three-dimensional (3D) cell culture. Here, FSH scaffolds were thoroughly characterized for their morphological, chemical, mechanical, and biological properties. 3D cell culture experiments were conducted using NIH-3T3 mouse fibroblast cells, and cell viability was assessed using live/dead and Alamar Blue assays. High cell viability was sustained for long term compared with 2D cell culture. Cell adhesion and 3D cellular morphology on FSH scaffold for 30 days were monitored by scanning electron microscopy analysis. Also, collagen type-I and F-actin expressions were analyzed by immunostaining after 30 days of culture, resulting in 5- and 4-fold increments of fluorescence intensity, respectively. Results indicate sustained cell viability in the long term and favorable cell-material interaction, demonstrating the potential of FSH as a scaffold. This study emphasizes the importance of the green extraction approach, improving the biocompatibility and functionality of FSH tissue engineering applications. Impact Statement Flaxseed hydrocolloid (FSH) is a promising scaffold for biomedical applications due to its biocompatibility and tunable properties. This study introduces a green extraction method for FSH and evaluates its use in 3D cell culture with NIH-3T3 mouse fibroblast cells. The findings indicate high cell viability and enhanced cell-material interactions over 30 days, highlighting the potential of FSH for tissue engineering.Article Evaluation of Partially Reduced Keratins Extracted From Wool Fibers as a Hydrogel Forming Biomaterial(inst Tecnologia Parana, 2024) Yalcin, Damla; Top, AybenIn this study, it was aimed to prepare low-cost hydrogel from reduced keratin. Keratin proteins were obtained from Merino wool via three extraction methods. In the first method, keratins were reduced using sodium sulfide. In the second method, keratins extracted with the first method were precipitated with HCl. Urea, EDTA, and sodium sulfide were used in the third method. Extraction yields of method 1, method 2, and method 3 were determined as 44 +/- 2, 27 +/- 1, and 42 +/- 2 %, respectively. For all extraction methods, the average value of the free thiol amounts was obtained as 0.06 +/- 0.02 mmol SH/g keratin. A considerable portion of the highly polydisperse keratins was separated between similar to 40 kDa and similar to 60 kDa in the SDS-PAGE gel, and this fraction corresponds to alpha-keratin proteins with low sulfur content. A strong band at similar to 1654 +/- 1 cm(-1) detected in the FTIR spectra of the keratins confirms mainly alpha-helical secondary structure. The self- standing hydrogel was obtained upon incubating 15 wt. % keratin solution at 37 degrees C. Storage modulus and loss modulus of the hydrogel were determined as 1.3 +/- 0.08 kPa and 0.1 +/- 0.015 kPa, respectively. The keratin hydrogel is not cytotoxic to L929 mouse fibroblast cells, suggesting that this affordable hydrogel can be applied as a drug delivery/encapsulation system and in wound healing.Article On the Rings Whose Injective Right Modules Are Max-Projective(World Scientific Publ Co Pte Ltd, 2024) Alagoz, Yusuf; Buyukasik, Engin; Yurtsever, Haydar BaranRecently, right almost-QF (respectively, max-QF) rings that is the rings whose injective right modules are R-projective (respectively, max-projective) were studied by the first two authors. In this paper, our aim is to give some further characterizations of these rings over more general classes of rings, and address several questions about these rings. We obtain characterizations of max-QF rings over several classes of rings including local, semilocal right semihereditary, right non-singular right Noetherian and right non-singular right finite dimensional rings. We prove that for a ring R being right almost-QF and right max-QF are not left-right symmetric. We also show that right almost-QF and right max-QF rings are not closed under factor rings. This leads us to consider the rings all of whose factor rings are almost-QF and max-QF.Article Citation - WoS: 1Effect of Mechanical Pre-Treatment on the Recovery Potential of Rare-Earth Elements and Gold From Discarded Hard Disc Drives(Springer, 2024) Habibzadeh, Alireza; Kucuker, Mehmet Ali; Gokelma, MertolThe growing demand for rare-earth elements (REEs) and their limited availability have made REEs critical with high supply risk. E-waste, particularly waste electrical and electronic equipment (WEEE), offers a valuable secondary source. This study assesses the impact of mechanical pre-treatment on the recovery of REEs and gold from discarded hard disk drives (HDDs). We compared recovery efficiencies of REEs and Au using separation techniques, particle sizing, and chemical analyses between two pre-treatment methods: shredding and manual disassembly. Shredding, common in electronic waste processing, leads to oxidation and significant loss of critical raw materials (CRMs), while manual disassembly preserves clean, and non-oxidized NdFeB magnets for magnet-to-magnet recycling. Manually disassembled HDDs were directly analyzed to determine recyclable quantities of REEs and gold. Shredded HDDs underwent sieving, density, and magnetic separation, followed by demagnetization and chemical analysis. Results indicate shredding causes a 73.9% loss of REEs and a 43.8% loss of Au compared to manual disassembly, with increased oxidation due to finer particles. These findings suggest that while shredding is adequate for recovering ferrous and aluminum fractions, manual disassembly is essential for maximizing REE recovery.Article Stabilisation of Linear Waves With Inhomogeneous Neumann Boundary Conditions(Taylor & Francis Ltd, 2024) Ozsari, Turker; Susuzlu, IdemWe study linear damped and viscoelastic wave equations evolving on a bounded domain. For both models, we assume that waves are subject to an inhomogeneous Neumann boundary condition on a portion of the domain's boundary. The analysis of these models presents additional interesting features and challenges compared to their homogeneous counterparts. In the present context, energy depends on the boundary trace of velocity. It is not clear in advance how this quantity should be controlled based on the given data, due to regularity issues. However, we establish global existence and also prove uniform stabilisation of solutions with decay rates characterised by the Neumann input. We supplement these results with numerical simulations in which the data do not necessarily satisfy the given assumptions for decay. These simulations provide, at a numerical level, insights into how energy could possibly change in the presence of, for example, improper data.Article Influence of Intra-Ply Discontinuities on the Mechanical Behavior of Continuous E-Glass Fiber Reinforced Composites(Sage Publications Ltd, 2024) Kilicoglu, Ahmet Suha; Tanoglu, Metin; Bilmez, Sinan Ali; Gunes, Mehmet Deniz; Erdogan, Hakan SalihThis study examines how structural discontinuities created during production affect glass fiber-reinforced composite plates. Due to geometrical constraints, the composite microstructure's discontinuities can be categorized as inter-ply and intra-ply. Material testing was conducted at the coupon level as an initial step to ascertain material characteristics. Two full-scale models of intra-ply composite samples were manufactured by employing layers of glass fiber-reinforced prepregs. Discontinuities were generated in the samples using a computer numeric control cutter and then manually applied. The discontinuities' impact on the composite laminate's mechanical properties was assessed through full-scale pieces using three-point bending quasi-static tests. Servo-hydraulic actuators were used to conduct tests on the items. The experimental test results were compared with CAE analysis predictions by evaluating sectional fiber volume fraction. The characteristics of local discontinuities were analyzed using a microscope to enhance the findings of the CAE model. This comprehensive approach offers insights into the intricate connection between internal structural inconsistencies and the mechanical properties of continuous glass fiber-reinforced materials. It supports optimizing composite manufacturing processes and improves composite parts' structural reliability. Dislocation areas were found to result in the formation of resin-rich zones in this investigation. The exothermic curing process in the component's zones results in elevated temperatures, leading to a color change in the resin from clear to yellow. The yellow areas are easily recognizable and show decreased mechanical durability.Article Citation - WoS: 8Citation - Scopus: 9Comprehensive Comparison of Different Gridded Precipitation Products Over Geographic Regions of Türkiye(Spie-soc Photo-optical instrumentation Engineers, 2024) Khorrami, Behnam; Sahin, Onur Gungor; Gunduz, OrhanThe traditionally used rain gauge stations provide the most reliable data on the spatiotemporal distribution of precipitation; however, they are limited in space and time. As an alternative to field observations, the gridded precipitation products (GPPs) offered by remote sensing missions are widely used. On account of the uncertainties associated with the GPPs, they have to be quality-checked for confidence in application over the region of interest. Although accuracy assessment of precipitation data is a common task, there is a gap in the literature regarding a comprehensive assessment of the currently available GPPs. In this study, 14 GPPs were used to investigate their performance in catching the spatio-temporal characteristics of precipitation over geographic regions of T & uuml;rkiye. According to the results, integrated multi-satellite retrievals for Global Precipitation Measurement (IMERG), multi-source weighted-ensemble precipitation (MSWEP), and Tropical Rainfall Measuring Mission (TRMM) show better performance on monthly and annual scales while on the climatology scale, CHELSA, Climate Hazards Group Infrared Precipitation with Station, ERA5, and ERA5-Land also manifest better performance. The mean monthly correlation over Aegean Region (AEG), Marmara Region (MAR), Central Anatolian Region (CAR), Mediterranean Region (MED), Black Sea Region (BSR), East Anatolian Region (EAR), and South East Anatolian Region (SEA) are 0.77, 0.81, 0.77, 0.80, 0.79, 0.77, and 0.77, respectively. The annual assessment suggests that over the MAR, CAR, MED, and SEA, the IMERG mission performs very well. While TRMM showcases its best performance in the AEG, MED, BSR, and EAR, MSWEP performs well in the BSR and SEA Region. Overall, taking the country-average results into account, it can be stated that among the used GPPs, TRMM, MSWEP, and IMERG yield the best results for T & uuml;rkiye as a whole.