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: 7Citation - Scopus: 7Bond-Based Peridynamic Fatigue Analysis of Ductile Materials With Neuber's Plasticity Correction(Springer, 2024) Altay, Ugur; Dorduncu, Mehmet; Kadioglu, Suat; Madenci, ErdoganThis study introduces an approach for performing bond-based (BB) peridynamic (PD) fatigue analysis of ductile materials. Existing BB PD fatigue models do not account for the effect of plastic deformation. The current approach addresses this by incorporating Neuber's plasticity correction concept into the fatigue model. Neuber's correction adjusts the stress and strain predictions of the PD elastic solution to account for local plastic deformation around crack tips. The PD fatigue simulations demonstrate the effectiveness of this method and improvements in fatigue life predictions by considering local plasticity effects. The numerical results first examine the response of a ductile plate without a crack under quasi-static monotonic loading. Subsequently, specimens exhibiting Mode I and mixed-mode crack propagation paths due to cyclic loading are analyzed. The PD predictions accurately capture the test data. Additionally, the model specifically investigates the effect of a stop hole on fatigue life.Article Citation - WoS: 4Citation - Scopus: 4Vo<sub>2</Sub>-based Dynamic Coding Metamaterials for Terahertz Wavefront Engineering(Springer, 2025) Akyurek, Bora; Noori, Aileen; Demirhan, Yasemin; Ozyuzer, Lutfi; Guven, Kaan; Altan, Hakan; Aygun, GulnurDigital coding metasurfaces (DCMS) offer a promising alternative to conventional metasurface designs for achieving common functionalities by controlling the phase of reflected or transmitted electromagnetic waves. Their simple unit cell designs allow for scalability across the THz spectrum and facilitate large-area fabrication. The true potential of DCMS lies in dynamical coding, which enables real-time reconfigurability through a tuning and/or switching mechanism. In this study, metasurfaces that achieve 1-bit dynamic coding of unit cells via thermally induced metal-insulator transition of VO2 layers are designed and fabricated. We investigate experimentally the beam splitting functionality at certain frequencies in the 0.50-0.75 THz range reflected from the stripe- and checkerboard patterned metasurface samples, and demonstrate the switching of this functionality under thermal illumination.Article Citation - WoS: 1Citation - Scopus: 1Phosphate Recovery From Digestate Using Magnesium-Modified Fungal Biochar(Springer, 2024) Surmeli, Recep Onder; Madenli, Ozgecan; Bayrakdar, Alper; Deveci, Ece Ummu; Calli, BarisMg-rich biochars have been used for the removal and recovery of phosphate (PO43-) and ammonium (NH4+) from waste streams. In this study, a novel magnesium-modified biochar (Mg-FBC) was synthesized by immobilizing waste magnesite dust (WMD) into Aspergillus niger fungal biomass for the adsorption of PO(4)(3- )and NH4+. Pyrolysis at various temperatures and analysis using techniques such as SEM-EDS, TGA, XRD, FTIR, and BET revealed that biochar produced at 650 degrees C (Mg-FBC650) exhibited enhanced surface properties favorable for effective adsorption. This improvement is attributed to the increased surface area facilitated by the hyphal structure of A. Niger and the effective dispersion of MgO on its surface. In experiments using a synthetic phosphate solution, the adsorption capacity reached 595 mg PO43-/g BC, fitting the Langmuir model at pH 9. In addition, experiments with the liquid fraction of a real digestate (LFD) showed adsorption capacities of 502 mg PO43-/g BC and 150 mg NH4+/g BC, respectively. The adsorption mechanism was elucidated through SEM-EDS, XRD, and FTIR analyses confirming that Mg-FBC650 facilitates a multifaceted adsorption mechanism, including adsorption, electrostatic attraction, chemical precipitation, and surface complexation. Consequently, PO43- was the primary adsorbate in the synthetic solution, while both PO43- and NH4+ were effectively removed from the LFD, indicating that Mg-FBC650 has substantial potential as an efficient adsorbent for nutrient removal. As a result, Mg-FBC650 is believed to hold significant potential as a slow-release and readily transferable bio-fertilizer, particularly suitable for application in soils deficient in organic matter, nitrogen, and phosphorus. [GRAPHICS] .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 Citation - WoS: 1Citation - Scopus: 1Studies on the Probiotic, Adhesion, and Induction Properties of Artisanal Lactic Acid Bacteria: To Customize a Gastrointestinal Niche To Trigger Anti-Obesity Functions(Springer, 2024) Kamber, A.; Albayrak, C. Bulut; Harsa, H. S.The primary goals of this work are to explore the potential of probiotic lactic acid bacteria's (LAB) mucin/mucus layer thickening properties and to identify anti-obesity candidate strains that improve appropriate habitat for use with the Akkermansia group population in the future. The HT-29 cell binding, antimicrobial properties, adhesion to the mucin/mucus layer, growth in the presence of mucin, stability during in vitro gastrointestinal (GI) conditions, biofilm formation, and mucin/mucus thickness increment abilities were all assessed for artisanal LAB strains. Sixteen LAB strains out of 40 were chosen for further analysis based on their ability to withstand GI conditions. Thirteen strains remained viable in simulated intestinal fluid, while most showed high viability in gastric juice simulation. Furthermore, 35.9-65.4% of those 16 bacteria adhered to the mucin layer. Besides, different lactate levels were produced, and Streptococcus thermophilus UIN9 exhibited the highest biofilm development. In the HT-29 cell culture, the highest mucin levels were 333.87 mu g/mL with O. AK8 at 50 mM lactate, 313.38 mu g/mL with Lactobacillus acidophilus NRRL-B 1910 with initial mucin, and 311.41 mu g/mL with Lacticaseibacillus casei NRRL-B 441 with initial mucin and 50 mM lactate. Nine LAB strains have been proposed as anti-obesity candidates, with olive isolates of Lactiplantibacillus plantarum being particularly important due to their ability to avoid mucin sugar consumption. Probiotic LAB's attachment to the colonic mucosa and its ability to stimulate HT-29 cells to secrete mucus are critical mechanisms that may support the development of Akkermansia.Editorial Preface(Springer, 2019) Daim,T.; Dabić,M.; Başoğlu,N.; Lavoie,J.R.; Galli,B.J.[No abstract available]Article Citation - Scopus: 9Enhancing Visible Light Photocatalytic Activity of Holmium Doped G-C3n4 and Dft Theoretical Insights(Springer, 2024) Yavuz,A.; Aydin,D.; Disli,B.; Ozturk,T.; Gul,B.; Gubbuk,I.H.; Ersoz,M.In the search of novel photocatalysts to increase the effect of visible light in photocatalysis, g-C3N4 (CN) has become a shining star. Rare earth metals have been used as dopant material to reinforce the photocatalytic activity of CN due to their unique electron configuration recently. In this present study, the pure and different amounts of Ho-doped g-C3N4 (HoCN) photocatalysts were successfully synthesized using urea as a precursor by the one-pot method. Morphological, structural, optical, and vibrational properties of the synthesized photocatalysts were characterized by SEM, EDX, XRD, TGA, XPS, FTIR, PL, TRPL, Raman, DRS, and BET analyses. In addition, theoretical calculations using density functional theory (DFT) were meticulously carried out to delve the changes in the structural and electronic structure of CN with holmium doping. According to calculations, the chemical potential, electrophilicity, and chemical softness are higher for HoCN, while HOMO–LUMO gap, dipole moment, and the chemical hardness are lower for the pure one. Thus, holmium doping becomes desirable with low chemical hardness which indicates more effectivity and smaller HOMO–LUMO gap designate high chemical reactivity. To determine the photocatalytic efficiency of the pure and doped CN photocatalysts, the degradation of methylene blue (MB) was monitored under visible light. The results indicate that holmium doping has improved the photocatalytic activities of CN samples. Most strikingly, this improvement is noticeable for the 0.2 mmol doped CN sample that showed two times better photocatalytic activity than the pure one. © The Author(s) 2024.Article Citation - WoS: 4Citation - Scopus: 3Enhancement of Post-Harvest Quality of Fresh Mandarins With Alginate-Based Edible Coating Containing Natamycin and Vanillin(Springer, 2024) Takma, Dilara Konuk; Korel, FigenEnvironmentally friendly technologies with regard to reducing the usage of commercial synthetic waxes are required for maintaining the quality of mandarin fruits during the post-harvest period. In this study, novel biocoatings that serve as a natural alternative to synthetic waxes were developed for obtaining sustained shelf life of freshly harvested mandarins. The effect of natamycin and vanillin as natural antimicrobial compounds on the post-harvest quality of mandarins were investigated by means of alginate-based edible coating. Alginate coating (1% w/v) formulations including 0.5% vanillin, 1.0% vanillin, 0.025% natamycin, 0.05% natamycin and without vanillin or natamycin were applied and compared with uncoated fruit as control. Weight loss, color change, fruit firmness, yeast and mold counts were examined over 21 days at 25 degrees C. Quality changes in mandarins such as losses of weight, color and softening changes were significantly delayed with alginate coatings. Brightness on the surfaces of fruits was improved by alginate coating layers. Fruit firmness decreased with storage time in control samples, while the firmness in coated samples remained relatively constant or increased. Moreover, yeast and mold counts considerably decreased (1.52 log cfu/g) for fruits coated with alginate coating incorporating 1% vanillin. Extension of the post-harvest storage of mandarin fruits could be performed by using alginate coating incorporating vanillin as an alternative to synthetic waxes.Article Citation - WoS: 1Citation - Scopus: 1Dynamic Compression of Metal Syntactic Foam-Filled Aluminum Tubes(Springer, 2024) Movahedi, Nima; Güden, Mustafa; Fiedler, Thomas; Taşdemirci, Alper; Sarikaya, Mustafa; Tasdemirci, Alper; Murch, Graeme E.; Belova, Irina V.; Guden, MustafaThe current research investigates the compressive properties of metal syntactic foam (MSF)-filled tubes at dynamic loads with an impact velocity of 4 m/s. For this purpose, A356 aluminum alloy syntactic foams were prepared using an infiltration casting technique with an incorporation of expanded perlite (EP) filler particles. The study involves the testing and comparison of both MSF samples and MSF-filled tubes under dynamic loading scenarios. In the case of MSF-filled tubes, aluminum tubes are either fully filled (FFT) or half-filled (HFT) with MSFs. The manufactured foams and foam cores have a similar macroscopic density across all tested samples. Under dynamic loading, the MSF, HFT, and FFT samples exhibit distinct and different deformation mechanisms. In MSFs, dynamic compression is controlled by shearing of the sample, whereas in HFTs and FFTs, dynamic deformation occurs through the folding and buckling of the tubes, accompanied by partial deformation of the MSF cores.Article Citation - WoS: 6Citation - Scopus: 6Microstructural Investigation of Discarded Ndfeb Magnets After Low-Temperature Hydrogenation(Springer, 2024) Habibzadeh, Alireza; Kucuker, Mehmet Ali; Cakir, Oznur; Gokelma, MertolDue to continuously increasing demand and limited resources of rare-earth elements (REEs), new solutions are being sought to overcome the supply risk of REEs. To mitigate the supply risk of REEs, much attention has recently been paid to recycling. Despite the more common recycling methods, including hydrometallurgical and pyrometallurgical processes, hydrogen processing of magnetic scrap (HPMS) is still in the development stage. Magnet-to-magnet recycling via hydrogenation of discarded NdFeB magnets provides a fine powder suitable for the production of new magnets from secondary sources. One of the crucial aspects of HPMS is the degree of recovery of the magnetic properties, as the yield efficiency can easily reach over 95%. The amount, morphology, and distribution of the Nd-rich phase are the key parameters to achieve the excellent performance of the magnet by isolating the matrix grain. Therefore, a better insight into the microstructure of the matrix grains and the Nd-rich phase before and after hydrogenation is essential. In this study, a low-temperature hydrogenation process in the range of room temperature to 400 degrees C was conducted as the first step to recycle NdFeB magnets from discarded hard disk drives (HDDs), and the hydrogenated powder was characterized by electron microscopy and X-ray diffraction. The results show that there are three different morphologies of the Nd-rich phase, which undergo two different transformations through oxidation and hydride formation. While at lower temperatures (below 250 degrees C) the degree of pulverization is higher and the experimental evidence of hydride formation is less clear, at higher temperatures the degree of pulverization decreases. The formation of neodymium hydride at higher temperatures prevents further oxidation of the Nd-rich phase due to its high stability.