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  • Öge
    A bibliometric analysis of metaverse technologies in healthcare services
    (Springer, 2024) Damar, Seçkin ; Hançerlioğulları Köksalmış, Gülşah ; 0000-0002-2713-2738 ; 0000-0002-2551-541X ; Endüstri Mühendisliği
    A bibliometric analysis was conducted to examine healthcare metaverse research using 3721 Web of Science publications covering the period 1994–2022. Using bibliometric and bibliographic link network analyses, this study aimed to uncover emerging trends, country and university contributions, author collaborations, and common metaverse themes. Contrary to expectations, inconsistent correlations between publication volume and citation impact emerged. This pioneering research evaluated empirical bibliometric laws, identified influential entities, and provided a structured thematic categorization for metaverse studies. Serving as the first comprehensive investigation of the healthcare metaverse, this study lays a solid foundation for subsequent research efforts and guides further scholarly research.
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    A comprehensive study on methane adsorption capacities and pore characteristics of coal seams: implications for efficient coalbed methane development in the Soma Basin, Türkiye
    (Springer, 2024) Esen, Olgun ; Fişne, Abdullah ; 0000-0001-8015-0962 ; 0000-0001-7449-0573 ; Maden Mühendisliği
    This study represents a comprehensive assessment of methane adsorption capacity and pore characteristics for the coal seams of the Soma Basin in Western Türkiye, with a focus on their implications for coalbed methane potential. Twenty-one exploration wells were utilized to obtain coal samples from the kP1 and kM2 coal seams in the Kınık coalfield of the Soma Basin. High-pressure methane adsorption experiments using the indirect gravimetric method were conducted to quantify the storage capacities of these coal seams. Results revealed a wide range of methane adsorption capacities, ranging from 10.5 to 28.3 m3/t (air-dry basis), indicating significant methane storage potential for the kP1 and kM2 coal seams. The gas contents, ranging from 1.1 to 4.3 m3/t (as-received basis), suggested that the coal seams were undersaturated. Low-pressure N2/CO2 adsorption tests, along with standard proximate and gross calorific value analyses, were performed to investigate the influence of coal quality and pore characteristics on methane adsorption capacities. The findings demonstrated correlations between coal quality parameters and adsorption capacity, with ash yield showing a moderately negative correlation and fixed carbon content and gross calorific values exhibiting moderately positive correlations. Microporosity was identified as the critical factor governing methane adsorption, with a strong positive correlation observed between micropore surface areas and volumes and adsorption capacity. These results highlight the significant methane storage capacities of the coal seams in the Soma Basin and underscore the importance of micropores in determining methane adsorption capacity. The findings provide valuable insights for optimizing methane extraction and utilization in the region and offer important considerations for reservoir characterization and development strategies in similar low-rank coal deposits.
  • Öge
    A distance-based approach to fuzzy cognitive maps using pythagorean fuzzy sets
    (Springer, 2024) Bozdağ, Erhan ; Kadaifçi, Çiğdem ; 0000-0001-6900-5238 ; 0000-0003-4522-9071
    Fuzzy Cognitive Maps (FCMs) have been attracting researchers from a wide application area due to being easy to apply and interpret. Since its proposal, the method has been improved to satisfy the diverse needs of practitioners such as solving different types of problems and representing particular types of uncertainty. The classical FCMs depend highly on the decision-maker judgments and the uncertainty inherent in the judgments deserves significant attention. Although there are several fuzzy extensions integrated into FCMs, the uncertainty caused by the lack of knowledge, the hesitancy of decision makers, and also the limited capacity of humans to deal with pre-defined rules should be considered. To address this issue, a new distance-based approach integrating Pythagorean Fuzzy Sets and FCMs is proposed. To the best of our knowledge, this is the first time this extension is integrated into FCMs. Besides allowing to represent the uncertainty until the end of the calculations, the new approach offers decision makers an easier and more flexible way to assess the strength of existing causal relationships. To provide a comparison between the proposed approach and the classical FCMs, two real-life applications are selected as case studies.
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    A drug prescription recommendation system based on novel DIAKID ontology and extensive semantic rules
    (Springer, 2024) Göğebakan, Kadime ; Ulu, Ramazan ; Abiyev, Rahib ; Şah, Melike ; 0000-0002-2584-9647 ; 0000-0003-1461-2764 ; 0000-0002-3085-6219 ; 0000-0003-3869-7205 ; Bilişim Sistemleri Mühendisliği
    According to the World Health Organization (WHO) data from 2000 to 2019, the number of people living with Diabetes Mellitus and Chronic Kidney Disease (CKD) is increasing rapidly. It is observed that Diabetes Mellitus increased by 70% and ranked in the top 10 among all causes of death, while the rate of those who died from CKD increased by 63% and rose from the 13th place to the 10th place. In this work, we combined the drug dose prediction model, drug-drug interaction warnings and drugs that potassium raising (K-raising) warnings to create a novel and effective ontology-based assistive prescription recommendation system for patients having both Type-2 Diabetes Mellitus (T2DM) and CKD. Although there are several computational solutions that use ontology-based systems for treatment plans for these type of diseases, none of them combine information analysis and treatment plans prediction for T2DM and CKD. The proposed method is novel: (1) We develop a new drug-drug interaction model and drug dose ontology called DIAKID (for drugs of T2DM and CKD). (2) Using comprehensive Semantic Web Rule Language (SWRL) rules, we automatically extract the correct drug dose, K-raising drugs, and drug-drug interaction warnings based on the Glomerular Filtration Rate (GFR) value of T2DM and CKD patients. The proposed work achieves very competitive results, and this is the first time such a study conducted on both diseases. The proposed system will guide clinicians in preparing prescriptions by giving necessary warnings about drug-drug interactions and doses.
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    A novel image denoising technique with Caputo type space–time fractional operators
    (Springer, 2024) Tanrıöver, Evren ; Kiriş, Ahmet ; Tunga, Burcu ; Tunga, M. Alper ; 0000-0003-4098-3155 ; 0000-0002-3687-6640 ; 0000-0001-7318-964X ; 0000-0003-3551-4549 ; Matematik Mühendisliği
    A novel image denoising model, namely Full Fractional Total Variation (TVFF), based on the Rudin-Osher-Fatemi (ROF) and the fractional total variation models is presented. The leading advantage of TVFF model is that it uses fractional derivatives with length scale parameters instead of ordinary derivatives with respect to both time and spatial variables in the diffusion equation. The Riesz–Caputo fractional derivative operator is used to disperse nonlocal influence throughout all directions, whereas the Caputo fractional derivative concept is employed for time fractional derivatives. Therefore, the influence of neighboring pixels is given greater weight compared to those situated farther away and this reflects the consideration behind denoising process better. Moreover, the numerical approach is constructed, and its stability and convergence properties are thoroughly examined. To show the superiority of our model, the denoised images are subjected to visual and numerical comparisons using metrics such as the Signal-to-Noise Ratio (SNR), the Structural Similarity Index Measure (SSIM) and the Edge-Retention Ratio (ERR). The performance of the TVFF method is evaluated under various types of noise, including Poisson, Speckle, and Salt & Pepper, and the results are compared with those obtained using Gauss and Median Filters. Furthermore, the proposed method is applied to both blind and synthetic images, thereby showcasing its versatility and applicability across diverse datasets. The outcomes showcase the substantial potential of our enhanced model as a versatile and efficient tool for image denoising.
  • Öge
    Alternative plant-based gluten-free sourdough pastry snack production by using beetroot and legumes: characterization of physical and sensorial attributes
    (American Chemical Society, 2024) Yolcu, Zeynep ; Demircan, Evren ; Mertdinç, Zehra ; Aydar, Elif Feyza ; Özçelik, Beraat ; 0000-0002-1810-8154 ; Gıda Mühendisliği
    Objective of this study was to design a formula of a sourdough pastry snack by adding starter inoculum into the formulation which was obtained by the fermentation process through beetroot (Beta vulgaris) puree with black-eyed pea (Vigna unguiculata) and fava bean (Vicia faba). With this development process, it was aimed to review the functional impact of legumes as gluten replacement and emphasize the importance regarding physical and sensory attributes in a pastry snack product. First, a starter inoculum was developed based on modification of the shalgam fermentation process with legumes. An experimental design suggested by the response surface methodology was used to optimize its microbial properties and level of antioxidants with the factors of amounts of beetroot puree, fava bean/black-eyed pea ratio, and fermentation time. In the second part, this starter inoculum was mixed with fava bean flour to obtain a sourdough pastry snack (FBS) with improved physical and sensory attributes and compared to the wheat control sourdough (WCS) pastry snack after the baking process. According to the optimization results to produce starter inoculum with the optimum results of lactic acid bacteria 9.55 log cfu/mL, the level of antioxidant activity 91.86 μM TE/mL, and total yeast level 6.96 log cfu/mL; 75 mL of beetroot puree, 100% for fava bean, and fermentation for 24 h were obtained. Compared to WCS, FBS has approximately 16% higher hardness values. Also, a significant difference was observed for stiffness and springiness among samples. The retention of moisture was higher in the first 4 days following the storage for 8 days; the moisture content continuously decreased with the final moisture content of 12.6%. When compared with the results of textural profile analysis in terms of hardness, stiffness, and springiness, sensory results were correlated. Comparing the overall acceptability of the FBS to WCS, FBS was from moderate to higher scores, which indicated that it could be a promising alternative to chemically developed snack products and a preferred product for people suffering from celiac disease and other gluten intolerances.
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    An integrated groundwater vulnerability and artificial recharge site suitability assessment using GIS multi-criteria decision making approach in Kayseri region, Turkey
    (Springer, 2024) Mouhoumed, Rachid Mohamed ; Ekmekçioğlu, Ömer ; Özger, Mehmet ; 0000-0001-7346-4699 ; 0000-0002-7144-2338 ; İnşaat Mühendisliği
    Groundwater resources worldwide face significant challenges that require urgent implementation of sustainable measures for effective long-term management. Managed aquifer recharge (MAR) is regarded as one of the most promising management technologies to address the degradation of groundwater resources. However, in urban aquifers, locating suitable areas that are least vulnerable to contamination for MAR implementation is complex and challenging. Hence, the present study proposes a framework encapsulating the combined assessment of groundwater vulnerability and MAR site suitability analysis to pinpoint the most featured areas for installing drywells in Kayseri, Turkey. To extrapolate the vulnerable zones, not only the original DRASTIC but also its multi-criteria decision-making (MCDA)–based modified variants were evaluated with regard to different hydrochemical parameters using the area under the receiver operating characteristic (ROC) curve (AUC). Besides, the fuzzy analytical hierarchy process (FAHP) rationale was adopted to signify the importance level of criteria and the robustness of the framework was highlighted with sensitivity analysis. In addition, the decision layers and the attained vulnerability layer were combined using the weighted overlay (WOA). The findings indicate that the DRASTIC-SWARA correlates well with the arsenic (AUC = 0.856) and chloride (AUC = 0.648) and was adopted as the vulnerability model. Groundwater quality parameters such as chloride and sodium adsorption ratio, as well as the vadose zone thickness, were found to be the most significant decision parameters with importance levels of 16.75%, 14.51%, and 15.73%, respectively. Overall, 28.24% of the study area was unsuitable for recharge activities with high to very high vulnerability, while the remaining part was further prioritized into low to high suitability classes for MAR application. The proposed framework offers valuable tool to decision-makers for the delineation of favorable MAR sites with minimized susceptibility to contamination.
  • Öge
    Analytical and numerical modeling on strengths of aluminum and magnesium micro-lattice structures fabricated via additive manufacturing
    (Springer, 2024) Sun, Yeting ; Akçay, Fuzuli Ağrı ; Wu, Dazhong ; Bai, Yuanli ; 0000-0002-5116-0069 ; Makina Mühendisliği
    Bioinspired lattice structures have a wide range of applications in aerospace, automotive, energy, and medical device industries due to their high strength-to-weight ratio. Although experimental and numerical modeling methods have been extensively used to characterize the compressive behavior of lattice structures, an accurate analytical model has great values in material/structure designs and applications. In this study, a new analytical model is developed for two configurations based on limit analysis in the plasticity theory to predict the compressive strengths of micro-lattice structures (MLS). The model is also discussed for determining the amounts of stretching-dominated deformation and bending-dominated deformation. A comparative study is performed between analytical solutions and experimental results of AlSi10Mg (aluminum alloy) and WE43 (magnesium alloy) MLS additively manufactured via selective laser melting (SLM). Finite element simulations using beam elements are conducted to evaluate the accuracy of the analytical solution. Analytical results, finite element simulation results, and the experimental results are in a good agreement with both AlSi10Mg and WE43 MLS. The shear band formation, as a main failure mode of MLS, is also studied and evaluated using the classical Rudnicki–Rice’s criterion, for which a reasonably good accuracy is demonstrated.
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    Antifungal Activities of Different Essential Oils and Their Electrospun Nanofibers against Aspergillus and Penicillium Species Isolated from Bread
    (American Chemical Society, 2022) Karbancıoğlu Güler, Funda ; Devecioğlu, Tuğba ; Türker, Mustafa ; 0000-0001-6576-0084 ; 0000-0001-6681-0944 ; Food Engineering
    Mold growth, especially Aspergillus spp. and Penicillium spp., deteriorates the quality of bakery products. Essential oils (EOs) have been categorized as good natural antimicrobials. Hereby, this study aimed to evaluate the antifungal activity of six EOs, ginger, cumin, cinnamon, black pepper, origanum, and clove, and their volatile compounds against fungal strains isolated from bread: Penicillium carneum DDS4, Aspergillus flavus DDS6, and Aspergillus niger DDS7 by disc diffusion and disc volatilization methods, respectively. Among EOs, cumin, cinnamon, origanum, and clove were found to be effective against fungal strains, and their minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were determined. The observed lowest MIC value of EOs was obtained at 1000 μg/mL concentration, and the lowest MFC value was obtained from the results of clove at a concentration of 1000 μg/mL. Based on the MIC and MFC values, clove and cinnamon EOs were found to be more effective at lower concentrations. Electrospun nanofiber films of clove and cinnamon were produced with 6% poly(vinyl alcohol) (PVA), 2% β-cyclodextrin (β-CD), and 2% EO to overcome the unfavorable sensory impact of EOs on food products. The inhibitory activity of cinnamon EO film (2.64–2.51 log(CFU/mg)) was considerably lower than clove EO film (3.18–3.24 log(CFU/mg)) against P. carneum DDS4 and A. niger DDS7. Furthermore, these nanofiber films prevented fungal growth on bread samples visibly and were shown to be an alternative application for active food packaging.
  • Öge
    Appraising science-policy interfaces in local climate change policymaking: Revealing policymakers’ insights from Izmir Development Agency, Turkey
    (Elsevier, 2022) Eroğlu, Mehmet ; Öğüt Erbil, Aslı ; https://orcid.org/0000-0003-3127-8905 ; Department of Sociology
    Developing knowledge-based and usable climate change policies requires establishing science-policy interfaces through which knowledge producers and policymakers cooperate. Current research reveals that co-production- based interfaces dominated neither by knowledge producers nor policymakers succeed in facilitating the transformation of knowledge into politics. From this point of view, this paper explores how Izmir Development Agency (IZKA), a regional development agency in Turkey, utilizes scientific knowledge and science-policy interfaces in its activities on climate change. Based on the analysis of agency documents and semi-structured interviews with experts from and outside IZKA, the findings indicate that IZKA thrives in integrating scientific knowledge on climate change in its activities drawing from multi-stakeholder and multi-level science-policy interfaces that have significant similarities with the co-production model. In these interfaces, international, national, regional, and local stakeholders share their resources, knowledge, and experience on climate change. Although legal, geographical, and demographic conditions also have an impact, the main reason behind IZKA’s success is the agency’s climate-focused vision that shapes decisions, strategies, organizational structure, and activities. In parallel to the indicated finding, this paper also discloses that the perspective of not prioritizing climate change and considering the potential benefits as only “co-benefit” does not yield results with the desired efficiency. Another finding is that even though the national government is the main actor on climate in Turkey, development agencies are capable of carrying out transformative activities in their regions, albeit limited.
  • Öge
    Assessment of geothermal power potential in Buyuk Menderes Basin, Turkey
    (Elsevier, 2020) Yamanlar, Şenol, ; Korkmaz Başel, Emine Didem ; Serpen, Ümran ; https://orcid.org/0000-0001-7713-9551 ; Petroleum and Natural Gas Engineering Department
    Turkey’s installed geothermal capacity for power generation as of December 2019 is 1500 MWe. Most of this installed capacity is generated by the power plants located in the Buyuk Menderes graben. Geologically Buyuk Menderes graben is a huge structure having several discovered geothermal resources and can be considered as a geothermal basin. The aim of this study is to estimate the geothermal power potential of Buyuk Menderes graben. To achieve this object, a stochastic methodology, which is used to evaluate hydrocarbon-bearing basins, is adapted from the oil and natural gas industry. This methodology provides a way to quantify the geothermal potential in a range of possible values by evaluating the individual fields in the basin using stored heat technique. A total of 34 (21 proven and 13 probable occurrences) geothermal fields having medium to high temperature (T ≥ 100 °C) values are evaluated using the Monte Carlo Simulation technique. In these simulations, available geological, geochemical, geophysical data are used along with the data obtained from the drilled wells in the region. The power potential (MWe) values for 21 proven fields in terms of P10, P50 and P90 values are determined to be 888, 1077 and 1311 MWe, respectively. Considering the 13 probable occurrences along with the proven fields, the lower and upper limits of the total power potential (P10 and P90) are 1156 and 1580 MWe, respectively. Moreover, the power potentials are also evaluated under the presence of uncertainty. By assigning 5/13, 6/13, and 7/13 probability values for the 13 probable occurrences, overall geothermal power potential P10 values are estimated as 1041, 1075, and 1101 MWe, respectively.
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    Assessment of Microbial Diversity during Thermophilic Anaerobic Co-Digestion for an Effective Valorization of Food Waste and Wheat Straw
    ( 2022-12-21) Yangın Gömeç, Çiğdem ; Agnihotri, Swarnima ; Ylitervo, Päivi ; Sárvári Horváth, Ilona ; 0000-0003-3519-4821 ; Environmental Engineering
    In this study, predominant bacterial and archaeal populations and their roles during anaerobic mono-digestion of food waste (FW) and co-digestion of FW with straw pellets (SP) at thermophilic temperature (53 ± 1 °C) were assessed by Next Generation Sequencing (NGS) analysis at organic loading rates (OLRs) of 3.0 and 7.0 gVS/L/d. Depending on the seed; results revealed that Firmicutes, Bacteroidetes, and Proteobacteria were, respectively the most prevalent bacterial phyla at both OLRs investigated. On the other hand, Euryarchaeota was dominated by methanogens playing crucial role in biogas production and correlated mainly with the activities of Methanobacteria and Methanomicrobia at class level. Acetoclastic Methanosaetae was the predominant genus at OLR = 3.0 gVS/L/d; however, shared the same predominance with hydrogenotrophic methanogens Methanospirillium at the highest OLR. Although no clear effect in response to straw addition at OLR of 3.0 gVS/L/d could be seen in terms of methanogenic archaea at genus level, hydrogenotrophic methanogens revealed some shift from Methanobacterium to Methanospirillium at higher OLR. Nevertheless, no prominent microbial shift in the presence of wheat straw at increased OLR was likely due to adapted inoculation at start-up which was also demonstrated by relatively stable biogas yields during co-digestion.
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    Bridging climate change science and policy through TMNs in Turkey : CoM as a boundary-object
    (Oxford University Press, 2022) Öğüt Erbil, Aslı ; Eroğlu, Mehmet ; Türk, Ebru Gönül ; https://orcid.org/0000-0003-3127-8905 ; Department of Sociology
    This paper qualitatively investigates one of the influential transnational municipal networks, Covenant of Mayors for Climate and Energy (CoM)’s position in three Turkish municipal governments in bridging the climate change science and climate change policy gap. In the last two decades, the importance of science-based policymaking for climate mitigation and adaptation and transnational municipal networks empowered by municipalities that guide city policies linked to international agreements has been recognized. In this paper, we argue that CoM has acted as a boundary-object in producing climate change policies and plans in Turkish municipal governments. However, CoM has done so to a certain extent; their effectiveness was limited due to the general atmosphere on climate change policies in Turkey. We substantiate this claim through a two-layer examination: a case-specific analysis of three municipalities and semi-structured interviews with thirteen experts in climate change policy-related issues.
  • Öge
    Career paths of the International Mathematics Olympiad (IMO) medalists
    (Springer, 2024) Yuret, Tolga ; 0000-0002-6667-3465 ; Ekonomi Bölümü
    Each year, six exceptionally talented high school students from each country participate in the International Mathematics Olympiad (IMO). We thoroughly searched the internet to find the career paths of 2785 IMO medalists who participated in the competition from 1986 to 2005. We have found that the career paths of IMO medalists depend on their home country, despite their similar levels of mathematical talent. For example, the extent to which medalists studied abroad varies significantly among countries in the same geographical region and with comparable income levels. We also found that there is a high concentration in medalists’ foreign education. For example, MIT educated more foreign medalists than any country except for the United States both at the undergraduate and Ph.D. levels. Roughly half of the medalists ended up working abroad. Education is found to be an important channel for the migrant medalists. Although majority of the medalists were educated in mathematics, more than three quarters of their non-academic jobs are either software or economics-finance related jobs. Most medalists who became academics are specialized in mathematics. While the rate of becoming a mathematician academic is not dependent on the income level of the medalists' home country, those from higher-income countries tend to have higher academic performance.
  • Öge
    Combination of polyethylenimine and vanillin-based benzoxazine as a straightforward self-healable system with excellent film-forming ability
    (American Chemical Society, 2024) Gülyüz, Sevinç ; Kışkan, Barış ; 0000-0002-3028-6455 ; 0000-0001-9476-2054 ; Kimya Bölümü
    This study introduces a straightforward and efficient route for synthesizing self-healable polybenzoxazine networks by utilizing dynamic imine bond exchanges under mild conditions. The process involves combining polyethylenimines with aldehyde-functional bisbenzoxazine, which was produced from vanillin, using a Sc(OTf)3 catalyst and subjecting them to moderate heating at 150 °C. Remarkably, the resulting polybenzoxazine films exhibit good self-healing capabilities at low temperatures and pressures, without requiring any additional additives to facilitate the healing process. The degree of recovery was assessed through tensile tests, while rheologic measurements were utilized to analyze stress relaxation and activation energy of dynamic bonding, providing insights into the self-healing process. Additionally, comprehensive spectral characterizations and investigations of thermal behaviors were conducted to gain a deeper understanding of the material’s properties and performance. Moreover, the polybenzoxazine networks demonstrated enhanced hydrolysis stability compared to conventional imine-based systems, benefiting from the specific Mannich linkages and inherent hydrophobic nature of polybenzoxazines.
  • Öge
    Combined effects of zein nanofiber coating containing laurel (laurus nobilis) and air fryer cooking on quality properties of fish fillets during cold storage
    (American Chemical Society, 2024) Ceylan, Zafer ; Meral, Raciye ; Alav, Aslıhan ; Torusdağ, Gülşen Berat ; Bildik, Fatih ; Altay, Filiz ; 0000-0002-5484-866X ; Gıda Mühendisliği
    In this study, the effects of zein nanofibers (Zn) containing ground laurel leaves (GLL) and air fry cooking on the quality characteristics of Rainbow trout (Oncorhynchus mykiss) were investigated. The zein nanofibers possessing 335.8 ± 43.6 nm average diameters were fabricated containing GLL. The Fourier transform infrared spectroscopy (FTIR) results of the zein, Zn, GLL, and zein nanofibers containing GLL (LZn) confirmed the electrospinning encapsulation of GLL into Zn and their interactions. The effects of the combination of LZn coating and air fryer cooking of fish fillets on the quality characteristics during storage at 4 °C for 10 days were monitored in terms of oxidative and microbiological stability, color, and sensory parameters. As compared to the control, the combination of LZn coating and air fryer cooking provided a microbial limitation of up to 45.21% during the analysis (p < 0.05). The changes in ΔE values between the control and the LZn-coated samples were obtained as ≤7.56 during 6 days, but then a dramatic color difference was observed. Besides overall sensory acceptability, particularly the odor parameter in the cooked fish samples coated with LZn was significantly preferred (p < 0.05). The combination of LZn coating and air fryer cooking delayed the thiobarbituric acid increase in the fish meat samples (3.51 to 2.57 mg malondialdehyde (MDA)/kg) up to the third day of storage. This study showed that LZn coating is a very functional layer on the fish meat and could be applied for not only fresh fish meat but also other fresh meat products.
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    Comparison of dye adsorption of chitosan and polyethylenimine modified bentonite clays : optimization, isotherm, and kinetic studies
    (American Chemical Society, 2024) Kahya, Nilay ; Şen, Begüm ; Berber, Demet ; Öztekin, Nevin ; 0000-0002-7884-5113 ; 0000-0003-3676-5147 ; Kimya Mühendisliği
    The aim of this study was to compare the effect of modifying calcium bentonite (Bent-Ca) clay with two cationic polymers, chitosan (Chi) and polyethylenimine (PEI), on the removal of remazol black B (RB-B) dye from an aqueous solution. The samples were characterized by using scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The fractional factorial design of 2(6–1) was applied to investigate the effects of pH, temperature, amount of adsorbent, initial dye concentration, contact time, and shaking rate on the adsorption process. To further optimize RB-B removal from an aqueous solution, a Box–Behnken design with three factors and a response surface methodology was used. The optimum conditions were a pH of 3.77, a temperature of 40.45 °C, and an initial RB-B concentration of 77.27 mg L–1 for Bent-Ca-Chi, whereas for Bent-Ca-PEI, the optimum conditions were a pH of 5.53, a temperature of 41.06 °C, and an initial dye concentration of 238.89 mg L–1. To understand the adsorption behavior, the Langmuir and Freundlich isotherms were fitted to the experimental data. It was found that the Langmuir isotherm model matched well with the dye adsorption by Bent-Ca-Chi and Bent-Ca-PEI. The kinetics study was performed using three kinetic models: pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. Among these models, the RB-B dye kinetics were best represented by the pseudo-second-order model equation for the adsorbents.
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    Cryo-assisted nitrogen treatment for the fabrication of nanoengineered, mixed transition metal oxide anode from inorganic domestic waste, for lithium-ion batteries
    (Springer, 2024) Ashraf, Humza ; Karahan, B. Deniz ; 0000-0002-7839-2222 ; Metalurji ve Malzeme Mühendisliği
    A novel method for the fabrication of nanoengineered, mixed transition metal oxide anode active material is proposed based on implementing liquid nitrogen treatment during the chemical precipitation process, for the first time in open literature. Such interference in the precipitation is believed to change the surface energy of the nuclei leading to differentiation in the growth process. To exemplify this hypothesis with an environmentally friendly approach, kitchen scourer pads, an existing waste, are used as a starting material instead of using a mixture of primary quality metals’ salts. Therefore, in this study, firstly, an optimization is realized to leach the scouring pad with 100% efficiency. Then, by applying a conventional chemical precipitation to this leachate at pH 5.5, Sample 1-P is produced. Herein, innovatively liquid nitrogen treatment is carried out during the chemical precipitation to produce Sample 2-P. Lastly, these precipitates (Samples 1-P, 2-P) are calcinated in the air to form mixed transition metal oxide powders: Samples 1 and 2, respectively. Structural, chemical, and morphological characterizations are carried out to examine the effect of liquid nitrogen treatment on the powders’ properties. To discuss the effect of nitrogen treatment on the electrochemical performances of the anode active materials (Sample 1 and Sample 2), galvanostatic tests are realized. The results show that Sample 2 demonstrates a higher 1st discharge capacity (1352 mAh/g) and retains 62% of its performance after 200 cycles when 50 mA/g current load is applied. Moreover, this electrode delivers around 500 mAh/g at 1 A/g current load. The remarkable cycle performance of Sample 2 is believed to be related to the superior chemical, structural, and physical properties of the electrode active material.
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    Data-driven modeling for the prediction of stack gas concentration in a coal-fired power plant in Türkiye
    (Springer, 2024) Mohammadi, Mandana ; Saloğlu, Didem ; Dertli, Halil ; Ghaffari-Moghaddam, Mansour ; Mohammadi, Mitra ; 0000-0002-1119-1047 ; 0000-0003-0503-056X ; 0000-0001-6498-7594 ; 0000-0002-2925-7286 ; 0000-0003-3231-0946 ; Afet ve Acil Durum Yönetimi Anabilim Dalı
    In this research, deep learning and machine learning methods were employed to forecast the levels of stack gas concentrations in a coal-fired power plant situated in Türkiye. Real-time data collected from continuous emission monitoring systems (CEMS) serves as the basis for the predictions. The dataset includes measurements of carbon monoxide (CO), sulfur dioxide (SO2), nitrogen oxides (NOx), oxygen (O2), and dust levels, along with temperatures recorded. For this analysis, deep learning methods such as multi-layer perceptron network (MLP) and long short-term memory (LSTM) models were used, while machine learning techniques included light gradient boosted machine (LightGBM) and stochastic gradient descent (SGD) models were applied. The accuracy of the models was determined by analysing their performance using mean absolute error (MAE), root means square error (RMSE), and R-squared values. Based on the results, LightGBM achieved the highest R-squared (0.85) for O2 predictions, highlighting its variance-capturing ability. LSTM excelled in NOx (R-squared 0.87) and SO2 (R-squared 0.85) prediction, while showing the top R-squared (0.67) for CO. Both LSTM and LGBM achieved R-squared values of 0.78 for dust levels, indicating strong variance explanation. Conclusively, our findings highlight LSTM as the most effective approach for stack gas concentration forecasting, closely followed by the good performance of LightGBM. The importance of these results lies in their potential to effectively manage emissions in coal-fired power plants, thereby improving both environmental and operational aspects.
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    Defect Tolerant Logic Synthesis for Memristor Crossbars with Performance Evaluation
    (IEEE, 2018) Tunali, Onur ; Morgül, M. Ceylan ; Altun, Mustafa ; Elektronik ve Haberleşme Mühendisliği ; Electronics and Communication Engineering
    In this paper, we study defect-tolerant logic synthesis of memristor-based crossbar architectures. We propose a hybrid algorithm, combining heuristic and exact algorithms, that achieves perfect tolerance for 10-percent stuck-at open defect rates. Along with defect tolerance, we also consider area, delay, and power costs of the memristor crossbars to elaborate on two-level and multi-level logic designs.