Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Optimizing Inhibitor Injection in Geothermal Wells With Electrical Submersible Pump(Elsevier Ltd, 2025) Aydin, H.; Tezel, S.I.; Erol, S.Electrical submersible pump (ESP) is a reliable artificial lift method to extend productive lifespan of geothermal wells. In the geothermal industry a common practice involves installing ESPs below the well's flashing depth. This placement approach aims to mitigate the risk of mineral precipitation, which can occur when hot geothermal fluids transition to a two-phase state (liquid and vapor) as pressure decreases. Positioning the pump below the flashing depth also prevents pump's underloading and gas cavitation. The inhibitor injection line usually integrated around the ESP string and installed downstream of the ESP motor. However, this standard practice introduces a challenge regarding inhibitor performance. While this placement ensures effective distribution of inhibitors throughout the production flow, the extended travel time from the surface to the point of application at the ESP can diminish inhibitor effectiveness due to continuous exposure to high temperatures throughout the wellbore. This study proposes relocating the inhibitor injection point within the production tubing closer to the flashing depth. This reduces inhibitor travel time from 108 min to 48 min and has the potential to significantly improve inhibitor effectiveness. Consequently, the implementation of capillary tubing is anticipated to yield annual cost savings per wellbore of approximately USD 10,000, coupled with the mitigation of mineral deposits within the studied well equipped with ESP. To evaluate this approach, a wellbore simulation tool and PHREEQC were employed to dynamically model the pressure and temperature profiles alongside the geochemical evolution of the produced fluids in the wellbore. This modeling approach offers significant value by potentially enabling the optimization of inhibitor usage and reducing the length of required inhibitor injection line. © 2024 Elsevier LtdArticle 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: 7Citation - Scopus: 7Development of a Dopamine-Based Surface Modification Technique To Enhance Protein Fouling Resistance in Commercial Ultrafiltration Membranes(Elsevier, 2025) Onuk, Ecem; Gungormus, Elif; Cihanoglu, Aydin; Altinkaya, Sacide AlsoyThis study introduces a new method for modifying ultrafiltration membranes using dopamine polymerization to overcome issues such as prolonged polymerization times, potential pore narrowing, and insufficient formation of hydrophilic groups. The technique involves continuously supplying oxygen (O2) gas from the porous backside of the membrane while simultaneously applying an aqueous dopamine solution to the active top surface. TGA and XPS analyses revealed that 10 kDa commercial polysulfone (PSF) membranes coated with O2 backflow contained more dopamine than those modified using the classical method. Additionally, changes in contact angle and zeta potential values were more pronounced with the O2 backflow method. Dopamine coating for 10 and 20 min improved the pure water permeance of the PSF membrane, whereas a 40-min coating decreased it. Notably, the reduction in permeance was 2.5 times less with the O2 backflow method than with the classical method. The classical dopamine coating method did not enhance the PSF membrane's resistance to fouling during whey filtration; in fact, 20 and 40-min coatings caused more significant flux declines compared to the unmodified membrane. Conversely, 10 and 20 min of PDA coating under O2 backflow improved fouling resistance, though this benefit disappeared with a 40-min coating.Article Citation - Scopus: 6Lithium Extraction From Geothermal Brine Using Γ-Mno2: a Case Study for Tuzla Geothermal Power Plant(Elsevier Ltd, 2024) Toprak, S.; Yılmaz, Selahattin; Öncel, Ç.; Baba, Alper; Yılmaz, S.; Demir, Mustafa Muammer; Baba, A.; Koç, G.A.; Demir, M.M.Geothermal brines contain high concentrations of ions and form a source of various valuable elements. The isolation of the elements from their water systems is a great challenge when the gradual depletion of ores in mining is considered. Attempts have been made for a long time to isolate valuable elements from aqueous mixtures prepared in the laboratory. However, those studies might not reflect the complexity of natural systems and might yield results that deviate significantly from the performance in real field systems. In this study, sorption is used to extract lithium ions from a representative field, Tuzla Geothermal Power Plant (TGPP) Turkey, using a mini-pilot reactor introduced to the reinjection well of the plant. Electrolytic manganese dioxide (γ-MnO2), a relatively inexpensive material widely used as the cathode material in lithium-ion batteries, was employed as a sorbent material for lithium. The sorption/desorption performance of the novel γ-MnO2 was investigated under various conditions. Sorption is performed at 360K and 2 bars. The maximum sorption performance was obtained at 1 h in Tuzla GPP. The desorption experiments were performed in acidic solutions. The concentration of Li+ in the desorption solution was found to be 25 mg/L on average when 10 g of γ-MnO2 was dispersed into 30 mL of the acidic aqueous solution. The first desorption solution was used consecutively for collecting more Li+ ions through the desorption of fresh brine-treated powder samples (cumulative desorption). By repeating this process four times consecutively, 230 mg/L of Li+ was obtained in the desorption solution. Moreover, the reusability of the γ-MnO2 sorbent was examined. The sorbent powder showed almost 40% performance efficiency compared to virgin powder under the conditions employed in this study. The use of electrolytic γ-MnO2 sorbent for lithium adsorption was found to be a promising process for practical use in the separation of lithium from geothermal brines. © 2024Article Citation - WoS: 2Citation - Scopus: 2Small Wins in Practice: Learnings From 16 European Initiatives Working Towards the Transformation of Urban Food Systems(Elsevier Sci Ltd, 2024) Rao, Madhura; Luger, Jonathan; Regeer, Barbara J.; Lopez, Cristina Yacoub; Wilde, Danielle; Wilde, David; vander Meij, Marjoleine G.In this study, we examine how 16 initiatives across Europe are addressing 'wicked' food system issues by mobilising local networks and implementing small-scale but impactful changes in urban and peri-urban regions. To map the potential of these initiatives to contribute to large-scale change, we apply the Small Wins Framework proposed by Termeer & Dewulf (2019). By analysing data collected through interviews with participants working on initiatives spanning 13 cities across 9 European countries, we identify the manifestation of six propelling mechanisms that signal the capacity of small wins to bring about systemic change. Findings from this study reveal the presence of most mechanisms across the included initiatives. However, the ways in which these mechanisms appear depend on various factors such as stakeholder motivation, the maturity of the initiative, the need for additional funding, local food culture, and the regional and national political landscape among others. Our analysis indicates that the Small Wins Framework could be successfully used as a mapping tool in urban transformation processes, but it is likely to be more effective as a tool for reflexive monitoring rather than ex-post evaluation. Drawing on the impacts of various large-scale disruptions on the initiatives, we suggest that social, political, and economic shocks can present windows of opportunity to accelerate change and that initiatives performing well under such pressure should be supported in their pursuit of systems transformation. Lastly, we recommend non-linear growth strategies such as spreading, deepening, and expanding, as ways to compound the impact of small wins.Article Citation - WoS: 2Citation - Scopus: 2Stabilization of the First-Order Phase Transition Character and Enhancement of the Electrocaloric Effect by Na<sub>0.5</Sub>bi<sub>0.5< Substitution in Batio<sub>3</Sub> Ceramics(Royal Soc Chemistry, 2024) Karakaya, Merve; Gurbuz, Irem; Fulanovic, Lovro; Adem, UmutThe electrocaloric properties of BaTiO3-based Pb-free ferroelectric materials are widely investigated. One approach to achieving a large electrocaloric response is making use of the substantial polarization change associated with the first-order phase transition at the Curie temperature. To make use of this approach, we have investigated the electrocaloric response of (1 - x)BaTiO3-xNa0.5Bi0.5TiO3 (BT-NBT) ceramics for x = 0.05, 0.10, 0.20 and 0.30. For this BT-rich part of the solid solution, it is established that increasing the NBT content increases the tetragonality of the BaTiO3. We show that this increase in tetragonality with NBT substitution helps to maintain the first-order nature of the phase transition in BaTiO3 and correspondingly a large electrocaloric response, despite the simultaneous enhancement of relaxor ferroelectric character with the NBT substitution. A significantly larger effective electrocaloric temperature change (Delta Teff) of 1.65 K was obtained for the x = 0.20 sample under 40 kV cm-1, using the direct measurement of the electrocaloric effect, which is in reasonable agreement with the indirect measurements.Article Citation - WoS: 7Citation - Scopus: 10Community Co-Creation Through Knowledge (co)production: the Engagement of Universities in Promoting Rural Revitalization in China(Pergamon-elsevier Science Ltd, 2024) Lang, Wei; Gkartzios, Menelaos; Yan, Jialing; Chen, Tingting; Tan, ShuyingThe global discourse on the role of universities in rural revitalization has gained significant attention. The proposition is to leverage university expertise and resources to support rural development, including knowledge (co)production, community co-creation, and volunteerism - a practice that essentially bridges local actors and their knowledge with external actors and their knowledge. As advocated by UN Habitat III, the collaboration between universities and rural communities is an initiative exemplified by China's "Jointly Create a Beautiful Environment and a Happy Life" to enhance the built environment. This study aims to comprehensively investigate the implementation and outcomes of the "Rural Four Small Gardens" projects, which serve as a vital community development initiative within the Hongtang Village in Fengqing County, Yunnan Province, China. The research discusses those processes, observing opportunities for knowledge (co)production across diverse stakeholders in line with neo-endogenous rural development thinking. By exploring the co-creation approach employed in these projects, we seek to unravel how academia and local communities collaborate to address multifaceted challenges in rural areas. We argue that: 1) The engagement of rural communities through collaborative planning workshops serves as the fundamental cornerstone for university paired-up assistance; 2) the co-creation model for improving rural settlement necessitates the collective efforts of multiple stakeholders; 3) university faculty and students play pivotal roles during the process of service learning, practice research, and knowledge (co)production with villagers; and 4) Knowledge (co)production entails a dynamic process of coconstruction, co-governance, and resource sharing, exemplified by co-creation initiatives of home development, farmyard enhancement, and infrastructure projects. The research offers insights for global universities seeking to engage in similar paired-up assistance initiatives, underscores the significance of co-creation in rural development, and enlightens planning education in practice and service.Article Citation - WoS: 8Citation - Scopus: 8A Comprehensive Study of the Effect of Scanning Strategy on In939 Fabricated by Powder Bed Fusion-Laser Beam(Elsevier, 2024) Dogu, Merve Nur; Ozer, Seren; Yalcin, Mustafa Alp; Davut, Kemal; Obeidi, Muhannad Ahmed; Simsir, Caner; Brabazon, DermotThis study provides a comprehensive investigation into the effects of different scanning strategies on the material properties of IN939 fabricated using the PBF-LB process. The scanning strategies examined included alternating bi-directional scanning with rotation angles of 0 degrees, 45 degrees, 67 degrees, and 90 degrees between adjacent layers (named as shown), as well as alternating chessboard scanning with rotation angles of 67 degrees and 90 degrees (named as Q67 degrees and Q90 degrees). The results revealed that the 45 degrees and 67 degrees samples had the highest relative density, while the 0 degrees and Q67 degrees samples showed the highest average porosity. Moreover, various types of cracks, including solidification, solid-state, and oxide-induced cracks, were observed. Among the bi-directional scan samples, the 0 degrees sample displayed the most extensive cracking and the highest sigma max residual stress values in both XZ and XY planes. Conversely, the 45 degrees and 67 degrees samples exhibited fewer cracks. Notably, the lowest sigma max residual stress in the XZ planes among the bidirectional scan samples was observed in the 67 degrees sample. Additionally, microstructural analyses indicated differences in grain size and morphology, among the samples. Texture analysis indicated that the 0 degrees and 90 degrees samples exhibited strong cube textures, whereas the texture intensity weakened for the 45 degrees and 67 degrees samples. Moreover, the alternating chessboard scanning strategy led to rougher surfaces (higher Sa and Sz values) compared to the alternating bi-directional scanning strategy, regardless of the rotation angles. Furthermore, the microhardness values among the samples showed minimal variance, ranging between 321 + 14 HV and 356+ 7 HV.Article Citation - WoS: 16Citation - Scopus: 17Integrating Experimental and Machine Learning Approaches for Predictive Analysis of Photocatalytic Hydrogen Evolution Using Cu/G-c3n4(Pergamon-elsevier Science Ltd, 2024) Arabaci, Bahriyenur; Bakir, Rezan; Orak, Ceren; Yuksel, AsliThis study addresses environmental issues like global warming and wastewater generation by exploring waste-toenergy strategies that produce renewable hydrogen and treat wastewater simultaneously. Cu/g-C3N4 is used to evolve hydrogen from sucrose solution and the impact of reaction parameters such as pH (3, 5, and 7), Cu loading (5, 10, and 15 wt%), catalyst amount (0.1, 0.2, and 0.3 g/L), and oxidant (H2O2) concentration (0, 10, and 20 mM) on the evolved hydrogen amount is examined. Characterization study confirmed successful incorporation of Cu without significantly altering g-C3N4 properties. The highest hydrogen production (1979.25 mu mol g- 1 & sdot;h- 1) is achieved with 0.3 g/L catalyst, 20 mM H2O2, 5 % Cu loading, and pH 3. The experimental study concludes that Cu/g-C3N4 is an effective photocatalyst for renewable hydrogen production. In addition to the experimental investigations, various machine learning (ML) models, including Random Forest, Decision Tree, XGBoost, among others, are employed to analyze the impact of reaction parameters and forecast the quantities of produced hydrogen. Alongside these individual models, an ensemble approach is proposed and utilized. The R2 values of these ML models ranged from 0.9454 to 0.9955, indicating strong predictive performance across the board. Additionally, these models exhibited low error rates, further confirming their reliability in predicting hydrogen evolution.Article Citation - WoS: 2Citation - Scopus: 1Gliflozins, Sucrose and Flavonoids Are Allosteric Activators of Lecithin-Cholesterol Acyltransferase(Nature Portfolio, 2024) Niemela, Akseli; Giorgi, Laura; Nouri, Sirine; Yurttas, Betul; Rauniyar, Khushbu; Jeltsch, Michael; Koivuniemi, ArtturiLecithin-cholesterol acyltransferase (LCAT) serves as a pivotal enzyme in preserving cholesterol homeostasis via reverse cholesterol transport, a process closely associated with the onset of atherosclerosis. Impaired LCAT function can lead to severe LCAT deficiency disorders for which no pharmacological treatment exists. LCAT-based therapies, such as small molecule positive allosteric modulators (PAMs), against LCAT deficiencies and atherosclerosis hold promise, although their efficacy against atherosclerosis remains challenging. Herein we utilized a quantitative in silico metric to predict the activity of novel PAMs and tested their potencies with in vitro enzymatic assays. As predicted, sodium-glucose cotransporter 2 (SGLT2) inhibitors (gliflozins), sucrose and flavonoids activate LCAT. This has intriguing implications for the mechanism of action of gliflozins, which are commonly used in the treatment of type 2 diabetes, and for the endogenous activation of LCAT. Our results underscore the potential of molecular dynamics simulations in rational drug design.