IYTE GCRIS Database (Izmir Institute of Technology)
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Effect of Degassing on Scaling in Hypersaline System: Tuzla Geothermal Field, Turkey
No full textA serious issue with geothermal power plants is the loss of production and decline in power plant efficiency. Scaling, also known as mineral precipitation, is one of the frequently-observed issue that causes this loss and decreasing efficiency. It is heavily observed in the production wells when the geothermal fluid rises from the depths due to a change in the fluid’s physical and chemical properties. Scaling issue in geothermal power plants result in significant output losses and lower plant effectiveness. In rare instances, it might even result in the power plant being shut down. The chemistry of the geothermal fluid, non-condensable gases, pH, temperature and pressure changes in the process from production to reinjection, power plant type and design, and sometimes the materials used can also play an active role in the scaling that will occur in a geothermal system. ICP–MS was used to evaluate the chemical properties of the fluids. On the other hand, XRD, XRF and SEM were used to investigate the chemical and mineralogical compositions of the scale samples in analytical methods. For the numerical approach, PhreeqC and GWELL codes were used to follow the chemical reactivity of the geothermal fluid in Tuzla production well. The novelty of this study is to determine potential degassing point and to characterize the mineralogical assemblage formed in the well because of the fluid composition, temperature and pressure variations. During production, geothermal fluids degas in the wellbore. This causes a drastic modification of the chemistry of the Tuzla fluids. This is why it is focused the calculations on the nature of the minerals that are able to precipitate inside the well. According to simulation results, the degassing point is estimated to be about 105 m depth, consistent with the field observations. If a small quantity of precipitated minerals is predicted before the boiling point, degassing significantly changes the fluid chemistry, and the model predicts the deposition of calcite along with smaller elements including galena, barite, and quartz. The simulation results are consistent with the mineral composition of scaling collected in the well. © The Author(s) 2024
Can Fish Kills in Izmir Bay Be Explained With Satellite Image Analysis
No full textMotivated by a significant environmental crisis that emerged, where large numbers of dead fish washed ashore in İzmir Bay in the summer of 2024, this study aims to analyze the spatial and temporal dynamics of water quality in the inner bay prior to this incidence. By calculating indices such as NDCI, SABI, and UWQV, and correlating them with climatic data (air temperature, wind speed and relative humidity), this research seeks to document the occurrence and drivers of algal blooms in the bay using Landsat 8 and Sentinel-2 satellite data from 2017 to 2025. This is the first comprehensive study conducted for İzmir Bay that investigates the relationships between water quality indices and climatic variables. It also incorporates aerial analysis of the inner bay to provide a broader spatial perspective. A customized code using Python is developed for this study to independently download and analyze raw satellite data with respect to defined corrections/masks. The results of eight years of analysis indicated that critical conditions arise every summer with air temperatures reaching 40 degrees in the study area. Estimated aerial averaged NDCI index and Chl-a concentration values show a strong positive correlation with air temperature, particularly in the Spearman’s rank correlation (rs = 0.67 and 0.62 respectively), indicating a significant relationship between these parameters. Aerial distribution of the indices for the selected critical dates also revealed a significant increase in estimated Chl-a levels during the summer months, specifically in the regions determined from the risk maps produced as a result of this study. The areas with the greatest vulnerability coincide where Poligon, Ilıca streams in the south and Bostanlı and Çiğli streams in the north discharging into the bay. It is recommended that any planned external intervention methods for managing algal blooms should start with these highly vulnerable areas as presented by this study. © 2025 by the authors
Açık bilim, veri yönetimi, yapay zeka ve GCRIS
No full text17 Haziran 2025 tarihinde Fenerbahçe Üniversitesi’nde rektör, rektör yardımcıları ve akademisyenlerin katılımıyla düzenlenen "Açık Bilim, Veri Yönetimi, Yapay Zeka ve GCRIS" başlıklı seminerde; Açık Bilim, Veri Yönetimi ve Yapay Zeka araçlarının akademik kullanımını ile GCRIS’in araştırma etkisini artırma stratejilerinin anlatıldığı sunumdur
Vosub>2/Sub>-based Dynamic Coding Metamaterials for Terahertz Wavefront Engineering
No full textDigital 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
Fatigue Assessment of Copper-Brazed Stainless-Steel Joints for Plate Heat Exchangers
No full textCyclic pressures can cause fatigue failure in the brazed joints and plates of the plate heat exchangers (PHEs). This study examines the fatigue behavior of PHEs made from 316L and 304L steels brazed with copper foils employing strain-controlled fatigue tests to explore if 304L could replace 316L in the existing production line for cost reduction. Fatigue tests were conducted at four different load levels with a stress ratio of zero and a frequency of 5 Hz. Finite Element Analysis was used to assess strain distribution and estimate PHE lifespan based on generated strain versus number of cycles to failure curves. The microstructural analysis revealed that copper diffuses more easily into 316L than 304L, and using 50 mu m thick foil causes more defects compared with 100 mu m foil. It was shown that 316L joints have a significantly increased fatigue life compared with 304L. Both 316L and 304L met the 15-year lifetime requirement set by manufacturers
Optimizing Lighting Design in Educational Settings for Enhanced Cognitive Performance: a Literature Review
No full textLighting has more functions than simply illuminating spaces. For humans, light is the main signal that aligns our body's internal clock, regulating circadian rhythms. This process instructs our bodies to wake up in the morning, become alert during the day, and feel sleepy at night. Disruption of these rhythms can impact neurological and psychiatric health, including cognitive performance. We can utilize light for mood improvements and better cognitive performance to create a suitable learning environment for students in educational buildings. These non-visual effects of light need to be considered from the beginning of the design process, making an interdisciplinary effort necessary. Even with adequate light and dark, the human eye reacts differently under various conditions, influenced by light's photometric and colorimetric properties. While natural sunlight is ideal for aligning with our biological clock, it is not always sufficient, making artificial lighting essential indoors. LED technology offers promising solutions, catering to our non-visual needs in the absence of natural light and providing energy efficiency. This study reviews the literature that includes students' cognitive performance and well-being, energy efficiency, running costs, and environment-related issues such as light pollution. It aims to explore the impact of lighting design in learning environments
Effect of Marination on the Formation of Polycyclic Aromatic Hydrocarbons in Grilled Vegetables
No full textThe effect of marination on the formation of polycyclic aromatic hydrocarbons (PAH) in charcoal-grilled vegetables was studied. Various marinade ingredients, including apple cider vinegar, red grape vinegar, lemon juice, garlic powder, black pepper, and the food additive tert-butylhydroquinone (TBHQ) were applied to vegetable samples before charcoal grilling. The total phenolic content (TPC) and total antioxidant capacity (TAC) of each marinade ingredient were assessed for their contribution to PAH inhibition. A substantial decrease in PAH4 formation was observed in marinated vegetables. Red grape vinegar exhibited the strongest average inhibitory effect on total PAH4 formation (75%), followed by apple vinegar (68%), lemon juice (52%), garlic powder (34%), and black pepper (30%). Additionally, the TBHQ (67%) demonstrated a strong inhibitory effect, reducing total PAH4 formation by 67%. These findings offer valuable insights for reducing PAH levels in grilled vegetables and preventing their formation. © 2025 The Author(s). Food Science ; Nutrition published by Wiley Periodicals LLC
An Ex Vivo Model for Evaluation of Prebiotic Activity of Xylan and Xylooligosaccharides
No full textEx vivo techniques can provide more physiologically significant insights into prebiotic activity and overcome some limitations of in vitro tests. In this study, an ex vivo model, formed of a large intestine of mice, was tested to assess the effects of the hydrocolloidal natural polymer, xylan (XY), and its hydrolysis product, xylooligosaccharides (XOS). XY and XOS were loaded separately into the cecum, proximal colon, and distal colon. Their utilization and short-chain fatty acid (SCFA) formation by the colonized microflora and levels of dominant phyla and key genera such as Bifidobacterium, Bacteroides, and Lactobacillus were followed. XY and XOS were metabolized in all sections, and SCFAs were released. The results suggest that the slower utilization of XY compared to XOS in the cecum can enable this polysaccharide to move towards distal parts of the large intestine and extend the sites of prebiotic activity. Unlike widely used in vitro models, the ex vivo model allowed testing the utilization pattern and effects of the prebiotics in the natural environment of the microflora and examining the intestinal sections separately
High-Performance Polyether Sulfone (PES) Membranes Modified With Sunflower Seed Shell-Derived Activated Carbon (SSAC)@zif-11 Nanoparticles for Enhanced Antibiotic Removal and Antifouling Properties
No full textThis study investigates the impact of incorporating a novel composite filler on the antibiotic removal efficiency and protein fouling resistance of polyether sulfone (PES) membranes. The filler was synthesized from activated carbon derived from sunflower seed shells (SSAC) and modified with zeolitic imidazolate framework-11 (ZIF-11). The adsorption capacities of the composite for two model antibiotics, tetracycline (TC) and rifampicin (RP), were evaluated. Mixed matrix membranes were fabricated using the phase inversion method with varying SSAC@ZIF11 contents (0.2-1 wt%). The membrane containing 0.8 wt% SSAC@ZIF-11 exhibited improved structural and surface characteristics, including increased porosity, larger pore size, smoother morphology, and enhanced hydrophilicity, as reflected by a reduction in contact angle from 60.72 degrees to 46.45 degrees. At this optimal loading, the pure water flux increased significantly from 10.52 to 39.1 L/m2h. Moreover, the modified membrane demonstrated outstanding removal efficiencies for TC (99.12 %) and RP (89.9 %), alongside excellent antifouling performance, as indicated by a flux recovery ratio increase from 42.85 % to 99.74 %. These results confirm the potential of SSAC@ZIF-11 as an effective nanofiller for developing high-performance PES membranes in advanced water purification applications
Numerical Study of Breaching at Upper Parts of Homogenous Earthen Dams
No full textIn this study, time-dependent finite element analyses of the breaching process in two homogenous earth-fill dams were performed using the finite element method. Breaching was initiated at the middle and corner sections of the upper part of the dam bodies. The numerical results were compared with the findings of the experiments realized on dams 60 cm high, 2 m wide at bottom, 20 cm wide at crest with 1 V:1.5H side slopes at upstream and downstream faces. This numerical study combines time-dependent hydraulic gradient distributions and groundwater flows to assess breach areas, velocities, and flow rates. A Python algorithm was integrated with the Jupyter console, allowing the simulation of the breach mechanism in multiple runs to determine breach parameters. Both numerical and experimental analyses revealed that the dams were exposed to backward erosion, starting at the downstream side of the dam and progressing inward. The compatibility between experimental and numerical results was sought by means of the parameters RMSE, MAE and the statistical performance of the numerical approach was evaluated by using RSR, NSE, and PBIAS. A fairly good agreement was obtained between the experimental and numerical results