Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Green Synthesis of Nanostructured Bioactive Glass for Dental Applications(01. Izmir Institute of Technology, 2023) Tüncer, Melisa; Yücesoy, Deniz Tanıl; Öksel Karakuş, CeydaBioactive glass is a biomaterial commonly used in dental care products and bone tissue engineering applications due to its biocompatibility, bone-forming ability, and remineralization capability. Bioactive glasses form a hydroxyapatite-like layer on dentinal tubules by releasing calcium and phosphorus ions after interaction with saliva. Bioactive 45S5 glass traditionally synthesized by wet chemical methods which require high-temperature heating and the use of a strong acid catalyst, bringing into question of the possibility of introducing toxic acid residues into the final product. Therefore, there is a need to develop environmental-friendly bioactive glass synthesis methods or to modify existing ones in a way to uplift their environmental friendliness. To satisfy this need, we greenized the traditional sol-gel method by replacing the acid catalyst with an environment-friendly alternative and successfully used it for the synthesis of nanostructured 45S5 bioactive glass. First, physicochemical characterization of the synthesized bioactive glasses was performed. Then, the apatite formation capability of bioglasses were investigated in saliva. Next, the mineralization kinetics of bioglasses were tested in Ca/P buffer. In vitro toxicity tests were performed to assess the cytotoxic potential of the synthesized bioactive glass. All analyses were repeated for the traditional synthesis method for comparison purposes. The results confirmed that green synthesis is more advantageous in terms of bioactivity and functionality required for dental applications. Increasing the safety and functionality of bioglass at the same time during the production phase has critical importance for ensuring the sustainability of current applications as well as creating new uses in the biomedical fieldMaster Thesis Modelling and Simulation of Zinc-Air Batteries(01. Izmir Institute of Technology, 2024) Durak, Ege; Ebil, ÖzgençRenewable energy sources are key components of a sustainable future. However, most of the renewable energy sources have intermittent natures, that can significantly affect the stability of grids. Thus, Energy Storage Systems (ESS) are introduced to store the energy produced for later use. Even though there are various ESS candidates, batteries are superior candidates due to technological readiness. Batteries still suffer from disadvantages that prevent their mass adoption as ESS for grid-scale applications. As an ESS, a battery that can last long cycles, have high power densities, and material availability should be designed and commercialized. Commercial batteries such as lead-acid and Li-ion batteries still suffer from material availability, environmental friendliness, or feasibility. Therefore metal-air batteries, especially zinc-air batteries (ZAB), have significant potential due to their high-power densities, material abundance, and technological readiness. However, ZABs are not ready enough to be commercialized as grid-scale ESS due to their low cycle lives due to aging mechanisms. Therefore, more research should be conducted to improve the rechargeability of a ZAB. However, experimental procedures are time and resource-consuming. To tackle this, accurate mathematical models and simulations should be implemented. In this study, the electrochemical behavior of zinc-air batteries was simulated with Finite Element Analysis (FEM) method. The motivation of the work was to demonstrate the feasibility of a simple 1-D zinc-air battery model to investigate the effect of various phenomena on the battery capacity and charge-discharge cycles. The results were compared to literature and experimental values to evaluate the model's accuracy.Master Thesis Assessment of Spatial Temporal Variability of Urban Heat Island Effect: a Case Study in the Central Districts of İzmir(01. Izmir Institute of Technology, 2024) Ay, Filiz; Kurt, Deniz GerçekThe rapid increase in urban population leads to changes in land use/land cover (LULC) and environmental problems such as Urban Heat Islands. Temperatures in cities being higher than their rural surroundings is a climatic phenomenon known as Urban Heat Island (UHI). Besides direct measurements of air temperature, Land Surface Temperature (LST) that characterizes Surface Urban Heat Island (SUHI) is widely used to determine the impact of UHI. This study aims to determine the spatial/temporal variability of the SUHI effect in the central districts of İzmir for the years 1990, 2000, 2006, 2012, and 2018. Landsat satellite images were used for LST, Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Normalized Difference Building Index (NDBI), Urban Index (UI), and albedo, while the CORINE land cover dataset was used for LULC maps. In the study, the relationship between LST and LULC, and spectral indices was analyzed using zonal statistics, correlation, and regression analyses. In 2018, the highest LST values were observed for pastures, industry, commercial areas, transportation units, and mines, respectively. There is a high positive correlation between LST and NDBI, UI, Albedo, and a negative correlation with NDVI, respectively, while there is a moderate positive correlation with NDWI. In the regression model, 60.4% of the variability of the dependent variable is explained by NDBI and NDVI. NDBI (71.3%) and NDVI (7.6%) indices were the most effective factors on SUHI formation. The SUHI effect was more comprehensively evaluated across five different regions adding built-up indices into the variable set. It is concluded that the changes in LST values, together with the built environment indices, are largely influenced by changes in LULC.Master Thesis Development of Carbon-Free Zinc-Air Batteries(01. Izmir Institute of Technology, 2024) Belet, Yunus Emre; Ebil, ÖzgençZinc-air batteries are thought to be among the greatest substitutes for present energy storage systems because of their high energy densities (~1000 Wh/kg), affordability, and safety. However, zinc-air batteries face several problems, such as carbon corrosion, pore-clogging, and electrode passivation. The main cause of these problems is carbon in the air electrode. Therefore, carbon should be eliminated from the air electrode to enhance its performance. This thesis aims to synthesize an electrocatalyst for air electrodes for secondary carbon-free zinc-air batteries within the scope of the M-Era.NET 'AMAZE' project. Initially, manganese oxide was selected as an electrocatalyst and synthesized using a co-precipitation method with different parameters such as concentration, pH, temperature, and precursor materials. The best MnxOy was obtained with a solution pH and temperature of 9.5 and 60°C, respectively. The main precursor for the catalyst was KMnO4, with a ratio of KMnO4:HCl as 20:4 by volume. α-MnO2 with a surface area of 85.68 m2g-1 was obtained. In addition, onset overpotentials for oxygen reduction and oxygen evolution reactions with 650mV and 271mV, respectively, and a maximum current density of 10.5 mA.cm-2 were obtained. Nickel and cobalt additions were evaluated to improve ORR and OER activity. Catalyst with MnxNiyCozOt(1:0.5:0.5) composition performed better than other samples and had the highest surface area (172.06 m2g-1), ORR and OER potentials of 463mV and 700mV, respectively, and current density of 96 mA.cm-2.Master Thesis Development of Strained Yogurt Ice Cream With Aronia and Hydrolyzed Collagen(01. Izmir Institute of Technology, 2024) Güler, Sevda; Korel, FigenYogurt ice cream, made using yogurt cultures Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, is integrated with freezing technology, and it is a healthy food that creates cooling effect on consumers. In this study, it was aimed to obtain strained yogurt ice cream that would allow consumption of hydrolyzed collagen and aronia together. Different concentrations of collagen were added to samples with and without aronia. Different amounts of stevia were also added to selected sample due to its antioxidant activity. The quality of the ice creams in the study were evaluated by analyses as follows; dry matter, protein, fat, ash, carbohydrates, pH, color, viscosity, overrun, melting rate, antioxidant activity, coliform and lactic acid bacteria counts, and sensory analyses. While aronia decreased pH, collagen increased pH; adding stevia did not cause any significant change on pH. A correct proportion was observed between the viscosity and fat content of formulations. Samples were examined for antioxidant activity by DPPH and total phenolic content analyses. According to DPPH analysis results, sample B containing 20g of aronia had highest antioxidant activity. According to total phenolic content analysis, sample F containing 20g of aronia and 2.5g of hydrolyzed collagen had the highest total phenolic content. After the antioxidant activity was evaluated, stevia was added as a sweetener to sample E, which contained 1g of hydrolyzed collagen. According to sensory analysis results, sample E1 containing 20g of aronia, 1g of collagen and 0.006g of stevia was the most liked yogurt ice cream in terms of taste.Master Thesis Investigation of a Novel Personal Sampler Material for the Identification of Human Exposure To Semivolatile Organic Compounds(2024) Akmermer, Zülfikar; Demirtepe, Hale; Sofuoğlu, Sait CemilSVOCs are widespread indoors, where they occur at high levels. Humans spend most of their time indoors and are regularly exposed to these compounds. Various methods exist to assess human exposure to SVOCs. However, a novel personal sampler material, i.e. silicone wristband, has been used for the last decade. Due to its commencing use, the uptake capacity of silicone wristbands for SVOCs still needs to be discovered. This study aims to investigate the SVOC uptake rate and equilibrium partitioning coefficients of silicone wristbands. To achieve this aim, an analysis method for determining SVOCs in silicone wristbands was developed and validated with wristbands worn by academic personnel of IZTECH. The results showed that among polycyclic aromatic hydrocarbons (PAHs) acenaphthylene, among organophosphate esters (OPEs), tris (2-butoxyethyl) phosphate and among phthalate esters, di(2- ethylhexl) phthalate were found as the dominant SVOCs in silicone wristbands. Then, the uptake capacity of silicone wristbands for PAHs was investigated by deploying them in a school environment for 36 days, together with polyurethane foam passive air samplers. The uptake rates varied three orders of magnitude for compounds reaching equilibrium, i.e. acenaphthene, acenaphthylene, fluorene, phenanthrene, and anthracene (0.010 – 25.93 m3/day), while for fluoranthene, chrysene, and pyrene uptake rates were close to each other (0.17 – 0.50 m3/day). Furthermore, silicone wristband-air partitioning coefficients were in the range of 5.93 to 7.43 for acenaphthene, acenaphthylene, fluorene, phenanthrene, and anthracene. Lastly, daily and chronic toxic exposures and lifetime cancer risk for school children were assessed using PUF-PAS concentrations, and no significant risk was identified.Master Thesis Evaluation of Heritage Characteristics and Conservation Problems of Bomonti Brewery(01. Izmir Institute of Technology, 2024) Koştu, Zeynep; Kul, Fatma NurşenThe Bomonti Brewery, established in the early 1900s in the Liman Arkası District, is an industrial site that has changed over time. It consists of several buildings around a central courtyard, reflecting the area's industrial history. This complex is a significant industrial heritage site that contributes to the distinct character of the Alsancak Liman Arkası District. However, shifts in urban planning, technology, and the privatization of Tekel have led to the cessation of industrial activities at the site. The property has been sold and is undergoing urban redevelopment. This study aims to analyze the conservation values and problems of the Bomonti Brewery and to assess the conservation and planning decisions made for it. The evaluation also includes the Liman Arkası District, of which the complex is a part. To achieve this goal, all historical archives related to the complex and subsequent decisions and relevant literature have been reviewed. Site surveys conducted at various times have assessed the current condition of the complex, including its built-up and open spaces. This study has revealed that the industrial complex holds significant documentary, historical, socio-cultural, architectural, economic, scientific, memory, and integrity values. However, its economic value has been prioritized due to its location, leading to planning decisions focused on profitability rather than comprehensive conservation. Out of the 46 buildings in the complex, only nine have been preserved, with the rest demolished. This has compromised the complex's integrity and changed the skyline of the Alsancak Liman Arkası District with the construction of new high-rise buildings.Master Thesis Evaluating Adoption Factors for Robotic-Assisted Surgery With the Analytical Hierarchical Process(01. Izmir Institute of Technology, 2024) Sarıgöl, Işın Sözen; Dindaroğlu, Burak; Başoğlu, Ahmet NuriThe objective of this master's dissertation is to evaluate adoption factors for robotic-assisted surgery (RAS) using the Analytical Hierarchy Process (AHP) as its evaluation methodology. Robotic-assisted surgery is used in various surgical fields. It is mainly used as a tool in numerous disciplines' minimally invasive surgery procedures (MIS). Since it has so many different application areas and actors, the determination of its adoption factors and evaluation process of these factors' priorities for surgeons is a highly complex issue that includes multicriteria of decision-making and numerous surgeons. A comprehensive list of these possible adoption factors recognized by conducting an extensive literature review, was picked and chosen. First, we had 310 factors mentioned in the literature that have a potential impact on the adoption process of the RAS. We have reduced these to 20 factors that are categorized under five different main criteria. By this, a unique AHP tree that is this thesis' contribution to the literature was developed. The research data was collected by an online survey from the surgeons of various disciplines working in Türkiye. Our final sample to evaluate priorities consisted of forty-one surgeon responses in total. The evaluation process consists of three steps: analyzing individual-based pairwise comparison matrices, their consistency rations, and their priority vectors. We executed the same workflow for the aggregated analysis for disciplined-based and all aggregation. Results are examined in detail and concluded with insightful interpretations.Master Thesis Hubble Tension in the Context of Cosmological Scalar Field Models(01. Izmir Institute of Technology, 2024) Alfar, Rand Abdel Latıf Suleıman; Erdem, RecaiThis thesis delves into the issue of Hubble tension that is the discrepancy between different types of measurements of the expansion rate of the universe at present (i.e. Hub- ble constant H0). Various techniques can be employed to measure H0. There are two types of measurements, namely, direct and indirect measurements for measurement of H0. Direct measurements involve determining the recession velocities of galaxies or supernovae at relatively small cosmological distances, so this type of measurements are direct local measurements. On the other hand, indirect measurements encompass both local methods, such as utilizing the Tully-Fisher relation, and non-local approaches, including cosmic microwave background (CMB) measurements and baryon acoustic oscillation (BAO) measurements of large-scale structures(LSS). The most precise local measurements are achieved through supernovae calibrated by Cepheid variable star measurements, while CMB measurements provide the most precise non-local measurements. However, even when considering measurement errors, there is a significant discrepancy between supernovae and CMB measurements. This is known as the Hubble tension. A milder discrepancy is also observed between local direct measurements and BAO measurements. Many different potential sources of this tension and many different models are proposed to resolve this tension. This thesis focuses on the subset of the proposed models that employ scalar fields in the context of general relativity. The primary objective is to provide a comprehensive understanding of the fundamental ideas underlying these models and emphasize their theoretical aspects.Master Thesis Optimization of Isolators Between Floors of a High-Rise Building(01. Izmir Institute of Technology, 2024) Sönmez, Berkan; Turan, GürsoyEarthquake vibrations are natural phenomena that can cause tremors on the ground surface and lead to serious loss of life and property. Especially large-scale earthquakes have the potential to significantly damage infrastructure systems and the durability of structures. Several strategies are available to reduce these damages and increase the resistance of structures to earthquakes. One of these strategies is the implementation of seismic isolators. Seismic isolation minimizes earthquake damage to structures. The main purpose of the study is to examine the effectiveness of the seismic isolator being installed at various story levels of 3D 20-story steel building model. The building had two sets of 20 evaluation models, each with a different isolator story. The first set had identical evaluation models, except for the isolation story which is incremented in each model. The second set is similar to the first set except that the lower stories are strengthened by shear walls. The goal was to determine the best dimensions for the isolator to minimize the inter-story drift values. For this purpose, a set of 12 earthquake records are selected. These records are scaled according to the determined design spectrum. The optimization is performed for one of these earthquake records. Nonlinear dynamic analyses are carried out to evaluate the building model responses for all 12 earthquake records. Response values such as story shear forces and story drift ratios were analyzed and interpreted. This analysis will contribute to a better understanding of the impact of isolators with optimization methods on structural performance.