Phd Degree / Doktora
Permanent URI for this collectionhttps://hdl.handle.net/11147/2869
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Doctoral Thesis Photonic Crystal Textiles(Izmir Institute of Technology, 2022) Çetin, Zebih; Sözüer, Hüseyin SamiPhotonic crystals are man-made structures that can be used to manipulate the flow of light. They are classified as one-, two- and three-dimensional photonic crystals according to the periodic variation of the dielectric profile in space. Apart from artificial photonic crystals there are numerous examples of naturally occurring photonic crystals which have evolved mostly for structural coloration, such as wings of butterflies, natural opal gem stone, peacock feathers to name a few. Using photonic crystal structures the propagation of electromagnetic waves can entirely be prohibited by means of photonic band gap. Considering the fact that approximately two thirds of the heat loss of the human body occurs through electromagnetic radiation with a wavelength around 10 microns, it becomes important to consider photonic crystals for the purpose of reducing heat loss in textiles. We observe that the textile, by virtue of the fact that it has been produced by weaving, already has a periodic structure, and thus is a potential candidate for a photonic crystal. With the right fiber that the textile is woven and the right weave pattern, the textile itself would be a photonic crystal. The most common weave patterns used in the textile industry are plain weave, basket weave, dutch weave and twill weave. In this thesis, we used the finite-difference time-domain method to search for the optimum weave pattern to minimize heat loss by the human body.Doctoral Thesis Design and Analysis of Deployable Reciprocal Frames(Izmir Institute of Technology, 2022) Özen, Gülçin; Korkmaz, Koray; Korkmaz, KorayA reciprocal frame (RF) is a type of structure used since early times. It consists of mutually supporting bars that can span large distances greater than the length of the bar. Although there are deficiencies in previous studies, there are movable RFs, but we cannot talk about the existence of a 3-dimensional deployable RF network. This study aims to contribute to the missing knowledge for movable RF fans and develop a deployable RF network. The study has conducted a comprehensive literature review to gain knowledge and identify the deficiencies of RFs. There are many studies about RFs, but it has been observed that very limited research has been done on movable RFs, and some geometric properties have not been made yet. Firstly, missing geometric knowledge has been found, which are the positions and orientations of the joints by using Denavit-Hartenberg parameters. Also, the effect of engagement length on the fan height and base edge is analyzed. A reconfigurable demountable RF fan is created with the obtained geometric knowledge. Then, mobility calculations are made, and kinematic diagrams are drawn for zero, single, and multi degrees of freedom (DoF) triangular, quadrilateral, and pentagonal fans. Their motions are investigated, and 3-dimensional (3d) simulations are generated. A two DoF quadrilateral fan with prismatic and revolute joints is produced. Then the possibilities of assembling the two DoF fans are searched to create a deployable RF network. While the network has a single DoF in the direction of vault curvature, it has multi DoF in the thickness direction. The network takes the form of a roll in its most closed state, and it takes the form of a vault in its most open state. The section of the curvature of the deployable network is the same as the Da Vinci bridge. However, while simple joints were used in the Da Vinci Bridge, revolute and prismatic joints are used in the proposed deployable RF network.Doctoral Thesis Determination of Vitamin D by Sensor Technologies Based on Molecular Imprinted Polymers(Izmir Institute of Technology, 2022) Ölçer, Yekta Arya; Eroğlu, Ahmet Emin; Demir, Mustafa MuammerVitamin D is an essential nutrient in the body; it plays important roles in human health. Both its lack and excess can have health risks. As a consequence, there is a great demand for development of simple and precise detection methods for vitamin D derivatives in different samples. Molecular imprinting polymers (MIPs) are artificial receptors that can recognize target molecules in solution. In this study, two different polymerization techniques were used to obtain MIP/NIP sorbents/films for the detection of vitamin D3. Firstly, molecular imprinted solid phase extraction (MISPE) method was proposed prior to HPLC-DAD analysis. Optimized parameters were as follows; sorbent amount of 5.0 mg for 5.0 mL of 1.0 mg/L vitamin D3 in 90:10 (v/v) ratio of H2O:MeOH solution, 5 hours sorption time and MeOH:HOAc ratio of 90:10 (v/v) as desorption solution. The accuracy of the method was verified with spike recovery test for PBS:MeOH in a ratio of 90:10 (v/v) and overall recovery was found as 85.1 (±4.3, n=3). In latter case, a quartz crystal microbalance (QCM) method was proposed for determination of vitamin D3. Electrochemical polymerization of poly(4-vinylpyridine) MIP/NIP films were achieved on gold working electrode by cyclic voltammetry (CV). Mass-transfer ability of the polymer films were analyzed by electrochemical impedance spectroscopy (EIS). The electrochemical QCM (eQCM) was used to develop thin polymer films on quartz crystals and vitamin D3 determination was achieved by QCM. In a preliminary test, as small a concentration as 0.0100 mg/L vitamin D was detected with the QCM method.Doctoral Thesis Conservation proposals for Göbekli Tepe enclosures(Izmir Institute of Technology, 2022) Çelik, Keziban; İpekoğlu, BaşakThe conservation of archaeological sites is of great importance as they provide physical remains of past civilizations. Göbekli Tepe, which is one of the most important archaeological site in human history was included in the World Heritage List in 2018. Remains in Göbekli Tepe archaeological site are enclosures surrounded by circular or rectangular wall rows, and containing monolithic T-shaped pillars in the center and peripheral walls in two layers. The aim of this study is to examine the construction technique and relations between structural elements and to define conservation problems in order to develop conservation proposals. The method of the study is the evaluation of the data collected during the field survey together with the information given in the literature. In order to determine the similarities and differences between the layers, components and alignment characteristics of enclosures were defined, the relations between these components were examined. It was found that there is relationship between the diameter of enclosure and height of central pillar, and this ratio was same in two enclosures and close in another enclosure. The state of conservation and preservation conditions of the structural elements of the enclosures were examined and risk classes were determined. The problems observed in the structural elements were determined as crack, deformation, fracture, material loss, disintegration. It had been suggested to stabilize the walls to prevent further damage, to design and develop the support system for the pillars, and to carry out regular monitoring to detect possible damage or problems for components.Doctoral Thesis Production and Characterization of Porous Ceramics for High Temperature Applications(Izmir Institute of Technology, 2022) Semerci, Tuğçe; Ahmetoğlu, Çekdar Vakıf; Akdoğan, YaşarThis thesis focuses on the production and characterization of different porous polymer derived ceramic (PDC) components (foams, additively manufactured (AM) honeycombs, and aerogels) and demonstrates their potential for high temperature applications, including gas permeability (up to ~700 o C), molten metal filtration, and heat exchanger. The foams were produced via the replica technique and different pore sizes, ranging from 300 μm to 2 mm, silicon oxycarbide (SiOC) ceramic foams were able to be formed. The average total porosity of the foams was 96 vol% with a specific surface area (SSA) of ~80 m2 /g. AM-made honeycomb-like cellular structures with different cell sizes (578 μm, 1040 μm) were obtained via fused filament fabrication. Finally, SiOC aerogels were synthesized using siloxane resin, then dried at ambient pressure and room temperature. The produced SiOC aerogels showed a total porosity of around 80 vol% and an SSA reaching 250 m2 /g. Regarding the high temperature applications of porous PDC components, initially, the gas permeability of SiOC foams was tested, and the results showed stability up to 700 °C in the air without any loss of functionality, offering reusability even in aggressive environments. In the subsequent studies, filtration of molten aluminum alloy was tested using various porous components. PDC foams demonstrated better performance in comparison to the AM-made cellular structures and commercial SiC foams. Finally, heat exchange analysis was performed to evaluate the heat transfer of SiOC foams, and an increase in pressure drop was found to be directly proportional to the rate of increase in air velocity.Doctoral Thesis Structural Engineering of Halide Perovskites and Their Association With Organics for Optoelectronic Applications(Izmir Institute of Technology, 2022) Yüce Çakır, Hürriyet; Demir, Mustafa Muammer; Yüksel Aldoğan, KıvılcımHalide perovskites show great potential for next-generation optoelectronic applications due to their unique photophysical properties with low production costs. However, their stability issues still prevent their commercialization on a large scale. The main objective of this dissertation is to understand the additive engineering strategy to improve the quality of halide perovskite films and nanocrystals for solar cells and lightemitting diodes. There are two sections to this dissertation: The first section focuses on halide perovskite films and solar cells while the second one focuses on halide perovskite nanocrystals and white light-emitting diodes. In the first section of this dissertation, in Chapter 2-3, the improvement of Sn-Pb and methylammonium-free Pb-based halide perovskite films by additives are investigated. The suppression of defects via additives is demonstrated through structural, elemental, and optical analyses. The improved performance of perovskite solar cells by decreasing defects is also shown. In Chapter 4-5, the change in stability and optical properties of the halide perovskite nanocrystals by means of additive engineering and their applications in white light-emitting diode are studied. The results in this dissertation represent a new approach to improving the structural and photophysical properties of halide perovskites and introduce a new perspective of additive engineering method in the field of halide perovskite-based optoelectronic applications.Doctoral Thesis Integration of Archaeological Sites With Urban Life in the Metropolitan City Centres: the Case of Agora of Smyrna/İzmir(Izmir Institute of Technology, 2022) Çalışkan, Merve; Turan, MineThis thesis aims to identify the parameters for the integration of archaeological sites in metropolitan city centres with urban life. The Agora of Smyrna was chosen as the case. The method proposed has five phases: Literature review, archival research, physical and social surveys; the Delphi study; and statistic evaluation. The Delphi study was used to define integration criteria and their weights. The correlation and regression analysis were carried out to define the content and level of integration of the citizens with the site. Sequential according of the criteria set with information coming from different sources such as literature, social surveys and Delphi study distinguishes this study from the previous work. Identification of weights of criteria via the structured communication technique made it possible to attribute significance to the outstanding aspects of integration. The indicators of each criterion were clarified and criteria were classified to define integration concepts. So, an integration framework with a hierarchical structure was developed. The integration concepts “Possesing physical access”, “Possessing social usage”, “Being a well-presented site”, “Being a well-managed site”, and the “Presence of public concern for the conservation of the site” were identified as significant for integration. New integration concepts such as “Providing benefits to its vicinity”, “Being surrounded by a qualified urban area”, and “Awareness and positive perceptions of the site’s vicinity” were identified. “Presence of public concern for the conservation of the site” is the most important integration concept whereas “Providing benefits to its vicinity” is the least important integration concept for the case of Agora. The integration level of Agora with urban life and the integration of the citizens with the site was determined as moderate.Doctoral Thesis Experimental Investigation of a Hybrid Thermal Management System for an Electric Vehicle Battery Module(Izmir Institute of Technology, 2022) Coşkun, Turgay; Çetkin, ErdalEnvironmental concerns and limited energy sources of the world are driving force in electric vehicle technology improvements. One of the main components of the electric vehicles is battery cell. Using batteries in electric vehicles brings up new concerns such as safety problems, limit of range and so on. The temperature of the battery cell increases during charging/discharging and operation. There is an optimal temperature range (15ºC ─ 35ºC) for battery cells to maximize efficiency and prevent safety issues. The high temperature values in the battery cells can be result with fire and explosion. In addition, the performance of the battery cells is highly affected by operating temperatures. Therefore, thermal management of the battery cells is a necessity to overcome safety issues and maximize the battery performance. The feasibility of microchannel heat sink for battery cooling is investigated numerically and it is decided to continue with conventional length scales because of the higher pressure drop values in micro scales. Thus, a hybrid cooling system, using air and liquid solely or simultaneously, is developed and is introduced to a battery module. The battery module created by connecting three lithium-ion pouch cells in serial. According to the results, air cooling gives the more homogeneous temperature distribution. The lowest temperature values are observed in hybrid cooling system and temperature difference between the cells are reduced by 30% when compared to the water-cooling system. The temperature profile in air cooling shows that any increase in the ambient temperature (23ºC) or discharge rate will undergo a temperature rise in battery cells and optimal temperature ranges will be exceeded in that case. A step function, in a sequence of various discharge rate, is introduced to the battery module to determine cooling capacity of the air system during operation. The result show that the temperature of the cells is kept below 30ºC. The hybrid cooling is enabled to select cooling systems for the battery module with respect to operating condition; hence, the efficiency of the system is increased.Doctoral Thesis Investigation of Bioelectrochemical Treatment Efficiency for Removal of Boron From Geothermal Waters(Izmir Institute of Technology, 2022) Gören, Ayşegül Yağmur; Ökten, Hatice Eser; Baba, AlperMicrobial desalination cell (MDC) is a promising technology due to its simultaneous features of electricity production, wastewater treatment, and desalination. In this thesis, boron (B) removal from geothermal water and organic matter removal from yeast wastewater with energy production was studied using a three chamber (anode/desalination/cathode) lab-scale MDC system. Among operational conditions, electrode surface area was proven to be significant on B removal efficiency. Then, anode chamber of the conventional MDC was modified to include three-dimensional (3D) cubic electrodes as a novel design. B and organic matter removal efficiencies and the produced power density results were promising for 3D-electrodes. Further studies in order to increase the efficiency of MDC system was conducted by synthesizing 3D hybrid sponge electrodes with activated carbon-chitosan (AC-CS). MDC with 3D AC-CS anode provided a higher power density of 970 mW/m2 , B removal efficiency of 75.9%, and COD removal efficiency of >90% under optimized conditions. Furthermore, phytoremediation performance of Lemna minor L. on B removal was found to be 96.7 %. Also, removal of B and heavy metals from reverse osmosis (RO) permeate and concentrate streams using RO-MDC hybrid process was studied. The performance of ROMDC system was proven to be significant on B and heavy metals removal efficiency. Lastly, feasibility of B removal from geothermal water using MDC-Donnan dialysis hybrid process was evaluated. The most important output of this study was decreased frequency for pH adjustment. Overall, MDC, being in its early levels of technology readiness, produced promising desalination and energy production results in removal of boron from geothermal brine.Doctoral Thesis Investigation of Liquefaction Potential of Sand-Tire Granulated Rubber Mixture That Used Around the Buried Pipes With Shake Table Tests(Izmir Institute of Technology, 2022) Karaman, Mustafa; Ecemiş Zeren, NurhanLiquefaction causes major deformations in infrastructures. The rapidly increasing of scrap car tires causes to find new areas to recycle them. It has been seen that granular rubbers to be an effective filling material with their density, permeability, compressibility and also damping characteristics for liquefaction remedation. Firstly, this study aims to explain the effect of rubbers mixed with sand on the liquefaction potential of the mixture during and after earthquakes. For this reason, one-dimensional shaking table experiments were carried out with granular rubbers-sand backfills in a large scale laminar box with varying rubber diameters and varying ratios of rubber. Secondly, the study aims to explain the effect of these mixtures on pipeline performance when used as filling around buried pipelines. Lastly, this study focuses on the possibility of rubber to contaminate groundwater with inorganics. For this purpose, a series of batch tests and column leaching tests were performed. Consequently, mixing rubbers with sand is effective in liquefaction remedation. They reduce the pore water pressure thanks to the high permeability, affect the consolidation characteristics with its permeability and compressibility, also reduce the earthquake loads with their damping facilities. In order to prevent the buried pipelines from uplifting during an earthquake, a limit criteria is suggested to design of the pipe diameter, burial depth and filling conditions with a predicted seismic load. Rubbers aren’t hazardous for contaminating the inorganics into groundwater. If granular rubbers are used in environmentally sensitive areas, it is recommended to use them after a prewash process or soaking in water for a day.