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Archived Theses
Kararsız endüstri alanının (yeniden) üretimi: Adana milli mensucat fabrikası örneği
In this thesis it is aimed to reveal a value model that can be referred to be able to reevaluation of the abandoned industrial assets which are industrial heritage, in the urban context. The main purpose is to construct a holistic approach for preservation and improvement of the abandoned industrial assets. In accordance with this purpose, the situation of abandoned industrial assets is expressed as industrial terrain vague, because of their values in the historical process in one hand and their obsolescence on the other hand. Spatial trialectic of Lefebvre clears up the required space inquiry for reproduction of industrial terrain vague in the basis of values. Accordingly changing dimensions of the industrial space (mental, physical and social) from genesis till presence of industrial terrain vague are examined. At the end, a cultural value model is presented which is supported by Lefebvrian analysis method. In this context Milli Mensucat Fabrikası [the National Textile Factory] which is in the old industry district at the city centre of Adana has been chosen as the research area. The factory, which is constructed in 1906, abandoned in the 1990s step by step and reserved for preservation in 2013, is examined with its environs. Factory and its environs are examined at five different time intervals based on the changes happened in mental, physical and social dimensions and different value gaining or value losing processes are seen. A new criticizing vision based on cultural value model is constructed for the reproduction of abandoned factory.
Tribenzoheterotrikuinan tabanlı moleküler yapıların sentezi, yapısal karakterizasyonu ve kimyalarının incelenmesi
The synthesis of heteroatom containing derivatives of triquinane structure by the Mascal group represents an important development in the field of fundamental organic chemistry. Some derivatives of hererotriquinane structures showed unusual reactivity and structure properties. For example, oxonium ions are known as fleeting intermediates in certain reaction mechanisms. However, oxatriquinane, the oxygen containing analogue of heterotriquinane family, shows extreme stability. It can be chromatographed and survives in boiling water for a week. Additionally, a pure SN2 on a tertiary center was showcased on a methylated derivative of oxatriquinane. Substituted oxatriquinanes were also shown to have extremely long C-O bond lengths, one derivate being the record holder in the literature. Moreover, azatriquinane which is nitrogen atom containing derivative of triquinane is known to be the most powerful simple trialkylamine base. Additionally, the tribenzotriquinane which is benzo derivative of triquinane has attracted much attention like the triquinane, and a variety studies have been performed on this scaffold in number of different fields, such as fundamental chemistry and material science. However, heteroatom containing derivatives of this molecule have not been available in the literature and it was expected that tribenzoheterotriquinane structures will exhibit unusual reactivity and structural properties as in the case of heterotriquinane derivatives. In this study, in order to synthesize target molecule, a multi-step synthetic approach was utilized. First, an important core unit in this synthetic approach has been synthesized successfully and with the functionalizations of this core unit tribenzooxatriquinane, the oxo analogue of tribenzotriquinane, was synthesized successfully first time in the literature. Synthesis of this molecule represents an important development for the field of fundamental organic chemistry as it represents the first bis-benzylic oxonium ion derivative in the literature. Furthermore, due to having three benzene rings in the structure, tribenzooxatriquinane opens number of possibilities for functionalization of the structure so that new derivatives with interesting structural properties can be synthesized.
Yüksek mukavemetli hafif yüksek entropi alaşımlarının (HYEA) geliştirilmesi
In this thesis, the HEA formation ability of low-density elements was carefully studied in detail. In this respect, lightweight or relatively lightweight elements such as B, Mg, Al, Si, Ti, V, Cr, Mn and combinations of these elements with high-density elements such as Cu, Ni were used to produce novel lightweight high entropy alloys (LWHEAs) relative to the density of steel parts (~7.86 g/cm3). This thesis involves the design, production, and characterization of LWHEAs. The design and selection of the proper elements to be used in such alloys were calculated based on thermophysical calculations, Thermo-Calc HEA database and first-principle calculation with Vienna Ab Initio Simulation Package (VASP). Firstly, the HEA formation ability of selected elements and their compositions were determined by these computational methods. Then, the selected compositions were produced by copper heart arc-melting set-up adapted with suction casting technique. The LWHEAs are investigated in detail by using electron microscopy (SEM, TEM), X-ray diffraction (XRD) and thermal analysis techniques. The specimens were analyzed to determine the corresponding mechanical properties under compression test. The most promising alloy was found to be Cu29Ni29Al14Ti14Cr14 with its relatively low density (6.76 g/cm3) among the investigated LWHEAs. The suction cast LWHEA is annealed at 900 °C for 2 h. based on the phase diagram constructed by Thermo-Calc software. The annealed Cu29Ni29Al14Ti14Cr14 LWHEA shows optimal mechanical behavior with 855 MPa compressive strength, 22.6 % ductility and 338 HV hardness. Also, Cu29Ni29Al14Ti14Cr14 LWHEA was produced from industrial grade raw materials at scale-up using the induction casting technique. The 5 mm cylindrical samples annealed at 900 °C for 2 h. show 902 MPa yield strength, 1332 MPa fracture strength and 12.7 % ductility.
Adana pamuğa dayalı endüstri mirasının değerlendirilmesi
The cotton-based industrial sites that effected urban development of Adana since the middle of the 19th century, were being persisted in the city center due to the extension of the urban area. Vast majority of cotton-based industry sites, that varying types of production occurred, having diverse area sizes and locations, and built in different periods, were ceased production or/and demolished. The three of the current sites were registered as cultural property and only one of them is being conserved. These conditions show that industrial heritage and heritage values are not appreciated adequately. This study aims to determine the heritage values of industrial sites at the study area, within 'value assessment of cultural heritage' and 'industrial heritage' conceptual frameworks. To reach this aim, following the research and examination of the conceptual framework, research and field studies were done to collect information about the case study. The study area was determined according to the distribution of industrial sites that were densely located in the urban area. The industrial sites were identified and building sheets were produced as inventory in this study. Due to varying characteristics of the sites, they were analyzed by classification and mappings of these classifications. Later present sites that ceased functioning were selected and examined regarding the buildings on these sites. Finally, cultural heritage values were defined within the light of these research and analyses, in order to guide decisions and studies about the conservation of cotton-based industrial heritage in Adana.
Bir intronik poliadenilasyon bölgesinin meme kanserlerinde kullanımı
Alternative polyadenylation is an important mRNA processing step in which the length and/or the sequence of 3'UTR of mRNAs are altered. This change in 3'UTRs may have significant effects on mRNA stability, localization and translational efficiency. One of the APA types, called intronic polyadenylation (IPA), occurs on intronic sites rather than 3'UTRs. Recent evidence shows that almost 20% of human genes have a poly(A) site in at least one intron. In fact, some introns even may have more than one poly(A) site. Since generation of IPA isoforms could potentially have serious consequences on both protein levels and function, the significance of intronic APA and its occurrence is of interest. Here, we describe such an IPA site in a eukaryotic initiation factor 2B-3 (EIF2B3). Using in silico, and in vitro tools, we studied this IPA site usage in response to estrogen in ER+ breast cancer cells. We confirmed expression of EIF2B3 IPA isoform in MCF7, ER+ breast cancer cells, as well as other breast cancer cell lines and patient samples. We confirmed the usage of this intronic poly(A) site by 3'RACE, cloning and sequencing. Moreover, we showed the expression of a protein from this IPA isoform. Overall, we provide confirmatory data on an in-silico prediction of an IPA case in breast cancers. Future experiments will show the consequence of this IPA event and provide insight into similar IPA events that may happen in cancer cells.
Yüzey modifikasyonu yapılmış kurşun teleryum kuantum nokta ve kurşun selenyum nanoçubuk temelli güneş hücrelerinin geliştirilmesi; kararsızlığın ve yüzey kaynaklı tuzak bantlarının ortadan kaldırılması
One of the underlying reasons for the 33% theoretical limit of solar cells (Shockley–Queisser limit) is the losses originating from non-absorbed ultra violet and infrared regions of the solar spectrum. PbTe Quantum Dots-(QDs) and PbSe Nanorods-(NRs) are two of the intriguing nanocrystals which can be utilized to overcome the efficiency limit due to unique properties such as band gap tunability, large exciton Bohr radius and highly absorbing nature in ultra-violet and infrared regions. However, air instability and limited knowledge on the surface properties hinder their utilization in the field of optoelectronics. In this respect, a detailed understanding on the instability of those nanocrystals was presented and combinatorial passivation protocols based on engineering of the surface during the growth phase and solid-state ligand exchange process were developed. Dual passivation approach controls shape, ligand exchange rate, packing direction and mid gap state formation by dictating the {111}/ {200} facet ratio and yield solar cells with outstanding stabilities. Optical properties, stability behavior and band energies depend mainly on the aspect ratio of the NRs which is tuned by reaction parameters such as injection temperature, concentration of oleic acid and diphenylphosphine. We also found that the ligand choice was the key factor in improving the solar cell performance as affecting the thin film morphology by controlling the NR packing. Optimization of the cell fabrication protocols yields PbSe NR based solar cells with 80% external quantum efficiency (EQE) and 2.60% power conversion efficiency (PCE) and enhanced stability up to 54 days under inert atmosphere for the first time in literature.
Değişken alanlı venturi'lerde kavitasyonlu akışın deneysel temelli nümerik incelenmesi
Variable area cavitating Venturi is a throttling device that can regulate the flow rate used in liquid and hybrid rocket motors. It has a pintle mechanism which adjusts the flow area by moving back and forth in the direction parallel to the outflow from the Venturi. The flow rate is independent of the downstream pressure due to cavitation. This makes the variable area cavitating Venturi a very critical component for liquid propellant rocket engine because it can create an isolation between the inlet and the outlet in addition to controlling the mass flow rate. In this thesis, the cavitating flow through the variable area Venturi is investigated both experimentally and numerically. In order to solve the multi-phase flow, the open-source OpenFOAM software has been utilized. Schnerr-Sauer mass transport method is used to model the cavitation together with k-omega SST turbulence model. The model and the solver have tried to be verified and validated by experimental studies conducted on a simple version of the cavitating Venturi. The pintle positions,the upstream and downstream pressures, and the divergence angle of the Venturi has been examined in terms of their effect on the Venturi performance.
Üç noktalı eğme örnek geometrileri için çekme modu çatlak tokluğu üzerinde destek aralık mesafesinin etkisi
Straight notched disk bending specimen geometry has a potential to find size independent mode I fracture toughness, since the thickness of the disk loaded by threepoint bending can be increased. Increasing the thickness and decreasing the loading span of bending reduces the severe bending action at the notch tip and a pure tensile mode stress state can be achieved at and ahead of the crack tip. 3D finite element program (ABAQUS) was used for computing the stress intensity factors by numerical modeling of circular disk geometry (SNDB). Modeling procedure and stress intensity computation work were verified by 3D modeling of square plate and semi-circular bend geometries under three-point bending loads and comparing the SIF results to the relevant analytical solutions of these two geometries. Tensile mode fracture toughness tests were conducted on notched circular plate type disk and semi-circular disk andesite rock specimens. Tests were carried out under three-point bending loads. 0.5 mm wide notches providing a crack length/radius ratio of a/R=0.20 were machined to the specimens by a saw. Mode I fracture toughness tests were performed on straight notched disk bending (SNDB) disk specimens of thicknesses 50 mm and 60 mm. Loading spans were varied between 40 mm and 90 mm corresponding to span/radius ratios of S/R=0.40 to 0.90. Using the same a/R and S/R configurations, three-point bend tests were conducted with the ISRM suggested semi-circular bending (SCB) core specimen geometry for comparison purposes. SCB tests were conducted with 50 mm thickness as suggested. Ankara Gölbaşı Andesite rock type was used in both test series. Mode I fracture toughness values of Ankara Gölbaşı Andesite were found as KIc=1.39 𝑀𝑃𝑎√𝑚 and KIc=1.23 𝑀𝑃𝑎√𝑚 for 60 mm and 50 mm thickness SNDB test specimens, respectively. In comparison, mode I fracture toughness value was found as KIc=0.93 𝑀𝑃𝑎√𝑚 for the tests with SCB specimen. The significant observation is KIc increases with decreasing span length for SNDB and SCB specimens. Another observation is the mode I fracture toughness value increases with increasing specimen thickness for SNDB. A tendency to the size independent fracture toughness value of 1.53 𝑀𝑃𝑎√𝑚 was observed as the result of the curve fitting process on the available test data.
Tek eksenli basınç dayanımı deneyi sırasında kayaların ısı oluşumunun termografik analizi
Mining activities concentrate on the production of underground resources for energy generation and raw material requirements worldwide, as it is also the case in Turkey. For this reason, the exploration of new resources proceeds consistently to meet the increasing raw material demand of the industry. Rock mechanics has a vital role in underground mining and surface mining. At present, the devices and instruments used in rock mechanics laboratory testing, for example, uniaxial compressive strength test, have inferior sensing capability of the initial formation of cracks. Therefore, some inferences must be made by analyzing the data collected during tests. However, this effort cannot be supported with crucial and reliable visual data at the initial crack formation. Regarding this, in this thesis study, the failure behavior of different types of rock specimens was analyzed by a thermal camera during uniaxial compressive strength tests. Hence, this thesis study is expected to become one of the current studies in rock mechanics literature. Therefore, it is foreseen that this subject will make a significant contribution to literature. The experiment results show that gneiss-schist specimens have greater uniaxial compressive strength values than andesite samples. Temperature increase at the failure moment was detected as 4.45 ℃ and 9.58 ℃ for andesite and gneiss-schist specimens, respectively. Higher temperature increase was observed with respect to UCS value. Besides, a temperature decrease was recorded during marble specimens. The amount of temperature decrease was detected about 0.5-0.6 ℃. The temperature change at the specimen causes the radiation energy release. As a result of the porosity tests, it was observed that increase in the porosity rate is parallel to higher radiation energy released, from 17.72 kJ to 107.81 kJ.
Serigrafi ile bor katkılanmış arka kontak arka eklemli (IBC) güneş hücresi üretimi
Interdigitated back-contact (IBC) solar cells with their unique structure, having both n and p doped regions as well all as contacts at the rear side, have the potential to achieve high-efficiency values. The record efficiency value at industrial scale have reached 25.2% for mono-crystalline silicon. This thesis focuses on the development of IBC cell structure which is one of the best performing cell structures. The scope of this thesis requires the full understanding of controlling the boron doping on an n-type wafer for decent process optimisation using Boron doping paste. The thesis also aims for the study of the necessary characterisation techniques, i.e. sheet resistance measurements, and electrochemical capacitance-voltage (ECV) profiling. Corresponding cell fabrication is based on screen-printing of Boron doping paste, annealing, and following metallisation steps. The bifacial structure is also demonstrated as a secondary proof-of-concept. The produced cells have been characterised and analysed with 8.70% efficiency on IBC and 7.43% efficiency on bifacial structures.