Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis B and Se Transport Modeling in Saturated/Unsaturated Zones(Izmir Institute of Technology, 2002) Yüreklitürk, O. Emin; Tayfur, GökmenThere has been renewed interest in the application of models to the transport of non-point source pollutants. However, very little work has been done to evaluate the performance of a functional transient-state model for the transport of a reactive solute over an extensive study period. This research consists of mathematical modeling to simulate water flow, boron and selenium transport through soil in tile-drained croplands.For Boron part a mathematical model was developed to simulate non-conservative boron transport. The dynamic two-dimensional finite element model simulates water flow and boron transport in saturated-unsaturated soil system, including boron sorption and boron uptake by root-water extraction. Two different models have been employed for the sorption of boron. Similarly, for selenium part a finite element model is developed to simulate species of selenium transport in two dimensions in saturated/unsaturated zones. The model considers water, selenate, selenite and selenomethionine uptake by plants. It also considers oxidation/reduction, volatilization, and chemical and biological transformations of selenate, selenite, and selenomethionine. Comparison of boron transport model results with observed data is satisfactory. The model employed with Langmuir isotherm was found to give slightly better simulation results when compared with the model employed with Freundlich. The sensitivity analysis results indicate that the irrigation scheduling and the irrigation water quality are very important parameters for boron accumulation in the soil. Also the adsorption isotherm parameters, which reflect us the soil properties, are found to be important for the boron movement in the soil. Comparison of selenium transport model with observed data is not quite satisfactory in accuracy when compared with the model for boron transport. This may be the result of the complexity of the mechanisms affecting the selenium transport in soil. There are too many parameters, and due to the errors depending on the parameters, the total error for the estimation of the total selenium increases.Master Thesis Experimental and Numerical Analysis of Heat Transfer Performance of Off-Set Strip Fins(Izmir Institute of Technology, 2009) Durmaz, Gürcan; Özkol, Ünver; Özkol, ÜnverThe aim of this study is to computationally and experimentally investigate the heat transfer and pressure drop characteristics of an offset-strip fin. In the present study, experiments are conducted at the range of Reynolds number from 150 to 3500 and a 3-D numerical domain, which is investigated as a conjugate problem, is created for finite volume computations. The computations are conducted by assuming that the flow in the offset-strip fin channels is steady and laminar at the range of Reynolds numbers from 200 to 5000. In this thesis, the effects of the flow behaviors in the offset strip fin channels on Colbourn j factor, which is the non-dimensional form of heat transfer coefficient, and fanning friction f factor, which is the non-dimensional form of pressure drop, are investigated. Also, the heat transfer boundary conditions and the Prandtl numbers of the fluids are kept different for these fins in order to see the effect of those.The effect of Prandtl number is investigated by using air, 0.707 < Pr < 0.71 and water, 2 < Pr < 4.35 and ethylene glycol, 94 < Pr < 138. The effect of the thermal boundary conditions is investigated by using constant heat flux and uniform temperature. Moreover, all results are compared with Kays and London.s experiments (1964) and also the results of Manglik and Bergles.s correlations (1995). The results show a very good agreement between the results of Kays and London (1964) and of Manglik and Bergles.s correlations (1995). It is also observed that results obtained from the two alternatives for the thermal boundary condition are very close to each other. According to obtained results, it is concluded that our computational results from laminar flow assumption and experiments are reliable at almost all the range of Reynolds numbers studied.Master Thesis Hydrothermal Preparation of Single Crystalline Ceo2 Nanoparticles and the Influence of Alkali Hydroxides on Their Structure and Optical Behavior(Izmir Institute of Technology, 2009) Kepenekci, Özlem; Eanes, Mehtap; Eanes, MehtapSingle crystalline cerium oxide nanoparticles were synthesized via hydrothermal method by mixing aqueous solution of cerium nitrate [Ce(NO3)3.6H2O] with an alkali base. Several characterization methods were used to identify morphology and crystalline nature such as X-ray Diffraction, Scanning and Transmission Electron Microscopes. This study is divided into three parts. In the first part, some controlling parameters like, that were affecting size and shape of CeO2 nanoparticles, were studied. It was found that size of CeO2 nanoparticles increased when increasing both reaction time and temperature. Alkali base concentration promoted the particle growth. Also, particle morphology was more uniform rather than aggregated in presence of higher concentrated alkali base. When the alkali base type was changed, the use of NaOH produced larger cubic nanocrystals of CeO2 than KOH and LiOH.Second part is related to determine the optical properties of CeO2 nanoparticles. Based on the UV-Vis and Fluorescence Spectroscopy results, size, bandgap and defect level of CeO2 nanoparticles can be easily determined. Nanoparticles in presence of NaOH alkali base were found to produce less defective CeO2 nanoparticles as compared to KOH and LiOH. The last part of this work is to evaluate the shape effect on morphology, size and optical properties of CeO2 nanoparticles. Rod crystals of CeO2 were produced when the hydrothermal synthesis temperature was low (120°C) or when the reaction time was short (1 hour). When the synthesis temperature was higher than 160°C well defined cubic crystals of CeO2 started to form.Master Thesis Effect of Storage Time on Olive Oil Quality(Izmir Institute of Technology, 2009) Yıldırım, Gaye; Tokatlı, FigenThis work reports changes in the major quality parameters of Turkish extra virgin olive oils stored at room and refrigerator temperatures in dark and monitored for 14 months. Peroxide values, specific absorbance values, total phenol content, free fatty acidity, fatty acid and phenolic profiles of extracted (Erkence and Ayvalık-Edremit) and commercial extra virgin olive oil samples (Altınoluk, Ezine, Bayındır and Ortaklar) from South and North of the Aegean were determined. The acidity and K232 values of samples were within the acceptable limits, the peroxide and K270 values exceeded the limits after 7 and 9 months storage. Hydroxytyrosol, tyrosol, caffeic acid, vanillic acid, vanilin, p-coumaric acid, ferulic acid, m-coumaric acid, cinnamic acid, luteolin, and apigenin were determined as the major phenolics in Turkish extra virgin olive oils. The concentration of hydroxytyrosol and tyrosol increased, while a decrease was observed in the amounts of other phenolics during storage.The highly unsaturated flaxseed oil was mixed with olive oil at 5-15 % levels and stored at room and refrigerator temperature to examine the effect of olive oil on the oxidative stability of flaxseed oil. 15% olive oil addition to flaxseed oil increased its oxidative stability. Fourier Transform (FT-IR) spectral data were used to predict the oxidative quality parameters, total phenol content and the fatty acid compositions by partial least square analysis (PLS). FT-IR spectra of samples subjected to accelerated oxidation were examined to determine the bandwidths, which can be considered as the finger-prints of the oxidation phenomenon (2924, 2852, 1746-1743, 1163 and 967-976 cm-1).Master Thesis Managing the Risk of Contractor Failure(Izmir Institute of Technology, 2009) Yağmuroğlu, Zeynep; Günaydın, Hüsnü MuratThe topic of contractor failure has become a major research domain since the beginning of the 1980s. Construction is a risky business with many features like long period of time, complicated process, financial intensity, environment and dynamic organizational structure. The aim of this thesis is to find out the factors effecting contractor failure. In the first phase contractor failure ratio for public procurement is found by investigating the data of the Turkish Ministry of Public Works and Settlement between the years 1999 and 2006. It is found that 10.5% of the public projects end in construction default. The second phase of the study involves a questionnaire survey to find out why construction companies fail in Turkey. The first part of the questionnaire includes the determinants used by Dun and Bradstreet as the causes of failure classified as organizational, environmental, and performance factors. The second part of the questionnaire includes questions about the organizational structure of the company. It is found that the most effective causes of contractor failure are receivable difficulties, insufficient capital, lack of managerial experience, lack of business knowledge, and family problems. It is observed that ego problems, removing performance barriers, monitoring of performance, adaptation to modern work models, and clarified directions are found as major problem areas for the organizational structure of the company. Key Words: Risk Management, Construction Industry, Contractor, Failures.Master Thesis Applications of Transparent Conductive Indium Tin Oxide Films in Automotive and Vitrifications Industries(Izmir Institute of Technology, 2009) Tuna, Öcal; Selamet, Yusuf; Selamet, YusufDue to its unique electrical and optical properties, highly doped n-type Indium tin oxide used for various applications such as smart glass, LCDs, OLEDs, solar cells and car windows. In this study Indium Tin Oxide (ITO) thin films were grown by both DC and RF magnetron sputtering techniques. To know deposition rate of ITO, system was calibrated for both DCMS and RFMS and then ITO were grown on glass substrate with the thickness of 70 nm and 40 nm by changing substrate temperature. The effect of substrate temperature, film thickness and sputtering method on structural, electrical and optical properties were investigated. Wan der Pauw method was used for electrical characterization and to use this method properly, we patterned ITO thin films by photolithography and Ion beam etching techniques. The results show that substrate temperature and film thickness substantially affects the film properties, especially crystallization and resistivity. The thin films grown at the lower than 150 oC showed amorphous structure. However, crystallization was detected with the further increase of substrate temperature. Substrate temperature and film thickness increment were lead to increase band gap of ITO which can be explained by BMS. Band gap of ITO was calculated to be about 3.64 eV at the substrate temperature of 150 oC, and it widened with substrate temperature increment. From electrical measurements the resistivity at room temperature was obtained 1.28*10 and 1.29*10 cm, for DC and RF sputtered films, respectively. We also measured temperature dependence resistivity and the Hall coefficient of the films, and we calculated carrier concentration and Hall mobility.Master Thesis Design Criteria of High Capacity Bus Transportation Systems(Izmir Institute of Technology, 2005) Caner, Cansu; Gür, Nazim Güneş; Gür, GüneşThis thesis proposes to figure out a new model of public bus transportation mode in Turkey which is more competitive and effective among the conventional public transportation modes.In theoretical framework, the focus is on the new concepts and implementations developed in the urban transportation sector. The effective transportation systems regarding lower expenditures were handled according to the travel demands they serve.However, in general, the effectiveness of the modes is determined according to the economic parameters; mainly the conventional modes are discussed and the effectiveness of BRT systems and LRT systems are compared.A brief survey of the BRT (Bus Rapid Transportation) systems is handled to some extent. The design considerations and the results of the implemented examples are handled to constitute a guideline. The major public transportation modes of Izmir are handled to constitute a guideline. The major public transportation modes of Izmir are discussed. A reserved bus-transportation system is designed in the case study stage.Meanwhile the reserved bus concept along the Inönü Street is not designed according to the existing proposals. A distinctive model is concluded regarding the local conditions of Izmir. At final stage, the energy consumption rates of the systems are calculated and the economic comparison of the systems is based on this parameter.Master Thesis Resonance Solitons and Direct Methods in Soliton Theory(Izmir Institute of Technology, 2009) Duruk, Selin; Pashaev, Oktay; Pashaev, OktayThe Long-Short Wave interaction equations with adding quantum potential term and the Davey-Stewartson equation with addition of both, the quantum potential and the Hamiltonian terms are studied. These equations are reduced to different cases according to the choice of the quantum potential strength. For over critical case reductions to the non-linear diffusion-antidiffusion systems are derived. By the Hirota Direct Method one dissipaton solution of the system is derived. Two and three dissipaton (soliton) solutions are constructed explicitly. For special choice of the parameters they show the resonance character of interaction by fusion and fission of solitons.Master Thesis Estimation of Suspendent Sediment Concentration Using Acoustic Methods(Izmir Institute of Technology, 2009) Aydın, Ramazan; Elçi, ŞebnemAcoustic Doppler current meters (ADCP, ADP, and ADV) can provide information about the suspended sediment concentration (SSC) in the water; although, they are designed for flow velocity measurements. Contrary to conventional samplers, those are labor intensive for measuring SSC, when an acoustic instrument is calibrated for a water system; no additional sensor is needed to measure SSC, enabling the researchers to measure velocity and concentration simultaneously which is required for most sediment transport studies. Recently, the acoustic instruments are investigated in different studies where signal to noise ratio (SNR) and SSC were related using different formulations. However, these studies were limited to single study site where neither the effect of particle size nor the effect of temperature was investigated. In the scope of this study, different parameters that affect the ADV.s performance prediction of SSC were investigated. In order to investigate the reliability of ADV in different environments, SSC measurements were made in different streams. Soil samples were collected from all measuring stations and particle size analysis was conducted. The multivariate data analysis was applied to the measurements to derive a relation formula between SNR and SSC. Multivariate analysis indicated that reported SSC values depended on at least three parameters; water temperature, mean diameter of the soil, and shape of the particle size distribution curve. Also, effect of high SSC conditions on ADV performance was investigated during and after rain events. Results indicated that ADV was not capable of measuring SSC when a limit concentration (SSC>400 mg/l) was exceeded.Master Thesis Investigation of Effects of Land Use Changes in Tahtalı River Basin on Water Quality(Izmir Institute of Technology, 2009) Selçuk, Pelin; Elçi, ŞebnemThe rapid increase of population, industrial growth and disorganized urbanization have put considerable stress on the available water sources, which are already scarce, not only by the increased usage but also by deterioration of the quality of available resources. Both statistical and GIS analyses were adopted in this study to examine the changes in water quality parameters associated with the changes in landuse within a major watershed in the city of Izmir, Turkey. In this study, the satellite images containing the periods prior and after filling of the main pool of the Tahtali reservoir, were analyzed and the effects of the land use changes on the water quality were investigated. For this purpose, the aerial photos of the basin taken in 1995 (October) composed of 130 sections having a scale of 1/5000 were obtained and these images were compared with images of the Ikonos satellite taken in 2005 (November) with a resolution of 1 meter. New residential buildings, greenhouses and industrial buildings were presented in separate layers to document changes in basin activities since 1995.Later on, changes in all 130 sections were merged and the thematic maps of the basin were obtained. This analysis utilized several GIS techniques including manual digitizing, remote sensing and use of existing digital base maps for the preparation of input data. The data analysis included transformation between map projections and data formats, editing of attributes and use of query functions, use of spatial overlaying and also both retrieval and classification.In order to investigate the effects of changes on the water quality, the water analysis values obtained from samples taken at 6 different reaches within the basin and at the main lake for the years of 1995-2005 were obtained. Seasonal Kendall and Mann Kendall tests were selected and applied to the water quality data to investigate which parameters increased/decreased and how these changes were related to the effects of urbanization and industrial development. This study also investigated and quantified soil erosion in the basin by the universal soil loss equation (USLE) for two different land use compositions and soil maps from two years: 1995 and 2005.