ABSTRACT PRODUCTION OF CARBON NANOTUBES BY CHEMICAL VAPOR DEPOSITION Ayhan, Umut BariS M.S., Department of Chemical Engineering Supervisor: Prof. Dr. G&uuml / ng&ouml / r G&uuml / nd&uuml / z Co-Supervisor: Assoc. Prof. Dr. Burhanettin &Ccedil / i&ccedil / ek July 2004, 75 pages Carbon nanotubes, which is one of the most attractive research subject for scientists, was synthesized by two different methods: Chemical vapor deposition (CVD), a known method for nanotube growth, and electron beam (e-beam), a new method which was used for the first time for the catalytic growth of carbon nanotubes. In both of the methods, iron catalyst coated silica substrates were used for the carbon nanotube growth, that were prepared by the Sol-Gel technique using aqueous solution of Iron (III) nitrate and tetraethoxysilane. The catalytic substrates were then calcined at 450 &deg / C under vacuum and iron was reduced at 500&deg / C under a flow of nitrogen and hydrogen. In CVD method the decomposition of acetylene gas was achieved at 600 &deg / C and 750 &deg / C and the carbon was deposited on the iron catalysts for nanotube growth. However, in e-beam method the decomposition of acetylene was achieved by applying pulsed high voltage on the gas and the carbon deposition on the silica substrate were done. The samples from both of the methods were characterized using transmission electron microscopy (TEM) and Raman spectroscopy techniques. TEM images and Raman spectra of the samples show that carbon nanotube growth has been achieved in both of the method. In TEM characterization, all nanotubes were found to be multi-walled carbon nanotubes (MWNT) and no single-walled carbon nanotubes (SWNT) were pictured. However, the Raman spectra show that there are also SWNTs in some of the samples.

In this study, the effects of bioprocess operation parameters on benzaldehyde lyase production were systematically investigated. For this purpose, the research program was carried out in mainly four parts. In the first part of the study, Escherichia coli K12 (ATCC 10798), having the highest benzaldehyde lyase production capacity, was selected as the host microorganism. Next, using the selected microorganism, the production medium was designed in terms of its carbon and nitrogen sources. Among the investigated media, the highest cell concentration and benzaldehyde lyase activity were obtained as 1.8 kg m-3 and 745 U cm-3, respectively, in the medium containing 8.0 kg m-3 glucose, 5.0 kg m-3 (NH4)2HPO4 and the salt solution. Thereafter, by using the designed medium, the effects of bioreactor operation parameters, i.e., oxygen transfer and pH, were investigated in pilot scale bioreactor. Oxygen transfer effects on benzaldehyde lyase production were investigated at QO/VR=0.5 vvm / N=250, 375, 500, 625, 750 min-1 and at QO/VR=0.7 vvm, N=750 min-1 conditions. The highest cell concentration and benzaldehyde lyase activity were obtained at 0.5 vvm, 500 min-1 condition as 2.3 kg m-3 and 860 U cm-3, respectively. Finally, the effect of pH was investigated for benzaldehyde lyase production process at Qo/VR=0.5 vvm, N=500 min-1 condition, at pHC=5.0, 6.4, 6.7, 7.0, 7.2 and 7.8 values. Among the investigated pH values, the highest cell concentration and enzyme activity were obtained at pHC=7.0 condition as 2.1 kg m-3 / 775 U cm-3. However, the values obtained at this condition, were lower than the values obtained at pHUC=7.2 uncontrolled pH operation. Hence, medium oxygen transfer condition and uncontrolled pH operation are found to be favorable for benzaldehyde lyase production.

Foam is one of the most frequently used multiphase fluids in underbalanced drilling operations because of its high carrying capacity of cuttings, compressibility property, formation fluid influx handling, etc. Foam rheology has been studied for many years. Researchers tried to explain foam behaviour by using conventional methods, i.e., determining rheological parameters of pre-defined rheological models like Power law, Bingham Plastic etc., as a function of gas ratio. However, it is known that bubble size and texture of the foam is also effective on foam behaviour. When foam is generated by using different foaming agents, even if the gas ratio is constant, different rheological parameters are observed. Therefore a more general foam characterization method that uses the bubble size and texture of foam is required. Improvements on image analysis, and computer technology allow monitoring the bubble size and texture of foam bubbles. A more comprehensive model of foam rheology definition in which the bubble size, and texture effects of the foam body is developed. Three different analysis methodologies are introduced / i) Generalized volume equalized approach, ii) Generalized volume equalized approach and image processing data, and iii) Image processing data only. The necessary information including the rheological information and image data is acquired from the experimental set-up developed for this study. It has been observed that, the pressure losses could be predicted as a function of bubble size, circularity and general rheological parameters, in &amp / #61617 / 20 % certainty limit. It is also observed that using only the image information is possible to characterize the foam in an accurate and fast manner.

Characterization of carbonate reservoirs by flow units is a practical way of reservoir zonation. This study represents a petrophysical-based method that uses well loggings and core plug data to delineate flow units within the most productive carbonate reservoir of Derdere Formation in Y field, Southeast Turkey. Derdere Formation is composed of limestones and dolomites. Logs from the 5 wells are the starting point for the reservoir characterization. The general geologic framework obtained from the logs point out for discriminations within the formation. 58 representative core plug data from 4 different wells are utilized to better understand the petrophysical framework of the formation. The plots correlating petrophysical parameters and the frequency histograms suggest the presence of distinctive reservoir trends. These discriminations are also represented in Winland porosity-permeability crossplots resulted in clusters for different port-sizes that are responsible for different flow characteristics. Although the correlation between core plug porosity and air permeability yields a good correlation coefficient, the formation has to be studied within units due to differences in port-sizes and reservoir process speed. Linear regression and multiple regression analyses are used for the study of each unit. The results are performed using STATGRAPH Version Plus 5.1 statistical software. The permeability models are constructed and their reliabilities are compared by the regression coefficients for predictions in un-cored sections. As a result of this study, 4 different units are determined in the Derdere Formation by using well logging data, and core plug analyses with the help of geostatistical methods. The predicted permeabilities for each unit show good correlations with the calculated ones from core plugs. Highly reliable future estimations can be based on the derived methods.

Xylan was extracted from cotton waste, characterized by DSC and TGA analysis and used in biodegradable film production. Pure cotton waste xylan did not form film. The presence of an unknown compound, as an impurity, yielded composite films. The unknown compound was determined as a phenolic compound, and most probably lignin, by using DSC and TGA analysis and Folin-Ciocalteau method. The effects of xylan concentration of the film forming solutions, glycerol (plasticizer) and gluten additions on thickness, mechanical properties, solubility, water vapor transfer rate, color and microstructure of the films were investigated. Films were formed within the concentration range of 8-14%. Below 8%, film forming solutions did not produce films, whereas xylan concentrations above 14% was not used because of high viscosity problems. The average tensile strength, strain at break, water vapor transfer rate and water solubility of the cotton waste xylan films were determined as about 1.3 MPa, 10%, 250 g/m2.24h and 99%, respectively. The addition of glycerol as the plasticizer resulted in a decrease in the tensile strength and an increase in strain at break. The change in water solubility due to the addition of glycerol was very small. In addition, water vapor transfer rate and the deviation of the color from the reference color for the plasticized films were found to be higher than the unplasticized films. The effect of addition of wheat gluten in cotton waste xylan film forming solutions on film formation was investigated at different concentration ratios. However, the incorporation of wheat gluten worsen the film quality.

In the last decade, the changes in living styles of people and shopping activities brought a new concept, &ldquo / shopping center&rdquo / . By the time the numbers of shopping centers increased and this big consumption market created a great competition among the investors. The investors had the necessity of examining their market share within the market and other social and spatial factors for the feasibility of their shopping centers. In this thesis considering the need of such a study, a market share analysis is carried out to determine the market share of shopping centers within the competition, analyze the important facts of the market share, estimate the market capacity and potential market regions. Ankara is chosen as the study area since it has an increasing trend for the development of shopping centers. Tthe study is carried out for Armada, Bilkent and 5M Migros shopping centers since they serve for the whole city and have different functions such as recreation, restaurants, cultural activities together with shopping activities. For the analysis a gravity model developed by Lakshmanan and Hansen is used. The model estimates the market share of the centers among regions considering the factors, as accessibility in terms of cost and time, economic conditions of regions, attractiveness of shopping centers and competitors of the market. For the application process Geographic Information Systems ESRI Arc GIS 8.1 and ESRI ArcView 3.2 are used as software to store and manipulate data, build regulations on road network structure, calculate distances and costs, and present maps and results.

In this study, DEMs and orthoimages were generated from ASTER imagery and their accuracies were assessed. The study site covers an area of approximately 60 x 60 km and encloses the city of Ankara. First, DEMs were generated from stereo ASTER images. In order to find the best GCP combination, different number of GCPs (8, 16, 24, and 32) was used. The accuracies of the generated DEMs were then assessed based on the check points (CP), slopes and land cover types. It was found that 16 GCPs were good compromise to produce the most accurate DEM. The post processing and blunder removal increased the overall accuracy up to 38%. It was also found that there is a strong linear relationship between the accuracies of DEMs and the slopes of the terrain. The accuracies computed for water, urban, forest, mountainous, and other areas were found to be 5.01 m, 8.03 m, 12.69 m, 17.14 m, and 10.21 m, respectively. The overall accuracy was computed as 10.92 m. The orthorectification of the ASTER image was carried out using 12 different mathematical models. Based on the results, the models First Order 2D Polynomial, Direct Linear Transformation and First Order Polynomial with Relief have produced the worst results. On the other hand, the model Second Order Rational Function appears to be the best model to orthorectify the ASTER images. However, the developed model Second Order Polynomial with Relief provides simplicity, consistency and requires less number of GCPs when compared to the model Second Order Rational Function.

ABSTRACT EFFECTS OF SCUBA DIVING ON MIDDLE EAR PRESSURE &Ouml / zyurt, Deniz MS. Department of Physical Education and Sports Supervisor : Prof. Dr. Feza Korkusuz Co-Supervisor: Dr. Mehmet &Ouml / zekmek&ccedil / i April 2006, 42 pages Since / the self-contained underwater breathing apparatus (scuba) was developed / the growth in the recreational diving population leaded an increase in diving-related injuries, mostly about the ear barotraumas. Previous findings show that inexperienced divers are more predisposed to ear barotraumas. This study was performed to see the dive related alterations of the middle ear pressure and the compliance of the tympanic membrane due to experience (experienced - skin divers and/or underwater rugby players and inexperienced -not use to skin diving or such water sports) and depth (3m and 12m) in 22 novice divers with normal pre-dive audiometry, tympanometry, and otorhinolaryngologic examination. Pre dive otologic inspections were taken and pre dive / post dive tympanograms were measured for each depth. In 8 ears of the 5 inexperienced divers either hyperemia or hemotympany were observed in the second day&amp / #8217 / s (12m) otoscopic inspections. In the first post dive tympanometric measurements / middle ear pressure changes were observed in 19 ears of 14 divers. The compliance was not changed in 5 ears of 3 divers and increased in the reminder. In the second tympanometric measurements, 12 ears of the 8 divers showed negative middle ear pressure and compliance was not changed in 10 ears of 5 divers and increased in the reminder. Due to experience and middle ear pressure changes of each day / no meaningful, statistically significant correlation was found. Also no meaningful correlations were found neither for experience and compliance. A correlation of .542 between experience status and otologic inspection prior to 12m depth dives was a contradiction to the hypothesis there would not be any significant difference between experienced and well trained inexperienced groups as the otologic variations such as hyperemia or hemotympany were only seen in inexperienced novices. Again / the correlation of .571 showed that 3m depth dives had grater frequency of middle ear pressure changes than 12m depth dives. Similarly / due to the compliance correlation of .516, 3m depth dives had a grater frequency of compliance increases than 12m depth dives. These results however should be reconsidered as the 3m depth was the first open water dive day and 12m depth was the next day which the novices could use to the open water conditions.

Thesis (Ph. D.)--Illinois State University, 1998. / Title from title page screen, viewed July 3, 2006. Dissertation Committee: Russell K. Rutter (chair), James R. Kalmbach, Dana K. Harrington. Includes bibliographical references (leaves 233-248) and abstract. Also available in print.

Thesis deals with teaching metodology physical-geographical Bohemia attractions. The main part of the thesis is design own set of teaching material {--} textbook, workbook and methodological guide for teachers. Part of the thesis is the teoretical part, worked with special literature, which was the basis for creating teaching materials.