Nanotechnology comprises of the understanding and control of materials and processes at the nanoscale. Among various nanostructured materials, semiconducting nanowires attract much interest for their novel physical properties and potential device applications. The unique properties of these nanowires are based on their high surface to volume ratio and quantum confinement effect. Zinc oxide, having a direct, wide bandgap and large exciton binding energy, is highly appealing for optoelectronic devices. Due to excellent optical and electrical properties, zinc oxide nanowires have been utilized to fabricate various devices such as solar cells, light emitting diodes, transistors and photodetectors. Furthermore, zinc oxide, in its natural state exhibits n-type conductivity. Addition of impurities often leads to remarkable changes in their electrical and optical properties, which open up new application areas. Among the many synthesis methods for zinc oxide nanowires, hydrothermal method is an attractive one due to its easy procedure, simple equipment and low temperature requirements. In this thesis, zinc oxide nanowires were grown and doped by hydrothermal method. Different metal dopants such as copper, silver and aluminum were used for this purpose. These metals were selected as dopants due to their effect on magnetic properties, p-type conduction and electrical conductivity of ZnO nanowires, respectively. Doped nanowires were fully characterized and the changes in their physical properties were investigated. In addition, hydrothermally synthesized pure and aluminum doped zinc oxide nanowires were used as the electrically active components in ultraviolet photodetectors. Silver nanowires were utilized as transparent electrodes. Optoelectronic properties of the detectors were examined. Effect of in-situ annealing and nanowire length was investigated. Short recovery time, around 4 seconds, with a decent on/off ratio of 2600 was obtained. This design provides a simple and cost effective approach for the fabrication of high performance ultraviolet photodetectors.

All the operational and measurement systems of Ankara Wind Tunnel was modified to operate automatically under the control of a central computer system programmed using the Lab View programming language. A cruciform air-to-air missile with triangular canard control and a trapezoidal wing model was tested by a 35mm diameter internal balance at Mach 0.2 and data was compared with the test data of the same model&rsquo / s test that was performed at NASA Langley Research Center.

In this study a microbial polyester, poly(3-hydroxybutyrate-co-3- hydroxyvalerate) (PHBV), and its blends were wet or electrospun into fibrous scaffolds for tissue engineering. Wet spun fiber diameters were in the low micrometer range (10-50 &amp / #956 / m). The polymer concentration and the stirring rate affected the properties the most. The optimum concentration was determined as 15% (w/v). Electrospun fiber diameters, however, were thinner. Solution viscosity, potential, distance between the syringe tip and the collector, and polymer type affected the morphology and the thickness of beads formed on the fibers. Concentration was highly influential / as it increased from 5% to 15% (w/v) fiber diameter increased from 284 &plusmn / 133 nm to 2200 &plusmn / 716 nm. Increase in potential (from 20 to 50 kV) did not lead to the expected decrease in fiber diameter. The blends of PHBV8 with lactide-based v polymers (PLLA, P(L,DL-LA) and PLGA (50:50)) led to fibers with less beads and more uniform thickness. In vitro studies using human osteosarcoma cells (SaOs-2) revealed that wet spun fibers were unsuitable because the cells did not spread on them while all the electrospun scaffolds promoted cell growth and penetration. The surface porosities for PHBV10, PHBV15, PHBV-PLLA, PHBV-PLGA (50:50) and PHBV-P(L,DL)LA were 38.0&plusmn / 3.8, 40.1&plusmn / 8.5, 53.8&plusmn / 4.2, 50.0&plusmn / 4.2 and 30.8&plusmn / 2.7%, respectively. Surface modification with oxygen plasma treatment slightly improved the cell proliferation rates. Consequently, all scaffolds prepared by electrospinning revealed a significant potential for use in bone tissue engineering applications / PHBV-PLLA blend appeared to yield the best results.

Ammunition Transfer System (ATS) is the electro-mechanical system of the Ammunition Resupply Vehicle (ARV) which will be used to meet T-155 mm Firtina howitzers&rsquo / ammunition demand for tactical requirements of higher firing rate by off-road mobility and survivability. The transfer of ammunitions from ARV to Firtina is to be optimized for an effective improvement of firing rate. In this thesis the transferring order of carried ammunitions is being optimized to minimize the total ammunition transferring time. This transfer problem is modeled as a modification of Travelling Salesman Problem (TSP). The given locations of the ammunitions are treated as cities to be visited and the gripper of ATS is treated as the traveling salesman. By GAMS / the small-size problems are solved optimally but large-size ones get only local optimum. A heuristic algorithm that contains nearest neighbor heuristics as construction method and 2-opt exchange heuristic as improvement method is developed to obtain same or better solutions obtained by GAMS with less computational time.

Indium tin oxide (ITO) thin films have been used as transparent electrodes in many technological applications such as display panels, solar cells, touch screens and electrochromic devices. Commercial grade ITO thin films are usually deposited by sputtering. Solution-based coating methods, such as sol-gel however, can be simple and economic alternative method for obtaining oxide films and also ITO. In this thesis, &ldquo / ITO sols&rdquo / and &ldquo / ITO nanoparticle-incorporated hybrid ITO coating sols&rdquo / were prepared using indium chloride (InCl3

Most materials used in many industries such as plastic, food, pharmaceuticals, electronics, dye, etc. exhibit viscoelastic properties under their processing or flow conditions. Due to the elasticity of such materials, deformation-stress in addition to their hydrodynamic behavior differ from simple Newtonian fluids in many important respects. Rod climbing, siphoning, secondary flows are all common examples to how a viscoelastic fluid can exhibit quite distinctive flow behavior than a Newtonian fluid would do under similar flow conditions. In industrial processes involving flow of viscoelastic materials, understanding complexities associated with the viscoelasticity can lead to both design and development of hydrodynamically efficient processes and to improved quality of the final products. In the present study, the main objective is to develop two dimensional finite volume based convergent numerical algorithm for the simulation of viscoelastic flows using nonlinear differential constitutive equations. The constitutive models adopted are Oldroyd-B, Phan-Thien Tanner (PTT) and White-Metzner models. The semi-implicit method for the pressure-linked equation (SIMPLE) and SIMPLE consistent (SIMPLEC) are used to solve the coupled continuity, momentum and constitutive equations. Extra stress terms in momentum equations are solved by decoupled strategy. The schemes to approximate the convection terms in the momentum equations adopted are first order upwind, hybrid, power-law second order central differences and finally third order quadratic upstream interpolation for convective kinematics QUICK schemes. Upwind and QUICK schemes are used in the constitutive equations for the stresses. Non-uniform collocated grid system is employed to discretize flow geometries. As test cases, three problems are considered: flow in entrance of planar channel, stick-slip and lid driven cavity flow. Detailed investigation of the flow field is carried out in terms of velocity and stress fields. It is found that range of convergence of numerical solutions is very sensitive to the type of rheological model, Reynolds number and polymer contribution of viscosity as well as mesh refinement. Use of White-Metzner constitutive differential model gives smooth, non oscillatory solutions to much higher Weissenberg number than Oldroyd-B and PTT models. Differences between the behavior of Newtonian and viscoelastic fluids for lid-driven cavity, such as the normal stress effects and secondary eddy formations, are highlighted. In addition to the viscoelastic flow simulations, steady incompressible Newtonian flow of lid-driven cavity flow at high Reynolds numbers is also solved by finite volume approach. Effect of the solution procedure of pressure correction equation cycles, which is called inner loop, on the solution is discussesed in detail and results are compared with the available data in literature.

ABSTRACT DEVELOPMENT OF A COMPUTER PROGRAM FOR FRICTION WINDING SYSTEM DESIGN &Uuml / nal, Fuat G&ouml / khan M.Sc., Department of Mining Engineering Supervisor: Prof. Dr. Naci B&ouml / l&uuml / kbasi September 2011, 99 pages As the trend to deeper mines continues, mine hoists and associated equipment will become more sophisticated, complex, large and expensive. Correct selection of the right type of hoist is imperative. In this vital link between underground and surface, crude estimates of hoist capacity are not good enough, and the mining engineer must design and select the right hoisting system to meet the design specifications and establish the most suitable operating parameters. This study aims to constitute a software model, which results all required design parameters of friction type winding system on minimum required power. The computer program has been structured on Microsoft Visual Basic programming language. The program requires user inputs (winding depth, hourly hoisting capacity) and selections (type and number of motors, type of friction wheel mounting) to run macros and equations so that the operating parameters such as skip capacity, rope type and diameter, hoisting speed, acceleration, cycle period, friction wheel diameter are determined to give the minimum motor power requirement.

Aprotic solvents are organic solvents which do not easily react with a substance dissolved in it and they do not exchange protons despite of their high ion and polar group dissolving power. Therefore, this characteristic property makes aprotic solvents very suitable intermediates in many industries producing pharmaceuticals, textile auxiliaries, plasticizers, stabilizers, adhesives and ink. Dehydration of these mixtures and recirculation of valuable materials are substantial issues in industrial applications. The conventional method for recovery of aprotic solvents has been distillation, which requires excessive amount of energy to achieve desired recovery. Hydrophilic pervaporation, which is a membrane based dehydration method with low energy consumption, may become an alternative. Because of high dissolving power of aprotic solvents only inorganic membranes can be employed for this application. In this study three types of inorganic membranes (NaA zeolite, optimized silica and HybSi) were employed. Main objective of this studys to investigate effect of membrane type and various operationg parameters (feed composition at a range of 50-5% and temperature at a range of 50-100oC) on pervaporative dehydration of aprotic solvents / dimethylacetamide, dimethylformamide and n-methylpyrrolidone. During the experiments, feed samples were analyzed with Karl Fischer Titration Method / permeate samples were analyzed with Gas Chromatography. Experiments showed that proper dehydration of aqueous aprotic solvent mixtures was succeded with all three membranes investigated. In the target feed water content range (50 to 20%wt), permeate water contents were higher than 98%wt which was quite acceptable for all membranes. Moreover, NaA zeolite membrane performed higher fluxes than optimized silica and HybSi in composition range of 50 to 15% water at 50oC. It was also observed that HybSi membrane had higher fluxes and permeate water contents than optimized silica membrane for all solvents. On the other hand, the rates of decrease in permeate fluxes changed depending on the type of solvent for optimized silica and HybSi membranes. With both membranes, permeate flux of dimethylformamide decreased much slower than that of n-methylpyyrolidone. Furthermore, the results showed that permeate fluxes of HybSi membrane increased with increasing operation temperature due to the change of solvent activity in mixture. In addition, an Arrhenious type equation was used to describe changes in fluxes with changing temperature. It was also found that activation energy of water for diffusion through HybSi membrane was calculated as 8980 cal/mol.

Tsunamis are characterized as shallow water waves, with long periods and wavelengths. They occur by a sudden water volume displacement. Earthquake is one of the main reasons of a tsunami development. Historical data for an observation period of 3500 years starting from 1500 B.C. indicates that approximately 100 tsunamis occurred in the seas neighboring Turkey. Historical earthquake and tsunami data were collected and used to develop two artificial neural network models to forecast tsunami characteristics for future occurrences and to estimate the tsunami return period. Artificial Neural Network (ANN) is a system simulating the human brain learning and thinking behavior by experiencing measured or observed data. A set of artificial neural network is used to estimate the future earthquakes that may create a tsunami and their magnitudes. A second set is designed for the estimation of tsunami inundation with relation with the tsunami intensity, the earthquake depth and the earthquake magnitude that are predicted by the first set of neural networks. In the case study, Marmara and Aegean regions are taken into consideration for the estimation process. Return periods including the last occurred earthquake in the Turkish seas, which was the izmit (Kocaeli) Earthquake in 1999, were utilized together with the average earthquake depths calculated for Marmara and Aegean regions for the prediction of the earthquake magnitude that may create a tsunami in the stated regions for various return periods of 1-100 years starting from the year of 2004. The obtained earthquake magnitudes were used together with tsunami intensities and earthquake depth to forecast tsunami wave height at the coast. It is concluded that, Neural Networks predictions were a satisfactory first step to implement earthquake parameters such as depth and magnitude, for the average tsunami height on the shore calculations.