The aim of this study is to form a theoretical model for simulation of glass forming ability of Fe &amp / #65533 / Based bulk amorphous alloys, to synthesize Fe &amp / #65533 / based multicomponent glassy alloys by using the predictions of the theoretical study, and to analyze the influence of crystallization and solidification kinetics on the microstructural features of this amorphous alloys. For this purpose, first, glass forming ability of Fe &amp / #65533 / (Mo, B, Cr, Nb, C) &amp / #65533 / X ( X = various alloying elements, selected from the periodic table) ternary alloy systems were simulated for twenty different alloy compositions by using the electronic theory of alloys in pseudopotential approximation and regular solution theory. Then, by using the results of the theoretical study, systematic casting experiments were performed by using centrifugal casting method. The alloying elements were melted with induction under argon atmosphere in alumina crucibles and casted into copper molds of different shapes. Characterization of the cast specimens were performed by using DSC, XRD, SEM, and optical microscopy. Comparison of equilibrium and nonequilibrium solidification structures of cast specimens were also performed so as to verify the existence of the amorphous phase. Good agreement of the results of experimental work, with the predictions of the theoretical study, and the related literature was obtained.

This study develops a systems integration project scheduling model which identifies the assignment of activity responsibilities that minimizes expected project implementation cost, considering the project risk. Assignment of resources to the individual jobs comprising the project is a persistent problem in project management. Mostly, skilled labor is an essential resource and both the time and the cost incurred to perform a job depend on the resource to which job is assigned. A systems integration project includes implementation issues in the areas of shipping, installation, and commissioning. Implementation problems lead to project delays, increased costs, and decreased performance, leading to customer dissatisfaction with the systems integrator. Activities can be performed in one of three ways: by the integrator, by the customer, or jointly between the integrator and customer. In this study we select the performer (mode) of each activity comprising the project network while taking into consideration the varying cost, duration and extreme event probability of each activity among different modes-integrator, joint work and customer. Use of the model will permit customers and integrators to mutually agree on an appropriate assignment of responsibilities in the contract. Systems integrators can also use the model to improve their implementation services offerings. An experimental design and a Monte-Carlo simulation study were conducted to see the effects of the parameters of the problem on the selection of modes.

The purpose of this thesis is to perform numerical solutions of hypersonic, high temperature, perfect gas flows over various geometries. Three dimensional, thin layer, compressible, Navier-Stokes equations are solved. An upwind finite difference approach with Lower Upper-Alternating Direction Implicit (LU-ADI) decomposition is used. Solutions of laminar, hypersonic, high temperature, perfect gas flows over flat plate and compression corners (qw=5&deg / , 10&deg / , 14&deg / , 15&deg / , 16&deg / , 18&deg / and 24&deg / ) with eight different free-stream and wall conditions are presented and discussed. During the analysis, air viscosity is calculated from the Sutherland formula up to 1000&deg / K, for the temperature range between 1000 &ordm / K and 5000 &ordm / K a curve fit to the estimations of Svehla is applied. The effects of Tw/T0 on heat transfer rates, surface pressure distributions and boundary layer characteristics are studied. The effects of corner angle (&amp / #952 / w) on strong shock wave/boundary layer interactions with extended separated regions are investigated. The obtained results are compared with the available experimental data, computational results, and theory.

The Black Sea, with its oxic, suboxic and anoxic layers, provides a unique environment for studying how biological and geochemical processes affect the composition of particulate matter. The elemental composition of particles in the Black Sea is controlled by their origin and sources. Particles from rivers are dominated by aluminosilicate material that has compositions similar to the earth&rsquo / s crust. In general this material is relatively unreactive. Biological processes in the upper oxic and suboxic layers of the water column result in enrichments of elements which used as nutrients. Cu, Ba and Mo have been proposed as tracers for planktonic material and new production. Geochemical processes like manganese and iron recycling between oxidized and reduced forms, metal sulfide formation, and biogenic matter decomposition can have a large impact on the composition of particles in the suboxic and anoxic zones. The aim of this thesis was to study the composition of particles suspended in the water column of the Black Sea, in regional rivers draining into the Black Sea, and of particles deposited in these rivers and Black Sea sediments. The objectives were to determine the chemical composition and distribution of particles supplied by rivers and produced in the Black Sea, and compare with those particles buried in the sediments. The chemical distributions can help us to understand the biogeochemical processes taking place. The ultimate goal is to understand if there is a chemical signature that characterizes sediments deposited in anoxic basins that can be used to determine if ancient sedimentary rocks were deposited under such conditions. Water column filter samples were collected from the central western basin and along transects to the SW shelf regions during several research cruises of R/V Bilim and R/V Knorr in the Black Sea. Samples were taken by using both in situ large volume filtration systems and on deck vacuum filtration of discrete samples. River samples were collected by hand from the bank of four Turkish rivers and the Danube River. Sediment samples were obtained from 0 - 25 cm interval of a box core from the deep western basin. All samples were digested and analyzed by inductively coupled plasma - mass spectrometry and combination of atomic absorption (flame &amp / graphite furnace) instruments. The elements analyzed included Al, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, Mo, Ag, Cd, Ba, Pb, and U. Great care was taken to avoid contamination and to obtain the highest level of precision and accuracy. The precision was typically about 5% for most elements. The accuracy, determined using standard reference materials, was also usually better than 5%. Another goal of this research was to determine the metal concentrations and best digestion methods using different types of filter materials. Blank filters were digested and analyzed and the analyses of various filter blanks are presented in the thesis. The analyses showed that the particulate matter data from Turkish Rivers were very similar to the composition of global average riverine particulate material and global average crust. The Danube River had elevated concentrations for some elements that were probably due to anthropogenic contamination. The Turkish river samples were closer to (but still higher than) the averages for the world&rsquo / s rivers but many elements in the Danube were much higher. These high values determined for major elements in the Danube samples strongly suggest considerable contamination of the Danube as compared to the Turkish Rivers. The Danube River samples were especially enriched in Pb, Zn, Ag, Cu, Cd, and Mn and slightly enriched with Cr and Ni. The first five elements, in particular, are well known indicators of pollution. The particulate matter in the water column of the Black Sea was influenced by lithogenic input from rivers, biological processes and geochemical processes. In order to examine the biogeochemical processes extensively, all the data were plotted as Metal/Al (Me/Al) ratios and compared with the ratios of the average crust and Turkish Rivers. Deviations were used to examine the anomalies due to biological and geochemical processes. In addition, the Al content of individual sample and the Me/Al ratio of crust or rivers were used to subtract the lithogenic component from the total composition. Enrichments due to biological processes were observed for Ba &gt / Fe &gt / Cr &gt / Mn &gt / Zn &gt / Ni &gt / Cu &gt / Mo &gt / V &gt / Co &gt / Cd &gt / U for the overall biogenic composition. Enrichments due to biology are most evident for Ba, Fe, Cr and Mn. This is a unique data set as there have been few previous analyses of biological enrichment for most of these elements. The results of particulate matter analyses showed that some elements including U, V, Cr, Ni, Cu, Co, Zn, Ba and Mo were enriched in the set of samples from the euphotic zone. Redox cycling in the suboxic zone was observed, as expected, for Mn and Fe, whose oxides play an important role in scavenging processes. The redox dependent processes in the suboxic &ndash / anoxic interface influence the vertical distribution of U, Ni, Co, Cu, Zn, Ba and possibly Mo, Cr and V. Elements influenced by sulfide formation in the anoxic layer are Fe, Cr, Ni, Co, Mo, and presumably Ag. The sediment data were also examined based on the same approaches. The elements Zn, Pb, U and Cd decreased with sediment depth over the top 5 cm suggesting that they were remobilized out of the sediments. In general the sediments from the Black Sea have Me/Al ratios very similar to local Turkish Rivers and average crust. There is no unique sediment signature (except possibly for Mo) indicating that these sediments were deposited under sulphidic conditions. This study does not support the hypothesis that the composition of ancient rocks can be used to characterize the environment of deposition.

ABSTRACT IMPLEMENTATION OF NORTHFINDING TECHNIQUES Oguz, Pinar MS, Department of Electrical and Electronics Engineering Supervisor: Assoc. Prof. Dr. T.Engin Tuncer June 2006, 131 pages The fundamental problem of navigation is to find the initial north angle of the body with respect to the reference frame. Determination of the north angle of the body frame is required in spacecraft, aircraft, sea-craft, land-craft and missile control and guidance. This thesis discusses implementation and comparison of four northfinding techniques. These are GPS (Global Positioning System) based with integer search, GPS based with Kalman filter, accelerometer based and IMU (Inertial Measurement Unit) based techniques. The north angle is determined by the processing of difference measurements of the GPS carrier phase between two antennas at GPS based northfinding techniques. Carrier phase ambiguity resolution is the main problem in GPS based techniques. Since, GPS receiver measures only the fractional part of the carrier phase. Therefore, integer part remains unknown. Two distinct ideas are applied to solve carrier phase ambiguities in two techniques. One of them is integer search on single phase difference. Suitable integer sets are checked on the cost function which is constructed from the single phase difference between two antennas. The other technique uses integer estimator and attitude estimator with Kalman filter rely on double difference phase measurements which are obtained from carrier phase differences of two antennas and two satellites at one instant. To test the GPS based techniques, a realistic GPS emulator is implemented. GPS emulator provides typical GPS raw navigation data including satellite positions, pseudoranges and carrier phases. Accelerometer based northfinding technique is composed of a vertically placed linear accelerometer on a rotating platform. The north angle is found by Coriolis acceleration due to Earth and platform rotation. Implementation problems of this technique in practice are discussed. IMU based northfinding technique has inertial sensor components such as gyroscopes and accelerometers to sense the Earth rotation rate and gravitational force respectively. The north angle is found by the processing of these inertial sensors output. Real set-up is established to test the IMU based technique.