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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Sensitivity Analysis Using Finite Difference And Analytical Jacobians

Ezertas, Ahmet Alper 01 September 2009 (has links) (PDF)
The Flux Jacobian matrices, the elements of which are the derivatives of the flux vectors with respect to the flow variables, are needed to be evaluated in implicit flow solutions and in analytical sensitivity analyzing methods. The main motivation behind this thesis study is to explore the accuracy of the numerically evaluated flux Jacobian matrices and the effects of the errors in those matrices on the convergence of the flow solver, on the accuracy of the sensitivities and on the performance of the design optimization cycle. To perform these objectives a flow solver, which uses exact Newton&rsquo / s method with direct sparse matrix solution technique, is developed for the Euler flow equations. Flux Jacobian is evaluated both numerically and analytically for different upwind flux discretization schemes with second order MUSCL face interpolation. Numerical flux Jacobian matrices that are derived with wide range of finite difference perturbation magnitudes were compared with analytically derived ones and the optimum perturbation magnitude, which minimizes the error in the numerical evaluation, is searched. The factors that impede the accuracy are analyzed and a simple formulation for optimum perturbation magnitude is derived. The sensitivity derivatives are evaluated by direct-differentiation method with discrete approach. The reuse of the LU factors of the flux Jacobian that are evaluated in the flow solution enabled efficient sensitivity analysis. The sensitivities calculated by the analytical Jacobian are compared with the ones that are calculated by numerically evaluated Jacobian matrices. Both internal and external flow problems with varying flow speeds, varying grid types and sizes are solved with different discretization schemes. In these problems, when the optimum perturbation magnitude is used for numerical Jacobian evaluation, the errors in Jacobian matrix and the sensitivities are minimized. Finally, the effect of the accuracy of the sensitivities on the design optimization cycle is analyzed for an inverse airfoil design performed with least squares minimization.
82

The European Union As A Normative Power And The European Neighbourhood Policy: Cases Of Morocco And Egypt

Tinas, Murat 01 September 2009 (has links) (PDF)
This thesis aims to examine the European Union (EU) as a normative power in the context of the European Neighbourhood Policy (ENP) through case studies of Morocco and Egypt. The uniqueness of the EU as a distinct actor in international politics has led many observers to claim that the EU is a normative power. The ENP, which emerged in 2004, has been one of the main instruments of the EU within this framework. This thesis studies the claim as to whether the EU is, in fact, a normative power in the context of the ENP with two cases studies. The selection of Morocco and Egypt originates from the existing similarities which render an opportunity to have a comparative study. The thesis will analyze this puzzle through an analysis of both primary documents published by the EU and the secondary literature. Through a close scrutiny of Morocco and Egypt, the normative power of the EU in its near abroad will be explored through the analysis of democratization process in these countries in terms of democracy, rule of law and respect for human rights and fundamental freedoms. Based on theoretical analysis and two case studies, this thesis argues that the EU faces several challenges in its claim to be a normative power within the context of the ENP.
83

A Qualitative Study On The Perceptions Of Early Childhood Teachers Towards Physical Design For Classroom Management

Sahin, Ikbal Tuba 01 December 2009 (has links) (PDF)
The aim of this study is to examine the perceptions of early childhood teachers in relation to the influence of the physical environment of the classroom on classroom management. More specifically, the present study examined teachers&rsquo / perceptions about the factors which influence their classroom management practices, how the physical environment of the classroom influences their instructional processes and teacher-student interactions. To collect the data for the study, a semi-structured interview schedule was developed by the researcher. The interview schedule contained 16 questions / six pertained to demographic items, while the remaining ten open-ended questions aimed to investigate the perceptions of teachers about the physical environment of the classroom and its influence on classroom management. The participants of this study consisted of 36 female early childhood education teachers who taught children from age 3 to 6. Twelve of them were employed in private schools and 24 worked in public schools. Qualitative analysis was performed at the end of the study and according to findings, 7 themes were categorized. These are were (1) factors influencing classroom management, (2) physical environment, (3) interest areas in the classroom, (4) strengths and weaknesses of the physical environment, (5) remedies for weaknesses of the environment, (6) the influence of the physical environment on instructional process and teacher-student interaction, and (7) suggestions for the improvement of the physical environment.
84

Statistical Inference From Complete And Incomplete Data

Can Mutan, Oya 01 January 2010 (has links) (PDF)
Let X and Y be two random variables such that Y depends on X=x. This is a very common situation in many real life applications. The problem is to estimate the location and scale parameters in the marginal distributions of X and Y and the conditional distribution of Y given X=x. We are also interested in estimating the regression coefficient and the correlation coefficient. We have a cost constraint for observing X=x, the larger x is the more expensive it becomes. The allowable sample size n is governed by a pre-determined total cost. This can lead to a situation where some of the largest X=x observations cannot be observed (Type II censoring). Two general methods of estimation are available, the method of least squares and the method of maximum likelihood. For most non-normal distributions, however, the latter is analytically and computationally problematic. Instead, we use the method of modified maximum likelihood estimation which is known to be essentially as efficient as the maximum likelihood estimation. The method has a distinct advantage: It yields estimators which are explicit functions of sample observations and are, therefore, analytically and computationally straightforward. In this thesis specifically, the problem is to evaluate the effect of the largest order statistics x(i) (i&gt / n-r) in a random sample of size n (i) on the mean E(X) and variance V(X) of X, (ii) on the cost of observing the x-observations, (iii) on the conditional mean E(Y|X=x) and variance V(Y|X=x) and (iv) on the regression coefficient. It is shown that unduly large x-observations have a detrimental effect on the allowable sample size and the estimators, both least squares and modified maximum likelihood. The advantage of not observing a few largest observations are evaluated. The distributions considered are Weibull, Generalized Logistic and the scaled Student&rsquo / s t.
85

Effect Of A Temperature Cycle On A Rotating Elastic-plastic Shaft

Arslan, Eray 01 February 2010 (has links) (PDF)
The stress distribution in a rotating solid shaft with temperature dependent yield stress subject to a temperature cycle is investigated. It is presumed that the shaft is in a state of generalized plane strain and obeys Tresca&rsquo / s yield criterion and the flow rule associated with it. By the temperature cycle it is meant that the surface temperature of the shaft is increased to a limiting value, it is held at this temperature for a while, and then slowly decreased at the same rate to the reference temperature. The isothermal shaft is rotated up to around elastic limit rotation speed and then the temperature cycle is applied to the surface of the shaft. Even in an initially purely elastic shaft, two plastic regions with different forms of the yield condition emerge simultaneously at the centre and expand into the elastic region. However, the expansion of the plastic zone ceases soon thereafter, and an unloaded region spreads into the plastic core. It is shown that the stress distribution is altered significantly by the temperature cycle, hence also leading to non-zero residual stresses at stand-still.
86

Classroom Teachers And Teacher Educators&#039 / Perceptions About The New Elementary School Curriculum In Kars

Yalcin, Tugba 01 June 2010 (has links) (PDF)
This cross sectional survey study examined the perceptions of classroom teachers in urban regions of Kars Province including its towns and teacher educators in Kafkas University about the new elementary school curriculum in Kars Province. It also revealed their perceptions about the strengths and weaknesses of the elementary school curriculum, students&rsquo / educational needs from the window of local characteristics of Kars, and classroom teachers&rsquo / needs with regard to the new elementary school curriculum. The data were collected from classroom teachers based on the responses they gave on a survey questionnaire and from interview data with teacher educators that was collected through a semi-structured interview form. Data gathered were analyzed utilizing content analysis method. The major findings of the study revealed the following about that the new elementary school curriculum: (1) active student understanding and common skills were mentioned / (2) its appropriateness to students&rsquo / level / (3) relevancy to students&rsquo / everyday life / (4) its comprehensiveness / and (5) variety that were somehow achieved. On the other hand, the findings also showed that there were problems with regard to the new elementary school curriculum: (1) lack of parental involvement to educational process in Kars / (2) over crowding of classrooms / (3) insufficient materials in schools / (4) insufficient in meeting local characteristics and conditions of Kars.
87

L2 Writing Teachers

Dokuzoglu, Selcen 01 October 2010 (has links) (PDF)
L2 WRITING TEACHERS&rsquo / PERCEPTIONS OF MISTAKES IN STUDENT WRITING AND THEIR PREFERENCES REGARDING FEEDBACK: THE CASE OF A TURKISH PRIVATE UNIVERSITY Dokuzoglu, Selcen M.A. Program of English Language Teaching Supervisor: Prof. Dr. H&uuml / sn&uuml / Enginarlar September 2010, 161 pages This study aimed to investigate L2 writing instructors&rsquo / perceptions of seriousness of different mistake types in upper-intermediate level students&rsquo / essays. It also set out to examine the teachers&rsquo / preferences related with feedback provision. Furthermore, whether there were discrepancies between the teachers&rsquo / claims about the issues mentioned above and their actual performance while marking the essays was looked into. The study was conducted at the Preparatory School of a private university in Turkey. Ten essays written by upper intermediate level students were marked by ten writing teachers who showed the most disturbing mistakes in these essays. They also gave feedback for these papers and half of the teachers were requested to think aloud while evaluating the essays. In addition, a questionnaire and a semi-structured interview were used by the v questionnaire were analyzed through SPSS 15.0. This data gathering instrument was implemented on ten writing teachers working at the institution. In analyzing the data, descriptive statistics were used. The averages showing the seriousness of different mistake types and the frequency at which the teachers use different feedback techniques were revealed. Semi-structured interviews were conducted with five teachers. The results of the interviews were analyzed through content analysis. The results of the study revealed that 80 % of the teachers viewed content related and organizational problems more disturbing than those related with accuracy. However, for 20 % of the teachers mistakes concerning the accuracy of the sentences were more serious. As for the feedback preferences of the teachers, 90 % of them used error codes while marking the essays and all the teachers preferred to write comments. While 60 % of the teachers were in favour of marking students&rsquo / mistakes comprehensively, the rest (40 %) believed selective marking was preferable. Moreover, it was found out that the teachers&rsquo / claims were compatible with their actual performances although some contradictions were observed in their performance.
88

Collagen Scaffolds With In Situ Grown Calcium Phosphate For Osteogenic Differentiation Of Wharton

Karadas, Ozge 01 February 2011 (has links) (PDF)
COLLAGEN IN SITU GROWN CALCIUM PHOSPHATE SCAFFOLDS FOR OSTEOGENIC DIFFERENTIATION OF WHARTON&rsquo / S JELLY AND MENSTRUAL BLOOD STEM CELLS Karadas, &Ouml / zge M.Sc., Department of Biotechnology Supervisor : Prof. Dr. Vasif Hasirci Co-Supervisor: Assoc. Prof. Dr. Gamze Torun K&ouml / se February 2011, 91 pages The importance of developing new techniques for the treatment of bone and joint diseases is increasing continuosly together with the increase of human population and the average life span. Especially bone fractures as a result of osteoporosis are often seen in humans older than 50 years old. The expenses of bone and joint disease operations are very high and the duration of recovery is long. Because of these reasons World Health Organization, The United Nations and 37 countries announced that the years 2000-2010 is the Bone and Joint Decade. Tissue engineering is an alternative approach to clinically applied methods. In this study collagen scaffolds crosslinked with genipin, to improve the stability of foams in culture media, were prepared by lyophilization. To mimic the natural bone structure calcium phosphate mineral phase in the foam was formed by wet chemical precipitation. Collagen concentration (0.75% and 1%, w/v), freezing temperature (-20 oC and -80 oC) of the collagen solution before lyophilization and immersion duration (2x4 h and 2x48 h) of the foams in calcium and phosphate solutions for wet chemical precipitation were changed as process v parameters of foam production. Pore size distribution and porosity analysis as well as compression test were performed for characterization of the scaffolds. The foam with 1% w/v collagen concentration, frozen at -20 oC before lyophilization and immersed for 2x4 h in calcium and phosphate solution was chosen for in vitro cell culture studies. The defined foam had 70% porosity and pore sizes varying between 50 and 200 &mu / m. The elastic modulus and compressive strength of the foam was calculated as 127.1 kPa and 234.5 kPa, respectively. Stem cells isolated from Wharton&rsquo / s jelly (WJ) and menstrual blood (MB) were seeded to foams to compare their osteogenic differentiation. Both cells are isolated from discarded tissues and used in this study as an alternative to the commonly used cells which are isolated by invasive techniques such as bone marrow stem cells. Cells were seeded to collagen foams with and without calcium phosphate (CaP). It was observed that WJ cells proliferated during 21 days on collagen foams without CaP, but MB cell number decreased after day 14. Collagen foams with CaP supported the alkaline phosphate (ALP) activity compared to tissue culture polystyrene (TCPS) and foams without CaP. Contrarily lower cell numbers achieved on CaP containing collagen foams, possibly because of the calcium and phosphate concentration changes in the medium and as the result of osteogenic differentiation. ALP activity of both cell types increased almost 10 times and specific ALP activity (activity per cell) increased 40 times and 150 times for WJ and MB cells, respectively on the CaP containing foams compared to TCPS. Therefore, in this study it was shown that in situ CaP formed collagen foams induce osteogenic differentiation of WJ and MB cells, and these cells isolated from discarded tissues can be used as alternative cell sources in bone tissue engineering applications.
89

Algebraic Curves Hermitian Lattices And Hypergeometric Functions

Zeytin, Ayberk 01 August 2011 (has links) (PDF)
The aim of this work is to study the interaction between two classical objects of mathematics: the modular group, and the absolute Galois group. The latter acts on the category of finite index subgroups of the modular group. However, it is a task out of reach do understand this action in this generality. We propose a lattice which parametrizes a certain system of &rdquo / geometric&rdquo / elements in this category. This system is setwise invariant under the Galois action, and there is a hope that one can explicitly understand the pointwise action on the elements of this system. These elements admit moreover a combinatorial description as quadrangulations of the sphere, satisfying a natural nonnegative curvature condition. Furthermore, their connections with hypergeometric functions allow us to realize these quadrangulations as points in the moduli space of rational curves with 8 punctures. These points are conjecturally defined over a number field and our ultimate wish is to compare the Galois action on the lattice elements in the category and the corresponding points in the moduli space.
90

Determination Of Performance Parameters For Ahp Based Single Nucleotide Polymorphism (snp) Prioritization Approach On Alzheimers

Kadioglu, Onat 01 September 2011 (has links) (PDF)
GWAS mainly aim to identify variations associated with certain phenotypes or diseases. Recently the combined p-value approach is described as the next step after GWAS to map the significant SNPs to genes and pathways to evaluate SNP-gene-disease associations. Major bottleneck of standard GWAS approaches is the prioritization of statistically significant results. The connection between statistical analysis and biological relevance should be established to understand the underlying molecular mechanisms of diseases. There are few tools offered for SNP prioritization but these are mainly based on user-defined subjective parameters, which are hard to standardize. Our group has recently developed a novel AHP based SNP prioritization algorithm. Beside statistical association AHP based SNP prioritization algorithm scores SNPs according to their biological relevance in terms of genomic location, functional consequence, evolutionary conservation, and gene-disease association. This allows researchers to evaluate the significantly associated SNPs quickly and objectively. Here, we have investigated the performance of the AHP based prioritization as the next step in the utilization of the algorithm in comparison to the other available tools for SNP prioritization. The user-defined parameters for AHP based prioritization have been investigated and our suggestion on how to use these parameters are presented. Additionally, the GWAS results from the analysis of two different sets of Alzheimer Disease Genotyping data with the newly proposed AHP based prioritization and the integrated software, METU-SNP, it was implemented, is reported and our new findings on the association of SNPs and genes with AD based on this analysis is discussed.

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