Graduate Schools - Theses

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This collection in Bilkent University Institutional Repository (BUIR) includes selected theses and dissertations from all departments of Bilkent University.

BUIR houses over 6000 theses completed at Bilkent University, dating back to the mid-1980s. Theses in this collection have either been scanned by the Technical Services team or submitted in electronic format by their authors.

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Now showing 1 - 20 of 6923

Open Access
Design and implementation of a tool for teaching programming
(1988) Göktepe, Mesut
In this thesis, a survey on computer applications for teaching programming and some graphical programming tools together with their underlying environments has been carried out and a graphical Pascal teaching tool is designed and implemented. Graphical programming tools provide the user the ability to solve the problems through the use of icons and symbols allowing very little text. Here, a Pascal teaching tool is presented in a very user friendly environment to teach programming through the use of flowcharts in a visual manner.
Open Access
Electronic structure of Si/Ge semiconductor superlattices
(1988) Gülseren, Oğuz
A brief review about the two dimensional electron systems and especially band offsets is given. The electronic properties of the Si„/Ge„(001) strained superlattices as a function of the superlattice periodicity and the band misfit is investigated by using the empirical tight-binding method. The difference between the direct and indirect band gaps is reduced from 2.01 eV for bulk Si to 0.01 eV for n = 6. Consequently, the superlattice with n = 6 can be considered as quasi-direct, while it is at least 0.15 eV for n = 4 case. For the cases n=5,6, and 8, the band gap might become direct for large values of band misfit.
Open Access
Congestion control in interconnected computer networks
(1988) Ulusoy, Özgür
A computer network has a collection of resources shared by multiple users. The capacity of the resources is limited, and if the user demands exceed the capacity, the network becomes ’congested’. The congestion causes a degradation in system performance. In interconnected networks there are two classes of traffic within a network. One class is the local traffic that is generated and transmitted within the network. The other class is the internetwork traffic transmitted to or from other networks. In this thesis, the effect of internetwork traffic on the performance of a network is investigated. Computer simulation of an interconnected network model is provided in order to evaluate the effectiveness of a window-based congestion control mechanism on preventing congestion in gateways and in attached networks caused by the overload of internetwork traffic. Also two dynamic window congestion control algorithms are provided and studied. These algorithms provide further control to window mechanism by adjusting the window size in accordance with the availability of the network resources at the destination. Dynamic algorithms are evaluated comparing them with static window control.
Open Access
Secondary storage management in an object-oriented database management system
(1988) Karaorman, Murat
In this thesis, a survey on object-orientation and object-oriented database management systems has been carried out and a secondary storage management and indexing module is implemented for an object-oriented database management system prototype developed at Bilkent University. First, basic concepts, characteristics, and application areas of objectoriented approach are introduced, then, the designed prototype system is presented, the secondary storage management module is explained in detail and the functions of the other modules are summarized. Finally, the current research issues in the object-oriented database systems are introduced.
Open Access
Atomic theory of the scanning tunneling microscope
(1988) Tekman, Ahmet Erkan
The Scanning Tunneling Microscope is proven to be one of the most powerful tools for surface structure determination. Present theories are able to explain the operation of the microscope when the tip is far from the surface. For the small tip height case the atomic-scale interaction of the tip and the surface has to be included in the theory. The electronic structure of the combined system of the tip and the surface is calculated with an Empirical Tight Binding approach for graphite. It is found that in the vicinity of the tip some Tip Induced Localized States are formed. These states play an important role in the tunneling phenomenon. The contribution of these states to the tunneling current is calculated.
Open Access
Steps to building a target market model for a new university
(1988) Kuruç, Kurt
In order to form a segmentation base for Bilkent University, and position accordingly, a model is developed which relates student performances at Bilkent University to their socio-economic and educational backgrounds. In addition, analyses of the information sources of the matriculants, in terms of both the assessments of the sources and the relative effects of the sources on the matriculant’s decision are performed. Similarly, the factors that influence the matriculants are analysed both in terms of how Bilkent University is perceived according to each factor, and the relative effect of that factor on the matriculant’s final decision.
Open Access
An Object memory for an object-oriented database management system
(1988) Kesim, F. Nihan
Object-oriented paradigm is an approach that can be applied in various areas of computing. In this approach, each entity is represented by an object which captures the state and the behaviour of the entity. In this thesis, a focused survey of object-oriented paradigm in general and object-oriented database management systems in particular has been carried out and an object memory module is designed and implemented for an object-oriented database management system prototype. The object memory module handles the representation, access and manipulation of objects in the system and provides the primitive functions that are necessary in the development of the prototype.
Open Access
Organizational structure and change: A Case study of the warehouse and stock control system in Tepe Co
(1988) Onarcan, Mehtap Emine
A sophisticated information processing system can cause a change in the organizational structure. In this work, the Warehouse and Stock Control System in TEPE CO. is chosen as a case study to examine a planned organizational change by the implementation of an MIS.
Open Access
A Parallel Prolog emulator
(1988) Gürsoy, Attila
There are various parallel Prolog execution models proposed so far. In this study, an emulator has been developed to test the execution model PPEM. The emulator is used to collect data to evaluate the performance of the model. The underlying architecture is assumed to be a tightly coupled multiprocessor system. Some implementation difficulties faced, which are not apparent in the definition of PPEM are discussed, and performance results are presented.
Open Access
Design and analysis of just-in-time production systems
(1988) Oğuz, Ceyda
Just-in-Time (JIT) production systems have initially appeared in the Japanese manufacturing environment due to the scarcity of their critical resources. The main aim in JIT production systems is to eliminate waste. To achieve this objective, setup times, lead times, in-process inventories, and defective production must all be minimized. In the design process of a JIT production system, several factors such as lot size, number of kanbans, unit load size, and buffer capacities must be taken into account. In this study, a mathematical model is developed for a single-item, single-line, multi-stage, and multi-period JIT production system. The original model is nonlinear in both objective function and constraints. To reduce the computational difficulties, the nonlinear model is then approximated by a linear model. Next, a simulation model is developed to incorporate the stochastic nature of the demand. A sensitivity analysis is performed on unit load size and on buffer capacity under different demand patterns to examine their effects on the behavior of the model. The results show that thofee unit load size values exceeding 10 percent of the maximum demand in the planning horizon have no effect on the model.
Open Access
Message passing in an object-oriented database management system
(1988) Özelçi, Sibel M.
In this thesis, a focused survey on object-oriented database management systems and on object-orientation in general was carried out and a single- user object-oriented database management system prototype was designed and implemented. A command language was defined and a message passing scheme was proposed and implemented. A compiler for the language was developed. The developed language is computationally complete and aims at solving the impedance mismatch problem. It contains both data definition and data manipulation statements. The statements can be used interactively or in the form of methods. After compilation, the statements are translated into integer codes and these codes are used to perform the necessary operations.Since the developed prototype is a single-user system, the message passing passing scheme does not provide any concurrency control mechanisms and stacks are used to implement message passing and argument handling.
Open Access
Stabilization of multivariable systems with constrained control structure
(1988) Ünyelioğlu, Konur Alp
The following problem is considered: Given a multivariable system with m inputs and r outputs and an m x r matrix whose nonnegative (i,j)’th element represents the cost of setting up a feedback link from the j ’th output to the i’th input, find a set of feedback links with minimum total cost, which does not give rise to fixed modes. Utilizing the graph-theoretic characterization of structurally fixed modes, the problem is decomposed into two subproblems, which are then solved by using concepts and results from network theory. The combination of the optimum solutions of the subproblems provides a suboptimal solution to the original problem.
Open Access
Continuous processing of images through user sketched functional blocks
(1988) Kaya, Aydın
An object oriented user interface is developed for interacting with and processing images. The software prepared for this purpose includes image processing functions as well as user friendly interaction tools both of a lower level such as menus, panels, windows and a higher level such as a schematics. The lower level utilities provide direct interface with the available image processing functions. At the higher level, the nodes of the schematics serve as image processing function instantiations and the arcs are the paths through which processed images flow. By constructing such a schematics, a complex set of operations can be applied to images continuously.
Open Access
Text, image, graphics editor
(1988) Coşar, Ahmet
The editor proposed in this study can manipulate textual, graphics and image data in a unified way. Each data type can be edited individually or dependencies can be set up between various data items so that modifying one might propagate its effects on others. The system is developed by using new software tools and techniques such as object oriented programming, multi window workstations running with event selection principles and iconic interfacing. Facilities for data protection, such as journaling are provided. Data storage and editing principles are handled within guidelines of well established standards. However, where such definitions fall short, proposals for new techniques are made especially with respect to relation sets binding various data types
Open Access
Design and implementation of a general purpose median filter unit in VLSI
(1988-10) Karaman, Mustafa
The median of a group, containing an odd number of elements, is defined as the middle element, when the elements of the group are sorted. A median filter finds the median of a number of elements at its inputs. Median filters are frequently used in many signal and image processing applications for smoothing of the noisy signals and images while at the same time preserving the edge information. The required window size, speed, and the word length of the median filters vary depending on the applications. In order to meet these changing demands a general purpose median filter unit configuration is proposed. The unit consists of two single-chip median filters. One of the chips is designed for unlimited word-length and extensibility to larger window sizes whereas the other one is for real-time video applications. The networks of the chips are based on the odd/even transposition sorting. The chips are implemented in 3-mu m MsquareCMOS by using full-custom VLSI design techniques. For physical testing of the chips, the test vectors and the corresponding outputs of the chips are generated by using software tools written for this purpose. In this thesis, the algorithms, VLSI implementations, simulation results, testing, and applications of the chips are presented.
Open Access
Forecasting the foreign currency prices using the Box Jenkins approach
(1989) İnan, Belgin
In this thesis, the Box Jenkins approach is applied to forecast the future prices of foreign currencies, American Dollar and German Mark, in Turkey’s Black Market using available observations made between the years 1985-1988. The forecasts obtained from this approach are compared to the real available observations. The results show that the Box Jenkins approach is not accurate enough in this case because of the large mean absolute deviation between the forecasted and the observed values of these currencies due to the significant residuals generated in the diagnostic checking stage.
Open Access
Purchasing power parity: An Application for Turkey (1980-1987)
(1989) Bilge, Cem
Purchasing Power Parity (PPP) is claimed to be the oldest and simplest theory in determining the exchange rates of currencies. With its three versions, absolute PPP, relative PPP, and efficient markets PPP, this theory argues that price index levels of the countries are considered while setting the exchange rates. In this study, a general review of the theorj' and its failures are initially summarized. As the main purpose of the paper, the relative PPP has been applied for Turkey between 1980 and 1987 by taking USA as the comparision country. The application has been concentrated on both the official and black-market exchange rate determinations.
Open Access
An Easy way to computerize an accounting system
(1989) Hamam, Sudad
This thesis is principally a conversion of the manual accounting system of a small firm to a computer-based one. Focus w ill be on the benefits of a computer-based accounting system together w ith the risks that may result due to the differences betw een manual and automated processing. Another related aim is to show that time has come to computerize the manual accounting systems of the small and medium sized firms.
Open Access
Is Culture a superficial barrier to global marketing?: A Case study of food and drink products in Turkey
(1989) Sezer, Sibel
In a world of converging needs and desires, globally standardizing products would lead to lower production costs, improved quality of products as well as management. The validity of this argument proposed by "global marketing" is discussed taking into consideration the differences existing within cultures and whether culture is in fact a barrier to globalization. A study was conducted in order to explore whether global marketing strategies can be successful in Turkey for food and drink products competing with local counterparts with regard to age, sex and so c i o economic status comparisons.
Open Access
Portfolio selection methods: An Application to İstanbul Securities Exchange
(1989) Seler, İ. Tunç
In this study, Modern Portfolio Theory tools -are used for constructing efficient portfolios. The Markowitz mean-variance model and Sharpe single index model are presented and calculated, for the construction of efficient portfolios from the Istanbul Securities Exchanges’ first market slocks for the 1986 - 1987 period. Constructed efficient portfolios are compared on the risk and return scales.

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