Graduate Schools - Theses
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This collection of Bilkent University Theses in BUIR contains selected theses and dissertations from all Bilkent University departments.
Bilkent University's DSpace contains more than 6000 theses completed at Bilkent dating as far back as the mid 1980's. Theses in this collection have been scanned by Technical Services or submitted in electronic format by thesis authors.
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Item 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.Item Open Access Stabilization of multivariable systems with constrained control structure(1988) Ünyelioğlu, Konur AlpThe 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.Item Open Access An Object memory for an object-oriented database management system(1988) Kesim, F. NihanObject-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.Item Open Access Organizational structure and change: A Case study of the warehouse and stock control system in Tepe Co(1988) Onarcan, Mehtap EmineA 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.Item Open Access A Parallel Prolog emulator(1988) Gürsoy, AttilaThere 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.Item Open Access Text, image, graphics editor(1988) Coşar, AhmetThe 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 typesItem Open Access Congestion control in interconnected computer networks(1988) Ulusoy, ÖzgürA 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.Item Open Access Design and implementation of a tool for teaching programming(1988) Göktepe, MesutIn 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.Item Open Access Design and analysis of just-in-time production systems(1988) Oğuz, CeydaJust-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.Item Open Access Atomic theory of the scanning tunneling microscope(1988) Tekman, Ahmet ErkanThe 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.Item Open Access Secondary storage management in an object-oriented database management system(1988) Karaorman, MuratIn 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.Item Open Access Continuous processing of images through user sketched functional blocks(1988) Kaya, AydınAn 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.Item Open Access Steps to building a target market model for a new university(1988) Kuruç, KurtIn 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.Item Open Access Electronic structure of Si/Ge semiconductor superlattices(1988) Gülseren, OğuzA 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.Item Open Access Design and implementation of a general purpose median filter unit in VLSI(1988-10) Karaman, MustafaThe 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.Item Open Access The Communicative curriculum of the Turkish language program at TOMER(1989) Songül, SibelItem Open Access Knowledge base verification in an expert system shell(1989) Polat, FarukAn important part of an expert system is its knowledge base which contains domain dei^endent knowledge. Knowledge base verification is one of the important ¡problems of knowledge acquisition. It is the process of checking that a knowledge base is complete and consistent. An analysis of the rules can detect many potential problems that may exist in a knowledge base. The knowledge base may be incomplete, inconsistent, or even partly erroneous. Those problems unless identified and corrected may cause the inference engine to produce inconsistent results such as conflicting conclusions and sometimes to enter infinite loops. In order to be general, rules with certainty factors are preferred for knowledge representation. This is partly because rules are used in many applications and certainty factors are necessary when knowledge has probabilistic characteristics. Our approacli is to develop a knowledge base verification tool that can be used as a part of a rule-based expert system shell.Item Open Access Ray tracing geometric models and parametric surfaces(1989) İşler, VeysiIn many computer graphics applications such as CAD, realistic displays have very important and positive effects on designers using the system. There axe several techniques to generate realistic images with the computer. Ray tracing gives the most effective results by simulating the interaction of light with its environment. Furthermore, this technique can be easily adopted to many physical phenomena such as reflection, refraction, shadows, etc. by which the interaction of many different objects with each other could be realistically simulated. However, it may require excessive amount of time to generate an image. In this thesis , we studied the ray tracing algorithm arid the speed problem associated with it and several methods developed to overcome this problem. We also implemented a ray tracer system that could be used to model a three dimensional scene and And out the lighting effects on the objects.Item Open Access Texture mapping on geometrical models(1989) Açıkgöz, Oktay AydınThe contribution of the visual effects of textures is an important aspect in generating images of real objects. Texture mapping is a very successful technique in this respect. Texture mapping can be subdivided into two fundamental topics; the geometric mapping and the filtering. The texture mapping system developed in this study is adaptable to different types of geometric models. Superqueadric, Bezier or b-spline surfaces can be mapped with textures. The geometric modeling and the texture synthesis subsystems were also implemented for this purpose. The system works in an interactive manner, the user describes the geometric model and the texture and gets the result in a reasonable amount of time. The speed and the usability of the system by a naive user are the keypoints of implementation.Item Open Access A Review of global marketing with an illustration from Turkey(1989) Pırnar, İgeGlobal marketing is a new topic in the marketing world. In this work a review of lobal strategy is done and as an illustration a study about four global products, the similarities and dissimilarities among their preferences and finally, liked and disliked factors about the products and their advertisement characteristics we reanalyzed from a global perspective . The study was conducted in Bilkent University and Hacettepe Medical Center.