Theses - Department of Computer Engineering

Permanent URI for this community

https://hdl.handle.net/11693/13801

Faculty of Engineering

Browse

Now showing 1 - 20 of 662

Open Access
Continuous processing of images through user sketched functional blocks
(Bilkent University, 1988) Kaya, Aydın; Özgüç, Bülent
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
Congestion control in interconnected computer networks
(Bilkent University, 1988) Ulusoy, Özgür; Baray, Mehmet
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
Message passing in an object-oriented database management system
(Bilkent University, 1988) Özelçi, Sibel M.; Arkun, Erol
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
Design and implementation of a tool for teaching programming
(Bilkent University, 1988) Göktepe, Mesut; Özgüç, Bülent
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
Secondary storage management in an object-oriented database management system
(Bilkent University, 1988) Karaorman, Murat; Arkun, Erol
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
An Object memory for an object-oriented database management system
(Bilkent University, 1988) Kesim, F. Nihan; Arkun, Erol
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
A Parallel Prolog emulator
(Bilkent University, 1988) Gürsoy, Attila; Baray, Mehmet
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
Text, image, graphics editor
(Bilkent University, 1988) Coşar, Ahmet; Özgüç, Bülent
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
Texture mapping on geometrical models
(Bilkent University, 1989) Açıkgöz, Oktay Aydın; Özgüç, Bülent
The 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.
Open Access
Ray tracing geometric models and parametric surfaces
(Bilkent University, 1989) İşler, Veysi; Özgüç, Bülent
In 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.
Open Access
Knowledge base verification in an expert system shell
(Bilkent University, 1989) Polat, Faruk; Güvenir, Halil Altay
An 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.
Open Access
Design and implementation of an object-oriented expert system shell
(Bilkent University, 1989) Toroslu, İsmail Hakkı; Güvenir, Halil Altay
Expert systems represent a new opportunity in computing. An expert system is a computing system capable of representing and reasoning about some knowledge-rich domain with a view to solving problems and giving advice. Expert system shells are developed to create expert systems in an easy way. In recent years the object-oriented paradigm has been developed. The objectoriented approach has many advantages such as data abstraction, program modularity, and structural data representation. Therefore, we are developing an expert system shell which stores knowledge and data in object-oriented style. Also, an object-oriented DBMS part of our shell satisfy the needs of several expert systems rec|uiring large base of fcvcts. Such shells can be used to build expert systems by only adding the domain-specific knowledge.
Open Access
A Run-time environment for an object-oriented database management system
(Bilkent University, 1989) Yengül, Can; Arkun, Erol
In this thesis, an object-oriented query processor, a database language executer, and the protocols for the system- defined classes are designed and implemented. The designed and implemented database language completely fulfills the requirements of the object-oriented paradigm. Query processing functions are implemented through the message passing paradigm, which results in a uniform treatment of data manipulation and query processing functions. The run-time environment also supports the implementation of inheritance mechanism, class hierarchy maintenance, instance access and modification, and access to class definitions.
Open Access
Free-form solid modeling using deformations
(Bilkent University, 1989) Güdükbay, Uğur; Özgüç, Bülent
One of the most important problems of available solid modeling systems is that the range of shapes generated is limited. It is not easy to model objects with free-form surfaces in a conventional solid modeling system. Such objects can be defined arl^itrarily but then operations on them are not transparent and complications occur. A method for achieving free-form effect is to define regular objects or surfaces, then deform them. This keeps various properties of the model intact while achieving the required visuaJ appearance. This thesis explains a number of geometric modeling techniques with deformations applied to them in attempts to combine various approaches developed so far. Regular deformations, which include twisting, bending, and tapering, and free-form deformation technique are combined as a new deformation method. This eliminates some of the disadvantages peculiar to each method and utilizes the advantages of both.
Open Access
Computing with causal theories
(Bilkent University, 1990) Tın, Erkan; Akman, Varol
Formalizing commonsense knowledge for reasoning about time has long been a central issue in Artificial Intelligence (AI). It has been recognized that the existing formalisms do not provide satisfactory solutions to some fundamental problems of AI, viz. the frame problem. Moreover, it has turned out that the inferences drawn by these systems do not always coincide with those one had intended when he wrote the axioms. These issues call for a well-defined formalism and useful computational utilities for reasoning about time and change. Yoav Shoham of Stanford University inti'oduced in his 1986 Yale doctoral thesis an appealing temporal nonmonotonic logic, the logic of chronological ignorance, and identified a class of theories, causal theories, which have computationally simple model-theoretic properties. This thesis is a study towards building upon Shoham's work on causal theories for the latter are somewhat limited. The thesis mainly centers around improving computational aspects of causal theories while preserving their model-theoretic properties.
Open Access
Storage management and indexing in object-oriented database management systems
(Bilkent University, 1990) Al-Hajj, Reda; Arkun, Erol
Storage management and indexing methods used in existing conventional database management systems are not appropriate for the object-oriented database management systems due to the distinctive features of the later systems. A model for storage management suitable for object- oriented database management systems is proposed in this thesis. It supports object identity, multiple inheritance, composite objects, a fine degree of granularity and schema evolution. An index provides fast access to data stored in files at the price of using additional storage space and an overhead in update operations. Work has been carried out on indexing and an indexing method for the object-oriented database systems is proposed. Identity and equality indexes are treated. Object identity and information hiding are provided. Schema changes are handled without affecting existing indexes. It is general enough to be applicable to most existing object-oriented database systems. The mapping of the proposed storage and indexing approaches into a relational database scheme is also presented.
Open Access
Implementation of the backpropagation algorithm on iPSC/2 hypercube multicomputer system
(Bilkent University, 1990) Ercoşkun, Deniz; Oflazer, Kemal
Backpropagation is a supervised learning procedure for a class of artificial neural networks. It has recently been widely used in training such neural networks to perform relatively nontrivial tasks like text-to-speech conversion or autonomous land vehicle control. However, the slow rate of convergence of the basic backpropagation algorithm has limited its application to rather small networks since the computational requirements grow significantly as the network size grows. This thesis work presents a parallel implementation of the backpropagation learning algorithm on a hypercube multicomputer system. The main motivation for this implementation is the construction of a parallel training and simulation utility for such networks, so that larger neural network applications can be experimented with.
Open Access
Animation of human motion : an interactive tool
(Bilkent University, 1991) Mahmud, Syed Kamran
Open Access
Design and implementation of a spelling checker for Turkish
(Bilkent University, 1991) Solak, Ayşın
Open Access
Parallel maze routing algorithms on a hypercube multicomputer
(Bilkent University, 1991) Kurç, Tahsin Mertefe