183
Archived Theses
1
DOIs Assigned
1%
DOI Rate
Departman Tezleri
Using kalman filtering methods for image restoration
A common problem in image processing is the restoration of an image from a given corrupted version. This problem is generally known as image restoration. There are various approaches to solve this problem like using restoration models or linear filtering. In this thesis, one of the linear filtering methods named Kalman filtering has been used for image restoration. For this purpose, two different image restoration scenarios have been defined and two different versions of Kalman filtering methods have been used for each of the scenarios. In the first part of the thesis, a simple scalar Kalman filter method is used for an image that contains multiple frames. In the second part of the thesis, a two-dimensional (2-D) full-plane block Kalman filter is used to restore noisy images. Simulation results are compared with some of the other restoration techniques.
Defence system modelling against computer worms
As computer networks become prevalent, the Internet has been a battlefield for attackers and defenders. One of the most powerful weapons for attackers is the computer worm. Computer worms are a self-propagating computer program that is being increasingly and widely used to attack the Internet. Because they spread extremely fast and usually install malicious code, computer worms are so dangerous.This thesis begins with definition, history and taxonomy. Also, it defines the structure and components of worms. It develops a life cycle model of worm defence, including prevention, prediction, detection and mitigation. It also discusses in detail about each of these techniques. It explains detection and defense techniques against to the computer worms. Group based model have been developed and discussed with the simulations results. It concludes that computer worms are dangerous but there are ways and means to mitigate their ill effects.
Heating control in smart clothes
With the new technologies, intelligent systems have been worked for many studies in recent years. These systems have been developed for different type of application area with the different functional ability. One of this area is textile industry. Intelligent systems have been applied with a wide frame in textile industry and improve day by day so fastly. New systems have been improved for textile industry as electronic substructures combine with textile material instead of basic textile materials, which reaction variously physical and chemical according to media temperature.One of these types of application is intelligent clothes, which use heat function according to media conditions. In the future, this kind of clothes will be more applicable in daily life. These clothes will be designed for especially people, who work outside. It is important that clothes need to supply their own basic clothes function but at the same time they need to supply their heater function with carrying of electronic body on the structure. Because of mobility of clothes body, studies are important about focusing on resisting and using time parameters of any intelligent clothes.In this project, heat functional clothes had been developed with carry on electronic property. Heater panels had been produced on the clothes by steal based conductor threads to supply heating function. Fit with the these panels, optimum power source, electronic user interface card, control card which activate or deactivate the heater panels and control the system and a waistcoat to carry all these materials, had been designed and produced. System had been tested on a thermal model and simulated cold media conditions.
Elimination of image blocking problem for single tuner IDTV applications
In this thesis, a specific dijital image blocking problem was solved for the single tuner IDTV application. A single hybrid tuner is used and the IF (intermediate frequency) output signals of the tuner are divided by two, as analog side (LCD-TV main board) IF input signals and digital side (digital module card) IF input signals. The digital module card is used for IF demodulating and MPEG (moving pictures expert group standard) decoding. The analog IF demodulating process is made in LCD TV main board. The hybrid tuner is located on that main board. The IF output of the tuner is carried to the digital module card by a cable. To distribute the IF output of the hybrid tuner to analog side and digital side and to use an IF cable for carrying the IF signal to the digital module card, impair the IF signal shape. In this thesis, the image blocking problem was solved. The source of the problem was found as impedance mismatching and IF signal impairing. The new high frequency emitter follower circuits were designed for solving this problem.
Data transfer over internet protocol
Session Initiation Protocol (SIP) is an application layer protocol which is generally used in ?voice over internet protocol? (VoIP) technology. This protocol is utilized in order to establish, modify and terminate variable kinds of sessions such as VoIP, videoconferencing or data. SIP is suggested as the signalling protocol of 3rd generation networks which increases its popularity and application area.Current trends in the telecommunication industry favour VoIP technology. In the future, this technology may substitute for ?public switched telephony network? (PSTN). Since PSTN network has been tuned for performance and evolved to become highly reliable with individual switches experiencing only a few seconds of downtime per year, the performance of VoIP network should be closer to the performance of PSTN in order to realize substitution of PSTN network. At that point, characterization of the performance of VoIP network becomes essential, which is directly related to the performance analysis of the SIP.In this paper, performance analysis is performed using an analytical model of SIP messaging with respect to varying arrival rates and service rates. The SIP messaging is modeled as a queuing network and performance analysis is based on this network model. The main performance criteria used in the analysis are total number of customers in the system and the mean waiting time. Real time SIP messaging data are obtained by using real server and clients systems and it is modeled as a known probability density function (PDF) by analytical analysis. This known PDF is used for realizing queuing network performance analysis. As a conclusion, the performance analysis of real time SIP messaging is realized.Keywords: Session Initiation Protocol, Queuing analysis
Reactive power compensation in distribution system
Thyristor controlled reactor is designed and analyzed to compensate the reactive power demand in balanced and unbalanced loads. The arc furnaces in the region of Aliağa-İzmir are considered the load in this type.This system is preferred in the application of reactive power compensation if the load is varying faster such that the traditional reactive power compensation algorithms having mechanical contactors are not fast enough. The system proposed here is used either with a fix capacitor or with the passive filter circuit.Simulations are carried out in MATLAB / Simulink and PSCAD. The application software is converted from MATLAB into TMS320F2812 eZdsp. The system is built at 3 kVAR rating in the Electrical Machines Laboratory. The PSPICE program is also used to design electronic circuit implemented in this work.
Effect of wind turbines on power system operation
In this thesis, effects of wind energy conversion systems on power system operation and vice versa is investigated by a case study of the wind farm. The electrical model of 12 wind energy conversion systems equipped with wound rotor induction machine is developed. After model verification on one machine, whole model of wind farm and power system , including point of common coupling, is used for simulation for power quality analysis.Site measurement was carried out at the point of common couplig as a part of project, ?Power Quality National Projects- Mobile Power Quality Measurements?. The measured results are used for model verification. Wind speed measurement result, which is used as input data in simulation, is obtained from wind farm operators. Effects of wind farm on power system operation is evaluated by the help of simulation results and site measurement results.Like in other countries, which have particular wind energy conversion system in their power system, in Turkey transmission system operator needs grid codes for wind energy conversion systems. Contribution have been done in thesis for developing grid codes by the help of results obtained, and developing an aggregated model for wind energy conversion system having wound rotor induction machine and its drive.
Yarı rezonans yapı ve yayılmış tayf metodu ile indüksiyon ocak tasarımı ve deneysel sonuçları
This thesis presents an induction cooker design and its detailed experimental results. The design is based on Quasi Resonant Topology and is unique in terms of the particular Jitter Method it employs to drive the semiconductor switches (IGBTs).Most induction cookers are based on Half Bridge Topology. Although Quasi Resonant Topology offers a more cost effective implementation, it introduces more EMI problems. However, we solve these problems with our Jitter Method. Although there are other works in the literature that solve the EMI issues by some sort of jitter methods (i.e., spread spectrum methods), these methods do not address the high voltage stress created across the IGBTs. However, the Jitter Method proposed in this thesis also reduces collector-emitter voltage stress besides improving EMI. Note that jitter methods also prevent mechanical vibration (i.e., resonance), which cause audible noise.Another thing that makes this thesis unique in the literature is the rich set of experimental results it contains ? based on an experimental prototype we built with a power rating of 2300W. While the existing literature mostly contains theoretical treatment, we have produced detailed experimental results for Quasi Resonant Topology and show that the current harmonics (drawn from the utility) stay within the published standards (TS EN 61000-3-2). We also include experimental results for Delivered Power Detection, Pan Detection, and Protection Circuits.
ALTO servisli eş görevli ağlarda gerçek zamanlı ölçeklenebilir video akıtımı
It has been measured that, as high as 80% of the average Internet traffic is now from peer-to-peer (P2P) applications, and upwards of 90% during peak hours. These results tell us that a significant portion of the traffic that ISPs route is P2P traffic. However, since the typical P2P application overlay network model is network-oblivious, due to its nature, it causes inefficient network utilization, and low qualityof experience, from the perspective of the network providers and the end users, respectively. This inefficient resource utilization increases inter-ISP traffic, and leads to serious disruptions on ISP economics as well as lower QoE by the users.A significant portion of the P2P traffic on the Internet is for video applications. Furthermore, real networks are heterogeneous in link rates. Thus a live video streamingservice should support streams with different qualities for users using different data rates. A possible solution to this problem is achieved by creating a different video file for each quality level. However, this solution is inefficient due to data duplication.To improve ISP economics, improve network efficiency and achieve acceptable QoE performance, we implement a P2P Live Scalable Video Streaming Mechanism and Application Layer Traffic Optimization (ALTO) Server, by using different peer ranking algorithms in this thesis. The main objective of this thesis, to show that the ALTO protocol reduces the inter-ISP traffic significantly while maintaining the application performance. Results reveal that, placing an ALTO Server decreases the inter-ISP traffic dramatically while maintaining a satisfactory QoE performance for the streaming video application.
Kenar bulma algoritması ve regresyon ile dct-tabanlı referanssız bloklanma ölçüm metodu
This thesis presents a blocking artifact detection algorithm and consists of detailed experimental results. Blocking artifacts are a serious problem in low data rate transmission of such videos (or image sequences), which employ DCT-based compression algorithms. Too much compression due to bandwidth constraints can introduce blocking artifacts. Online quality measurement techniques for artifacts such as blockiness are required to for broadcasters and internet service providers to inspect their streaming systems. Blockiness measurement can be done through full-reference (FR), reduced-reference (RR), or no-reference (NR) methods. NR is the most efficient one as accessing reference content may not be always possible. NR methods also offer the possibility of real-time inspection. We propose a novel NR blockiness measurement method. The method is based on DCT and uses a model of the human visual system like some of the literature. However, it is unique as it uses Sobel edge detection algorithm to avoid miscalculations and also employs regression analysis to match mean opinion scores (MOS) of human observers. These unique features of our method let us achieve results that are more correlated to the MOS for LIVE dataset, which is used to train and test our algorithm. To measure how well our results match the MOS values in LIVE, we use Pearson and Spearman correlation formulations. The best Spearman correlation obtained in the literature for LIVE dataset is 94% while we get 95%. On the other hand, we get a Pearson correlation of 98% and surpass the best in the literature by 94%.