Tubitak Uzay

Ankara, Turkey

Tubitak Uzay

Ankara, Turkey
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Topcu O.,Tubitak Uzay | Kalem A.,Bilkent University | Esen E.,Tubitak Uzay
2013 21st Signal Processing and Communications Applications Conference, SIU 2013 | Year: 2013

Moving object segmentation with a nonstationary camera is a difficult problem due to the motion of both camera and the object. A moving object segmentation method is proposed in this work to be used in pan-tilt-zoom (PTZ) cameras. The method is based on composing scene mosaic and applying Gaussian mixture background subtraction algorithm after constructing a background model using the mosaic. Background subtraction is performed by mapping the frames captured during camera's course of motion to the background mosaic. The proposed mosaic building method requires less number of picture correspondences when compared to known methods. The success of the proposed segmentation method is demonstrated by the conducted experiments. © 2013 IEEE.

Atar O.,Tubitak UZAY | Sazli M.H.,Ankara University
Journal of the Faculty of Engineering and Architecture of Gazi University | Year: 2011

The most difficult design issue for turbo codes, which is the most recent and successful channel coding method to approach the channel capacity limit, is the design of the iterative decoders which perform calculations for all possible states of the encoders. BCJR (MAP) algorithm, which is used for turbo decoders, embodies complex mathematical operations such as division, exponential and logarithm calculations. Therefore, BCJR algorithm was avoided and the sub-optimal derivatives of this algorithm such as Log-MAP and Max-Log-MAP were preferred for turbo decoder implementations. BCJR algorithm was reformulated and wrapped into a suitable structure for FPGA implementations at previous works [1]. Reformulated BCJR algorithm is implemented in this work. Complex mathematical operations which run slowly on hardware (division, exponential and logarithm calculations) are read from look-up-tables and high performance calculation structures are established. Implemented system is verified through simulations. It is observed that the BER performance obtained is better than the Log-MAP algorithm as expected.

Khamis A.,National University of Malaysia | Khamis A.,University Technical Malaysia Melaka | Shareef H.,National University of Malaysia | Mohamed A.,National University of Malaysia | Bizkevelci E.,Tubitak Uzay
Neurocomputing | Year: 2015

The high penetration level of distributed generation (DG) provides numerous potential environmental benefits, such as high reliability, efficiency, and low carbon emissions. However, the effective detection of islanding and rapid DG disconnection is essential to avoid safety problems and equipment damage caused by the island mode operations of DGs. The common islanding protection technology is based on passive techniques that do not perturb the system but have large non-detection zones. This study attempts to develop a simple and effective passive islanding detection method with reference to a probabilistic neural network-based classifier, as well as utilizes the features extracted from three phase voltages seen at the DG terminal. This approach enables initial features to be obtained using the phase-space technique. This technique analyzes the time series in a higher dimensional space, revealing several hidden features of the original signal. Intensive simulations were conducted using the DigSilent Power Factory® software. Results show that the proposed islanding detection method using probabilistic neural network and phase-space technique is robust and capable of sensing the difference between the islanding condition and other system disturbances. © 2014 Elsevier B.V.

Khamis A.,National University of Malaysia | Khamis A.,University Technical Malaysia Melaka | Shareef H.,National University of Malaysia | Bizkevelci E.,Tubitak Uzay | Khatib T.,National University of Malaysia
Renewable and Sustainable Energy Reviews | Year: 2013

Islanding detection of distributed generations (DGs) is one of the most important aspects of interconnecting DGs to the distribution system. Islanding detection techniques can generally be classified as remote methods, which are associated with islanding detection on the utility sides, and local methods, which are associated with islanding detection on the DG side. This paper presents a survey of various islanding detection techniques and their advantages and disadvantages. The paper focused on islanding detection using a conventional and intelligent technique. A summary table that compares and contrasts the existing methods is also presented. © 2013 Elsevier Ltd. All rights reserved.

Khamis A.,National University of Malaysia | Khamis A.,University Technical Malaysia Melaka | Shareef H.,National University of Malaysia | Mohamed A.,National University of Malaysia | Bizkevelci E.,Tubitak Uzay
Jurnal Teknologi (Sciences and Engineering) | Year: 2014

Voltage stability is one of the major concerns in operational and planning of modern power system. Many strategies have been implemented to avoid voltage collapse, which the load shedding considered as the last option. However, optimization is needed to estimate the minimum amount to shed so as to prevent voltage instability. In this paper, an effective method is presented for estimating the optimal amount of load to be shed in a distribution system based on the gravitational search algorithm (GSA). The voltage stability margin (VSM) of the system has been considered in the objective function. The optimization problem is formulated to maximize the VSM of the system and at the same time satisfying the operation and security constraints. The optimum solution depends on the predefined constraints such as the number of load buses available to shed and the maximum amount of load permitted to shed. Simulation result conducted on the IEEE 33 bus radial distribution system shows that the system voltage stability can be improved by optimally shedding the loads at critical system buses. The results also indicate that the numbers of load buses available for load shedding does not have a significant impact on voltage stability margin, but it is highly dependent on the maximum amount of load permitted to shed. © 2014 Penerbit UTM Press. All rights reserved.

Tor O.B.,Tubitak Uzay | Guven A.N.,Middle East Technical University | Shahidehpour M.,Illinois Institute of Technology
IEEE Transactions on Power Systems | Year: 2010

This paper presents a transmission expansion planning (TEP) model which coordinates investment decisions in monopolistic transmission and decentralized generator sectors. The proposed planning approach gauges transmission congestion and security constraints with respect to transmission investments while promoting investments on independent power produces (IPPs) through incentive payments. The paper includes discussions on incentive mechanisms and prioritization among qualified IPPs for several planning scenarios. Such incentives might be necessary to trigger investments on IPPs earlier than those projected by the decentralized generation system, when the power system security is threatened. The proposed planning approach would optimize the sum of transmission investments, incentive payments to IPPs, and congestion costs along the planning horizon. The case studies illustrate how the proposed planning algorithm could be utilized in order to determine incentive payments to candidate generators when necessary, and prioritize such incentives among multiple IPP candidates. © 2010 IEEE.

Kucuk D.,Tubitak Uzay | Yazici A.,Middle East Technical University
INISTA 2011 - 2011 International Symposium on INnovations in Intelligent SysTems and Applications | Year: 2011

Video texts -if available- constitute a valuable source for automatic semantic annotation of large video archives. In this paper, we present our attempts towards the improvement of a text-based semantic annotation and retrieval system for Turkish news videos through automatic Web alignment and event extraction. The results of our initial experiments turn out to be promising and these two features are incorporated into the existing system. Although the ideas of automatic Web alignment and text-based event extraction are not the novel contributions of the current paper, to the best of our knowledge, their first implementation and employment in a system for Turkish news videos is a significant contribution to related work on videos in lesser studied languages such as Turkish. Also overviewed in the current paper is the prospective version of the system encompassing components for several other tasks including topic segmentation, keyphrase extraction, news categorization and summarization to enhance the overall system. © 2011 IEEE.

Elma I.,Tubitak Uzay | Tor O.B.,Tubitak Uzay
IET Conference Publications | Year: 2011

In this study, impact of wind power generation penetration level on transmission expansion planning (TEP) problem is discussed. Main focus is to address the following contradiction: wind power generation contributes to TEP problem by delaying the necessary transmission enforcements due to local demand growth. On the other hand, if the installed capacity of wind power plants is much higher than load growth rate of the region, then backdating of transmission enforcement might be necessary. A TEP algorithm, which minimizes summation of transmission investment cost and the cost that appears due to limitation of wind power generation in case of transmission line constraints, is proposed. The proposed planning approach is performed on a simple numerical example. Main conclusion is that, if the difference between the penetration level of wind power generation and local load in any year along the planning horizon is smaller than the steady-state thermal capacity rating of the existing transmission lines, this will result in transmission enforcement delay. Otherwise, there will be risk of congestion which might necessitate transmission enforcement, and therefore, needs optimum transmission planning analysis.

Sakarya U.,TuBITAK UZAY | Topcu O.,TuBITAK UZAY | Leloglu U.M.,TuBITAK UZAY | Soysal M.,TuBITAK UZAY | Tunali E.,TuBITAK UZAY
Forensic Science International | Year: 2012

One of the significant problems encountered in criminology studies is the successful automated matching of fired cartridge cases, on the basis of the characteristic marks left on them by firearms. An intermediate step in the solution of this problem is the segmentation of certain regions that are defined on the cartridge case base. This paper describes a model-based method that performs segmentation of the cartridge case using surface height image of a center fire cartridge case base. The proposed method detects the location of the cartridge case base center and specific circular contours around it iteratively by projecting the problem to a one-dimensional feature space. In addition, the firing pin impression region is determined by utilizing an adaptive threshold that differentiates impression marks form primer region surface. Letters on the cartridge case base are also detected by using surface modeling and adaptive thresholding, in order to render the surface comparison operation robust against irrelevant surface features. Promising experimental results indicate the eligibility of the proposed method to be used for automated cartridge case base region segmentation process. © 2012 Elsevier Ireland Ltd.

Yaglioglu B.,Tubitak Uzay | Utku A.,Tubitak Uzay | Yilmaz O.,Tubitak Uzay | Ozdemir B.G.,Tubitak Uzay
RAST 2013 - Proceedings of 6th International Conference on Recent Advances in Space Technologies | Year: 2013

As the number of satellite launches increases, space debris has become a significant issue for satellite manufacturers, owners and operators. Timely and accurate information regarding possible collisions or near misses is critical not only to avoid spacecraft damage, but also to avoid unnecessary maneuvers or spacecraft downtimes. However, the information about the details and extent of collision risks is obtained from external sources and these data may contain various levels of accuracy, detail, secrecy and continuity depending on the preferences of the supplier countries. In this manner, it is important to initiate a capability to acquire space surveillance data independently for protecting the national space assets which are critical for the economy, security and scientific research. In this study, we review the space surveillance systems and related activities around the world including Turkey. Then we outline the importance of establishing a national space surveillance system and, finally, we propose a basic architecture of such a system and a roadmap to develop it. © 2013 IEEE.

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