Browsing by Subject "Computers"

Now showing 1 - 12 of 12

Open Access
3D forest fire propagation simulation
(IEEE, 2008-05) Köse, Kıvanç; Grammalidis, N.; Yılmaz, E.; Çetin, A. Enis
The increase in the number of forest fires in the last few years dispatch governments to take precautions. Besides prevention, early intervention is also very important in fire fighting. If the firefighters know where the fire will be in some time, it would be easier for them to stop the fire. Therefore a big need for simulating the fire behavior exists. In this paper we are proposing a system which can simulate the propagation of fire in time. Also this system can visualize the propagation of fire in any 3D-GIS environment, that accepts KMZ as a file format. Besides, any user demanded data can be visualized on the map of the system. This gives the chance of fire planning to firefighters. The system can visualize its results on 3D screens in 3D. Therefore, a better understanding of the terrain can be obtained. ©2008 IEEE.
Open Access
Analysis of design parameters in safety-critical computers
(IEEE Computer Society, 2018) Ahangari, H.; Atik, F.; Ozkok, Y. I.; Yildirim, A.; Ata, S. O.; Ozturk, O.
Nowadays, safety-critical computers are extensively used in many civil domains like transportation including railways, avionics, and automotive. In evaluating these safety critical systems, previous studies considered different metrics, but some of safety design parameters like failure diagnostic coverage (C) or common cause failure (CCF) ratio have not been seriously taken into account. Moreover, in some cases safety has not been compared with standard safety integrity levels (IEC-61508: SIL1-SIL4) or even have not met them. Most often, it is not very clear that which part of the system is the Achilles heel and how design can be improved to reach standard safety levels. Motivated by such design ambiguities, we aim to study the effect of various design parameters on safety in some prevalent safety configurations, namely, 1oo2 and 2oo3, where 1oo1 is also used as a reference. By employing Markov modeling, we analyzed the sensitivity of safety to important parameters including: failure rate of processor, failure diagnostic coverage, CCF ratio, test and repair rates. This study aims to provide a deeper understanding on the influence of variation in design parameters over safety. Consequently, to meet appropriate safety integrity level, instead of improving some parts of a system blindly, it will be possible to make an informed decision on more relevant parameters. IEEE
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Bilgisayarlı yayıncılık
(1994) Özel, Sevgi
Open Access
Comparison of two image-space subdivision algorithms for direct volume rendering on distributed-memory multicomputers
(Springer, 1995-08) Tanin, Egemen; Kurç, Tahsin M.; Aykanat, Cevdet; Özgüç, Bülent
Direct Volume Rendering (DVR) is a powerful technique for visualizing volumetric data sets. However, it involves intensive computations. In addition, most of the volumetric data sets consist of large number of 3D sampling points. Therefore, visualization of such data sets also requires large computer memory space. Hence, DVR is a good candidate for parallelization on distributed-memory multicomputers. In this work, image-space parallelization of Raycasting based DVR for unstructured grids on distributed-memory multicomputers is presented and discussed. In order to visualize unstructured volumetric datasets where grid points of the dataset are irregularly distributed over the 3D space, the underlying algorithms should resolve the point location and view sort problems of the 3D grid points. In this paper, these problems are solved using a Scanline Z-buffer based algorithm. Two image space subdivision heuristics, namely horizontal and recursive rectangular subdivision heuristics, are utilized to distribute the computations evenly among the processors in the rendering phase. The horizontal subdivision algorithm divides the image space into horizontal bands composed of consecutive scanlines. In the recursive subdivision algorithm, the image space is divided into rectangular subregions recursively. The experimental performance evaluation of the horizontal and recursive subdivision algorithms on an IBM SP2 system are presented and discussed. © Springer-Verlag Berlin Heidelberg 1996.
Open Access
ConceptMap: mining noisy web data for concept learning
(Springer, 2014-09) Gölge, Eren; Duygulu, Pınar
We attack the problem of learning concepts automatically from noisy Web image search results. The idea is based on discovering common characteristics shared among subsets of images by posing a method that is able to organise the data while eliminating irrelevant instances. We propose a novel clustering and outlier detection method, namely Concept Map (CMAP). Given an image collection returned for a concept query, CMAP provides clusters pruned from outliers. Each cluster is used to train a model representing a different characteristics of the concept. The proposed method outperforms the state-of-the-art studies on the task of learning from noisy web data for low-level attributes, as well as high level object categories. It is also competitive with the supervised methods in learning scene concepts. Moreover, results on naming faces support the generalisation capability of the CMAP framework to different domains. CMAP is capable to work at large scale with no supervision through exploiting the available sources. © 2014 Springer International Publishing.
Open Access
Data-parallel web crawling models
(Springer, 2004) Cambazoglu, B. B.; Turk, A.; Aykanat, Cevdet
The need to quickly locate, gather, and store the vast amount of material in the Web necessitates parallel computing. In this paper, we propose two models, based on multi-constraint graph-partitioning, for efficient data-parallel Web crawling. The models aim to balance the amount of data downloaded and stored by each processor as well as balancing the number of page requests made by the processors. The models also minimize the total volume of communication during the link exchange between the processors. To evaluate the performance of the models, experimental results are presented on a sample Web repository containing around 915,000 pages. © Springer-Verlag 2004.
Open Access
Efficient parallel spatial subdivision algorithm for object-based parallel ray tracing
(Pergamon Press, 1994) Aykanat, Cevdet; İşler, V.; Özgüç, B.
Parallel ray tracing of complex scenes on multicomputers requires the distribution of both computation and scene data to the processors. This is carried out during preprocessing and usually consumes too much time and memory. The paper presents an efficient parallel subdivision algorithm that decomposes a given scene into rectangular regions adaptively and maps the resultant regions to the node processors of a multicomputer. The proposed algorithm uses efficient data structures to identify the splitting planes quickly. Furthermore the mapping of the regions and the objects to the node processors is performed while parallel spatial subdivision proceeds. The proposed algorithm is implemented on an Intel iPSC/2 hypercube multicomputer and promising results have been obtained. © 1994.
Open Access
Molecular logic: from single logic gates to sophisticated logic circuits, from fundamental science to practical applications
(Wiley, 2017) Akkaya, E. U.; Katz, E.; Pischel, U.
Open Access
Multicriteria inventory classification using a genetic algorithm
(Elsevier, 1998) Guvenir, H. A.; Erel, E.
One of the application areas of genetic algorithms is parameter optimization. This paper addresses the problem of optimizing a set of parameters that represent the weights of criteria, where the sum of all weights is 1. A chromosome represents the values of the weights, possibly along with some cut-off points. A new crossover operation, called continuous uniform crossover, is proposed, such that it produces valid chromosomes given that the parent chromosomes are valid. The new crossover technique is applied to the problem of multicriteria inventory classification. The results are compared with the classical inventory classification technique using the Analytical Hierarchy Process. © 1998 Elsevier Science B.V.
Open Access
rtPS uplink scheduling algorithms for IEEE 802.16 networks
(Boğaziçi University, 2008-06) Ertürk, Mustafa Cenk; Akar, Nail
IEEE 802.16 MAC provides flexible bandwidth allocation and QoS mechanisms for users with different requirements. However, QoS scheduling is not specified by the 802.16 standard and is thus left open for vendors' implementation. In this paper, we propose an uplink scheduler to be used in WiMAX Base Station (BS) for rtPS type of connections. We propose that the base station maintains a leaky bucket for each rtPS connection to police and schedule rtPS traffic for uplink traffic management. The proposed scheduler is studied via simulations in MATLAB and throughput and fairness properties of the scheduler are demonstrated. Copyright ©2008 by Boǧaziçi University.
Open Access
Visual transformation aided contrastive learning for video-based kinship verification
(IEEE, 2017-10) Dibeklioğlu, Hamdi
Automatic kinship verification from facial information is a relatively new and open research problem in computer vision. This paper explores the possibility of learning an efficient facial representation for video-based kinship verification by exploiting the visual transformation between facial appearance of kin pairs. To this end, a Siamese-like coupled convolutional encoder-decoder network is proposed. To reveal resemblance patterns of kinship while discarding the similarity patterns that can also be observed between people who do not have a kin relationship, a novel contrastive loss function is defined in the visual appearance space. For further optimization, the learned representation is fine-tuned using a feature-based contrastive loss. An expression matching procedure is employed in the model to minimize the negative influence of expression differences between kin pairs. Each kin video is analyzed by a sliding temporal window to leverage short-term facial dynamics. The effectiveness of the proposed method is assessed on seven different kin relationships using smile videos of kin pairs. On the average, 93:65% verification accuracy is achieved, improving the state of the art. © 2017 IEEE.
Open Access
WiSAP: a wireless personal access network for handheld computing devices
(Institute of Electrical and Electronics Engineers, 1998) Bisdikian, C.; Bhagwat, P.; Gaucher, B. P.; Janniello, F. J.; Naghshineh, M.; Pandoh, P.; Korpeoglu, I.
New short-range wireless communication technologies would enable environment-aware, mobile, personal area networks. These new technologies will serve as enablers for ubiquitous, low-cost, low-complexity, small-sized information appliances. These appliances will serve as interaction tools between humans and computer-driven services and applications existing in either the close or distant vicinity of humans. In this article the new application paradigms these new technologies will enable are explored. Furthermore, an experimental wireless personal access networking platform called WiSAP, developed to research these new technologies and applications paradigms, is presented. Finally, some of the experiences gained from WiSAP while designing a consumer-oriented portable wireless communication system suitable for wireless mobile personal access networks are also presented.