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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3

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Quartile: search.filters.quartile.Q1Subject: search.filters.subject.Electrical electronics engineering

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    Performance measures for video object segmentation and tracking
    (IEEE-Inst Electrical Electronics Engineers Inc, 2004) Erdem, Çiğdem Eroğlu; Sankur, Bülent; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207
    We propose measures to evaluate quantitatively the performance of video object segmentation and tracking methods without ground-truth (GT) segmentation maps. The proposed measures are based on spatial differences of color and motion along the boundary of the estimated video object plane and temporal differences between the color histogram of the current object plane and its predecessors. They can be used to localize (spatially and/or temporally) regions where segmentation results are good or bad; and/or they can be combined to yield a single numerical measure to indicate the goodness of the boundary segmentation and tracking results over a sequence. The validity of the proposed performance measures without GT have been demonstrated by canonical correlation analysis with another set of measures with GT on a set of sequences (where GT information is available). Experimental results are presented to evaluate the segmentation maps obtained from various sequences using different segmentation approaches.
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    Emerging 3-D imaging and display technologies
    (Institute of Electrical and Electronics Engineers (IEEE), 2017) Javidi, Bahram; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207
    We have become an information-centric society vastly dependent on the collection, communication, and presentation of information. At any given moment, it is likely that we are in the vicinity of some form of a display as displays play a prominent role in a variety of devices and applications. Three-dimensional imaging and display technologies are important components for presentation and visualization of information and for creating real-world-like environments in communication. There are broad applications of 3-D imaging and display technologies in computers, communication, mobile devices, TV, video, entertainment, robotics, metrology, security and defense, healthcare, and medicine.
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    Lossless watermarking for image authentication: a new framework and an implementation
    (IEEE-Inst Electrical Electronics Engineers Inc, 2006) Çelik, Mehmet Utku; Sharma, Gaurav; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207
    We present a novel framework for lossless (invertible) authentication watermarking, which enables zero-distortion reconstruction of the un-watermarked images upon verification. As opposed to earlier. lossless authentication methods that required reconstruction of the original image prior to validation, the new framework allows validation of the watermarked images before recovery of the original image. This reduces computational requirements in situations when either the verification step fails or the zero-distortion reconstruction is not needed. For verified images, integrity of the reconstructed image is ensured by the uniqueness of the reconstruction procedure. The framework also enables public(-key) authentication without granting access to the perfect original and allows for efficient tamper localization. Effectiveness of the framework is demonstrated by implementing the framework using hierarchical image authentication along with lossless generalized-least significant bit data embedding.
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    Transport methods in 3DTV - a survey
    (IEEE-Inst Electrical Electronics Engineers Inc, 2007) Akar, Gözde B.; Fehn, Christoph; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Civanlar, Mehmet Reha; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; College of Engineering; 26207; 16372
    We present a survey of transport methods for 3-D video ranging from early analog 3DTV systems to most recent digital technologies that show promise in designing 3DTV systems of tomorrow. Potential digital transport architectures for 3DTV include the DVB architecture for, broadcast and the Internet Protocol (IP) architecture for wired or wireless streaming. There are different multiview representation/compression methods for delivering the 3-D experience which provide a tradeoff between compression efficiency, random access to views, and ease of rate adaptation, including the "video plus-depth" compressed representation and various multiview video coding (MVC) options. Commercial activities using these representations in broadcast and IP streaming have emerged, and successful transport of such data has been reported. Motivated by the growing impact of the Internet protocol based media transport technologies, we focus on the ubiquitous Internet as the network infrastructure of choice for future 3DTV systems. Current research issues in unicast and multicast mode multiview video streaming include network protocols such as DCCP and peer-to-peer protocols, effective congestion control, packet loss protection and concealment, video rate adaptation, and network/service scalability. Examples of end-to-end systems for multiview video streaming have been provided.
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    Client-driven selective streaming of multiview video for interactive 3DTV
    (IEEE-Inst Electrical Electronics Engineers Inc, 2007) Kurutepe, Engin; Civanlar, Mehmet Reha; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207
    We present a novel client-driven multiview video streaming system that allows a user to watch 3-D video interactively with significantly reduced bandwidth requirements by transmitting a small number of views selected according to his/her head position. The user's head position is tracked and predicted into the future to select the views that best match the user's current viewing angle dynamically. Prediction of future head positions is needed so that views matching the predicted head positions can be prefetched in order to account for delays due to network transport and stream switching. The system allocates more bandwidth to the selected views in order to render the current viewing angle. Highly compressed, lower quality versions of some other views are also prefetched for concealment if the current user viewpoint differs from the predicted viewpoint. An objective measure based on the abruptness of the head movements and delays in the system is introduced to determine the number of additional lower quality views to be prefetched. The proposed system makes use of multiview coding (MVC) and scalable video coding (SVC) concepts together to obtain improved compression efficiency while providing flexibility in bandwidth allocation to the selected views. Rate-distortion performance of the proposed system is demonstrated under different experimental conditions.
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    Video object tracking with feedback of performance measures
    (IEEE-Inst Electrical Electronics Engineers Inc, 2003) Erdem, Çiğdem Eroğlu; Sankur, Bülent; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207
    We present a scalable object tracking framework, which is capable of tracking the contour of nonrigid objects in the presence of occlusion. The framework consists of open-loop boundary prediction and closed-loop boundary correction parts. The open-loop prediction block adaptively divides the object contour into subcontours, and estimates the mapping parameters for each subsegment. The closed-loop boundary correction block employs a suitably weighted combination of low-level features such as color edge, color segmentation, motion models, and motion segmentation for each subcontour. Performance evaluation measures are used in a feedback loop to evaluate the goodness of the segmentation/tracking in order to adjust the weights assigned to each of these low-level features for each subcontour at each frame. The framework is scalable because it can be adapted to track a coarse estimate of the boundary of selected objects in real-time, as well as pixel-accurate boundary tracking in off-line mode. The proposed method does,not depend on any single motion or shape model, and does not need training. Experimental results demonstrate that the algorithm is able to track the object boundaries under significant occlusion and. background clutter.
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    Dual-wavelength temporal dynamics of a gain-switched 2-mu m Tm3+:Lu2O3 ceramic laser
    (IEEE-Inst Electrical Electronics Engineers Inc, 2018) N/A; N/A; Department of Physics; Toker, Işınsu Baylam; Canbaz, Ferda; Sennaroğlu, Alphan; PhD Student; PhD Student; Faculty Member; Department of Physics; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; 23851
    We provide a detailed experimental investigation of the energy efficiency and rich temporal dynamics of a gain-switched 2-mu m Tm3+:Lu2O3 ceramic laser pumped near 800 nm. A tunable Ti3+:sapphire laser was used to determine the full excitation spectrum and the optimum pumping bands for the 1.5% Tm3+:Lu2O3 ceramic gain medium. These bands were centered at 774, 796, and 811 nm. The highest output pulse energy was obtained when the pump wavelength was set to 796 nm. In the experiments, a free-running x-cavity was used to investigate the energy efficiency of the Tm3+:Lu2O3 ceramic laser. Extracavity grating-dispersed output and prism-tuned resonator were used to further assess the role of cross-relaxation for the 1.5% Tm3+:Lu2O3 ceramic. Finally, we demonstrate that as the pump energy was increased, a transition occurred from-single-wavelength output (2068 nm) to dual-wavelength multipulse output (2068 and 1968 nm). We performed systematic temporal and spectral characterization measurements by using the free-running resonator, extracavity-grating-dispersed laser output, and prism-tuned resonator to investigate how the laser pulses at 1968 and 2068 nm evolved in time. A plane-wave rate equation model was further used to investigate the temporal dynamics of the Tm3+:Lu2O3 ceramic laser and provided predictions in qualitative agreement with experimental data.
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    Photonic studies on polymer-coated sapphire-spheres: a model system for biological ligands
    (Elsevier, 2015) Murib, M. S.; Yeap, W. S.; Martens, D.; Liu, X.; Bienstman, P.; Fahlman, M.; Schöning, M. J.; Michiels, L.; Haenen, K.; Wagner, P.; Department of Physics; Serpengüzel, Ali; Faculty Member; Department of Physics; College of Sciences; 27855
    In this study we show an optical biosensor concept, based on elastic light scattering from sapphire micro-spheres. Transmitted and elastic scattering intensity of the microspheres (radius 500 mu m, refractive index 1.77) on an optical fiber half coupler is analyzed at 1510 nm. The 0.43 nm angular mode spacing of the resonances is comparable to the angular mode spacing value estimated using the optical size of the microsphere. The spectral linewidths of the resonances are in the order of 0.01 am, which corresponds to quality factors of approximately 10(5). A polydopamine layer is used as a functionalizing agent on sapphire microspherical resonators in view of biosensor implementation. The varying layer thickness on the microsphere is determined as a function of the resonance wavelength shift. It is shown that polymer functionalization has a minor effect on the quality factor. This is a promising step toward the development of an optical biosensor.
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    Direct experimental determination of the optimum chromium concentration in continuous-wave Cr2(+): ZnSe lasers
    (Institute of Electrical and Electronics Engineers (IEEE), 2007) Demirbaş, Ümit; Department of Physics; Department of Chemistry; Department of Chemistry; Sennaroğlu, Alphan; Somer, Mehmet Suat; Kurt, Adnan; Faculty Member; Faculty Member; Teaching Faculty; Department of Physics; Department of Chemistry; College of Sciences; College of Sciences; College of Sciences; 23851; 178882; 194455
    We employed several experimental techniques to measure the concentration dependence of the important laser parameters, and directly determine the optimum ion concentration for continuous-wave (CW) operation in room temperature Cr2+:ZnSe lasers. By using diffusion doping, 40 polycrystalline Cr2+ :ZnSe samples with ion concentrations in the range of 0.8 x 10(18) to 66 x 10(18) ions/cm(3) were prepared and used in this paper. Based on the spectroscopic measurements, empirical formulae showing the concentration dependence of the passive laser losses, fluorescence lifetime, and the fluorescence efficiency were obtained. By using the fluorescence efficiency data, the optimum chromium concentration, which maximizes the 2400-nm fluorescence intensity at a fixed excitation power, was determined to be 6 x 10(18) ions/cm(3). The dependence of the optimum concentration on sample length was further discussed. The CW power performance of the samples was also evaluated. At an incident pump power of 2.1 W, the optimum concentration for lasing was determined to be 8.5 X 10(18) ions/cm' that was in good agreement with the fluorescence measurements. The predictions of the fluorescence analysis and laser power measurements were in good agreement at low chromium concentrations. The observed discrepancy at higher doping levels was attributed to thermal loading.
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    Cooperative MIMO-OFDM based inter-vehicular visible light communication using brake lights
    (Elsevier, 2018) Narmanlıoğlu, Omer; T; Uysal, Murat; N/A; Department of Electrical and Electronics Engineering; Turan, Buğra; Ergen, Sinem Çöleri; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 7211
    Inter-vehicular connectivity to enhance road safety and support highly autonomous driving is increasingly becoming popular. Despite the prevalent works on radio-frequency (RF) based vehicular communication schemes, visible light communication (VLC) is considered to be a promising candidate for vehicular communications due to its low complexity and RF interference-free nature. Deployment of multiple light emitting diodes (LEDs) enables multiple-input multiple-output (MIMO) transmission in the context of vehicular VLC. This paper investigates applicability of both point-to-point (direct) vehicular VLC and decode-and-forward relaying based cooperative vehicular VLC including relay terminals between source and destination terminals to enhance road safety based on real world measurements. We consider direct current biased optical orthogonal frequency division multiplexing (DCO-OFDM) based MIMO transmission scheme and evaluate the performances of different MIMO modes including repetition code (RC) and spatial multiplexing (SM), different modulation orders with different transmitter receiver selection mechanisms to support line-of-sight (LoS) and beyond LoS multi-hop vehicular VLC. The results reveal that the selection of the closest transmitters to the receivers provides better performance due to high signal-to-noise-ratio requirements for RC mode whereas SM suffers from channel correlation. Usage of all possible transmitters does not always yield better performance due to the power division at the transmitter side. on the other hand, the performance of RC shows more degradation on higher-order modulations that are required to yield the same throughput with SM. Therefore, considering the higher order modulation requirement for RC based VLC, SM is concluded to be a favorable MIMO scheme for cooperative vehicular VLC. We further demonstrate the benefits of multi-hop transmission over direct transmission with respect to different number of relay vehicles as a consequence of varying inter-vehicular distances between source and destination vehicles.