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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only Robust speech recognition using adaptively denoised wavelet coefficients(IEEE, 2004) Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; N/A; Tekalp, Ahmet Murat; Erzin, Engin; Akyol, Emrah; Faculty Member; Faculty Member; Master Student; Department of Electrical and Electronics Engineering; College of Engineering; College of Engineering; Graduate School of Sciences and Engineering; 26207; 34503; N/AThe existence of additive noise affects the performance of speech recognition in real environments. We propose a new set of feature vectors for robust speech recognition using denoised wavelet coefficients. The use of wavelet coefficients in speech processing is motivated by the ability of the wavelet transform to capture both time and frequency information and the non-stationary behaviour of speech signals. We use one set of noisy data, such as data with car noise, and we use hard thresholding in the best basis for denoising. We use isolated digits as our database in our HMM based speech recognition system. A performance comparison of hard thresholding denoised wavelet coefficients and MFCC feature vectors is presented.Publication Metadata only Optimal rate and input format control for content and context adaptive video streaming(IEEE, 2004) Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; N/A; Tekalp, Ahmet Murat; Civanlar, Mehmet Reha; Özçelebi, Tanır; Faculty Member; Faculty Member; PhD Student; Department of Electrical and Electronics Engineering; College of Engineering; College of Engineering; Graduate School of Sciences and Engineering; 26207; 16372; N/AA novel dynamic programming based technique for optimal selection of input video format and compression rate for video streaming based on "relevancy" of the content and user context is presented. The technique uses context dependent content analysis to divide the input video into temporal segments. User selected relevance levels assigned to these segments are used in formulating a constrained optimization problem, which is solved using dynamic programming. The technique minimizes a weighted distortion measure and the initial waiting time for continuous playback under maximum acceptable distortion constraints. Spatial resolution and frame rate of input video and the DCT quantization parameters are used as optimization variables. The technique is applied to encoding of soccer videos using an H.264 [1] encoder. The improvements obtained over a standard H.264 implementation are demonstrated by experimental results.Publication Metadata only E_coach(IEEE, 2004) Department of Electrical and Electronics Engineering; Department of Computer Engineering; Civanlar, Mehmet Reha; Baykan, Eda; Faculty Member; Undergraduated Student; Department of Electrical and Electronics Engineering; Department of Computer Engineering; College of Engineering; College of Engineering; 16372; N/AWe developed the necessary software to control the playback speed of exercise videos playing on a personal computer, using the heart rate of an individual performing the recorded exercise routine. Moderate exercise, at an appropriate heart rate, is widely regarded today as an excellent way to improve one's health when performed on a regular and frequent basis. One popular form of an indoor exercise program is to use a video "workout" program of aerobic exercise and/or weight training exercises. The "off-the-shelf" exercise videos, while they may target various fitness levels (such as "beginner", "regular", and "advanced"), cannot offer precise adjustments to address each user's current fitness level. The software developed allows for the playback of an exercise video to be adjusted to accommodate the fitness level of the individual user through a closed loop feedback mechanism. The project is being improved for logging and analyzing the performance of an individual who uses the system regularly and for exercise planning. The closed loop feedback mechanism that models the relationship between the heart rate and exercise level, is being improved with the experiments in which subjects incude fit people as well as ones who are sedementary. © 2004 IEEE.Publication Metadata only Seed-based distributed group key selection algorithm for ad hoe networks(IEEE, 2007) N/A; Department of Computer Engineering; Atsan, Emre; Özkasap, Öznur; Master Student; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 113507Key establishment has a significant role in providing secure infrastructure for ad hoc networks. For this purpose, several key pre-distribution schemes have been proposed, but majority of the existing schemes rely on a trusted third party which causes a constraint in ad hoc platforms. We propose a seed-based distributed key selection algorithm, namely SeeDKS, for groups of nodes in ad hoc networks. Our approach is inspired by the earlier work on distributed key selection (DKS) and is based on the idea of common group key pool generated with group seed value for each different group. Simulation results show that using very small key ring sizes compared to DKS, we can achieve satisfactory results which DKS cannot accomplish in means of finding at least one common key among group members.Publication Metadata only Efficient continuous-wave operation of a diode-pumped Nd:YVO4 laser at 1342 nm(Elsevier Science Bv, 1999) Department of Physics; Sennaroğlu, Alphan; Faculty Member; Department of Physics; College of Sciences; 23851The experimental study described in this paper investigates the continuous-wave power performance of an efficient diode-pumped Nd:YVO4 laser at 1342 nm by employing four different end pumping configurations. When pumped by a high-power fiber-coupled diode array at 806 nm, the compact resonator consisting of a 9.25-mm long Nd:YVO4 crystal and a 3.6% transmitting output coupler produced as high as 3550 mW of output power. The absorbed power slope efficiency was measured to be 28.1%. By using the experimentally measured threshold data, the stimulated emission cross-section of the gain medium was determined to be 13 X 10(-19) cm(2) at 1342 nm. Above absorbed pump powers of 11 W, strong thermal loading caused saturation of the output power and the focal length of the induced thermal lens was measured as a function of the pump power. Results further showed that the laser output was insensitive to variations in the crystal boundary temperature between 20 degrees C and 40 degrees C.Publication Metadata only Symplectic and Lagrangian surfaces in 4-manifolds(Rocky Mt Math Consortium, 2008) Department of Mathematics; Etgü, Tolga; Faculty Member; Department of Mathematics; College of Sciences; 16206This is a brief summary of recent examples of isotopically different symplectic and Lagrangian surfaces representing a fixed homology class in a simply-connected symplectic 4-manifold.Publication Metadata only Batch fabrication of self-assembled nickel-iron nanowires by electrodeposition(IEEE, 2006) N/A; Department of Electrical and Electronics Engineering; Department of Mechanical Engineering; Şardan, Özlem; Yalçınkaya, Arda Deniz; Alaca, Burhanettin Erdem; Master Student; Researcher; Faculty Member; Department of Electrical and Electronics Engineering; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; 144523; 115108Lack of batch-compatible fabrication techniques can be considered as the most important challenge in the integration of nanostructures with microelectromechanical systems (MEMS). a solution to the micro-nano integration problem is offered by introducing a batch-compatible nanowire fabrication technique based on basic lithographic techniques and guided self-assembly. the basic principle is obtaining cracks at predetermined locations in a sacrificial SiO2 layer on Si and filling these cracks with a suitable metal by electrodeposition. the technique is demonstrated by using Nickel-Iron as the deposition material and verifying the magnetic behavior of resulting nanowires.Publication Metadata only Nonlinear phase noise in optical-fiber-communication systems(IEEE-Inst Electrical Electronics Engineers Inc, 2007) Department of Electrical and Electronics Engineering; Demir, Alper; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 3756Gordon and Mollenauer, in their famous paper published in 1990, laid out how the interplay between the nonlinear Kerr effect in optical fibers and the amplified spontaneousemission (ASE) noise from the optical-amplifiers results In enhanced levels of noise and degrades the performance of modulation schemes that encode information in, particularly, the phase of the optical carrier. This phenomenon has been termed as nonlinear phase noise in the literature. In this paper, we first present a comparative and critical review of previous techniques that have been proposed for the analysis of nonlinear phase noise by forming a classification framework that reveals some key underlying features. We then present a unifying theory, and a comprehensive methodology and computational techniques for the analysis and characterization of nonlinear phase noise and its impact on system performance by building on and extending previous work that we identify as most favorable and systematic. In our treatment, we consider a multichannel multispan optically amplified dense wavelength-division multiplexed system and develop general techniques for the analysis of the intricate interplay among Kerr nonlinearity, chromatic dispersion, and ASE noise, and for computing the bit-error-ratio performance of differential phase-shift-keying (DPSK) systems. By means of the extensive results we present, we demonstrate and argue that correlated noise behavior plays a most significant role in understanding nonlinear phase noise and its impact on DPSK system performance.Publication Metadata only Principles and performance analysis of second: a system for epidemic peer-to-peer content distribution(Academic Press Ltd- Elsevier Science Ltd, 2009) N/A; Department of Computer Engineering; Department of Mathematics; Department of Computer Engineering; Özkasap, Öznur; Çağlar, Mine; Alagöz, Ali; Faculty Member; Faculty Member; Other; Department of Mathematics; Department of Computer Engineering; College of Engineering; College of Sciences; College of Engineering; 113507; 105131; N/AWe propose and design a peer-to-peer system, SeCond, addressing the distribution of large sized content to a large number of end systems in an efficient manner. In contrast to prior work, it employs a self-organizing epidemic dissemination scheme for state propagation of available blocks and initiation of block transmissions. in order to exploit heterogeneity of peers, enhance the utilization of system resources and for the ease of deployment, scalability, and adaptivity to dynamic peer arrivals/departures, we propose mechanisms for adjusting protocol parameters dynamically according to the bandwidth usages. We describe design and analysis details of our protocol SeCond. Comprehensive performance evaluations and comparison with the BitTorrent system model have been accomplished for a wide range of scenarios. Performance results include scalability analysis for different arrival/departure patterns, flash-crowd scenario, overhead analysis, and fairness ratio. The major metrics we study include the average file download time, load on the primary seed, uplink/downlink utilization. and communication overhead. We show that SeCond is a scalable and adaptive protocol which takes the heterogeneity of the peers into account. The protocol is as fair as BitTorrent although it has no explicit strategy addressing free-riding. We also illustrate the applicability of an analytical fluid model to the behavior of SeCond.Publication Metadata only Experimental determination of fractional thermal loading in an operating diode-pumped Nd: YVO4 minilaser at 1064 nm(Optical Soc Amer, 1999) Department of Physics; Sennaroğlu, Alphan; Faculty Member; Department of Physics; College of Sciences; 23851A practical in, situ method is described and used for determination of the fractional thermal-loading parameter eta(h) in an operating diode-pumped Nd:YVO4 minilaser at 1064 nm. Readily applicable to the thermal characterization of other solid-state media, the method is based on the fact that thermally induced lensing will cause the laser oscillation to be quenched at a critical pump power whose magnitude depends on the cavity configuration, thermo-optical properties of the gain medium, and, in particular, on the value of eta(h). In the experiments described here, a 0.5-mm-long coated Nd:YVO4 crystal with 3-at. % Nd concentration was used to construct the diode-pumped laser with a flat highly reflecting end mirror and an intracavity lens. For the method to be effective, the resonator was set up close to the edge of the stability range. Above the oscillation threshold, the pump power at which lasing was quenched because of the onset of the thermally induced resonator instability was measured as a function of the intracavity lens position. A numerical model that accounted for absorption saturation and pump-induced thermal lensing was then used to analyze the experimentally measured data with eta(h) as an adjustable parameter. The average best-fit value of eta(h) was determined to be 0.40 with an estimated statistical variation of 8%.