Yayın tarihi için Bilgisayar Mühendisliği / Computer Engineering listeleme
Toplam kayıt 177, listelenen: 120

A synthesis tool for the multiplierless realization of FIRbased multirate DSP systems
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Yayıncı ve Tarih:(IEEE, 2000)In this study a synthesis tool using a novel multirate folding technique which handles each FIR filter in a multirate DSP system as a single node is developed. A new architecture is presented for the multiplierless realization of a fold of multirate FIR filters. This synthesizer fully exploits the redundancies (i.e. `idle' and `missing' cycles) and common terms in multirate systems without sacrificing from overall system quality to produce multiplierless multirate systems. It also enables the usage ...

Cosmic ray intensity variation during a CME
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Yayıncı ve Tarih:(PergamonElsevier Science Ltd, 2002)The June 6 2000 coronal mass ejection was an exceptional full halo which made it possible to measure cosmic ray (CR) decrease with a simple experimental setup. Variation in the local secondary cosmic ray density has been investigated by means of gamma rays. The experiment site was located in Istanbul (41.1N 29.0E). CR electrons and slow gamma rays have been eliminated. The CR density has dropped drastically starting on June 8 2000. The counts have been compared with the preshock levels and some ...

Zerocrossing based demodulation of minimum shift keying
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Yayıncı ve Tarih:(2003)Minimum shift keying (MSK) modulation has features such as constant envelope compact spectrum and good error performance which are all desirable in many digital applications including mobile radio. Numerous receiver structures to demodulate MSK have been suggested such as correlation receivers differential detectors and frequency discriminators MSK is a form of biphase keying and can be detected by a zerocrossing based phase demodulator which gives near optimum performance. In this paper the bit ...

Active reconfigurable control of a submarine with indirect adaptive control
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Yayıncı ve Tarih:(2003)An indirect adaptive controller is designed for submersibles. The design is developed using a linearized MIMO model of a submarine. Standard recursive least squares estimation method is used to estimate the parameters. Depth and pitch angle of the submarine is controlled by means of the wellknown indirect selftuning method. In case of a system fault estimated parameters of the submarine model have been used to update the controller coefficients.

Nonuniform sampling for detection of abrupt changes
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Yayıncı ve Tarih:(Birkhauser Boston Inc, 2003)In this work detection of abrupt changes in continuoustime linear stochastic systems and selection of the sampling interval to improve the detection performance are considered. Cost functions are proposed to optimize both uniform and nonuniform sampling intervals for the wellknown cumulative sum algorithm. Some iterative techniques are presented to make online optimization computationally feasible. It is shown that considerable improvement in the detection performance can be obtained by using ...

An open software architecture of neural networks: Neurosoft
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Yayıncı ve Tarih:(2004)Software architecture of generic distributed neural networks and its relevant information model have been developed. Principles of online architecture building training controlling (managing) and topological optimization guidelines are provided and extensively discussed.

Optimal input design for the detection of changes towards unknown hypotheses
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Yayıncı ve Tarih:(Taylor & Francis Ltd, 2004)The effects of auxiliary input signals on detecting changes in ARMAX processes via statistical tests are discussed. Two extensions to the Cumulative Sum Test are considered. The first is applicable when the direction of the change in the parameter space is known but its magnitude is unknown. The second is applicable when neither is known. The performance criteria for the design of stationary stochastic inputs are based on the asymptotic properties of the tests. It is shown that powerconstrained ...

A reconfiguring slidingmode controller with a ustable robustness
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Yayıncı ve Tarih:(PergamonElsevier Science Ltd, 2004)In this paper a controller design method for underwater vehicles is presented which is based on reconfiguration of a slidingmode controller in case of disturbances caused by shallow water conditions. The disturbance distribution information can be obtained and used to update the corrective gain vector of the slidingmode controller. This increases the robustness of the controller and hence keeps the system performance within acceptable limits. Proposed method is validated with simulations on a ...

Pilotaided bayesian MMSE channel estimation for OFDM systems: Algorithm and performance analysis
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Yayıncı ve Tarih:(2004)This paper proposes a computationally efficient pilotaided minimum mean square error (MMSE) channel estimation algorithm for OFDM systems. The proposed approach employs a convenient representation of the discrete multipath fading channel based on the KarhunenLoeve (KL) orthogonal expansion and estimates uncorrelated series expansion coefficients. Moreover optimal rank reduction is achieved in the proposed approach by exploiting the optimal truncation property of the KL expansion resulting in a ...

A lowcomplexity KL expansionbased channel estimator for OFDM systems
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Yayıncı ve Tarih:(2005)This paper first proposes a computationally efficient pilotaided linear minimum mean square error (MMSE) batch channel estimation algorithm for OFDM systems in unknown wireless fading channels. The proposed approach employs a convenient representation of the discrete multipath fading channel based on the KarhunenLoeve (KL) orthogonal expansion and finds MMSE estimates of the uncorrelated KL series expansion coefficients. Based on such an expansion no matrix inversion is required in the proposed ...

Frequency selective fading channel estimation in OFDM systems using KL expansion
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Yayıncı ve Tarih:(2005)This paper proposes a computationally efficient linear minimum mean square error (MMSE) channel estimation algorithm based on KL series expansion for OFDM systems. Based on such expansion no matrix inversion is required in the proposed MMSE estimator. Moreover truncation in the linear expansion of channel is achieved by exploiting the optimal truncation property of the KL expansion resulting in a smaller computational load on the estimation algorithm. The performance of the proposed approach is ...

A lowcomplexity timedomain MMSE channel estimator for spacetime/frequency blockcoded OFDM systems
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Yayıncı ve Tarih:(Hindawi Publishing Corporation, 2006)Focusing on transmit diversity orthogonal frequencydivision multiplexing (OFDM) transmission through frequencyselective channels this paper pursues a channel estimation approach in time domain for both spacefrequency OFDM (SFOFDM) and spacetime OFDM (STOFDM) systems based on AR channel modelling. The paper proposes a computationally efficient pilotaided linear minimum meansquareerror (MMSE) timedomain channel estimation algorithm for OFDM systems with transmitter diversity in unknown ...

Linear expansions for frequency selective channels in OFDM
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Yayıncı ve Tarih:(Elsevier GMBH Urban & Fischer Verlag, 2006)Modeling the frequency selective fading channels as random processes we employ a linear expansion based on the KarhumenLoeve (KL) series representation involving a complete set of orthogonal deterministic vectors with a corresponding uncorrelated random coefficients. Focusing on OFDM transmissions through frequency selective fading this paper pursues a computationally efficient pilotaided linear minimum mean square error (MMSE) uncorrelated KL series expansion coefficients estimation algorithm. ...

The effects of higherorder approximations in a fluidfilled elastic tube with stenosis
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Yayıncı ve Tarih:(Verlag der Zeitschrift fur Naturforschung, 2006)Treating arteries as thinwalled prestressed elastic tubes with a narrowing (stenosis) and blood as an inviscid fluid we study the propagation of weakly nonlinear waves in such a fluidfilled elastic tube by employing the reductive perturbation method in the long wave approximation. It is shown that the evolution equation of the firstorder term in the perturbation expansion may be described by the conventional Kortewegde Vries (KdV) equation. The evolution equation for the secondorder term is ...

Influence of pH on the optical and structural properties of spin coated CeO2TiO2 thin films prepared by solgel process
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Yayıncı ve Tarih:(Elsevier Science Bv, 2007)Optical and structural properties of mixed CeO2TiO2 thin films have been investigated by varying the pH of the coating sol. The films were prepared by solgel process using spincoating technique with a spin speed of 2500 rpm. The optical and structural properties of films were examined by a spectrophotometer AFM and XRD. Optical constants and thickness of the CeO2TiO2 thin films have been determined with respect to the pH of the coating bath before deposition. The refractive index at 550 nm ...

The effect of a bump in an elastic tube on wave propagation in a viscous fluid of variable viscosity
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Yayıncı ve Tarih:(Elsevier Science, 2007)In the present work treating the arteries as a thin walled prestressed elastic tube with a bump and the blood as a Newtonian fluid of variable viscosity we have studied the propagation of weakly nonlinear waves in such a medium by employing the reductive perturbation method in the longwave approximation. KortewegdeVriesBurgers equation with variable coefficients is obtained as the evolution equation. Seeking a progressive wave type of solution to this evolution equation it is observed that the ...

Optical and structural properties of Ta2O5CeO2 thin films
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Yayıncı ve Tarih:(Elsevier Science Bv, 2007)In this study the solgel spincoating method has been used to make Ta2O5CeO2 thin films. These films have been prepared in various composition ratios to observe changes in their optical and structural properties. Reflectance and transmittance spectra were collected in the spectral range of 3001000 nm and were accurately fit using the TaucLorentz model. Film thicknesses refractive indices absorption coefficients and optical band gaps were extracted from the theoretical fit. The highest refractive ...

Distributed estimation with channel estimation error over orthogonal fading channels
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Yayıncı ve Tarih:(IEEE, 2007)We study distributed estimation of a source corrupted by an additive Gaussian noise and observed by sensors which are connected to a fusion center with unknown orthogonal (parallel) flat Rayleigh fading channels. The fading communication channels are estimated with training. Subsequently source estimation given the channel estimates and transmitted sensor observations is performed. We consider a setting where the estimated channels are fedback to the sensors for optimal power allocation which ...

Text area detection in digital documents images using textural features
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Yayıncı ve Tarih:(Springer, 2007)In this paper we propose a new texturebased method for extraction of text areas in a complex document image. Gabor filter motivated by the multichannel filtering approach of Human Visual System (HVS) has been employed to create energy map of the document. In this energy map we assumed that text areas were rich in high frequency components. Connected components (probable text characters) were extracted by binarization of the energy map with Otsu's adaptive threshold method. First nontext components ...

An Integrated Software Architecture for Bandwidth Adaptive Video Streaming
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Yayıncı ve Tarih:(World Acad Sci Eng & TechWaset, 2008)Video streaming over lossy IP networks is very important issues due to the heterogeneous structure of networks. Infrastructure of the Internet exhibits variable bandwidths delays congestions and timevarying packet losses. Because of variable attributes of the Internet video streaming applications should not only have a good endtoend transport performance but also have a robust rate control furthermore multipath rate allocation mechanism. So for providing the video streaming service quality some ...