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Electrical Engineering, Computing Science and Automatic Control, 2008. CCE 2008. 5th International Conference on

Date 12-14 Nov. 2008

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Displaying Results 1 - 25 of 108
  • A priori error estimates of mixed finite element methods for nonlinear quadratic convex optimal control problem

    Publication Year: 2008 , Page(s): 120 - 124
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1476 KB) |  | HTML iconHTML  

    In this paper, we study an a priori error analysis for the quadratic optimal control problems governed by nonlinear elliptic partial differential equations using mixed finite element methods. The state and the co-state are approximated by the lowest order Raviart-Thomas mixed finite element spaces and the control is approximated by piecewise constant functions. A priori error estimates for the mixed finite element approximation of nonlinear optimal control problems is obtained. Some numerical examples are presented to confirm our theoretical results. View full abstract»

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  • A note on “pth moment exponential stability of stochastic Cohen-Grossberg neural networks with time-varying delays”

    Publication Year: 2008 , Page(s): 263 - 267
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (713 KB) |  | HTML iconHTML  

    In a very recent paper, Zhu et al. [Neural Process Lett (2007)26:191-200] proposed an interesting approach to study pth moment exponential stability of stochastic Cohen-Grossberg neural networks with time-varying delays. Unfortunately, since the constructed Lyapunov function is invalid for p=2k+1, kisinN, the main results obtained are not correct for the general case. This note intends to circumvent these problems by modifying the approach proposed in Zhu et al. [Neural Process Lett (2007) 26:191-200]. View full abstract»

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  • Super-twisting sliding mode control for unified power flow controller in power systems

    Publication Year: 2008 , Page(s): 56 - 61
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (748 KB) |  | HTML iconHTML  

    In this paper, robust stabilizing controllers for the synchronous generator speed, series power flows, voltage magnitude and DC link voltage are designed for a power system with FACTS device (UPFC). To design these controllers, a combined super-twisting sliding mode (SM) and block control (BC) technique is implemented. The block control approach is used to design linear and nonlinear sliding manifolds with desired motions. Super-twisting SM control is applied to reject perturbations and avoid the chattering effect. The effectiveness of the proposed algorithm is illustrated by means of simulations. View full abstract»

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  • Two-stage crystallization process in Ge2Sb2Te5 alloys

    Publication Year: 2008 , Page(s): 475 - 477
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (685 KB) |  | HTML iconHTML  

    The aim of this work is to investigate the amorphous-to-crystalline phase transformation process in Ge2Sb2Te5 ternary alloys. The experiments were carried out using impedance and X-ray diffraction measurements. The results have shown that the crystallization process in an amorphous Ge2Sb2Te5 alloy starts from nuclei, which appear below Tc and which were identified as the crystalline Ge1Sb4Te7. As the temperature increases above Tc these nuclei were transformed into fcc-Ge2Sb2Te5 crystals. In order to establish the mechanism of crystallization for this system, the Brugerman effective medium approximation was implemented to analyze nucleation and growth of the two stage involved (i.e., metastable Ge1Sb4Te7 and stable Ge2Sb2Te5) through impedance measurements. The results of the simulations demonstrate a close agreement with experimental ones showing that phase transformation in Ge2Sb2Te5 is carried in two steps. View full abstract»

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  • Development of a mechatronic unit applied to the manipulation of explosives

    Publication Year: 2008 , Page(s): 368 - 373
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1107 KB) |  | HTML iconHTML  

    This paper presents the development of a mecatronic unit EOD/IEDD (explosive ordinance disposal/improvised explosive device disposal), by carrying out a modeling and simulation of a proposed PID control, this unit is applied to perform hazardous-duty operations. The mechatronic unit uses an interchangeable gripper, a robotic arm with 5 degrees of freedom Stanford type, a climbing system and 3 CCD cameras, from which one of them is controlled through wireless signal. Two simulations are executed, one simulation for the arm and the other for the vehicle, such that the errors in the model can be detected and later confined by control. View full abstract»

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  • Preservation of hyperbolic equilibrium points and synchronization in dynamical systems

    Publication Year: 2008 , Page(s): 108 - 113
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (796 KB) |  | HTML iconHTML  

    Classic results of the dynamical systems theory are extended and used to study the preservation of synchronization in chaotical dynamical systems. This results show that synchronization can be preserved after changes are made to the linear part of the dynamical system. When the Jacobian matrix of the system is evaluated in the hyperbolic points, the sign structure of the eigenvalues of this matrix determines if the system is stable or unstable. In this work, we establish the sufficient conditions to preserve the structure of this hyperbolic points. Also, control tools are used to achieve synchronization in dynamical systems. Numerical simulations to very the effectiveness of the method are presented. View full abstract»

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  • Spinodal decomposition in the GaSbxNyAs1−x−y alloys

    Publication Year: 2008 , Page(s): 481 - 484
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (709 KB) |  | HTML iconHTML  

    Spinodal decomposition of the GaSbxNyAs1-x-y quaternary alloys lattice-matched to the GaAs as the result of the internal deformation and coherency strain energies is described. The alloys are represented as quasiternary regular solutions. The internal deformation energy is presented by the interaction parameters between the constituent compounds estimated within the framework of the valence force field model. Ranges of spinodal decomposition of the GaSbxNyAs1-x-y alloys up to yles0.035 with and without coherency strain energy are demonstrated. View full abstract»

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  • Numerical methods for Stackelberg-Nash equilibrium calculation with favorable and unfavorable followers

    Publication Year: 2008 , Page(s): 125 - 130
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1082 KB) |  | HTML iconHTML  

    Regularized versions of the rdquoProjectional Gradient Techniquerdquo and the ldquoExtraproximal Methodrdquo are suggested to be applied for finding Stackelberg-Nash equilibrium in a multi-participant static game. A comparative between these methods is shown. There exist two levels of hierarchy in decision making: the first one consists of a leader decision and the second one is formed by the decisions of (N - 1)-followers. The followers react to the leaderpsilas announced strategy by playing according to the Nash equilibrium concept among themselves selecting those of equilibriums which is most favorable or unfavorable for the leader. The convergence of the suggested procedure is analyzed. Simulation results illustrate the feasibility of this method. View full abstract»

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  • Physical concepts for improving solar cells based upon graded CuInGaSe2

    Publication Year: 2008 , Page(s): 503 - 507
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (701 KB) |  | HTML iconHTML  

    Some basic concepts related to variable band-gap absorbing semiconductors in solar cell structures such as the associated quasi-electric field will be discussed. The effects of this quasi-electric field upon the minority carrier drift-diffusion length and the back surface recombination velocity will cause a larger generated carrier collection with the corresponding increase of the illumination current density. It will also be shown that an additional improvement of the open-circuit voltage is possible when the band-gap is reduced within the space charge region so that the dark saturation current density is reduced there. Our estimation is that in the case of a solar cell where the band-gap reduces from 1.35 eV to 1.15 eV, at the space charge region (of the order of 0.2 mum), an increase of the open-circuit voltage by around 65-70 mV will be observed with respect to the single gap absorbing material case. A similar (increasing) band-gap variation in the bulk of the material will cause an increase of the drift-diffusion length of minority carriers by a factor of 4 with respect to a single band-gap material. Therefore, based on these physical concepts, two possible structures with variable band-gap CIGS layers are proposed in order to have higher efficiencies than for cells without any band-gap grading. View full abstract»

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  • Testing the Gaussianity of UWB TH-PPM MUI with imperfect power control and multipath

    Publication Year: 2008 , Page(s): 242 - 247
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (845 KB) |  | HTML iconHTML  

    We study the statistical nature of the multiuser interference (MUI) from pulse-based ultrawideband (UWB) signals with time-hopping (TH) and pulse position modulation (PPM). We determine the domain of validity for the Gaussian assumption for three different conditions: An ideal propagation channel with perfect and imperfect power control, as well as a multipath channel with rdquoperfect averagerdquo power control. Results for imperfect power control suggest that the Gaussian approximation can be used if we consider a large enough number of active users Nu and/or number of pulses per symbol Ns, e.g., for low data rate systems with large number of users. Results for multipath suggest that in dense multipath environment a low number of Nu and/or Ns is enough to reach Gaussianity. View full abstract»

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  • Prototype chip and methodology for characterization of phototransistor and photodiodes

    Publication Year: 2008 , Page(s): 443 - 448
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (892 KB) |  | HTML iconHTML  

    A prototype chip for characterization of optical devices is presented based on a simple architecture. This is very useful for the characterization of Phototransistors and photodiodes and also for custom design pixels for image cameras. Phototransistors and photodiodes in a matrix of 6times4, have been used, this is, six rows by four columns. Reading is carried out in the voltage-mode which is different from other reported architecture, where current-mode is used. The pixel architecture is based on four p-channel transistors: shutter, reset, row-select and buffer integrator. The transistor called buffer-integrator in the pixel, converts the photocurrent from the photosensor into voltage. Both, the transistor buffer-integrator and a current source, form a voltage amplifier, with gain close to 32 dB. The capacitance in the integrating node was estimated from the L-Edit software extractor. Photocurrent, dark current, dynamic range and quantum efficiency, were estimated from data such as, capacitance, integrated voltage, voltage gain and time of integration. Good approximation between simulation during design and measurement on chip, was obtained which demonstrates the great powerful application of design tools. View full abstract»

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  • Epilepsy stages diagnosis by Gabor atom density according to their aspect ratio

    Publication Year: 2008 , Page(s): 158 - 163
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (682 KB) |  | HTML iconHTML  

    During epilepsy seizure Electrocorticogram (ECoG) may change dramatically from a nearly chaotic signal (basal state) into a highly synchronized signal during a seizure, characterized by high amplitude and low frequency, and suddenly go back to the basal sate, making hard to identify them from time series. The epileptic seizure shows some stages as it is evolving, the here studied are: basal, preictal, ictal and posictal. As most of the bioelectrical signal, ECoG is a highly non periodical signal, so the most suitable techniques to analyze them are the Time-Frequency algorithms (T-F), allowing to follow up its frequency evolution through the seizure. Each seizure stage has a set of frequency components (atoms), showing up at different time. These components have their own particular characteristics, depending on the influence on time (duration) and frequency (bandwidth) they can be rated in three different classes: Rhythmic, Intermediate and Transitory. There are different amount of these components among stages, based on the density of this atoms, here we try to identify each of the epilepsy stages, decomposing short signal segments (epochs) into their atoms by means of the Matching Pursuit algorithm, an adaptive T-F algorithm. Signals were recorded intracranially from Wistar rats at the cortex level, seizures were elicited by kindling model before recording. View full abstract»

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  • ABBA-VBLAST hybrid space-time code for MIMO wireless communications

    Publication Year: 2008 , Page(s): 257 - 262
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (684 KB) |  | HTML iconHTML  

    Hybrid MIMO communication systems combine spatial multiplexing with diversity gain to achieve both high spectral efficiency and link reliability. We present a novel hybrid scheme that allows the use of any number of spatial multiplexing layers, plus one quasi-orthogonal layer (ABBA) of either 3 or 4 antennas. We transform the system equations in terms of linear dispersion codes, from which we derive a low-complexity, ordered, successive interference cancellation receiver based on sorted QR decomposition. Symbol detection is carried out in a unified manner, both for spatial and space-time coded symbols. We show that this novel scheme outperforms other recent proposals in terms of bit error rate, even those using CSI at the transmitter to precode. We also show our proposal has lower complexity, achieved by exploiting the structure of the linear dispersion matrices. View full abstract»

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  • Raman scattering and photoluminescence studies on Cu2O

    Publication Year: 2008 , Page(s): 421 - 424
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (697 KB) |  | HTML iconHTML  

    Cuprous oxide (Cu2O) crystals were grown by the two step crystallization method in air atmosphere conditions from polycrystalline copper plates. The method comprises two stages; in the first one the copper plates are oxidized at 1020degC by some hours in line with its initial thickness. In the second stage the growth of large crystalline areas is promoted by annealing the Cu2O samples at 1100degC for long periods. The effects on the crystalline structure and photoluminescence (PL) response were studied as a function of the conditions used in the second stage of the synthesis method. Raman scattering and X-ray measurements demonstrates the existence of the single phase Cu2O. PL spectra were taken from 10 to 180 K to define the main radiative recombination paths. Besides of the near band excitonic transitions, two strong emission bands at 720 and 920 nm associated with relaxed excitons at oxygen and copper vacancies were detected. Both excitonic-vacancy bond transitions presented similar intensities which can be associated with the preparation method. The PL and the Raman scattering measurements were used to assess the evolution of the crystalline quality. View full abstract»

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  • An easy wireless multi-waveform Urinary Electrical Stimulator “UES”

    Publication Year: 2008 , Page(s): 201 - 206
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB) |  | HTML iconHTML  

    This paper proposes a simple wireless multi-waveform Urinary Electrical Stimulator (UES) to stimulate electrically patients with urinary incontinence. This system can generate a set of different programmable bipolar and monopolar waveforms, since pulse generator systems most provide different waveforms suitable for each individual patient [1]. This application discloses 6 distinct types of programmable waveforms. The waveform parameters can be modified by physician changing easy instructions with a software interface (SI). The proposed system lets long distance manipulation of the waveform generator by sending codes that change the characteristics of the waveforms even when the stimulator is implanted in the patientpsilas body. The waveforms used in this work can be applied in other electrical-stimulations in body or tissues. We will show that a multi-waveform stimulator can be built with common electronic circuits. The paper discusses the waveforms code generator in UES consisting on a Radio Frequency device connected between a multi-waveform stimulator and the nerves. View full abstract»

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  • Nonlinear partial state feedback controller for a single phase active rectifier

    Publication Year: 2008 , Page(s): 20 - 25
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1090 KB) |  | HTML iconHTML  

    This paper presents a partial state feedback controller for an active rectifier to regulate dc output voltage and to guarantee a power factor close to unity. The partial information controller is based on the Exact Tracking Error Dynamics Passive Output Feedback (ETDPOF) technique in conjunction with an Immersion and Invariance based inductor current observer. Numerical simulations are presented to evaluate the performance of the proposed control scheme. View full abstract»

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  • Application of a leak detection algorithm in a water pipeline prototype: Difficulties and solutions

    Publication Year: 2008 , Page(s): 26 - 30
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (762 KB) |  | HTML iconHTML  

    The main aim of this paper is to comment about the difficulties encountered during the implementation of a well known analytic leak detection algorithm on a short length water pipeline prototype. In addition, the proposed solutions to overcome these difficulties are described. To improve the algorithm, extra filtering to all input signals is added and a freezing-method for the friction coefficient estimation is proposed. Real data are obtained from flow and head pressure sensors installed upstream and downstream of the pipe, then they are supplied to the algorithm. The estimation of the leak size and leak position are presented. View full abstract»

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  • Electromagnetic field interaction with a dielectric body of ellipsoidal shape

    Publication Year: 2008 , Page(s): 234 - 237
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (723 KB) |  | HTML iconHTML  

    The objective of this work is to create a theoretical model and to conduct the detail research of the electromagnetic radiation interaction with granular product and insects. The theoretical research on the electromagnetic wave interaction with granular agricultural product and insects is done in the present work through the solving of electromagnetic boundary problem [1]. It is well-known that boundary problems of electrodynamics are the most complicated ones in the mathematical physics and are urgent in the theory of wave processes. We use the methods based on integral equations of macroscopic electrodynamics to avoid complications at consideration of proper boundary problems. View full abstract»

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  • A reversible data hiding algorithm for radiological medical images

    Publication Year: 2008 , Page(s): 280 - 285
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (817 KB) |  | HTML iconHTML  

    In this paper we introduce a reversible data hiding algorithm for medical images. Using the advantages of some proved methods and the characteristics of radiological medical images we obtain a large embedding capacity with minimum distortion of the original image using an easy control for recovering the hidden data and the original image. View full abstract»

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  • Genetic optimization of a Type-2 fuzzy controller for output regulation of a servomechanism with backlash

    Publication Year: 2008 , Page(s): 268 - 273
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (754 KB) |  | HTML iconHTML  

    A genetic-type-2 fuzzy logic controller (FLC) is proposed to achieve the output regulation of a servomechanism with backlash. The problem is the design of a type-2 FLC, which will be optimized by a genetic algorithm (GA) to obtain the closed-loop system in which the load of the driver is regulated to a desired position. The provided servomotor position is the only measurement available for feedback. Simulations results illustrate the effectiveness of the optimized closed-loop system. View full abstract»

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  • Waveform generator system to transcorneal stimulation based on a digital adaptive model

    Publication Year: 2008 , Page(s): 207 - 211
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1066 KB) |  | HTML iconHTML  

    The present work proposes an electronic waveform generator for transcorneal electrical stimulation (TES). The applied waveform model is generated into a digital processor by means of an adaptive finite impulse response (FIR) filter, which output waveform is synthesized from the original one registered using a multi-focal electroretinograph (MF-ERG). The stimulation waveform applied in patients with central retinal artery occlusion (CRAO) in this procedure, is qualitatively different from the one reported by others like Tano et. al. [1, 2]. Results show that CRAO patients stimulated with the proposed waveform, reported phosphenes associated with variations of the filter coefficients. View full abstract»

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  • A theoretical approach for familiarization with techniques of interleaved Echo-Planar imaging for Functional Magnetic Resonance Imaging and their features

    Publication Year: 2008 , Page(s): 143 - 148
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (691 KB) |  | HTML iconHTML  

    This paper deals with an analysis of techniques of interleaved Echo-Planar imaging (EPI) method for Functional Magnetic Resonance Imaging (fMRI). In order to have optimum echo time and consequently achieving low image distortion, an approach has been emphasized upon a technique that acquires six images, each with a different echo time, in a single shot. Also investigation has been initiated for the feasibility and pragmatism of this technique. Techniques of reduction of image artifact and Nyquist or N/2ghost are compared for effectiveness on fMRI data sets are also demonstrated. Again this approach focused on the benefits and problems of interleaved EPI system. View full abstract»

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  • Closed-loop identification of a velocity controlled DC servomotor

    Publication Year: 2008 , Page(s): 31 - 36
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (740 KB) |  | HTML iconHTML  

    This paper presents a methodology for closed-loop identification of velocity controlled servomotors. The approach considers a PI controller applied simultaneously to the real servomotor and its model. It is shown that under persistently exciting conditions the parameter estimates converges. Experimental results using a laboratory test bed validate the proposed approach. View full abstract»

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  • Photobiostimulation effects caused by a high power IR laser with λ=850nm in wheat (Triticum aestivum L)

    Publication Year: 2008 , Page(s): 495 - 497
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (676 KB) |  | HTML iconHTML  

    This paper has as principal objective to determine the value of some parameters of light that are determinants in the activation or inhibition of the growth stimulus of wheat seeds (Triticum aestivum L). In this case intensity and dose, as important parameters, were considered. GaAlAs laser with lambda=850 nm was used to irradiate the biological system. The growth of main shoot was considered. All data were processed using statistical methods. Results obtained indicate that when the appropriate light parameters are used activation can occur. View full abstract»

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  • Toward the semantic search by using ontologies

    Publication Year: 2008 , Page(s): 328 - 333
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (675 KB) |  | HTML iconHTML  

    This work describes a Web search approach taking into account the semantic content of Web pages. Eliminating irrelevant Web pages, the time-consuming task of revise the obtained results from actual search engines is reduced. The proposed approach is focused on Web pages that are not defined with semantic Web structure (most of the actual Web pages are in this format). The challenge is extract the semantic content from heterogeneous and human oriented Web pages. The approach integrates structures of ontologies, WordNet, and a hierarchical similarity measure to determine the relevance of a Web page. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.