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Electrotechnical Conference, 1998. MELECON 98., 9th Mediterranean

Date 18-20 May 1998

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  • MELECON '98 - 9th Mediterranean Electrotechnical Conference

    Page(s): 0_2 - 0_3
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    Freely Available from IEEE
  • Table of contents

    Page(s): V - XVIII
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    Freely Available from IEEE
  • Design and demonstration of a vertical SSFLC coupler switch

    Page(s): 1395 - 1398 vol.2
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    In this paper, we report the results of the analysis and experimentation on a thin-film surface-stabilized ferroelectric liquid-crystal (SSFLC) electro-optic waveguide switch. The optical coupling between a pair of planar waveguides is controlled by application of voltage to SSFLC film. The switch design, carried out by using beam propagation method (BPM) technique, has shown that a coupling length less than 60 /spl mu/m with a crosstalk of about -21 dB with a refractive index change at the surface /spl Delta/n=0.013, a FLC layer with a thickness of 2 /spl mu/m and cone axis tilted at about 19/spl deg/ from the propagation direction of the lightwave. View full abstract»

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  • Author's index

    Page(s): I - IV
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    Freely Available from IEEE
  • The new generation of coding techniques for wireless multimedia: a performance analysis and evaluation

    Page(s): 820 - 824 vol.2
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    This paper presents the performance evaluation of the Mobile Audio Visual Terminal (MAVT) audio coder, candidate to the new standard, MPEG-4. By exploiting the embedded property of the object oriented coding technique, which allows scalability of the signal bandwidth as well as of the delivered bit rate, it is possible to achieve a strong interaction between the system and the bit-stream. In this way, the run-time quality of the service may be modified without changing the encoder configuration. We estimate the speech quality degradation due to bit rate reduction, and the robustness to packet losses due to network congestion, to determine the acceptable reduction and discarding thresholds. Both narrowband and wideband speech services are evaluated View full abstract»

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  • ICARO: an expert system approach to automated ionospheric radio communications

    Page(s): 806 - 810 vol.2
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    This paper describes the work accomplished to develop the system ICARO (Ionospheric Communications Automatic Radio Operator) based on an expert system applied to the frequency management of a digital communication system using the high frequency band (HF), with frequencies between 3-30 MHz. The proposed expert system activates an ionospheric propagation forecast program and a selective radio station listening process and, with the provided data, puts under way adequate strategies in order to set up and to maintain the requested radio link View full abstract»

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  • Temperature effects on the large signal transient response of long-wavelength MQW lasers

    Page(s): 1432 - 1435 vol.2
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    In this paper we investigate the effect of temperature on the transient response of multiple quantum well (MQW) 1.3 μm InP-InGaAsP lasers of the Fabry-Perot type when the injection current changes by steps from zero to a value above threshold. For the structure under study the rate equations were numerically solved for each temperature taking into account the appropriate values of the maximum gain, the threshold current density and the photon and carrier lifetime, which change with temperature. As expected the carrier and photon transients change with temperature, their evolution depending on the current density values considered at each temperature. When the ratio between the current density and the threshold current density is kept constant we observe that for an increase of temperature there is an increase of the amplitude and frequency of the oscillations and a decrease of their relaxation time and turn-on delay time. However for a constant current density the increase of temperature can lead to opposite conclusions View full abstract»

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  • Telecom deregulation and fast-changing internetworking technologies: current status, major impacts and trends in the Mexican market

    Page(s): 816 - 819 vol.2
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    The objective of this paper is to present a broad scope of the current status and the challenges to be faced by Mexico due to the telecommunications industry (TI) deregulation process and internetworking technologies (IWT) penetration after a major economic shock suffered by this country at the end of 1994. This issue created important constraints and a negative impact on the growth rate in these areas during 1995 and in part of 1996, in comparison with trends showed in the 1990-1994 period View full abstract»

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  • Effect of the single and three phase switching in the transient stability of an electric power system using the extended equal area criterion

    Page(s): 950 - 953 vol.2
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    In this paper the transient stability of a test power network is studied and analysed when a phase-to-ground fault occurs on a transmission line. A single and three phase reclosure of the tripped circuit breakers poles in the two ends of the faulted line were simulated. The software package TRANsySTEM that the authors developed for transient security assessment of a multimachine power system was used. These computer programs use the extended equal area criterion. This direct formulation reduces drastically the computing time, since it does not require numerical solution of the differential motion equations of the system. The results obtained with this direct approach were compared with the solutions produced by the Runge-Kutta method View full abstract»

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  • A model based decomposition method for temporally overlapping evoked potential components

    Page(s): 1449 - 1452 vol.2
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    The authors present a robust model-based decomposition method for temporally overlapping evoked potential (EP) components. The model assumes linear superposition of the EP constituent components, and Gaussian distributed firing instants of the neuronal population associated with each component. The decomposition provides a loss-less description of the EP complex, which is demonstrated via computer simulations as robust to violations of the model assumptions. The decomposition method is applied to experimental data, demonstrating its separation performance of severely overlapping EP components View full abstract»

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  • Voltage sag analysis through wavelet transform

    Page(s): 959 - 963 vol.2
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    The objective of the paper is an in-depth voltage sag characterization. Attention is turned in particular to detect the frequency range associated to the main transients contained in the voltage waveform during sag. A suitable tool for this study is the wavelet transform, which allows decomposition of a transient signal into a series of wavelet components, each being a time domain signal that covers a specific frequency band. Different actual voltage sags are analyzed through the wavelet transform and the results compared and commented upon View full abstract»

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  • Threshold analysis of phase-shifted distributed feedback lasers

    Page(s): 1436 - 1439 vol.2
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    Optimum structure parameters in phase-shift (PS) distributed-feedback (DFB) laser diodes are determined in order to ensure an emission with high mode selectivity, zero-frequency detuning and an almost uniform field distribution. In the present paper we analyze several multiphase shifted DFB structures using the transfer matrix method (TMM). The results allow the comparative analysis of single and multi-phase shifted DFB lasers in the near threshold regime, regarding their typical figures of merit, and will conclude about the main features associated with either the corrugation (coupling coefficient, length, ...) or the phase-shift discontinuities (amplitude, location) View full abstract»

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  • On iterative phase trellis based noncoherent detection of coded MPSK in a noisy phase regime

    Page(s): 834 - 838 vol.2
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    A family of interleaved systems for communicating over the AWGN channel with noisy phase is investigated. Each system comprises convolutional or turbo error correcting code (ECC), interleaver, BPSK or QPSK modulation and differential encoding. The receiver performs jointly and iteratively the ECC decoding and the channel demodulation in the presence of unknown phase utilizing a Markovian model of the noisy phase. The systems exhibit good performance with various levels of phase noise. The convolutional code outperforms the turbo code slightly over AWGN channels due to the limited capability of the iterative algorithm in this setting; the turbo code is superior in bursty channels, modeling for example a block erasures fading environment View full abstract»

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  • 1/f noise in ion selective field effect transistors compared to MOSFETs

    Page(s): 1456 - 1460 vol.2
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    pH ISFETs are very interesting sensors for biomedical microsystems including in vivo measurements of pH. The noise phenomena and related resolution of these sensors are still not understood. In this paper measurements of low frequency noise in pH ISFETs are presented and compared to similar measurements performed in MOSFETs. Various bias conditions are used corresponding to the gate voltage changing from subthreshold to saturation, in the frequency range between 1 Hz to 100 kHz ISFET noise measurements were performed in solutions with pH in the range of pH4 to pH10, at room temperature. The measured ISFETs exhibit clearly 1/f noise. The dependence of the drain current noise power spectral density upon average drain current follows the same behavior of 1/f noise that the observed in MOSFETs. The measured noise characteristics shown here indicate that the Si/SiO2 interface dominates the noise behavior of the ISFET. No pH dependent effects are observed and the interface between the solution and the gate insulator does not contribute measurable noise View full abstract»

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  • Operational costs modeling improvements in short term hydrothermal coordination

    Page(s): 916 - 920 vol.2
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    This paper deals with the total operational costs modeling in the short term hydro-thermal coordination. An improvement concerning the thermal unit start-up and shutdown costs is presented. The treatment of final reservoir states in different type of hydroplants is analyzed and its modeling using the penalty term in the objective function is suggested. In other words, the approach to the modeling of costs associated with the excessive usage of water during the optimization period is defined in detail. Besides, the model is completed with pumping plants which, as far as the authors know, have not been covered in technical literature up to now View full abstract»

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  • CORBA-based remote instrumentation

    Page(s): 1294 - 1298 vol.2
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    Fast development in two of the most important technologies used in our proposal led to a new implementation of the concept of remote instrument access over public computer networks. As CORBA (Common Object Request Broker Architecture) is emerging into a widespread technology for interconnection of distributed objects our aim was to investigate its applicability on remote instrument access, at the same time trying to reduce implementation complexity as much as possible. The second key technology previously used in our proposal, the Java programming language, is gradually maturing and gaining necessary functionality to be used in more complex applications. Our focus in this paper is on using JavaBeans components both for flexible remote instrument access and, at the same time, for visual programming in various GUI-based application/applet development tools View full abstract»

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  • A new approach to rotor position estimation for a PM brushless motor drive

    Page(s): 1199 - 1203 vol.2
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    The paper presents a new technique for sensorless control of brushless permanent magnet motors. The technique relies on estimating rotor position from motor terminal voltage and current information. The technique avoids signal differentiation and integration, and their associated problems of noise amplification and drift, respectively. This simplifies implementation considerably. The paper presents the equations used to develop the technique. It also presents experimental results on the implementation and performance of the technique View full abstract»

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  • Expression of the bit error rate for the direct sequence spread spectrum receiver equipped with Wiener interference rejection filter

    Page(s): 839 - 843 vol.2
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    This paper is dedicated to an experimental validation of an improved analytic expression of bit error rate (BER) previously given by Negrescu and Stanomir (1996). The results of the simulation are compared with Kalouptisidis and Teodoridis (1993) and Iltis and Milistein (1984). The new improved formula predicts the BER with a significant higher degree of accuracy View full abstract»

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  • Prediction of distribution transformer no-load losses using the learning vector quantization neural network

    Page(s): 1180 - 1184 vol.2
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    This paper presents an artificial neural network (ANN) approach to classification of distribution transformer no-load losses. The learning vector quantization (LVQ) neural network architecture is applied for this purpose. The ANN is trained to learn the relationship among data obtained from previous completed transformer constructions. For the creation of the training and testing set actual industrial measurements are used. Data comprise grain oriented steel electrical characteristics, cores constructional parameters, quality control measurements of cores production line and transformers assembly line measurements. It is shown that ANNs are very suitable for this application since they present classification success rates between 78% and 96% for all the situations examined View full abstract»

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  • Network management applications for wireless local loop

    Page(s): 787 - 791 vol.2
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    In the last several years, wireless local loop (WLL) has emerged as an attractive alternative to wireline access to telephone services. This paper focuses on the wireless local loop market, technology, management and operations. WLL has applications in both highly developed areas, as well as in rural and remote areas with underdeveloped or no telephone infrastructure. To support network management in WLL, the terminals should include an extended protocol in addition to standard call processing capabilities. This protocol enables the following network management features: secure access, remote configuration, software download, control, maintenance, diagnostics, performance measurement, statistics collection, programmable scheduled reports, dialing rules and services, security, alarm generation, billing, as well as management of the operations and maintenance staff in a network operations center of a telephone company. The proposed wireless local loop terminals with the network management system can be adapted easily and remotely (over the air) to different international telephony standards and services, or remotely upgraded with new software versions. This system solution also provides privacy, fraud detection and authentication, as well as efficient maintenance and repair View full abstract»

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  • An optimal detection of multicomponent signal on background of complex jamming

    Page(s): 784 - 786 vol.2
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    The paper presents a main approach to the joint detection of signals of various structures in multistatic reception systems. The conditional relations are of the likelihood for non-Bayesian problems. The necessary structure of a multistatic system with an adaptive threshold is based on the structure of optimal processing, characterized by the presence of the analyzer of the radar environment, are discussed. The examples of its functioning under simplified conditions are presented View full abstract»

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  • Unbalanced availability and the grade of service of overlapping radio ports

    Page(s): 792 - 796 vol.2
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    This paper discusses the problem of limited availability, where users of a wireless system do not enjoy equal access opportunity to the systems' radio ports. The paper discusses two common scenarios where that can occur. One where there is an overlap in the coverage of two neighboring stations and the other where the coverage of one radio port is completely contained within that of the other. The paper analyzes two possible policies of radio port selection for the users who can access more than one port. One access policy is a that of a completely random choice, while by the other the user selects only one of the free ports. The analysis demonstrates that system capacity may drop substantially if a proper balance is not maintained View full abstract»

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  • All-optical FSK mo-demodulation through four-wave interactions

    Page(s): 749 - 753 vol.2
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    An all-optical FSK mo-demodulation device using four-wave mixing in a Kerr-like medium is presented. Through numerical simulation, the authors theoretically demonstrate a method of format conversion from on-off modulation to FSK modulation. The proposed device performs the desired conversion through nonlinear frequency mixing occurring in interaction lengths of about 50 μm View full abstract»

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  • Word candidate generation in Cyrillic OCR based on ALN classifiers

    Page(s): 870 - 874 vol.2
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    The process of recognizing characters from a scanned image can be divided into three main operational steps: document layout analysis, character recognition, and contextual postprocessing. This paper addresses the step of contextual postprocessing using the extended information received from the pattern classifiers as well as the information about the pattern preclassification according to its shape. Every pattern is examined by several classifiers, and their decisions are combined in a list of character candidates along with their levels of confidence. Combining the character candidates on different letter positions generates a list of word candidates and the lexicon is being checked for their existence. Word candidates are generated one at a time, in sequence of descending word confidence, and the first candidate found in the lexicon is accepted View full abstract»

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  • Methods of no-load thermal testing of induction motors

    Page(s): 1165 - 1169 vol.2
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    A new method for determining the equivalent parameters of a simplified thermal model of induction motors (IM) based on the no-load testing of IM is presented. The full thermal network of IM is reduced to a system of only three simultaneous equations. By solving these equations, three equivalent thermal parameters of the simplified thermal model are obtained. The calculation is based on accurate measurements of the temperature rise in stator windings and the power absorbed by the tested motor. The thermal tests are done in the no-load running of IM (one test is like an open-circuit test and the other two are like short-circuit tests). Hence these methods of testing may be carried out without expensive equipment and their power consumption does not exceed the losses which occur under full load conditions. With the help of this thermal model the final temperature rise at the full load run according to rated losses, can be easily estimated. Three totally enclosed IM were tested by these methods and the difference in the predicted and measured temperature rise of the stator winding was within 2-3°C View full abstract»

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