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Electrical and Computer Engineering, 1994. Conference Proceedings. 1994 Canadian Conference on

Date 25-28 Sept. 1994

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Displaying Results 1 - 25 of 206
  • Proceedings of Canadian Conference on Electrical and Computer Engineering

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    Freely Available from IEEE
  • Elevator group supervisory control using fuzzy logic

    Page(s): 825 - 828 vol.2
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    The paper describes the use of fuzzy logic in the scheduling of a group of elevators. A new “orbital” paradigm is introduced that offers a simple unified framework under which scheduling can be completed. The principle is to choose a configuration of elevator placements upon an “orbital circle” that best fits a number of fuzzy constraints. To our knowledge, fuzzy logic has traditionally been used to support the more established techniques, such as expert knowledge base approaches. Our system uses fuzzy logic alone to make non predetermined control decisions. The “fuzzy orbital” scheduler was implemented and simulation results illustrate the viability of this paradigm View full abstract»

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  • Doppler processing for coherent “chirp” radars

    Page(s): 767 - 770 vol.2
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    Northern Radar Systems Limited has built a high frequency radar system at Cape Race, Newfoundland, for over-the-horizon (OTH) detection of targets. The radar uses a frequency modulated interrupted continuous wave (FMICW) signal, specifically developed for long range target detection. For the detection of fast targets, conventional processing is constrained by the limited time that a target is present in a range cell. This problem can be eliminated by using velocity matched filters to process the FMICW signals. The analytical derivation of these filters is presented, followed by numerical simulations of the filter performance. Results of OTH detection of low-flying aircraft using the high frequency ground wave radar (HF-GWR) system are also presented View full abstract»

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  • Telemanipulators with large time delays

    Page(s): 806 - 809 vol.2
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    The paper describes system enhancements that improve telemanipulator performance in the presence of large communication delays. The enhancements include: a carefully tuned local controller which shapes the manipulator response; and a predictive display which increases the telemanipulator system bandwidth to acceptable levels View full abstract»

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  • Real number TCM design for given peak-to-average power ratio

    Page(s): 222 - 225 vol.1
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    This paper is dedicated to the design method for constructing optimal real number trellis coded modulation (TCM) under a given peak-to-average power ratio (PAPR). The design uses continuous optimization. The optimization model is formulated and some examples of the solution codes are demonstrated View full abstract»

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  • Performance analysis of growable packet (ATM) switch under nonuniform traffic

    Page(s): 320 - 323 vol.1
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    This paper reports the results of the performance analysis of a growable switch architecture based on the generalized knockout principle under a nonuniform traffic pattern. It is observed that with output traffic imbalance, there is degradation in the overall cell loss probability factor of the switch. We also find the variation in cell loss probability over the different output modules. We further show that by optimizing the input trunk size going to different output modules, it is possible to keep the overall cell loss probability below a given target and reduce the variability of cell loss probability over the different output modules. The resizing or reconfigurability required in the interconnection structure is then shown to be a function of the variability of the projected traffic going to an output module View full abstract»

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  • Near-field measurement of power absorption in a lossy dielectric at microwave frequencies

    Page(s): 572 - 575 vol.2
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    The lack of adequate techniques for measuring the specific absorption rate (SAR) of microwave energy in such lossy structures as biological bodies is pointed out. A non-invasive method, based on the use of an array of small, non-perturbing electric field probes, is proposed. The feasibility of the method is demonstrated, using a circular cylindrical model of the human body. The simplifying assumptions on the nature of the incident signal are discussed View full abstract»

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  • Cell voice transport considerations for ATM

    Page(s): 324 - 327 vol.1
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    This paper discusses the cell transport characteristics for a viable ATM voice implementation. A system approach to cell voice, both backbone switching and access, is considered. Bandwidth utilization opportunities, in addition to speech processing requirements are discussed. Special attention is given to private networks View full abstract»

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  • Efficient method for calculating the grounding resistance of a buried grounding grid in a homogeneous soil

    Page(s): 136 - 139 vol.1
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    The grounding resistance of grounding grid conductors is calculated based on Galerkin's moment method. This method, due to its error reduction property, yields a high accurate resistance values for the parallel and perpendicular grounding conductors. The integral of the effective distance between the perpendicular conductors converged quickly and enabled us to use small resistance matrix size (NXN) for ground grid made of N conductors. The outcome of the present technique is compared with the published values (from sophisticated analysis and using supercomputers) and the agreement is very good View full abstract»

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  • On exponential bounds for the waiting time of TES/GI/1 queues

    Page(s): 647 - 651 vol.2
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    The TES (Transform-Expand-Sample) technique has emerged as a general methodology for modeling autocorrelated random processes with arbitrary marginal distributions. Because of their generality and practical applicability, TES models can be readily used to accurately characterize bursty traffic streams in ATM networks (e.g., variable-bit-rate compressed video). Although TES models can be easily implemented for simulation studies, the need still exists for analytical results on the performance of queueing systems under TES traffic. Of particular interest are the tail probabilities of waiting time or buffer occupancy in queues driven by bursty traffic. Such probabilities may be difficult to obtain via conventional simulation when they become exceedingly small. In this paper we present a general result concerning exponential bounds for the waiting time under continuous state-space Markov chains. We apply this result to a TES/GI/1 queue, show a numerical example, and compare our bound with simulation results. In order to obtain accurate estimates of extremely low probabilities fast simulation techniques based on importance sampling are used View full abstract»

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  • Priority analysis of a shared-buffer ATM switch with imbalanced bursty traffic

    Page(s): 304 - 307 vol.1
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    In this paper, we apply an aggregation method to analyze a shared-buffer ATM switch with priorities with two traffic classes. Each input port of the switch is assumed to be bursty and is modeled by an interrupted Bernoulli process. Both traffic classes share a common buffer of size M cells. High priority cells are served before low-priority cells. As an example, the analysis shows that a 4×4 switch with traffic rate of 0.2 per input lines requires a buffer size of 30 cells to achieve cell loss rate less than 10-9 View full abstract»

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  • Automatic segmentation of the heart in 3D MR images

    Page(s): 584 - 587 vol.2
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    This paper presents an approach to a fully automated system for segmenting the heart in 3D MR images of the torso. The system initially processes one axial slice containing a cross-section of the heart with significant sectional area. The system then hierarchically segments this image by first separating the torso from the background and then the lung fields from the torso. The heart location is estimated from the lung fields. This estimate is used as the region of interest for finding the edges of the heart in the image. The region is refined to straddle the detected edge, and is then projected onto adjacent images to provide a starting point for further segmentation. All thresholds are determined from the image data. Anatomical knowledge of the locations and relative sizes of the various structures is used to guide segmentation. The approach attempts to use easily-detected structures to constrain the search space for structures which are more difficult to determine. The algorithms also use the structures detected in a given image to constrain the search space in adjacent images, thereby reflecting the inherent spatial coherence of the heart View full abstract»

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  • Design considerations for a general purpose systolic processing element using bit serial techniques

    Page(s): 636 - 639 vol.2
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    The demands of modern high performance numerical applications are such that they must be met in principle by special-purpose computational architectures. Processing architectures fall into two distinct categories, serial-data and parallel-data. For fixed-function, real-time computational requirements, serial data architectures exhibit many advantages over equivalent bit-parallel architectures, especially when size and area are of primary concern. Advantages of serial data hardware include: performance and efficiency, functional parallelism, physical partitioning and testability. Single wire communication, as opposed to parallel busses, ease interconnection problems and decrease layout area. With the new technology available today, serial techniques must be seriously reconsidered View full abstract»

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  • Generating 3-phase modulation signals for variable speed AC drives using the TMS320c26 DSP chip

    Page(s): 93 - 96 vol.1
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    This paper describes a motor drive controller for a three-phase PWM voltage source variable speed inverter drive using a TI TMS320c26 digital signal processor (DSP). By choosing different reference signals, many kinds of PWM strategies can be implemented using the same principle as the normal sinusoidal PWM. A method is developed to use the single timer in the DSP to generate 3-phase PWM signals, to realize the minimum dwell time control, and to perform variable speed control. All the timing signals associated with the pulse width modulation, signal generation and motor speed control functions are implemented using DSP assembly language software. As a result, minimal hardware is required, and the controller has high flexibility and reliability View full abstract»

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  • The effect of modelling on the accuracy of the estimation of harmonic voltages in distribution systems

    Page(s): 131 - 135 vol.1
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    This paper discusses the evaluation of both off-line and on-line harmonic estimation techniques. For this purpose, the estimation of distribution system harmonics was performed by both techniques. In the off-line technique, the effect of sampling rate, harmonic order and outliers upon the accuracy of the estimated harmonics was discussed by the state space model. The on-line estimation was conducted by two different approaches: the time series analysis approach and the artificial neural networks (ANN) approach. A comparison between the results of the two approaches is presented View full abstract»

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  • Implementation of a rule based controller for wind energy induction generator conversion scheme

    Page(s): 652 - 655 vol.2
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    The paper presents laboratory testing of a novel error driven modulated impedance scheme for voltage/wind power stabilization of a stand alone squirrel cage induction generator driven wind energy conversion scheme (WECS). The generator has self excitation capacitors and a novel modulated impedance-filter to stabilize the load bus voltage and ensure maximum wind power utilization under wind gusting and electric load excursions. The voltage/power is regulated by a modulated passive tuned arm filter using the error driven, error scaled controller View full abstract»

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  • A modem combining fast frequency hopping and direct sequence spread spectrum for radio LAN

    Page(s): 352 - 355 vol.1
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    This paper proposes a new spread spectrum modem configuration for a radio local area computer network to be implemented by combining fast frequency hopping (FFH) and direct sequence spread spectrum. To confirm the performance of the proposed modem, the average bit error probability under the multi-user Rayleigh fading channels is theoretically analyzed. Numerical results using a practical indoor microcellular channel parameter show that the proposed modem reduces the error floor without increasing the complexity of the modem View full abstract»

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  • Improved diffraction loss prediction for land mobile radio communication

    Page(s): 242 - 247 vol.1
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    This paper examines and improves the diffraction loss obtained by the Communications Research Centre (CRC) in two main aspects. One is to create a higher resolution and more accurate digital terrain data based on the CRC database. For a given area of interest first the complete quadratic two-dimensional interpolation for elevations is applied to augment the CRC database from 500 meters spacing to 100 meters spacing. If the contour from the augmented database is not checked with the topographic map, then the data of missed critical terrain features are taken directly from the topographic map and are used to correct the augmented database. In this step, the triangular interpolation scheme is introduced to modify the elevations and the weighted vote method is used to modify the surface codes. Thus the modification of the database makes the evaluation of diffraction loss more accurate View full abstract»

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  • A new connectionist expert system scheme for distribution system fault diagnosis

    Page(s): 50 - 54 vol.1
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    This paper proposes a new connectionist expert system (CES) scheme for distribution system fault diagnosis by effectively combining expert system (ES) and artificial neural network (ANN) technologies. Successful test results on a real life distribution system, located within the Taipei West District Office of Taiwan Power Company, derived from the application of this scheme are also presented. When presented with distribution system trouble tickets, the proposed CES analyzes these tickets for fault conditions, based upon human heuristic reasoning encoded in the knowledge base of the ES component, and provides recommended corrective actions to the operator. The CES is characterized by three functional modules. The ANN module, which runs in real time, receives diagnostic messages from a trouble ticket and classifies the failure status and component status, The ES module receives the component status, performs the expert analysis function and provides recommended actions to system operators. The operation interface (OI) module, which is built in a window-based environment, provides the system operator with a user-friendly interface to the developed system. The performance of the proposed CES is evaluated, both with respect to accuracy and running time, in comparison with two other existing solution methods, namely, the fuzzy logic-based expert system and discrete event simulation View full abstract»

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  • On the implementation of a 32-channel FFT-based MFSK demodulator

    Page(s): 186 - 189 vol.1
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    This paper discusses the implementation of an M-ary FSK demodulator based on the FFT process. The goal was to design an hybrid receiver where the front end is still analog up to the A/D subsystem (I and Q), the rest being entirely digital. A digital implementation offers many advantages over an analog counterpart, e.g. SAW decoders, such as flexibility and improved dynamic range. The paper discusses the design and implementation of a 32-channel 8-FSK FFT-based demodulator where the signal bandwidth is in the excess of 10 MHz View full abstract»

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  • Detecting corners using the `patchy' Hough transform

    Page(s): 576 - 579 vol.2
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    Relative vehicle motion estimation continues to be difficult. Current approaches are generally based on either optical flow or tracking feature points. In heavily carpentered environments such as institutional settings, the feature-point tracking approach requires significantly less computational effort. Algorithms which result in reduced computational effort are very attractive for the autonomous, vision-guided wheelchair project currently underway in our laboratory. We present a new method for detecting corners as feature points using a `patchy' Hough transform. Corners are detected as intersections of straight lines extracted with the Hough transform. The image is initially segmented into patches, and only the intersections that occur within a patch due to edges also within the patch are deemed to be corners. This helps to avoid the localization problem inherent in the normal Hough transform. The use of patches also reduces the tendency of the Hough transform to ignore short edges because they are `swamped' by longer ones. Edge pixels are initially enhanced by the Sobel operator, then detected using a histogram-derived threshold. The thresholded images are `thinned' to produce edges of single-pixel width so as to avoid the line orientation ambiguity that arises with thick edges. The Hough transform is then computed for each patch. Peaks in the Hough accumulator array are generally poorly defined, with many adjacent accumulator `bins' having similar values. To sharpen peaks, the Hough accumulator array is convolved with an `annulus' kernel. The peaks are then detected as the local maxima of the convolution result. Finally, the intersections of all possible combinations of lines corresponding to the detected peaks are found. If the points of intersection lay inside the current patch, the lines are deemed to intersect. Algorithm performance is demonstrated with both synthetic and real image data View full abstract»

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  • Analysis of the Fourier split-step method for resolution of radio propagation over the sea

    Page(s): 421 - 424 vol.2
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    This method of solving the parabolic equation of propagation over the sea has proved the most popular on account of its performance in terms of computation time, and is equally well adapted to analysis in the presence of atmospheric ducts. The authors present an analysis of the method starting from the parabolic equation. They then show their implementation of the Fourier split-step algorithm as well as the boundary conditions necessary for its application. The algorithm is applied to the study of wave propagation over a sea surface. The results of calculation are presented for an atmosphere and a sea state often occurring in coastal regions View full abstract»

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  • Nonlinear load reactive compensation and power factor correction using modulated power filter

    Page(s): 34 - 37 vol.1
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    The paper presents a novel switched passive filter scheme for power factor correction of nonlinear, nonsinusoidal type loads. The scheme is controlled by an error driven, error scaled rule based controller to ensure effective compensation of dynamically varying nonlinear load View full abstract»

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  • Computer controlled carbon dioxide laser

    Page(s): 367 - 370 vol.1
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    Describes research work that has resulted in the availability of a development-class medium size carbon dioxide laser system, suitable for research, micro-machining, and medical applications. The control computer allows the laser output power to be adjusted to any level up to 20 W, and the output beam frequency to be line tunable across the 10.6 μm spectral band View full abstract»

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  • A novel efficient rule based controller for electric vehicles switch mode battery charger

    Page(s): 117 - 120 vol.1
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    The paper presents a laboratory prototype implementation of a novel low distortion battery charger. The battery charger is controlled by an error driven error scaled gain adjusting voltage regulator with a supplementary harmonic reduction and ripple elimination loop. The charger regulator ensures minimum harmonic distortion during the charging period. The proposed scheme is suitable for a large charger (5-10 kW) used in electrical vehicle fast battery charging View full abstract»

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