Showing papers in "Canadian Electrical Engineering Journal in 1985"
TL;DR: An approximate queueing model is described to evaluate system performance for finite buffer lengths larger than one unit and results showing the effect of buffer length variations on the system performance are presented.
Abstract: In much of the literature related to the queueing analysis of random multiple access schemes, the analysis has been made assuming user buffer lengths of either one unit or infinity. However, the buffer lengths used in practice are finite and, in general, larger than one unit. The authors describe an approximate queueing model to evaluate system performance for finite buffer lengths larger than one unit. The system state is represented by a two-dimensional vector v=(n,k), where n and k are the number of busy terminals and the total number of outstanding packets in the system, respectively. A numerical procedure is described to calculate the expected delay, expected throughout, expected buffer occupancy and the probability of buffer overflow. Numerical results showing the effect of buffer length variations on the system performance are presented for the Optimal Aloha and the Urn schemes.
10 citations
TL;DR: In this article, a combined optimization/reliability technique is presented in which the system control parameters are optimized to maximize the load power supplied subject to the power flow equations as well as upper and lower bounds on the optimization variables.
Abstract: The loss of load probability (LOLP) represents an important index in the reliability evaluation of electric power systems. The LOLP denotes the probability of customer demand curtailments due to random outages of various system components. A combined optimization/reliability technique is presented in which the system control parameters are optimized. This simulates practical contingency situations where suitable controls are invoked in order to preserve, as much as possible, the continuity of supply. A DC representation of the power network is used and the optimization problem is solved by linear programming. The active component of the net injected power and the voltage angles at all buses represent the optimization variables of the problem. The optimal solution maximizes the load power supplied subject to the power flow equations as well as upper and lower bounds on the optimization variables. A description of the computerized algorithm developed and numerical results for a test power system are also included.
10 citations
TL;DR: In this paper, the authors conducted a study of induction heating of fossil fuels for the Alberta Oil Sands Technology and Research Authority (AOSTRA) as part of a comprehensive evaluation of electromagnetic heating techniques for in-situ recovery of bitumen from the Athabasca Oil Sands.
Abstract: The authors have conducted a study of induction heating of fossil fuels for the Alberta Oil Sands Technology and Research Authority (AOSTRA) as part of a comprehensive evaluation of electromagnetic heating techniques for in-situ recovery of bitumen from the Athabasca Oil Sands. The results of this study provide a proper description of the mechanisms whereby currents are induced, and the heating that will occur when an induction coil is embedded in a fossil fuel formation. The authors describe how some of these findings relate to the coil configurations proposed by Fisher and presents several relevant results of physical scale model experiments of buried induction coil systems. The information provided permits an engineering assessment of Fisher's induction heating proposal to be made.
6 citations
TL;DR: In this article, the effect of choosing a very small sampling interval for the identification of continuous-time systems for input-output data samples is illustrated and a method to obtain the optimum sampling interval is proposed.
Abstract: The effect of choosing a very small sampling interval for the identification of continuous-time systems for input-output data samples is illustrated and a method to obtain the optimum sampling interval is proposed. This method allows one to start with an arbitrarily small sampling interval without computational problems and at length converge to the proper sampling interval. Several simulated examples show the usefulness of the method even if the measurements are contaminated with a considerable amount of noise.
5 citations
TL;DR: In this article, the effects of varying the substrate parameters on characteristics such as radiation pattern, directivity, bandwidth, efficiency, and location of the feed-point to match a 50 ohm line are investigated.
Abstract: The input and radiation characteristics of circular microstrip antennas operated at higher order modes to generate conical patterns are studied. The effects of varying the substrate parameters on characteristics such as radiation pattern, directivity, bandwidth, efficiency, and location of the feed-point to match a 50 ohm line are investigated. Also, a multi-feed technique to operate the antenna at any particular higher order mode is proposed. Successful experiments have used this technique to operate the antenna at the desired higher order modes and the experimental results are in close agreement with the theoretical analysis.
4 citations
TL;DR: An array architecture is presented for implementing a finite impulse response (FIR) digital filter in a residue number system (RNS) and it offers most efficient performance for continuous input data stream applications.
Abstract: An array architecture is presented for implementing a finite impulse response (FIR) digital filter in a residue number system (RNS). A FIR filter requires only the high speed residue operations, i.e. addition and multiplication. VLSI is used as a fabrication medium to support the modular implementation. A general computation element is proposed as a building block unit. It is a multi look-up table module whose function is determined by the programmed contents of its associated tables. The proposed array is based on the systolic concept which provides high throughput and simplicity offered by identical processing elements, all operating in parallel on data synchronously flowing through the structure. The proposed architecture lends itself to the pipelining systems. It offers most efficient performance for continuous input data stream applications. An example of implementing a 24th-order filter is also given. The performance measures (area and time) of this filter are analyzed based on a developed memory model.
3 citations
TL;DR: In this article, the problem of designing decentralized optimal controllers for the load frequency control (LFC) of interconnected power systems is considered, and the optimal control parameters are obtained by solving a nonlinear two-point-boundary-value problem.
Abstract: The problem of designing decentralized optimal controllers for the load frequency control (LFC) of interconnected power systems is considered. An especially attractive feature of the proposed scheme is that it implements current practice in the area of LFC and current optimal control techniques to design the system supplementary controllers. The control law is assumed to have a proportional and/or integral form and is a function only of the measurable states (present-day-practice). The LFC problem is formulated in a parameter optimization form. By employing Pontryagin minimum principle, the optimal control parameters are obtained by solving a nonlinear two-point-boundary-value problem (present-day control theory). The values obtained for these parameters do not depend on the strength of the disturbance.
3 citations
TL;DR: In this paper, a barrel-type distribution transformer is modelled by an electrical network and methods of calculating the values of the network elements are discussed, and the response of the transformer to standard and chopped impulse waves is evaluated through the use of the electromagnetics transients program (EMTP).
Abstract: A barrel-type distribution transformer is modelled by an electrical network and methods of calculating the values of the network elements are discussed. The response of the network to standard and chopped impulse waves is evaluated through the use of the electromagnetics transients program (EMTP) with comparison of experimental and computed results included. The phenomenon of surge transfer is also considered by application of the EMTP to the detailed models of two different designs of the same transformer. A method of simplifying the electrical network is also discussed.
2 citations
TL;DR: A comprehensive region clustering and region labelling algorithm based on label propagation is described, which can provide, in addition to the features of the image, the boundaries of each feature, a label map and the region adjacency matrix for identifying the inter-regional relations.
Abstract: A comprehensive region clustering and region labelling algorithm based on label propagation is described. The segmentation algorithms developed can provide, in addition to the features of the image, the boundaries of each feature, a label map (each region is associated with a specific name) and the region adjacency matrix for identifying the inter-regional relations. Using this algorithm, an efficient microprocessor implementation can be realized since the algorithm does not involve any computational complexities. Performance criteria for effective segmentation are developed and tested extensively on a variety of images.
2 citations
TL;DR: In this article, the exact model matching problem of single input-single output (SISO) systems using feedback control is considered, where the closed loop transfer function of a given system is described by its 3D transfer function, equal to a ''desired'' transfer function.
Abstract: The exact model matching problem of single input-single output (SISO) systems using feedback control is considered. The closed loop transfer function of a given system is described by its 3-D transfer function, equal to a `desired' transfer function. Since the numerator of a SISO transfer function is not affected by static state feedback, series compensation is used in order to achieve the desired numerator. The problem of selecting the series compensators in the present 3-D case is generally quite involved. However, the model matching problem is very much simplified if the desired 3-D transfer function is factorizable and the state feedback is used to factorize the given transfer function. A step-by-step example is provided to illustrate the procedures.
2 citations
TL;DR: In this paper, a modified algorithm to form ACE with time-varying weights on the two variables is proposed, which shows improved system performance over conventional linear control with constant weights.
Abstract: Area control error (ACE) is used as the input variable in conventional load-frequency controllers. ACE is a sum of total tie-line powder deviation and area frequency error with constant weights on each variable. Because the systems are nonlinear, the relative strength of these two variables should be adjusted to match the system operating conditions. A modified algorithm to form ACE with time-varying weights on the two variable is proposed. Results for a two-area system show improved system performance over conventional linear control with constant weights.
TL;DR: In this article, a procedure for the appropriate design of 2-OA GIC (generalized impedance converter) simulated inductances, suitably compensated for the nonideal aspects of the OA such as finite bandwidth, signal handling capability, output resistance, etc.
Abstract: The design philosophy for RC-active highpass filters has not received as much consideration as lowpass and bandpass structures. The highpass filter (HPF) has a reasonable passband behaviour at high frequencies, at least up to 10 times the corner frequency. This is difficult to achieve due to the deteriorating behaviour of the practical operational amplifier (OA). In high order ladder structures, widely used because of their low sensitivity, improving the HPF behaviour is equivalent to designing a high quality grounded inductor at high frequencies. This evolves a procedure for the appropriate design of 2-OA GIC (generalized impedance converter) simulated inductances, suitably compensated for the nonideal aspects of the OA such as finite bandwidth, signal handling capability, output resistance, etc. Experimental results for 0.1 dB 7th order Cauer-Chebyshev highpass filters with corner frequencies at 10 KHz and 30 KHz are presented to evaluate the procedure. The two filters are studied at different signal levels using two types of OAs with gain-bandwidth products of 3 and 4.5 MHz.
TL;DR: In this paper, the true inductance, apparent inductance and the self-resonant frequency of spiral stripline inductors are estimated both experimentally and analytically, and it is shown that optimizing the properties of the inductors for a given application is straightforward.
Abstract: Equations for estimating the true inductance, the apparent inductance and the self-resonant frequency of spiral stripline inductors are presented. Estimates of the unloaded Q and the frequency at which the maximum unloaded Q will appear are found both experimentally and analytically. It is also shown that optimizing the properties of the inductors for a given application is straightforward.
TL;DR: In this article, the structure and operation of a submicron resolution camera system for fabricating high frequency interdigital electrode transducers (IDTs) was described, and the system was subsequently used to fabricate a modified chirp transducer with linewidth ranging from 1 μm to 24 μm.
Abstract: Describes the structure and operation of a submicron resolution camera system for fabricating high frequency interdigital electrode transducers (IDTs) A high resolution, 10× reduction lens is central to the system which produces IDTs by direct optical projection lithography The camera resolution was determined experimentally to be approximately 075 μm The system was subsequently used to fabricate a modified chirp transducer with linewidths ranging from 1 μm to 24 μm
TL;DR: Error bounds are formulated for a noncoherent Frequency Shift Keying channel under worst case jamming plus white Gaussian noise and show the adequacy of the new technique for narrowband interference rejection in two-way SS channel.
Abstract: A new system for narrowband interference rejection using a two-way Spread Spectrum (SS) communication has been presented. The system employs the inherent capability in a two-way Frequency Hopping (FH) channel to reject these hops hit by narrowband interference (intentional or unintentional). Following the initial acquisition of synchronization, the system undergoes a testing-telling process and, once these interference tones are detected, simple convolutional codes can be effectively used without interleaving or other sophisticated coding techniques. Error bounds are formulated for a noncoherent Frequency Shift Keying (FSK) channel under worst case jamming plus white Gaussian noise. These bounds show the adequacy of the new technique for narrowband interference rejection in two-way SS channel.
TL;DR: In this article, the authors focus on a new optimization model in which the economic design of the plant depends on the characteristics of the electric power system in which it is embedded and incorporate the data from a previous study into the optimization model to obtain the two different views of economic design problem, one based on the criterion of maximum net benefits and the other on maximum benefit-cost ratio.
Abstract: The design of tidal power plants is one of the most important engineering challenges in Canada In a previous study sponsored by the Bay of Fundy Tidal Power Review Board, consulting firms developed detailed civil, mechanical and electrical designs for plant subsystems They gathered extensive data on the tidal basins and then used the criterion of minimum `at-site cost of energy' to design the tidal power plant at a given location The authors focus on a new optimization model in which the economic design of the plant depends on the characteristics of the electric power system in which it is embedded They incorporate the data from a previous study into the optimization model to obtain the two different views of the economic design problem, one based on the criterion of maximum net benefits and the other on maximum benefit-cost ratio The computational results give the optimal design for each of the new criteria and the sensitivity of each design to changes in some system parameters and design variables The authors show that the strengths and weaknesses of criteria such as net benefits and benefit cost ratio differ from those of the `at-site cost of energy' criterion used previously The new optimization model is described and a computational results are clarified with analytic results displaying similar properties
TL;DR: Discusses the application of block-pulse functions to a number of problems in system theory, including the numerical solution of state equations, identification of multivariable systems from the samples of input-output data, and analysis and identification of distributed-parameter systems.
Abstract: Discusses the application of block-pulse functions to a number of problems in system theory. These include the numerical solution of state equations, identification of multivariable systems from the samples of input-output data, estimating the states from the samples of the input and output, and analysis and identification of distributed-parameter systems.
TL;DR: A formula to count the maximum number of mutually dissimilar directed graphs and two algorithms are presented to generate and test similarity of two directed graphs.
Abstract: Introduces the concepts of similarity of nth order symmetric sign patterns and similarity of n-vertex labelled directed graphs. Two sign patterns are similar if and only if their corresponding directed graphs are similar. A formula to count the maximum number of mutually dissimilar directed graphs and two algorithms are presented. One algorithm generates a set of mutually dissimilar directed graphs and the other tests similarity of two directed graphs.
TL;DR: A computationally efficient representation of the discrete Wigner distribution function is suggested, which allows the investigation of the spectral properties of a real analytic signal to be performed and the possibility of its recovery from the distribution.
Abstract: A computationally efficient representation of the discrete Wigner distribution function is suggested. It allows the investigation of the spectral properties of a real analytic signal to be performed and the possibility of its recovery from the distribution. A 2-D discrete representation is also introduced with special applications to image processing.
TL;DR: An error control scheme based on convolutionally-coded frequency diversity transmission and soft-decision Viterbi decoding and a real-time microprocessor implementation of the system are proposed for HF data transmission.
Abstract: An error control scheme based on convolutionally-coded frequency diversity transmission and soft-decision Viterbi decoding is proposed for HF data transmission. Simulation and experimental results are presented that show that the block error rate performance of the system is much better than that of conventional frequency diversity systems. It is also shown that the new scheme achieves significant throughput under channel conditions where conventional systems fail. A real-time microprocessor implementation of the system is described.
TL;DR: In this article, a dielectric filled, slotted metal cylinder is considered and the incident field is a plane wave with E-vector parallel to the axis of the cylinder, and the problem is solved using a convergent low frequency solution as well as by the method of moments.
Abstract: Studies scattering by a dielectric filled, slotted metal cylinder. The incident field is a plane wave with E-vector parallel to the axis of the cylinder. The problem is solved using a convergent low frequency solution as well as by the method of moments, and the two solutions are found to be in good agreement. They also agree quite well with experiment. Explicit expressions for the scattered far field are obtained in the low frequency limit, and many curves are presented in the range 1≤2π×radius/wavelength≤10.
TL;DR: In this article, a mathematical model is presented for computing the frequency of losing two rights-of-way due to tornadoes, and the usefulness of the model is demonstrated in an example.
Abstract: A mathematical model is presented for computing the frequency of losing two rights-of-way due to tornadoes. Relevant tornado characteristics are discussed and the usefulness of the model is demonstrated in an example. It is shown that the model can provide useful information for the transmission planning process.
TL;DR: In this article, a simple method of measuring harmonic flows and potential electromagnetic interference levels in power systems and communication circuits is proposed, which is correlated with existing plant susceptibility, leading to valuable information for rectifier design and filtering requirement identification.
Abstract: A simple method of measuring harmonic flows and potential electromagnetic interference levels in power systems and communication circuits is proposed. Harmonic emission is correlated with existing plant susceptibility, leading to valuable information for rectifier design and filtering requirement identification. A theoretical model based on an actual Canadian utility proves that modelling at harmonic frequencies is very limited. This model also points out the need for field tests versus simulation for design purposes.
TL;DR: The multi-gap shift keying MGSK technique is introduced and used in conjunction with the classic MFSK and MPSK techniques to increase the signal's immunity to noise and interferences.
Abstract: The classic problem of transmitting digital information with minimum probability of error in the presence of noise, fading and various interferences is investigated. The multi-gap shift keying MGSK technique is introduced and used in conjunction with the classic MFSK and MPSK techniques to increase the signal's immunity to noise and interferences. The same bits of information will control the phase, frequency and gap location of a composite MGSK/MPSK/MFSK signal (word) and, at the composite receiver, maximum likelihood decisions will minimize the probability of word errors. Modest amount of convolution error correction is needed so that the total effective rate is not sacrificed. The average performance of the new 3-dimensional signaling scheme was analysed and the average probability of bit errors with and without coding in the presence of AWGN and Raleigh fading was determined.
TL;DR: Considers methods for co-ordinating the converters of parallel multiterminal HVDC systems and describes current reference balancers and a telecommunication delay simulator.
Abstract: Considers methods for co-ordinating the converters of parallel multiterminal HVDC systems. The principle is based on balancing the converter current orders and two different balancing methods are described. The first uses a centralized current reference balancer and therefore requires some means of communication. The second method is slower but it is decentralized. The decentralized current reference balancer may be used to back-up the first when communication links are not operational. These current reference balancers and a telecommunication delay simulator are described. The performance of both controls are evaluated on the IREQ DC simulation of a parallel multiterminal HVDC system with two rectifiers and two inverters.
TL;DR: In this article, Park's vector was used to analyze the stator's sinusoidal voltages in a slip ring induction motor with quasi square wave currents and sinusoid voltages.
Abstract: A method of analysis for a slip ring induction motor with quasi square wave currents in the rotor and sinusoidal voltages in the stator is presented using the machine equations in terms of Park's vector. A close form solution to the stator flux linkage is obtained. The analysis shows that the stator currents are essentially sinusoidal superimposed by slip dependent harmonics. The torque developed is found to contain pulsations both at six times and twelve times the rotor frequency. At lower speeds where the rotor frequency is large, the higher order torque pulsations become insignificant. At very low rotor frequencies, the frequency range of these pulsations may cause dangerous vibrations.
TL;DR: In this paper, an efficient method of transient performance analysis of three-phase SCR voltage controlled induction machines is presented based on phase-variable modelling, where the induction machine is modelled in a three phase stationary frame and the transition from motor to generator operation with the in-line thyristors is considered.
Abstract: An efficient method of transient performance analysis of three-phase SCR voltage controlled induction machines is presented based on phase-variable modelling The induction machine is modelled in a three-phase stationary frame Consideration is given to transition from motor to generator operation with the in-line thyristors present Examples illustrate applications of the proposed method and the results obtained