Abstract: A new configuration is proposed for indoor optical wireless communication systems. The main features are the use of spot diffusing, multiple lines of sight and fly-eye receivers. Design issues such as the power budget, ambient-light interference and farsighted-eye designs for the receivers are discussed using simple models. An experimental set-up demonstrating the feasibility of the spot-diffusing concept is also described.

Abstract: Fast algorithms of a transform, like fast Fourier transform (FFT) algorithms, are based on different decomposition techniques. It is shown that these decomposition techniques can also be applied to the computation of the discrete Hartley transform (DHT) for a real-valued sequence. Recently, an efficient decomposition technique for radix-3 decimation-in-time (DIT) FFT and fast Hartley transform (FHT) algorithms has been demonstrated. Such a decomposition technique is implemented for radix-3 and -6 decimation-in-frequency (DIF) FHT algorithms and found to improve the operation count. Efficiency in these algorithms is derived by pairing the rotating factors with an appropriate reordering of the input sequence. From the results, it is seen that the radix-3 and -6 FHT algorithms presented are comparable to the split-radix FHT algorithm in terms of their operation count and will be more efficient when the sequence length is closer to an integer power of the corresponding radix.

Abstract: Characterizes several techniques for the distributed, dynamic management of telecommunications network transmission facilities. Several methods are presented for changing trunk-group sizes in order to respond to extraordinary network loads. These methods are given the generic title of self-traffic-engineering (STE), because the network effectively reengineers itself to adapt to unforeseen circumstances. Self-traffic-engineering is a new network management application for telecommunication facilities networks. One of these methods is based on a new interpretation of network reliability, which is embodied in a metric called connectability. The paper reports the results of a simulation study in which self-traffic-engineering is used to enable the Telecom Canada network to adapt to a focused overload.

Abstract: This paper describes a microprocessor-based measuring unit which is suitable for use in high-speed digital distance relays. The unit uses an algorithm that provides accurate estimates of apparent resistance and inductance of the line in relatively short times. The algorithm deals effectively with the presence of nonfundamental frequency components in signals without making assumptions about their compositions. The hardware and software of the unit are described. Test results indicate that the estimates converge to their true values within about 10 ms after fault inception. Also, the ability of the unit to provide accurate estimates is not adversely affected by the system frequencies drifting from its nominal value and by the distortion of the input signals.

Abstract: The authors present queuing-theoretic formulations for trading nodal storage capacity (i.e., buffers) requirements for the incremental transmission capacity of the links in supra-high-speed packet-switching nets. The performance criterion used is the mean nodal forwarding time. The results are useful for designing all-optical packet-switching telecommunication networks where the designer must compute the amount of incremental transmission capacity needed to eliminate a prespecified number of nodal buffers while preserving the same mean (or average) nodal forwarding time. A single optical buffer can be easily implemented by using a simple optical delay line. An example is included using a very-high-speed regular digraph as an architecture of a macro-switching fabric.

Abstract: A technique for accurately determining the resistivity and relative permeability of tubular stock is presented. The technique is based on measurements of the inductance of a coil wound on a toroidal sample of the material, with circular cross section. Measurements for J-55 material are also included.

Abstract: The authors extend their previous work (1990, 1991) on solving data acquisition and processing problems in power systems. The proposed methodology applies pattern analysis techniques to solve the network configuration, observability analysis and bad-data processing problems. Further associative memory models are investigated for the solution of the observability analysis and bad-data processing tasks. Special emphasis has been put on pattern analysis tools suitable for massively parallel implementations, such as artificial neural network models. Test results have been obtained for the IEEE 24- and 118-bus test systems.

Abstract: Short-reach interconnect requirements in digital computers and telephone switches may require throughputs of 10 Gb/s (50 parallel lines at 200 Mb/s each) in the near future. Time-division multiplexing (TDM) baseband transmission methods require high-speed multiplexing and precise clock recovery, and/or multiple fibres for such applications. As an alternative, the authors propose and analyze a quasi-orthogonal subcarrier multiplexing technique (QO-SCM) for short-reach digital fibre-optic interconnect applications. QO-SCM signal processing exploits the symbol-time synchronism which is inherent among the parallel lines of a typical data bus, to permit simplified filtering and higher spectral efficiency than conventional SCM. One can achieve bandwidth efficiencies of up to 2 b/s/Hz while eliminating RF channel filters and guard bands, and requiring only simple baseband pulse shaping. Link performance is studied through simulation to derive worst-case noise margins for a 50-channel QO-SCM pay-load signal with 10 Gb/s total capacity using a numerical model of the laser rate equations. Results predict that 10 Gb/s could be transmitted over 100 m at a bit error rate (BER) ≤10-12 on a single fibre-optic link, given a laser RIN of -155 dB/Hz.

Abstract: The paper presents an adaptation of the general-purpose SIMNON software for the study of alternating-current drives. With the objective of designing and dimensioning converter-AC machine-regulator systems, a simulation module named SEMAS is constructed in modular form using SIMNON. This software package shows great capabilities in terms of computing power, optimization, robustness of the algorithms and graphical interaction. Asynchronous and synchronous machine models implemented in SEMAS are presented. The different methods for modelling static converters and switches, with the particularities of each, are also presented. The results show evidence of a good agreement between simulations and experiments.

Abstract: The general requirements for electrical equipment used in traction applications are reviewed. These requirements and conditions include high inertia load, smooth torque control over the full range, high reliability, low maintenance, high efficiency, low mass, extended weak-field range for the motors, high top speed, dynamic or regenerative braking, motor and gearing exposed to heavy shock loading, limited motor diameter and length, and limited space for control circuitry. A system approach is required to obtain the most effective design for each application. The advantages and disadvantages of different motor types are discussed. It is concluded that the series motor is still the motor against which all other traction motors must be judged. Its disadvantages are all related to the mechanical commutator. Possible replacement by the squirrel-cage induction motor and the brushless synchronous motor is considered. The characteristic features of different converter types are considered, including the three-phase bridge converter/inverter, the pulse-width-modulated (PWM) inverter and the cycloconverter. A current control and voltage control strategy is discussed.

Abstract: A general estimation model is defined in which two observations are available; one is a noisy version of the transmitted signal, while the other is a noisy filtered and delayed version of the same transmitted signal. The time-varying delay and the filter are unknown quantities that must be estimated. A joint estimator is proposed. It is composed of an adaptive delay element in conjunction with a transversal adaptive filter. The same error signal is used to adjust the delay element and the filter such that the minimum mean squared error is attained. Two joint gradient-based adaptation algorithms are studied. The joint steepest-descent (SD) algorithm is first investigated. The possibility of a multitude of stable solutions is established and a condition of convergence is presented. A stochastic implementation of the joint SD algorithm, under the form of a joint least-mean-square (LMS) algorithm, is then presented. It is analysed in terms of convergence in the mean and in the mean square of both the delay estimate and the adaptive filter weight vector estimate. The conditions of convergence of the joint LMS algorithm are established as a function of the power spectral densities of the observed signals and the minimum mean squared error.

Abstract: Closed formulas for computing the time-domain voltage between the contact points of a ground plane produced by conducted currents are presented. The approach takes into account realistic effects such as the transient skin effect and the confinement of current lines at the contacts, known as the transient striction or constriction effect. The contribution of external inductance depends on the geometry and relative position of the return conductor and is not addressed in the present paper. Calculated results are presented for various parameters, such as the dimensions of the ground plane and contacts and the type of current time-function. Using a simple geometrical model, computed results show that the ground voltage may become non-negligible when short rise-time signals are considered.

Abstract: The paper investigates the robustness of the nonblocking asynchronous transfer mode (ATM) switch architecture with input-output buffering and backpressure control under correlated input traffic conditions. The traffic correlation is modelled by two parameters; namely, the mean active duration of the ON-OFF source feeding each input port, and the spacing between the cells generated within an active period. This spacing can be fixed or random. The effect of these parameters on the switch performance in terms of the cell-loss behaviour and the mean switching delay is investigated. The performance of different selection mechanisms needed to resolve output-port contention is evaluated, taking into consideration the performance enhancements obtained by incorporating different arbitration criteria within the selection mechanisms. The study indicates that the burst-length factor significantly affects the buffering requirements of the switch to achieve a certain cell-loss probability, even if the switch is operated at fairly low utilization. The spacing between cells within a burst has a considerable effect on the cell-loss performance of the switch. Using the longer-input-queue criterion as the arbitration criterion between cells contending for the same output port results in smaller buffer sizes for given cell-loss probability and value of applied load, than is the case when the arbitration criterion is implemented according to the earlier arrival time at the head-of-line (HOL) position of the input queues. Since the longer-queue criterion does not involve time-stamping, as is the case with the HOL-time criterion, it is also the more attractive solution from an implementation point of view. This result confirms previously reported conclusions under the uniform random traffic case.

Abstract: The problem of electric power transmission limitations due to finite reactive resources is studied. Maximum system load, i.e., loadability, is determined using a nonlinear optimization technique (Modified Augmented Lagrangian) which accommodates limits on reactive generation as well as other practical constraints. The sensitivities of the system loadability with regard to transmission-element primitive admittances are by-products of the proposed optimization method. These parameters indicate the relative strength of the transmission elements at the voltage stability limit. The weakest element is considered to be the one exhibiting the greatest sensitivity. Electrical strengthening of this element would enhance the system loadability. Sample results are presented for a 30-bus system.

Abstract: The representation of scientific data as a visible surface using a natural scene paradigm is an attractive and intuitively meaningful way of visualizing data. Representation using this paradigm organizes the data in a manner which is closely related to the digital image; the data are represented as a scalar variable sampled over a two-dimensional spatial field. However, scientific data are seldom available in any uniformly sampled, regular form, thus requiring the use of some sort of modelling or interpolation scheme to produce the image-like representation of the data. The author discusses one approach to the visualization of randomly sampled data which produces an image in a single pass through the data, requires no high-resolution surface modelling, and suppresses moderate amounts of noise. The scheme is capable of interpolating between samples to fill in missing data regions. The technique is demonstrated using LIDAR data of coastal-region water depth. Data visualization using classical image processing methods is illustrated, once again using the LIDAR images as an example.

Abstract: The radar cross section of a target is a complex quantity possessing both an amplitude and a phase. Most of the work done up to the present day restricts itself to discussing the former, the latter being almost completely ignored. Yet it seems reasonable to assume that a study of both the amplitude and phase characteristics would lead to a more complete picture of the target under consideration. The present paper focuses on the analytical and experimental aspects of the phase behaviour (with a few remarks on the amplitude), giving detailed descriptions in the case of a cylinder and a dart (examples of a simple and complex target respectively).

Abstract: The paper presents a new method for optimal power flow calculations, using the generalized power balance constraint, obtained from the power flow equations by elimination of all state variables. The reduced optimization problem in the control variables is subsequently decoupled into two stages: a primary stage in the primary control variables (generator active power injections) and a secondary stage mainly in the secondary control variables (generator voltages). The primary stage is solved by economic generation scheduling, where the power system losses are accounted for by the coefficients of the generalized power balance constraint. The secondary stage is solved by linear programming, subject to all power system constraints. The linear programming formulation is such that the solution of the primary stage is maintained, if feasible, or otherwise optimally adjusted. Thus, the method takes full advantage of decoupling, if it is applicable, and otherwise inherently reverts to a coupled approach. A step-limit control strategy successfully damps the oscillations that are always present in successive linear programming, and ensures the optimality and feasibility of the solution.

Abstract: The dynamical equations of a power system are usually obtained by applying the laws of electrotechnics and Newton's second law. The authors extend the use of Lagrange's laws, classically used to model mechanical systems, to the derivation of the dynamical model of an autonomous power system. One of the major advantages of the proposed approach is its simplicity, which directly derives from the unified aspect of the modelling procedure. The obtained dynamical model is transformed into a generalized state-space model, and is used to simulate the transient behaviour of the autonomous power system to the presence of variable speed.

Abstract: The notion of the commutation cell has been introduced and used to study the local and systemic aspects of the commutation process, such as the functioning modes of a switch and the commutation mechanism The authors show that this notion can also be a tool in a computer-aided design software, for the study and synthesis of the topologies of static converters In this light, general laws and rules for electronic commutation are defined Their application in an elementary commutation cell allows a graphical analysis of input and output waveforms (current and voltage at the switches)

Abstract: A data analysis program utilizing the boundary discrete points (BDP) technique is developed to predict the effect of runway approach-light systems (ALSs) on the microwave landing system (MLS) signal in space in terms of angle guidance error, path following error (PFE) and control motion noise (CMN) Various ALS configurations are modelled and field-tested In this study, the MLS peak guidance errors caused by the presence of the ALS are found to be small, but such that they could cause out-of-tolerance conditions Initial field-test results are in agreement with those predicted by the developed model

Abstract: The authors present the principle of indirect measurement of temperature in heat-transfer problems. They apply the principle of indirect measurement of power flow and temperature distribution on the surface of the test limiter of the Tokamak at Varennes (TdeV) using the method of finite elements in 3-D. During a 200-kA Tokamak discharge, the hemispherical head was submitted to a power of 30 kW over a period of 770 ms.

Abstract: The characteristics of a carrier-based pulse-width modulator under different modulation techniques are evaluated. Modulation with the most commonly used carrier waveforms (triangular and sawtooth waveforms) and sampling methods (uniform, double and natural sampling) is studied. In each case, the switching harmonics at the modulator output are calculated and the frequency response of the modulator is determined. Different modulation techniques are then compared, and the one that best suits switchmode magnet power supply applications is identified.

Abstract: Coastal HF radar in the ground-wave mode may be useful for monitoring the movement of ships, aircraft and icebergs over vast areas of ocean. At HF frequencies an aircraft is in the `resonance range' of size. The paper studies the radar cross-section (RCS) of a 30-m aircraft-like object for nose-on and broadside incidence, by direct measurement and by wire-grid modelling, with good agreement. The `generic aircraft' RCS is demonstrated to be dominated by the vertical stabilizer at low HF frequencies, but by the fuselage for broadside incidence at higher HF, in level flight. Resonant effects in the RCS are related to resonant-length paths on the airframe. It is shown that a wire antenna carried for HF communication can introduce sharp resonance peaks and troughs into the aircraft RCS. The changes in RCS due to nose-up and nose-down flight attitude, and to steep banking are briefly investigated.