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    A projection-based joint probabilistic data association algorithm [multi-target tracking applications]

    van Wyk, B.J. ; van Wyk, M.A. ; Noel, G.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406682
    Publication Year: 2004 , Page(s): 313 - 317 Vol.1

    IEEE Conference Publications

    A novel projection-based joint probabilistic data association (PJPDA) algorithm is presented. The JPDA problem is formulated as a constrained optimization problem and solved using projection onto convex sets (POCS) methods. The PJPDA algorithm is extremely simple to implement, has no strenuous memory requirements and completely avoids the generation of feasible event matrices. Algorithm complexity is discussed and simulation results presented View full abstract»

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    A wavelet-time frequency analysis on torsional vibration response of a rotor with a switching crack and a dominant twisting torque

    Alugongo, A.A. ; Munda, J.L.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401643
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (1)

    IEEE Conference Publications

    A parametric excitation due to a crack on a rotor shaft in torsional vibration is the core of the investigation in this paper. A coherent hinge model derived on the basis of local flexibility theory and fracture mechanics is adopted to represent the cyclic and the nonstationary signal of a deep breathing crack in an uncoupled transient torsional vibration of a rotating cracked rotor shaft. A special treatment of the system governing equation for a deep switching crack under a dominant twisting torque is presented. Consequently, a wavelet time-frequency technique is employed to explore the cracked rotor system response. The numerical simulations results are consistent with existing literature and offer a sufficient criterion for crack identification. Interesting scenarios including sub harmonic resonance are discussed to emphasize the investigation. View full abstract»

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    Bottom-up ontology development reusing semi-structured life sciences diagrams

    Keet, C.M.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071987
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    Bio-ontology development is a resource-consuming task despite the many open source ontologies available for reuse. Various strategies and tools for bottom-up ontology development have been proposed from a computing angle, yet the most obvious one from a domain expert perspective is unexplored: the abundant diagrams. To speed up and simplify bio-ontology development, we propose guidelines to formalise such diagrams in several logic languages availing also of a foundational ontology to achieve a more precise representation of the subject domain semantics and increase interoperability. The guidelines are demonstrated with a transformation of the Pathway Studio diagrams into an OWLized bio-ontology with BFO and RO. View full abstract»

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    Switched reluctance motor measurements and simulation models

    Wang, S. ; Burton, B. ; Harley, R.G.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406870
    Publication Year: 2004 , Page(s): 1161 - 1167 Vol.2

    IEEE Conference Publications

    This Paper describes an experimental process used to produce a model in Matlab and Simulink for a prototype 8/6 switched reluctance motor, and some methods used to validate the model. The inductance, flux and torque characteristics of switched reluctance motors are nonlinear, and must usually be numerically determined from real experimental data. Torque can be measured directly or calculated from measured phase current, and rotor position, and numerically determined inductance. This paper explains how two different lookup tables are used to simulate the electrical, magnetic and mechanical characteristics of the motor. Simulation results are shown to closely agree with practical current and rotor position responses under locked and free rotor conditions. It is also explained how the validated simulation models will be used in the future design of a power converter and nonlinear torque (current) and speed control loops. View full abstract»

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    Design of broadside, uniformly fed, planar aperture coupled microstrip patch arrays

    Botha, M.M. ; Davidson, D.B.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821912
    Publication Year: 1999 , Page(s): 1021 - 1024 vol.2

    IEEE Conference Publications

    The design of broadside, uniformly fed, planar aperture coupled microstrip patch arrays is addressed. Individual elements were designed using Mstrip40, a MoM microstrip analysis program, Designing, measuring and performing a FEM analysis on a 3 GHz element successfully validated the procedure. 4 and 16 element, 9 GHz arrays were designed. Pattern and S11 measurements as well as theoretical patterns are presented View full abstract»

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    Automated surveillance and detection of foreign stationary objects

    Kiewiet, N.G. ; Roodt, Y. ; Roos, H. ; Clarke, W.A.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072153
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    CCTV systems are frequently monitored manually by a human observer. This human observer is typically responsible for dealing with tens or hundreds of cameras at a time. Potential security threats may easily be missed by the system's human operators due to fatigue or being overwhelmed by the amount of change in the images. The timely detection of security threats is an important attribute for any security system. A robust algorithm for detecting potential threats from a surveillance video is presented. View full abstract»

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    Progress report on an engineering bridging programme

    du Plessis, G. ; Pauw, C.K. ; van Harmelen, T.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563073
    Publication Year: 1996 , Page(s): 28 - 31 vol.1

    IEEE Conference Publications

    The paper reports on the progress of the 1995 intake of freshman engineering students on the extended engineering programme at the University of Pretoria, South Africa. The programme is described briefly. Encouraging results are presented. A list of references with more detail is also provided View full abstract»

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    Neural-model reference control of an air motor

    Marumo, R. ; Tokhi, M.O.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406717
    Publication Year: 2004 , Page(s): 467 - 472 Vol.1
    Cited by:  Papers (3)

    IEEE Conference Publications

    Neural networks are known for their unique properties of universal approximation. A description of a nonlinear plant in state space is obtained using a recurrent Elman network. Learning is implemented off-line with a truncated back propagation through time algorithm. Based on the neural model, a reference control strategy is implemented as a sequence of control actions computed by solving an optimisation problem iteratively. The past decade has seen an increase in research into the control of pneumatic drives. Two main reasons motivate this study: the response of pneumatic drives is slow, leading to an inability to attain set points due to high hysteresis; the dynamic model of the system is highly non linear, which greatly complicates controller design and development. Two streams of research efforts have evolved: using conventional methods to develop a modeling control strategy; adopting a strategy that does not require a mathematical model of the system. The paper presents investigations into the modeling and control of an air motor incorporating a pneumatic equivalent of the electric H-bridge. The pneumatic H-bridge has been devised for speed and direction control of the motor. The system is divided into three main regions: low speed (below 390 rev/min); medium speed (390 to 540 rev/min); high speed (540 to 680 rev/min). The system is highly nonlinear in the low speed region and hence an intelligent controller system, such as a neuro model and reference controller, is proposed View full abstract»

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    A novel LCD backligth with mixed white and colorful LEDs

    Huaxia Wu ; Qibin Feng ; Guoqiang Lv
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308184
    Publication Year: 2009 , Page(s): 1 - 5

    IEEE Conference Publications

    With improved luminous efficiency, reduced cost, long lifetime, wide color gamut, fast response, LEDs are becoming a suitable solution for LCD backlight. Backlight consisting of white LEDs has the merit of high luminous efficiency while is not possible to change color temperature. Backlight with colorful LEDs of red, green, blue to form white lights can reach various color temperatures while luminous efficiency is not as high as white LED backlight. A mixed backlight combining white and colorful LEDs is presented in this paper to preserve the merits of both kinds of LED backlights. High luminous efficiency white LEDs provide most of luminance and colorful LEDs are only lightened when color temperature is to change. An implementation is realized. The experimental results show that the theoretical model is appropriated and the mixed backlight presents the high luminous efficiency with less LEDs and possibility to change color temperature. View full abstract»

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    A proposed empirical model of the effective Earth radius factor for telecommunications use in South Africa

    Baker, D.C. ; Palmer, A.J.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159960
    Publication Year: 2002 , Page(s): 511 - 516 vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    Available data for the cumulative probability of occurrence of various values of the radio refractive k-factor for South Africa have been subjected to regression analysis in terms of a proposed equation to describe such a distribution. The results presented have considerable promise in predicting the average cumulative trend of the k-factor in the inland summer rainfall areas. The model is expected to be of value in predicting large values of the k-factor, which may only be exceeded relatively rarely, but which could give rise to long-range interference in radio communication systems. View full abstract»

  • Freely Available from IEEE

    2002 IEEE Africon. 6th Africon Conference in Africa [front matter]


    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159956
    Publication Year: 2002 , Page(s): i - xiv

    IEEE Conference Publications

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    A four-transistor CMOS SRAM cell

    Joubert, T.-H. ; Seevinck, E. ; du Plessis, M.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821945
    Publication Year: 1999 , Page(s): 1173 - 1176 vol.2

    IEEE Conference Publications

    In CMOS, an SRAM cell containing six transistors is generally used. If a smaller number of transistors and fewer connection lines were possible, the packing density of SRAM chips may be improved. A reduce-area four-transistor SRAM cell for implementation in a standard digital CMOS process is proposed in this paper View full abstract»

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    Ubiquitous health care framework for the rural African environment

    Mark, M. ; Ngwira, S.M.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072068
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    With the advancement of technology and telecommunication, ICT is in a position to play a major role in Public Health planning, disease eradication and containment. The introduction of Ubiquitous computing into the health care system will ensure that patient data is readily available to those authorized and can be collected and analyzed in real time. In this paper we designed and developed a Ubiquitous health care framework that is best suited for developing African states that will assist in health care planning, collection and management of patient records, decision and basic diagnostic support. The system proposed looks at all aspects of public health and envisages to integrate them into one. View full abstract»

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    Rate-compatible pruned convolutional codes and Viterbi decoding with the Levenshtein distance metric applied to channels with insertion, deletion, and substitution errors

    Ling Cheng ; Ferreira, H.C.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406648
    Publication Year: 2004 , Page(s): 137 - 143 Vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    Viterbi decoding is a path maximum-likehood decoding algorithm widely used in modems and error correction devices. The Levenshtein distance has been postulated to be a suitable branch comparison metric for the Viterbi algorithm on channels not only with substitution errors, but also with insertion/deletion errors. However, to a large extent, this hypothesis has still to be investigated. Pruned convolutional codes are constructed by periodically deleting branches in a high rate convolutional code trellis diagram to create a time varying code. The application of rate compatible pruned codes to hybrid ARQ/FEC schemes is proposed here for channels with insertion, deletion and substitution errors. A new type of Viterbi algorithm based on the Levenshtein distance metric is used as the decoding algorithm. Our experiments give evidence that the Viterbi algorithm with the Levenshtein distance metric is suitable as a decoder on channels with both substitution errors and insertion/deletion errors, and furthermore that rate-compatible pruned codes can improve the performance of the decoding View full abstract»

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    Comparing the RealNeuron with spiking neurons

    Erasmus, L.D.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401544
    Publication Year: 2007 , Page(s): 1 - 6

    IEEE Conference Publications

    The model of the RealNeuron is compared with that of perceptrons and spiking neurons. It is shown that special instances of the RealNeuron can implement perceptrons and spiking neurons. Also, a theoretical evaluation of the RealNeuron performance, in the presence of noise, is presented. The performance is dependant on the the refractory function's output value of the sensor neurons in the network. The range for the the refractory function is presented for a sensor neuron to function correctly in a noisy environment. The range is dependant on the pump parameters in the main membrane of the sensor neurons. View full abstract»

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    Maintenance management-a neglected dimension of engineering management

    Visser, J.K.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146885
    Publication Year: 2002 , Page(s): 479 - 484 vol.1

    IEEE Conference Publications

    Engineering management comprises the management of resources as well a number of life-cycle engineering processes, such as development, production and maintenance. A life-cycle approach towards the management of technical assets calls for a balanced approach in which all life-cycle phases are addressed. The management of maintenance is a relatively new academic and knowledge area. Within the engineering management body of knowledge the management of maintenance has not yet received the attention that it should get. The focus is still on development of new systems rather than maintenance and support. This paper outlines the role of maintenance in the business enterprise and how the discipline of maintenance management can be enhanced in organisations. View full abstract»

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    Assesment of harmonics generation on an off-shore mine and determination of mitigation equipment

    Batista, A.B. ; Awodele, K.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308113
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    The aim of this paper is to assess the level of harmonics on a diamond mining ship in accordance with the NRS048 standards. The investigation was done on a DeBeers mining vessel, Debmar Pacific. After the measurements were obtained simulations of the ship's electrical system were carried out using DIgSILENT. The results of the simulation indicated the effectiveness of some proposed mitigation equipment in reducing the generated harmonics to acceptable levels. View full abstract»

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    Evaluation of a reduced topology phase-converter for rural areas in Southern Africa

    Cruise, R.J. ; Landy, C.F. ; McCulloch, M.D.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821881
    Publication Year: 1999 , Page(s): 859 - 864 vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    A reduced topology phase-converter driving a three-phase induction motor is identified as a possible solution for operating large motors off single-phase supplies. This is a common problem faced by rural communities in Southern Africa. The performance of the reduced topology phase-converter is evaluated, with particular reference to the harmonic content of the voltage waveforms and its effect on the starting and run-up torque of the three-phase induction motor View full abstract»

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    A software interface for an industrial control network using the CAN protocol

    Travis, A.R.L. ; Collier, M.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.563049
    Publication Year: 1996 , Page(s): 1081 - 1082 vol.2

    IEEE Conference Publications

    The band period of a controller area network (CAN) interface written in software cannot be less than the time taken for a bit move, bit comparison and count with branch. Such an interface has been demonstrated, and baud rates of 0.5 MHz may be possible View full abstract»

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    Infra-red and ultra-violet imaging techniques applied to the inspection of outdoor transmission voltage insulators

    Bologna, F. ; Mahatho, N. ; Hoch, D.A.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159976
    Publication Year: 2002 , Page(s): 593 - 598 vol.2
    Cited by:  Papers (3)

    IEEE Conference Publications

    The high voltage transmission network in South Africa contains a relatively high percentage of non-ceramic insulators. Techniques for assessing the condition of these insulators are under investigation. Such techniques include imaging techniques that take either an infra-red image or an ultra-violet image of the insulator. Such images may indicate some changes to either the external (visible) components of the insulator or to the internal (non-visible) components that may impact the long-term integrity of the insulator. This paper discusses the results of an investigation into these two imaging techniques applied to non-ceramic insulators. View full abstract»

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    Characteristic function based method for SVM classification of maneuvering over the horizon targets

    JalaliRad, A. ; Amindavar, H. ; Kirlin, R.L.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072027
    Publication Year: 2011 , Page(s): 1 - 4

    IEEE Conference Publications

    In this paper, we propose a new classification method based on characteristic function (CF) and support vector machine (SVM). In order to validate the new approach, we classify three groups of airborne over-the-horizon radar (OTHR) targets. Since signal models make the basis for analysis and enhancement of OTHR performance, choosing an appropriate model has always been a matter of concern. On the other hand, the returned signal from a maneuvering target is more often a multi-component signal with time-varying frequency, hence, we model the received signal as being comprised of a chirp faded by the radar cross section (RCS) plus Gaussian white noise and K-distributed (un)correlated clutter. Little work has been done on OTHR target classification. In order to assess the new classification approach based on CF, we compare our method with discriminant analysis (DA), decision tree (DT), and multi-layer Perceptron neural network (NN). It will be depicted through extensive simulations that the proposed CF and multi-phase SVM method's error in classifying airborne targets is about 3.5% less than existing classification methods'. View full abstract»

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    Multiband Doherty RF power amplifier

    Juschke, P. ; Wiegner, D. ; Luz, G. ; Machinal, R. ; Pascht, A. ; Quay, R.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072119
    Publication Year: 2011 , Page(s): 1 - 5
    Cited by:  Papers (1)

    IEEE Conference Publications

    In era of exploding energy consumption and thus equipment operating cost as well as the parallel environmental need to reduce the carbon footprint, energy efficient mobile radio is a very important issue and future challenge. Additionally, increased number of standards, frequency bands and applications require flexible and sustainable solutions. On both fields the power amplifier constitutes one of the setscrews to be addressed. On the one hand, the power amplifiers cause up to 60 % of the power dissipation of a base station, on the other hand it constitutes a bottleneck concerning transmit bandwidth. The following paper presents a very promising concept of a highly efficient Doherty which supports multiband capability in order to enable future efficient, flexible and sustainable mobile radio applications. The basic functionality of the proposed concept is verified by simulation and promising simulated results, based on AlGaN/GaN-HEMTs from FhG-IAF (Fraunhofer Freiburg) indicate the benefits of the new concept compared to conventional Class-AB and Doherty amplifiers. View full abstract»

  • Freely Available from IEEE

    [Breaker page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406730
    Publication Year: 2004 , Page(s): 523

    IEEE Conference Publications

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    Adaptive time-varying beamforming for source localization and tracking in nonstationary environment

    Katkovnik, V.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820832
    Publication Year: 1999 , Page(s): 309 - 314 vol.1

    IEEE Conference Publications

    The proposed beamformer in two aspects is different from the conventional one. The weights are dependent on time and two parameters θ and θ'. Maximization of the beamformer power on θ and θ' gives estimates of direction-of arrival (DOA) and its first derivative. Simulation confirms an improved tracking ability of the new algorithm View full abstract»

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    Analytical model for evaluating blocking probability in wireless ad hoc networks

    Gugrajah, Y. ; Takawira, F.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146848
    Publication Year: 2002 , Page(s): 277 - 282 vol.1
    Cited by:  Papers (2)

    IEEE Conference Publications

    Routing protocols for ad hoc networks need to overcome the problems associated with dynamic and unpredictable topologies due to mobile nodes and the absence of base stations and central controllers. Currently, routing protocols are evaluated using discrete event simulators. Analytical methods to evaluate the end to end blocking probability are required in order to generate faster results for routing protocol comparison and network optimization. This paper proposes a semi-analytical method that incorporates fixed point approximation to account for mobility in ad hoc networks. Results are compared to those obtained by discrete event simulation. View full abstract»

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    Channel sharing policies for a mobile radio network providing wireless telephone and dispatch services

    Nofal, M.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563096
    Publication Year: 1996 , Page(s): 139 - 144 vol.1

    IEEE Conference Publications

    Channel sharing policies are proposed for a mobile radio network that provides telephone and dispatch services. The two services have different features and different service fields. The salient features and operational principles of both services are described. Based on these features, channel sharing policies are proposed. Analytical models are established for the proposed policies in order to gauge the performance of the network. Numerical results are provided and discussed for nominal network parameters View full abstract»

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    Closed-loop system identification of a MIMO plant controlled by a MPC controller

    de Klerk, E. ; Craig, I.K.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146811
    Publication Year: 2002 , Page(s): 85 - 90 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    In this paper a simulation concerning the closed-loop system identification of a multivariable plant model, where the plant is controlled by a model-based predictive control (MPC) controller, is discussed. A motivation for closed-loop system identification in this context is given. Then the identification methodology is discussed and demonstrated, and the method evaluated. View full abstract»

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    Evaluation of quality concepts influencing a manufacturing environment in South Africa

    Erasmus, P. ; van Waveren, C.C.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401566
    Publication Year: 2007 , Page(s): 1 - 9

    IEEE Conference Publications

    This research article evaluates the influence from quality concepts and tools in a manufacturing environment on parameters that may affect future design and development of products in the same company. It attempts to establish how quality results can be utilised to determine the level of quality control tools such as quality function deployment and concurrent engineering in a company that designs for manufacture. By establishing links from quality results and customer requirements, the research determines what critical quality tools are necessary to determine the capability of manufacturing an item without the use of excessive planning resources. Research was performed on four distinct subject matters namely design, manufacture, quality control and concurrent engineering and the results of the research was implemented in a design and manufacturing environment with the purpose of establishing direct links between quality control results and design parameters to increase future development. The research also establishes, by means of a questionnaire, the level of certification to quality standards of South African manufacturing companies, while determining their knowledge in regard to quality, its tools and concepts, as well as the level to which these are implemented and utilised in manufacturing entities. View full abstract»

  • Freely Available from IEEE

    [Blank page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406803
    Publication Year: 2004 , Page(s): 840

    IEEE Conference Publications

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    The application of fuzzy logic for the solving of conflicts in the dispositional tasks of a railway traffic control center

    Heray, T. ; Rozsa, G. ; Koczy, L.T. ; Tompe, I.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308167
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    The paper considers a railway timetable related problem in a simplified form, generated by the delay of one or several incoming trains at a given station. Usually there are connecting trains in the timetable, especially in up to date periodic timetables and thus incoming delays might indicate the necessity of introducing a delay with connecting outgoing trains. A hierarchical fuzzy rule base is applied in order to determine the optimal outgoing delay, taking also usual restrictions into consideration. Three examples are shown. View full abstract»

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    Bandwidth allocation for the Rainbow Services network

    Ojong, G.E. ; Takawira, F.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406675
    Publication Year: 2004 , Page(s): 285 - 288 Vol.1

    IEEE Conference Publications

    The popularity of the current best effort Internet has fuelled growing interest by researchers to modify the current Internet to make it accommodate real-time multimedia traffic. The Rainbow Services architecture has recently been proposed as a novel QoS architecture for the future Internet. In this paper, we show how bandwidth is allocated to the service classes of this new architecture in order to utilise the network cost-effectively. Bandwidth is partitioned amongst the five service classes. Each of GCR and ADS classes is allocated constant bandwidth values. Each of the other classes is initially allocated a minimum threshold bandwidth but can be increased to a maximum threshold value. We also provide the service interfaces for each service class of this architecture. The Rainbow Services network is being designed to allow different classes of traffic to make efficient use of network bandwidth while at the same time guaranteeing the QoS of each traffic class View full abstract»

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    Spatio-temporal perception nets

    Pongratz, M. ; Velik, R. ; Machajdik, J.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072061
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    State of the art approaches to autonomous systems face the challenge of sensor data fusion, abstraction, classification, and prediction of events. The trend is going towards the integration of more and more sensors into automation systems, which will reach a number of sensors comparable to the amount of sensory receptors in the human body in the not too distant future. While today's technical systems cannot cope with such a flood of information to be processed rapidly, these challenges are mastered exceptionally well by the human brain. Based on this observation, in prior work, a biologically inspired model for sensor data processing has been proposed [1]. This socalled neuro-symbolic information processing model is based on a functional model of the human perception system. Here, an extension of this concept to spatial and temporal aspects of perception is presented. The challenges for solving these tasks as well as the strategies to master these challenges based on perception-nets are presented. View full abstract»

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    Insulator pollution monitoring program for Namibia

    Vosloo, W.L. ; Engelbrecht, F. ; Heger, N. ; Holtzhausen, J.P. ; Strauss, J.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401630
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    The presence of a wet, conducting pollution layer on the surface of insulators installed within an electrical power network can affect the performance of the system negatively. It is therefore important to have reliable information on the distribution and severity levels of insulator pollution as well as climate conditions in a region. This publication describes the methodology of setting up an insulator pollution monitoring program for Namibia and presents the first series of data obtained from the test stations. View full abstract»

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    PWM current rectifier-five NPC level inverter cascade. Application to the PM synchronous machine

    Chibani, R. ; Berkouk, E.M. ; Manesse, G.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821852
    Publication Year: 1999 , Page(s): 705 - 710 vol.2

    IEEE Conference Publications

    The aim of this paper is to present the working principle of the PM synchronous machine fed by a five level NPC voltage inverter. This inverter has a PWM current rectifier as DC source. Firstly, the authors present a model of the inverter by elaborating its knowledge model. Then, they present a control strategy of this inverter based on pulse width modulation. To prove the efficiency of this inverter, the authors use it in the speed control of a PM synchronous machine (suppose that the DC source of the inverter is ideal in the first time). After that, they present the PWM current rectifier and use it as a DC source of the inverter and give the results of the cascade which have the five level inverter as the output bridge View full abstract»

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    Acceleration of nonparametric time-varying phasor estimation

    Jordaan, J.A. ; van Wyk, M.A. ; van Wyk, B.J.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401619
    Publication Year: 2007 , Page(s): 1 - 6

    IEEE Conference Publications

    In this paper we present an acceleration procedure for an application of a robust nonparametric signal modelling technique for tracking time-varying phasors of voltage and current in power systems. A first degree polynomial is used to approximate these voltage and current signals locally on a sliding window of fixed length. The least-squares criterion and non-quadratic criteria (quadratic-squares-root, quadratic- tangent and quadratic-constant) was used to fit the linear function to the data, and methods to speed up the procedures was introduced. The paper concludes with the presentation of the representative testing results. View full abstract»

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    Assessing the written word: The engineering students' experience

    Israel, H.F. ; de Jager, H.J.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308073
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    Vygotsky's (1987) premise is that students write to learn, and that this learning stretches across the curriculum. The lecturer in the field of engineering has therefore to evaluate teaching and learning through writing tasks as they are traditionally known, and ask why assessment focuses on students' weaknesses - why does assessment instead not meet the student at his point of strength, and lead him from there? It is at this point that the various factors contributing to the learning experience of the student merge into one multi-faceted concept - assessment. Assessment skills are part of the learning process, yet equipping engineering lecturers with such skills in theory and practice is minimal. Assumptions are that if one is qualified in a content area, one can teach that content and objectively assess one's students. This is not always true. Reviewing assessment of the written word is vital because language is the means to academic success. The responsibility lying with the engineering lecturer when assessing writing tasks is further compounded by the education context, the worldview of the educator and the experience of the learner. Common issues confronting engineering educators and students emerge. This paper addresses some such issues. View full abstract»

  • Freely Available from IEEE

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    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406743
    Publication Year: 2004 , Page(s): 573

    IEEE Conference Publications

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    Scraper winch motors on South African gold mines-an investigation into their failure

    Pritchard, J.F. ; Landy, C.F.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563152
    Publication Year: 1996 , Page(s): 435 - 440 vol.1

    IEEE Conference Publications

    This paper investigates some of the probable reasons for failure of squirrel cage induction machines driving scraper winches in South African gold mines. The paper shows the results of load current and voltage unbalance measurements that were recorded on winches in operation. There are further measurements showing the presence of time harmonics in the supply to some winches. More importantly, the paper shows the measured torque-speed curve of a typical scraper winch machine. This curve seems to indicate that there are significant space harmonics present in the air-gap of the winches, which may be causing rotor heating and premature bearing failure View full abstract»

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    Microprocessor control of hybrid energy systems

    van der Linde, H.A. ; Clark, I.
    AFRICON '92 Proceedings., 3rd AFRICON Conference

    DOI: 10.1109/AFRCON.1992.624458
    Publication Year: 1992 , Page(s): 217 - 220
    Cited by:  Papers (1)

    IEEE Conference Publications

    Remote area power supplies in the form of a hybrid system can be a very effective alternative in that the different components can be complementary. The authors describe a project whose aim was to develop a dedicated microprocessor control system to effectively manipulate a hybrid energy system so that available energy is efficiently utilized while at the same time the life span of battery banks is extended. The system was referred to as a Hybrid Energy System Manager (HESM). The HESM was connected to simulated and real energy sources and loads, and subjected to a series of tests. The results were very gratifying in that it performed as expected View full abstract»

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    Synthesis of a decentralised fuzzy controller for level control of a four stage cascaded tank system

    Bart, Q.J.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146818
    Publication Year: 2002 , Page(s): 119 - 122 vol.1

    IEEE Conference Publications

    A plethora of information exists to aid in the development of fuzzy controllers for both industrial and commercial applications. However, a very small subset of fuzzy set theory is really utilised for the synthesis of a fuzzy controller. In this paper it is shown how a decentralised fuzzy controller was designed to independently control the water levels in a four stage cascaded tank system. View full abstract»

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    Rogowski coils for short duration (<10 μS) pulsed current (>10 kA) measurements

    Turner, G.R. ; Hofsajer, I.W.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821863
    Publication Year: 1999 , Page(s): 759 - 764 vol.2
    Cited by:  Papers (3)  |  Patents (4)

    IEEE Conference Publications

    Rogowski coils present a useful and accurate means of current measurement, especially where high rise times limit the use of magnetic materials. In this paper, a Rogowski coil design is presented, for application in pulsed power experiments. The use of digital processing as an aid to data analysis is introduced and experimental results are given View full abstract»

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    PID control of a nonlinear half-car active suspension system via force feedback

    Ekoru, J.E.D. ; Dahunsi, O.A. ; Pedro, J.O.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071979
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (3)

    IEEE Conference Publications

    This paper presents the design of a two-loop, force/suspension travel PID control system, for a four degree-of-freedom (DOF), nonlinear, half-car active vehicle suspension system (AVSS). The two-loop system consists of an inner PID hydraulic actuator force control loop and an outer PID suspension travel control loop. Performance of the PID based AVSS is compared to a passive, nonlinear, half-car suspension system with the same model parameters. The simulation results showed the superior performance of the AVSS in the presence of the deterministic road disturbance. View full abstract»

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    PMIPv6 and MIH-enhanced PMIPv6 for mobility management in heterogeneous wireless networks

    Magagula, L.A. ; Falowo, O.E. ; Chan, H.A.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308159
    Publication Year: 2009 , Page(s): 1 - 5
    Cited by:  Papers (4)

    IEEE Conference Publications

    Next generation wireless networks will interwork hence combine resources of the available heterogeneous networks for connection support. Mobility across these networks will be inevitable. Thus, to support seamless connection migration between the networks, seamless handover is a necessary requirement. One of the requirements for ensuring seamless handover is the reduction of the delay that occurs during a handover procedure. Various mobility management protocols have been proposed and standardized to support mobility across heterogeneous networks but they cannot provide seamless handover in their current form. However, proxy mobile IPv6, which is a networked-based mobility management, goes a long way towards reducing handover delay. Enhancing it with a handover optimization mechanism, such as IEEE 802.21 MIH services, improves the handover performance even further. This paper therefore evaluates the performance of PMIPv6 versus PMIPv6 enhanced with MIH services. The results show that indeed PMIPv6 performs even better when enhanced with MIH in terms of reducing handover delay and reducing packet losses during handover across heterogeneous wireless networks. View full abstract»

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    A LabVIEW courseware customized for pre-college learners

    du Preez, S.J. ; Sinha, S. ; Hutton, M.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401571
    Publication Year: 2007 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    The paper details the development of a courseware for LabVIEW. LabVIEW is a graphical programming language that serves as a platform for measurements and automation. The courseware is intended to be customized for South African school leaving candidates, further referred to as pre-college learners. The courseware is aimed at authenticated remote learning (online training) as well as classroom-based facilitated training. The development is an integrated compilation of experiments based on LabVIEW and PHP/SQL (to administer and manage the learners). The courseware is developed in alignment with the outcomes proposed in the new curriculum statements for South Africa, but is also applicable to other countries, in general. View full abstract»

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    Multiconverter controller design for an infrared heater grid

    Adonis, M. ; Mte, K.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308139
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    Power control methods are introduced for the regulation of a multiple-input-multiple-output (MIMO) dc-dc converter. The sliding-mode control and the synergetic mode control techniques are contrasted. These two methods are studied for the stability that each portrays to a disturbance. The advantages and disadvantages of each scheme is studied. Simulation results are used in order to predict the most stable control scheme. The simulation and experimental results reinforced the argument for the efficacy of the desired control implementation. View full abstract»

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    Efficient spectral domain analysis of planar circuits using higher order expansion functions combined with fast system matrix computation methods

    Vaupel, T. ; Hansen, V.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.562987
    Publication Year: 1996 , Page(s): 765 - 770 vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    This article deals with several improvements of the spectral domain analysis of microstrip and coplanar circuits. Thus different kinds of expansion functions allow nonuniform meshing strategies with an improved current description. Furthermore a combination of acceleration methods with respect to the evaluation of the spectral domain integrals and special matrix fill techniques leads to a drastic reduction of the computational effort View full abstract»

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    The UMTS business case in emerging markets economic considerations of network upgrade

    Frisanco, T.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401635
    Publication Year: 2007 , Page(s): 1 - 8

    IEEE Conference Publications

    With universal mobile telecommunications system (UMTS) technology reaching maturity stage, current third generation (3G) mobile network deployment increasingly spreads to developing, "follower" markets; at the same time, technical feasibility issues are gradually replaced by economic considerations. We introduce a technology migration model explaining end-user market behaviour, and propose a modular, structured business modeling approach to simulate the economic impacts of an operator's go/no-go decision regarding new technology network roll-out. Our model is illustrated by applying it to a realistic case based on an emering-market incumbent operator. View full abstract»

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    Some observations on time varying harmonics and inter harmonics

    Lazenby, W.H. ; Zivanovic, R.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821879
    Publication Year: 1999 , Page(s): 849 - 852 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    Today, most international standards like the IEC, the IEEE, and the SA standards make use of discrete frequencies to calculate their power quality indices, like total harmonic distortion. This paper presents the shortcoming in using these formulae. This paper also represents some possible remedies for the above mentioned shortcomings View full abstract»

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    A comparison of controllers for improving the time response of NiTi wires

    Velazquez, R. ; Pissaloux, E.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308412
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper presents a comparative theoretical study of the performance of a set of controllers for improving the speed of actuators based on shape memory alloys (SMAs), especially on Nitinol (NiTi). To prevent overheating and thermal fatigue, these controllers take into account the maximum heating current at which a NiTi element can safely be heated. The thermal behavior of NiTi is first modeled for calculating the time response and, based on the suggested model, we show that hysteresis due to phase transformation can be neglected for rapid heating, thus simplifying the model to a linear problem. We present then the design and performance of a set of linear controllers. Simulation results show a substantial increase in actuation speed. View full abstract»

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    Bit error probability for a M-ary QAM OFDM-based system

    van Wyk, J. ; Linde, L.P.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401578
    Publication Year: 2007 , Page(s): 1 - 5

    IEEE Conference Publications

    Results and the general expression for the bit error rate (BER) of M-ary QAM for single carrier systems are well known, but are not readily available for M-ary QAM combined with orthogonal frequency division multiplexing (OFDM). In this paper, a generalized closed-form BER expression of M-ary QAM OFDM is empirically derived and verified in the presence of additive white Gaussian noise (AWGN), using a Monte Carlo simulation. Theoretical BER graphs up to 1024-QAM over up to 256 subchannels are also presented. View full abstract»

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    Point-to-point rural telephone system

    Robertson, I. ; Evans, B.
    AFRICON '92 Proceedings., 3rd AFRICON Conference

    DOI: 10.1109/AFRCON.1992.624566
    Publication Year: 1992 , Page(s): 641 - 644
    Cited by:  Patents (1)

    IEEE Conference Publications

    A novel, low cost, UHF radio product has been introduced into the rural telephone market. It is one of a portfolio of products for rural telephone applications and is intended specifically for low density point-to-point use. The strategy during the design phase was not only to design a low-cost radio, but to allow savings in power costs as well. A further aim was to ensure that rural personnel, with basic training only, could easily maintain the new product in remote areas. Key issues in the development were: reduction in installed system cost, ease of maintenance, power management and lowering of current consumption, alarm and status reporting, high and low power transmitter options, fast installation, low initial capital outlay, and flexibility and adaptability View full abstract»

  • Freely Available from IEEE

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    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406882
    Publication Year: 2004 , Page(s): 1211

    IEEE Conference Publications

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    Promoting technology and technological careers. The role of non-formal education in South Africa

    Kramer, D.
    AFRICON '92 Proceedings., 3rd AFRICON Conference

    DOI: 10.1109/AFRCON.1992.624467
    Publication Year: 1992 , Page(s): 255 - 259

    IEEE Conference Publications

    It is noted that the promotion of careers in technology is difficult in South Africa. Good formal education in necessary for development. The crisis in formal education has resulted in the development of nonformal education which has been the vehicle for nongovernment involvement in education. Technology promotion has been via nonformal education. PROTEC, a privately funded nonformal program which is a good example of how technology and technological careers can be successfully promoted is discussed View full abstract»

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    Discrete wavelet analysis of the auditory brainstem response: effects of subject age, gender and test ear

    Wilson, W.J. ; Aghdasi, F.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820824
    Publication Year: 1999 , Page(s): 291 - 296 vol.1

    IEEE Conference Publications

    The effects of subject age, gender and test ear on auditory brainstem response (ABR) discrete wavelet transform (DWT) results were examined at a fixed stimulus intensity in 120 normal subjects. Subject age and gender were shown to affect the ABR DWT results and must therefore be considered in any clinical ABR DWT analysis View full abstract»

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    Convergence analysis of iterative interference cancellation receivers for turbo-coded DS-CDMA systems

    Bejide, E.O. ; Takawira, F.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406658
    Publication Year: 2004 , Page(s): 197 - 202 Vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    We investigate the behaviour of iterative interference cancellation receivers in turbo-coded DS-CDMA systems. We propose a methodology for the convergence analysis of the receivers. Our method is based on the Gaussian approximation technique. Analytical expressions for the SNR transfer function of the interference cancellation stage of the receiver are presented. This is in contrast to the semi-analytical approach that has been used in the literature to determine the variance transfer function of the interference cancellation stage. Results show that the proposed methodology is accurate for the convergence analysis of the iterative interference cancellation receiver View full abstract»

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    Hybrid-hoists for ultra deep-level mines

    Cruise, R.J. ; Landy, C.F.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821833
    Publication Year: 1999 , Page(s): 621 - 622 vol.2

    IEEE Conference Publications

    Hybrid-hoists have been proposed as a possible solution for ultra deep-level hoists. The hybrid hoist consists of a combination of a conventional hoist and a linear motor. Instead of the entire load being supported by the hoisting rope, the linear motor will take up most of the work during times when peak stresses would usually be placed on the rope. Consequently, only a short section of the linear motor primary has to be installed at the bottom of the shaft. Capital costs are thus greatly reduced when compared to the installation of a full linear motor system View full abstract»

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    Induced currents on optical fibre cables installed in high voltage transmission line environments

    Khan, M.F. ; Hoch, D.A.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159982
    Publication Year: 2002 , Page(s): 623 - 628 vol.2

    IEEE Conference Publications

    Specialized fibre optic cables may be installed by suspending the cables from transmission line towers such that they are situated under the high voltage conductors in an outdoor environment. Long term accumulation of wind-borne pollutants followed by periods of wetting may result in leakage currents flowing axially along the optical fibre cables. Under certain severe conditions, small arcs may form on the surface of the cable. The objective of this paper is to present two simulation processes that may be used to determine these leakage currents and compare the predicted values with experimentally determined values. The effects of system voltage, attachment point of the cable at the tower and span length on the magnitude of the leakage currents have all been investigated. The feasibility of using these models to predict dry-band arcing on these cables was also determined. View full abstract»

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    Design of a DSP based controller for power electronics applications

    van Heerden, G.J. ; Mouton, Hdu.T.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160006
    Publication Year: 2002 , Page(s): 743 - 747 vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    Power electronics engineers frequently need a flexible way to implement the control of a new design. This paper discusses the design of a digital signal processor based power electronics controller, which provides the level of flexibility needed. To test the first prototype of the controller, the current supplied to an inductive load by a phase arm, was controlled. View full abstract»

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    Why electronic and not electromechanical ELCBs ?

    Cohen, V.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.562977
    Publication Year: 1996 , Page(s): 715 - 719 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    South Africa's 40 years of experience in the manufacture and application of sensitive earth leakage protection devices, together with the global experiences covering millions of installed units over several decades have resulted in a better understanding of not only the advantages, but also of the limitations of ELCBs. In Europe, where electromechanical ELCBs are used almost exclusively, the question of reliability of installed ELCBs has become a subject of major concern and attention. The popular hype regarding perceived reliability of electronic components was not sufficient to prevent the major South African manufacturer, some five years ago from changing their entire ELCB range from electromechanical to electronic technology ELCBs. The improvements in reliability that resulted from this decision are complemented by their freedom from safety performance limitations often found in lower specification electromechanical earth leakage circuit breakers View full abstract»

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

    The architectural design of DSP based embedded parallel processors

    Smit, W.A.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146856
    Publication Year: 2002 , Page(s): 323 - 326 vol.1

    IEEE Conference Publications

    This paper discusses the issues related to the design of embedded multiprocessor systems, with the focus on DSP-based systems. Issues that are discussed include indicators of when applications will scale into multiprocessor designs, central processing unit (CPU) benchmarking, algorithm partitioning and the applicability of symmetric multiprocessor (SMP) and asymmetric multiprocessing (ASMP) architectures on embedded DSP based multiprocessor design. View full abstract»

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    Finding an optimal PV panel maximum power point tracking method

    Bekker, B. ; Beukes, H.J.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406864
    Publication Year: 2004 , Page(s): 1125 - 1129 Vol.2
    Cited by:  Papers (18)

    IEEE Conference Publications

    The need for a maximum power point tracker in a photovoltaic system is explained. A variety of photovoltaic panel maximum power point tracking methods are then briefly compared. The optimal method from those compared, where the photovoltaic panel power-voltage curve is scanned periodically, and the maximum power point tracker is controlled by current, is discussed in detail. Problems with this implementation are highlighted, and the design of a voltage-controlled implementation using the same power-voltage curve scan is presented. Problems and advantages of this system are given. View full abstract»

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    Cryptographic processor architectures for DES algorithm

    Korkishko, T. ; Melnyk, A.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820788
    Publication Year: 1999 , Page(s): 175 - 180 vol.1
    Cited by:  Patents (1)

    IEEE Conference Publications

    The use of cryptographic processors permits, at the expense of special architectural decisions, essentially to increase the productivity of operations, and to increase the protection level of key information from not permitted access. Cryptographic processor architectures for the DES (data encryption standard) algorithm are considered. The costs of the hardware, the hardware efficiency of use and processor performance are evaluated View full abstract»

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    Development of a directional coupler to be used on the two-wire sections of dial-up telephone lines

    Nel, E.J. ; Braun, R.M.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.562951
    Publication Year: 1996 , Page(s): 570 - 575 vol.2

    IEEE Conference Publications

    This project aims to develop a directional coupler for use on dial-up telephone lines. The need for such a coupler originated with the acceptance of the CCITT's (International Telegraph and Telephone Consultative Committee) V.32 bis recommendation regarding the operation of high-speed modems. This standard allows modems to communicate on the telephone network both simultaneously as well as within the same frequency band. The modems involved use a mechanism called echo cancellation to overcome this problem (with echo cancellation the modem subtracts that which it transmits from the signal on the line to get the signal it wishes to receive). However, a third party surveying the (two-wire sections of the) line is unable to interpret the signals on the line as there appears to be only one garbled signal. This paper develops the theoretical basis necessary for a directional coupler that will separate this garbled signal into its constituent signals and thus enable interpretation of such signals by a third party View full abstract»

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    Applying soft magnetic materials to conductive surfaces to realise a novel conformal HF antenna concept

    Dresel, J. ; Clark, A.R. ; Fourie, A.P.C.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821922
    Publication Year: 1999 , Page(s): 1069 - 1074 vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    This paper presents a novel conformal HF antenna concept. Soft magnetic materials are used to suppress currents on conductive surfaces in order to realise conformal HF antennas. The concept is verified by comparing predicted HF antenna characteristics to measured results. The efficiency of the conformal HF antenna is compared to a tuned whip and loop antenna. The conformal antenna shows superior performance above 15 MHz View full abstract»

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    Fast decryption algorithms for the RSA cryptosystem

    Penzhorn, W.T.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406693
    Publication Year: 2004 , Page(s): 361 - 364 Vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    We present four methods to increase the decryption speed of the RSA cryptosystem. The decryption exponent d is obtained by means of special constructions, and the two secret primes p and q are chosen such that the difference between them has low Hamming weight. The suggested methods do not shorten the length of the secret decryption exponent. By applying the Chinese remainder theorem to the special decryption exponent, the decryption speed of the RSA algorithm is significantly increased View full abstract»

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    Self-excitation in PWM inverter excited single-phase induction generator

    Jimoh, A.A. ; Ojo, O.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821883
    Publication Year: 1999 , Page(s): 871 - 876 vol.2

    IEEE Conference Publications

    The basis for design, analysis and quantification of the conditions for self-excitation in a sourceless PWM inverter excited and controlled single-phase induction generator are established and demonstrated in this paper. Three system configurations of the generating system are investigated for self-excitation View full abstract»

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    Neural network implementation on a FPGA

    Chen, Y. ; du Plessis, W.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146859
    Publication Year: 2002 , Page(s): 337 - 342 vol.1
    Cited by:  Papers (4)

    IEEE Conference Publications

    This work implemented a feedforward neural network on a FPGA (field programmable gate array). A study was conducted to find the minimum precision required to maintain a recognition rate of at least 95% for two characters within an optical character recognition application. To reduce the circuit size, the bit serial architecture was realised to perform the arithmetic operation. This resulted in an optimal use of the FPGA resources. View full abstract»

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    Diode laser absorption spectroscopy for teaching undergraduate physics

    Otieno, A.V. ; Muthoka, B.M.J.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821961
    Publication Year: 1999 , Page(s): 1247 - 1252 vol.2

    IEEE Conference Publications

    We describe the application of a 780 nm diode laser in studying the rubidium D2 transitions (52P3/2-52S 1/2) at 780.2 nm., which has a well known energy structure, by frequency scanning the resonance lines and observing the absorption spectrum to illustrate the role of the nucleus in atomic structure beyond the first order leading to hyperfine interaction in 87Rb. The experiment yields very high resolution and illustrates that with diode lasers it is possible to teach undergraduate physics without recourse to expensive laboratory facilities View full abstract»

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    Analysis of the semi-parametric spectral estimation problem for power systems

    Jordaan, J.A. ; van Wyk, M.A. ; van Wyk, B.J.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401620
    Publication Year: 2007 , Page(s): 1 - 5

    IEEE Conference Publications

    This paper shows an analysis of a fast solution method for the system of linear equations encountered in the semi-parametric spectral estimation problem. Spectral analysis forms the basis of a major part of signal processing applications typically used for tracking and distinguishing signals of interest, and for estimating dominant harmonics in signals. Power utility companies uses spectral analysis in analysing signals recorded from the power system. The signals recorded during power system disturbances could be analysed to determine the characteristics of the disturbance. The test results show that an increase in the order of the local polynomial filter used in the semi- parametric method affects the condition number of the coefficient matrix, and this results in an inaccurate solution. View full abstract»

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    A survey of wireless sensor network applications from a power utility's distribution perspective

    Isaac, S.J. ; Hancke, G.P. ; Madhoo, H. ; Khatri, A.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072184
    Publication Year: 2011 , Page(s): 1 - 5
    Cited by:  Papers (5)

    IEEE Conference Publications

    The task of monitoring and controlling power distribution networks is very challenging given the huge number of assets involved and their wide geographic distribution; this frames a role for wireless sensor network (WSN) applications. This paper provides an overview of the highlights from a comprehensive survey commissioned by Eskom regarding the feasibility of WSNs on the transmission and distribution network; the aim is to direct power utility investment and research and development effort. View full abstract»

  • Freely Available from IEEE

    2004 IEEE Africon. 7th Africon Conference in Africa (IEEE Cat. No.04CH37590)


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406604
    Publication Year: 2004

    IEEE Conference Publications

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    The value of supplemental instruction in conceptual learning

    Hillman, J.C.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563124
    Publication Year: 1996 , Page(s): 288 - 292 vol.1

    IEEE Conference Publications

    Engineering undergraduates have difficulty with courses that are conceptual in nature. The internalisation of concepts and the development of problem solving skills is achieved by individuals in a variety of ways, relatively few of which are either known by lecturers or actively taught. A self-teaching initiative known as supplemental instruction (SI) can overcome these problems by encouraging students to learn from the experiences of others by participating in structured group discussions which are facilitated by senior students. This paper describes the development and results of an SI programme within a first year electrical engineering course and concludes that it is both an efficient and cost effective method of improving student learning, particularly for those from an educationally disadvantaged background View full abstract»

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    Mass-losses relationship in an optimized 8-pole radial AMB for Long Term Flywheel Energy Storage

    Bakay, L. ; Dubois, M. ; Viarouge, P. ; Ruel, J.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308164
    Publication Year: 2009 , Page(s): 1 - 5

    IEEE Conference Publications

    This paper presents the effect of losses on a radial active magnetic bearings (AMB), used in the long term flywheel energy storage (LTFES). The study does not take into account the losses due to power electronics and windage losses (due to the friction between external rotor surface and the air). Therefore, we restricted the loss computation to those of radial AMB only. To simplify this work, we focused on the effect of external disturbance on unbalance force induced by rotor eccentricity for instance. The unbalance force has fixed the maximum radial load capacity of the rotor in order to design the radial AMB. 2-D finite element method (FEM) has been used to validate the theoretical model. We have optimized AMB system in order to search the best design which minimises overall losses (Copper and iron Losses) for different magnitudes of external force. Then, mass versus losses curve of AMB has been shown for the same angular velocity speed of rotor namely 9000 rpm. View full abstract»

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    Use-cases for performance evaluation of human-mind inspired control units

    Deutsch, T. ; Kohlhauser, S. ; Perner, A. ; Muchitsch, C.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072046
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    With the advent of artificial general intelligence architectures, comparison between different architectures became more complicated. Small isolated tasks like box stacking, path finding, chess, or collecting objects is sufficient for highly specialized algorithms like the ones used in artificial intelligence. The holistic control systems are designed to cope with rich, dynamic, and complex real world environments and tasks. The approaches used to design these architectures differ in many ways but all share the goal to create human like “intelligence.” Each project uses its own approach to evaluate its success which is usually tightly coupled with the target application. We propose the usage of a simulated virtual world with embodied autonomous agents. These agents should be equipped with control systems from the architectures that should be compared and exposed to situations where their performance is assessed. The situations-or test-cases-have to be designed with tests from psychology in mind. Thus in a top-down design approach, tests from psychology have to be refined and converted such that they can be implemented into the simulation. We discuss different approaches and introduce the use-cases developed for project ARS. View full abstract»

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    Denial of service and distributed denial of service-today and tomorrow

    Meyer, L. ; Penzhorn, W.T.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406828
    Publication Year: 2004 , Page(s): 959 - 964 Vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    The most common method of attacks experienced today is by means of denial of service (DoS) and distributed denial of service (DDoS) attacks. This work gives a detailed overview of these attacks. It presents the current trends that a DDoS attack follows and the rate of infection today, compared to previous infections. Furthermore this paper introduces the possibility of a DDoS attack with the mobile phone as the master. It predicts the rate of infection and the consequences of such an attack. View full abstract»

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    Effect of motor-cage temperature on motor speed sensing characteristics of magnetostrictive amorphous wire

    Nderu, J.N. ; Kihato, P.K. ; Hinga, G.M.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308206
    Publication Year: 2009 , Page(s): 1 - 5

    IEEE Conference Publications

    Magnetostrictive amorphous wires have been shown to possess various important sensing characteristics. Previously we presented results of speed sensing of induction motor using the amorphous wire, in which the speed sensing capability was seen to match that of conventional speed sensors such as tachometer. However, one concern was the fact that the properties of amorphous wire change when exposed to certain temperature ranges for a long time (as would be expected to occur inside the motor cage) in a process termed relaxation. In the present work we have shown that the amorphous wire sensing characteristics are completely lost when the wire is exposed to elevated motor-cage temperatures. Furthermore, we have suggested and tested a simple, but effective remedy to this problem. View full abstract»

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    Optical fiber bending limits for optical fiber infraestructures

    Andre, P.S. ; Rocha, A.M. ; Neto, B. ; Martins, A. ; Facao, M. ; Pinto, J.L. ; Teixeira, A.L.J. ; Nogueira, R.N. ; Lima, M.J. ; Incerti, G. ; Forin, D. ; Beleffi, G.T.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308083
    Publication Year: 2009 , Page(s): 1 - 3
    Cited by:  Papers (4)

    IEEE Conference Publications

    In this work the high power propagation in tight bent fibers was studied. The signal losses and the temperature increase have been experimental measured for single mode optical fibers (SMF) as function of the bending diameter. These results were used to propose an approach to limit the bending diameter, as a function of the injected power, in order to maintain the operational condition bellow the safety limit. View full abstract»

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    Image registration, parameter tuning and approximate function evaluation, using the genetic algorithm and digital image warping

    Pagliari, G.M. ; Greene, J.R.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.562943
    Publication Year: 1996 , Page(s): 536 - 541 vol.2

    IEEE Conference Publications

    A common problem in image processing is image registration. The problem is finding the parameters of a noisy, multi-modal, multi-dimensional, image warping function which aligns two images. An image registration program, which used a genetic algorithm as the function optimiser, was designed. The settings of the program were automatically tuned with a second genetic algorithm. Monte Carlo analysis was used to improve the results View full abstract»

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    GPU-based 3D-FDTD computation for electromagnetic field dosimetry

    Nagaoka, T. ; Watanabe, S.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072180
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    Numerical dosimetry with the computational human model using the finite-difference time-domain (FDTD) method has recently been used for a safety assessment of electromagnetic field applications. However, the FDTD calculation runs very slowly and requires a large amount of computational memory. We focus, therefore, on general purpose programming on the graphics processing unit (GPGPU). We implemented the three-dimensional (3D) FDTD method on GPUs using Compute Unified Device Architecture (CUDA). In this study, we used the NVIDIA Tesla C2070 as a GPGPU board and tested the performance of FDTD computation on GPUs. The results indicated that while the single GPU/CPU speed ratio varies depending on the calculation domain, 3D-FDTD computation using a GPU requires significantly less run time than that using a conventional CPU. We confirmed that the FDTD computation on a multi-GPU is much faster than that on a single GPU, and we also found that eight GPUs can compute faster than a vector supercomputer. View full abstract»

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    Solid state tap changers for utility transformers

    Bauer, P. ; de Haan, S.W.H.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821888
    Publication Year: 1999 , Page(s): 897 - 902 vol.2
    Cited by:  Papers (9)

    IEEE Conference Publications

    The voltage in the medium voltage (10 kV) and low voltage (400 V) utility networks is controlled with the change of the transformer ratio tap changing. Continuous development of high power switching devices and especially devices with turn-off capability allows the use of power electronics in new areas of application. Replacement of the mechanical or hybrid switch of the tap changer with solid state switches for two power and voltage levels is studied in the paper View full abstract»

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    Modelling and measurement of focused ellipsoidal and parabolic reflector antennas for free space material measurements

    Matlacz, J. ; Palmer, K.D.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821924
    Publication Year: 1999 , Page(s): 1081 - 1086 vol.2

    IEEE Conference Publications

    This paper reports on two reflector antenna options investigated to improve the bandwidth of a free space material measurement system. An offset ellipsoidal reflector and a pair of offset parabolic dishes are considered as the options to generate the required focused beam. Both are shown to be viable, but the parabolic dishes are preferred due to suitable low cost ones being available for the domestic satellite TV market. Measured and computed results show that the operating frequency band of the original system may be doubled View full abstract»

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    Intelligent static VAr compensator control for supply loading optimization

    Van Harmelen, G.L. ; Enslin, J.H.R.
    AFRICON '92 Proceedings., 3rd AFRICON Conference

    DOI: 10.1109/AFRCON.1992.624441
    Publication Year: 1992 , Page(s): 154 - 157

    IEEE Conference Publications

    A digitally adaptive static Var compensator (SVC) controller for supply-side loading minimization is proposed. The control scheme is based on a model reference control structure where a model (which includes its nonlinear behavior) for the thyristor controller reactor is present within the digital signal processor. This allows minimization software to use time-domain samples of three-phase line voltages and load currents to minimize the supply side loading (i.e., maximize power factor). This type of control uses the minimization of a cost function and therefore this same controller automatically also compensates for imbalance in a multiphase supply View full abstract»

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    Two moment analysis of channel reservation in cellular networks

    Rajaratnam, M. ; Takawira, F.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820809
    Publication Year: 1999 , Page(s): 257 - 262 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    The main contribution of this paper is a two-moment analysis of channel reservation as applicable to cellular networks. This work is part of a larger research endeavour to derive an analytical method for performance analysis of cellular networks using generalised call arrival and generalised channel holding time distributions View full abstract»

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    Experience-based learning in electrical and electronic engineering: An effective and affordable approach

    Greene, J.R.
    AFRICON '92 Proceedings., 3rd AFRICON Conference

    DOI: 10.1109/AFRCON.1992.624406
    Publication Year: 1992 , Page(s): 10 - 13
    Cited by:  Papers (2)

    IEEE Conference Publications

    The author argues that extensive `hands-on' exposure is central to engineering education, and more necessary than ever in the light of superficial and alienated learning resulting from increasing abstraction and curricular overload. He urges a broader approach to the provision of experiential learning opportunities, examines a range of alternative modes of laboratory work, and attempts to articulate some principles to guide the design of laboratory programs, reporting on a number of case studies currently being undertaken at the University of Cape Town. This is a coordinated program of demonstrations, `tasks', and projects supported by the development a cost-effective set of modules with a strong emphasis on simplicity and conceptual clarity View full abstract»

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    CRC assisted high rate single parity check product codes

    Hongjun Xu
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308271
    Publication Year: 2009 , Page(s): 1 - 5

    IEEE Conference Publications

    The single parity check (SPC) product code is one of the most popular error detection codes because it is easy to implement. But there are unrecoverable errors in the conventional two dimensional SPC product codes. To further improve the performance we propose cyclic redundancy check (CRC) assisted SPC product codes in this paper. The proposed CRC assisted SPC product codes can detect most of unrecoverable errors in the SPC product codes by use of the Chase-like algorithm, and then improve the BER performance. This is verified through simulation. Simulation of rate 0.923 CRC assisted SPC II product codes also yields a BER of 10-5 at 4.9 dB and only 1.3 dB away from Shannon limit. That is a very good result for frame size of 1024 bits. View full abstract»

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    Information and Communication Technology policy imperatives for rural women empowerment: focus on South Africa

    Joseph, M.K. ; Andrew, T.N.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308397
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    It has been established that information and communication technologies (ICTs) are key drivers for rural development. However, while many countries such as India and South Africa have made significant investments in rural ICT infrastructure and its developmental spin-offs, rural women are still neglected when it comes to access to ICTs. This neglect is evident in the ICT policy initiatives in South Africa as an example, where the relevant policies lack any significant or direct attention to rural women's development. If ICT policies do not address the gendered digital divide in rural areas gender inequality will be encouraged. This paper gives insights on how information exchange by means of ICTs such as Internet, mobile phones and radio could foster economic growth and empowerment of rural women in South Africa. In addition, the paper discusses the role of relevant stakeholders in ICT policy formulation for more effective and appropriate communication, and innovative ways of using ICTs for women empowerment in rural areas. The authors make recommendations for ICT policy development that would better serve the needs of rural women leading to their empowerment. View full abstract»

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    802.11 Mesh mode provides rural coverage at low cost

    Naidoo, K. ; Sewsunker, R.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401647
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (2)

    IEEE Conference Publications

    The paper discusses the use of Mesh technology as a strategy to extend coverage to provide rural telecommunications services. Wireless Mesh Networks (WMNs) provide a reliable & cost effective solution to extending coverage in a rural fixed network. The research investigates range extension using a hybrid wireless local area network (WLAN) architecture running both infrastructure & client wireless mesh networks. For a rural scenario the infrastructure network provides the connectivity to the Internet using WiFi and WiMax, while the routing capabilities of the nodes provide improved connectivity and coverage around the WMN. This paper serves to extend the use of the 802.11 g protocol in a WMN for a rural application. The applicability of a star mesh network solution was evaluated for a rural South African scenario. Simulation results assisted in drawing the conclusion that the star mesh network is a feasible, low- cost, robust solution. For a maximum throughput of 100 Kbps on each node in the network the distance of the first hop from the access point is 1.302 Km resulting in a total coverage area of 8.06 Km2. View full abstract»

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    AfriCampus-energy management on campus

    Delport, G.J. ; Calmeyer, J.E.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821874
    Publication Year: 1999 , Page(s): 819 - 824 vol.2

    IEEE Conference Publications

    African academic institutions have an ideal opportunity to initiate energy management programmes on their campuses. AfriCampus is an energy management collaboration between all universities, technikons and secondary schools in Africa, and particular Southern Africa. The purpose of this collaboration is to establish an energy management co-operation channel by which expertise, equipment and information can be transferred View full abstract»

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    A silicone based hydrophobic coating for high voltage insulators

    Hoch, D.A. ; Reynders, J.P. ; Macey, R.E.
    AFRICON '92 Proceedings., 3rd AFRICON Conference

    DOI: 10.1109/AFRCON.1992.624524
    Publication Year: 1992 , Page(s): 470 - 473

    IEEE Conference Publications

    The use of hydrophobic coatings as a treatment of insulators for the prevention of pollution-related flashovers is increasingly widespread. A great deal of research into the performance of these coatings has been performed worldwide and has resulted in a good understanding of the important parameters determining the field performance of these coatings. This authors discuss these parameters and present the results of the tests performed on a coating that meets these parameters. The test techniques are also presented and discussed in some detail. The important parameters influencing the field performance of a permanent silicon-based hydrophobic coating are tracking and erosion resistance, hydrophobicity recovery after dry band arcing and hydrophobicity transfer to pollution layers. Test techniques such as a salt spray system greatly accelerate any tracking and decomposition of a poorly chosen polymer. Test results indicate that this coating meets the requirements for successful field performance View full abstract»

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    Static VAr compensators components and design considerations

    Tyll, H.
    AFRICON '92 Proceedings., 3rd AFRICON Conference

    DOI: 10.1109/AFRCON.1992.624442
    Publication Year: 1992 , Page(s): 158 - 161

    IEEE Conference Publications

    Static VAr compensators (SVCs) in thyristor technology are presently the most economic solutions for dynamic reactive power compensation. The arrangements, components, and design criteria of conventional SVCs using thyristors are described View full abstract»

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    The effect of leakage inductance and snubbing on electromagnetic interference generated by a flyback converter

    Wooding, G.N. ; de Beer, A.S.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072057
    Publication Year: 2011 , Page(s): 1 - 5
    Cited by:  Papers (1)

    IEEE Conference Publications

    Leakage inductance is known to affect power transfer of transformers and coupled inductors, as well as causing voltage spikes across converter switches possibly damaging them. The standard solution is to implement a snubber to reduce these voltage spikes. This paper investigates the effects of leakage inductance as well as snubbing on conducted EMI emissions. View full abstract»

  • Freely Available from IEEE

    [Front cover]


    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401651
    Publication Year: 2007 , Page(s): c1 - c2

    IEEE Conference Publications

  • Freely Available from IEEE

    [Blank page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406643
    Publication Year: 2004 , Page(s): 114

    IEEE Conference Publications

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    Management and application of protection performance data on the Eskom transmission system

    Keller, P.G.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160036
    Publication Year: 2002 , Page(s): 919 - 922 vol.2

    IEEE Conference Publications

    The performance of protection systems on the Eskom Transmission network is very important for the safety of human life and in limiting damage to plant. Measuring the performance of these protection systems enables better maintenance to be done and assists in refurbishment programs. This paper explains how protection performance data is managed and how it can be used. View full abstract»

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    Flexible AC transmission systems simulation and control

    Spee, R. ; Zhu, W.
    AFRICON '92 Proceedings., 3rd AFRICON Conference

    DOI: 10.1109/AFRCON.1992.624419
    Publication Year: 1992 , Page(s): 65 - 68
    Cited by:  Papers (1)

    IEEE Conference Publications

    Concepts relating to flexible AC transmission systems (FACTS) are gaining popularity for enhancing the power transfer limits as well as the stability characteristics of power systems. The authors present an overview of FACTS devices and associated nonlinear, modern control strategies. Simulation results based on the Electromagnetic Transients Program (EMTP) are presented for dynamic brakes, devices for rapid adjustment of network impedance, and subsynchronous resonance (SSR) phenomena. Emphasis is placed on power systems with geographically concentrated generation and load centers, long transmission lines, and potential for loop flow. While these are characteristics of the Western North American Power System (WNAPS), the concepts presented can readily be applied to the power system in Southern Africa View full abstract»

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    Developing a novel laboratory program in electrical engineering for first year students

    Lawrance, W.B.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.562945
    Publication Year: 1996 , Page(s): 548 - 551 vol.2

    IEEE Conference Publications

    This paper describes a teaching initiative in the Department of Electrical Engineering at Curtin University of Technology. The initiative involved the development of a new laboratory program for first year engineering students with the specific aims of enhancing team work and communication skills. Action research was used to implement the new program which also focussed on cross cultural cooperation View full abstract»

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    Predictive torque control of an induction machine fed by a flying capacitor converter

    Stolze, P. ; du Toit, D. ; Tomlinson, M. ; Kennel, R. ; Mouton, T.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071967
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (3)

    IEEE Conference Publications

    This paper presents a model predictive control strategy for an induction machine fed by a three-level flying capacitor converter. In order to reduce the calculation effort (64 different switching possibilities for one prediction step) in a first step the best one of the 19 voltage vectors is determined. After that the best switching state which delivers this voltage vector is determined regarding the flying capacitor voltage balancing and the switching effort, making use of a hysteresis-based algorithm. The proposed control algorithm is verified by several simulations which clearly verify that an effective control of speed, torque, flux and of the flying capacitor voltages is possible. View full abstract»

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    Change-the future of the telecommunications industry

    Harker, R.A.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563067
    Publication Year: 1996 , Page(s): 1 - 6 vol.1

    IEEE Conference Publications

    A tidal wave of change is headed towards the telecommunication industry, and it will ultimately transform the economic, social and political environment for nearly every person in the world. Much of this change is being brought about by technological innovation and the information revolution-the convergence of computing, communication and information. Organisations that acknowledge and prepare for this revolution will emerge as winners. When mains electricity first became generally available many firms went out of business, the steam engine became obsolete, and suppliers of gas lighting closed their doors. Digital technology represents a similar step change for the communications and information industries. Digital technology creates homogenised, easily delivered information that is instantly convertible into whatever form the user chooses. Four primary factors are driving this change: government and regulation, competition, technology and market demand View full abstract»

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    Investigating opportunistic spectrum access from a pricing perspective

    Hailing Zhu ; Nel, A.L.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072102
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    In this paper, we extend the work in [1] to model the use of opportunistic spectrum access (OSA), which allows secondary users (SUs) to share the spectrum with primary users (PUs) on an opportunistic basis, using a Stackelberg game model from a pricing perspective. In this game model, the service provider (SP) as the leader aims to enhance its revenue while improving the utilization of its channel by allowing OSA without violating the PUs non-zero tolerated interference probability. We propose an analytical model, in which the SUs are charged based on the resource they could be allocated dynamically while the PUs are charged a discounted price as a compensation for the interference induced by the SUs. Our analysis provides characterization of the optimal price for the SUs and the optimal revenue of the SP as functions of channel utilization of the PUs and the number of potential SUs. It is shown through simulations that allowing OSA would improve revenue and channel utilization significantly for the SP when the channel is under-utilized, while it could potentially result in revenue loss when the channel is close to saturation. Moreover, we demonstrate that, by exploiting the SUs' willingness to pay, the SP could earn more from less SUs when the channel is under-utilized. View full abstract»

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    Modelling of the third generation mobile system

    Buczyriski, J. ; Gajewski, P. ; Krygier, J.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820807
    Publication Year: 1999 , Page(s): 251 - 256 vol.1

    IEEE Conference Publications

    This paper describes a model of a system with wideband CDMA that is a proposal for user access in the future UMTS. This model has been implemented using the OPNET tool. The model enables network architecture, radio interface, mobile station moving, call generation, signalling, etc. to be considered. The interference is discussed for two approaches: testing of the signal to interference ratio as well as analysis of the interference parameter of pseudorandom sequences. The simulation results are also presented View full abstract»

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