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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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    Loudspeaker, narrator and language influences on speech intelligibility

    Esterhuizen, H.D.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401618
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    Results obtained during a very limited budget experiment obtaining speech intelligibility levels with word lists in English and Afrikaans and a panel of listeners. A variety of selected loudspeakers were used, with electrical gain set at ten decibels below the onset of acoustical feedback for each loudspeaker, using the same microphone in each case, in a sound reinforcement configuration in the presence of equalised random noise. Good correlations were obtained between some tests using the same recorded word lists in the same listening locations with the same loudspeakers. Different speech intelligibility score profiles were obtained, however, for different word lists, in which the differences were attributed to the narrators and language only. Attempts were made to explain the differences, by investigating the data. Poor correlation was found between actual speech intelligibility scores and theoretical predictions using the Articulation Index. View full abstract»

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    Emerging Behavior as driver for the sustainability of a modular, “skills-centric” production system

    Maffei, A. ; Akilliuglu, H. ; Neves, P. ; Ferreira, J. ; Onori, M.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072121
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    The current main challenge for the future production system lies in the correct integration of the issues related to sustainability and to agility. The “Evolvable Paradigm” addresses this concern with a new way of engineering the whole production system. The concept of Skill is declined as common denominator between the definitions of manufacturing process and manufacturing equipment. Each production module holds some of the skills that compose the process definition and it is endowed with the necessary intelligence to come together with the other modules in an organized society. This work introduces the approach adopted in the IDEAS project (Instantly Deployable Evolvable Assembly System) to cope with the above mentioned requirement through the presented paradigm. While fully featured and described IDEAS mechatronic architecture allows rapid reconfiguration of the system, the issue of sustainability is targeted by the open definition of the concepts of skill and skills interaction. The result of skill aggregation is hereby called Emergent Behavior and in the proposed model it can be seen as the main driver for the sustainable use of the system. View full abstract»

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    Development of an electrochemical sensor array for determination of food analytes

    Jawaheer, S. ; Rughooputh, H.C.S. ; White, S. ; Cullen, D.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146871
    Publication Year: 2002 , Page(s): 407 - 409 vol.1

    IEEE Conference Publications

    With modern techniques of sensor fabrication and the processing power of modern microelectronic, sensors can be conferred a degree of miniaturisation and integrated into a small portable devices to allow in situ real-time monitoring. We report here the development of a multi-analyte electrochemical sensor array tailored to monitor the quality of fruits of economical importance to tropical countries. The array sensor has the ability to simultaneously monitor a range of food quality indicator analytes offering a robust analytical output. For this work, one-shot array sensors were mass fabricated using screen-printing (thick film) technology. View full abstract»

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    Adaptive CIR prediction of time-varying channels for OFDM systems

    Oyerinde, O.O. ; Mneney, S.H.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308342
    Publication Year: 2009 , Page(s): 1 - 5
    Cited by:  Papers (5)

    IEEE Conference Publications

    Channel impulse response (CIR) prediction is important because it makes possible the provision of up-to-date channel state information which is essential for coherent detection of transmitted message symbols. Different prediction techniques have been proposed for OFDM systems. These range from the minimum mean square error (MMSE) techniques to adaptive techniques. However, it has been confirmed that the adaptive predictors present better performance than its MMSE counterpart. Besides, the computational complexity of the MMSE class of predictors is more costly than the adaptive predictors. In this paper we propose an improved version of an adaptive normalized least mean square (NLMS) predictor named variable step size normalized least mean square (VSSNLMS) predictor. The proposed VSSNLMS predictor is employed for the implementation of decision directed channel estimation (DDCE) for OFDM systems. Simulation results demonstrate that the proposed VSSNLMS predictor outperforms the NLMS predictor at a cost of a negligible high complexity, and its performance is very close to that of the recursive least square (RLS) predictor that exhibits an enormous computational complexity. View full abstract»

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    An efficient grid placing technique for 2-D method of moments analysis of coupled line structures

    de Villiers, D.I.L. ; Meyer, P.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401509
    Publication Year: 2007 , Page(s): 1 - 6

    IEEE Conference Publications

    In this paper an analysis routine is presented for a two dimensional method of moments analysis of coupled line structures to find the capacitance matrix. A method is proposed to significantly reduce the number of unknowns. The method borrows from physical optics to predict electrical 'shadows' where the charge density is negligible and can be ignored. This new method is implemented, and a significant improvement in analysis time is achieved with very little loss of accuracy. The analysis routine is used in an optimization loop to synthesize an interdigital filter which displays excellent performance. View full abstract»

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    Flexible network for Internet access in rural areas

    Kilenga, A.I. ; Mneney, S.H.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146836
    Publication Year: 2002 , Page(s): 211 - 216 vol.1

    IEEE Conference Publications

    The emergence and growth of wireless networks is driven by the need to lower the cost associated with network infrastructures by deploying wireless networks that offer access flexibility, at an affordable cost. Proliferation of wireless data communication and the Internet in urban areas have changed how people and businesses communicate. This is not the case in rural areas of developing countries where 80% of the population is found. We propose a flexible network for Internet services using CDMA access, which has the potential to cover the longer ranges characteristic of rural areas. We study the performance of the RAKE receiver with parallel interference canceller (PIC) structure in mitigating multiple access interference in rural multipath channels. 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 (2)

    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»

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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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    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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    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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    Optimization of SiO2-Si3N4 antireflective coating on P+NN+ photodiode

    Resnik, D. ; Vrtacnik, D. ; Amon, S.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821940
    Publication Year: 1999 , Page(s): 1153 - 1156 vol.2

    IEEE Conference Publications

    Optimization of anti-reflective coating on planar 1.8 mm2 area monocrystalline silicon photodiode was performed. Thermally grown SiO2 and LPCVD Si3N4 of different thicknesses were fabricated on the top of p+nn+ structure. Short circuit current density Jsc, open circuit voltage Voc and spectral response were measured as a function of both layers thickness and the results are discussed. Considerable improvement, particularly of Jsc was achieved with matched thicknesses of the two layers over single layer. It is shown that by tailoring the thickness of individual layers, spectral response can be efficiently varied along the wavelength axes View full abstract»

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    Generalized analysis of electrical circuits by using hypernion matrixes

    Berkovich, Y. ; Shenkman, A.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401600
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    In this paper a novel method for circuit analysis is proposed. It is based on using symbolic analysis in matrix form, which is especially appropriate for repetitive similar calculations of the same circuit. The method, which applies hyper-complex numbers (hypernions), was first developed by the authors for analyzing the non-sinusoidal operation of electrical circuits. Now, the method has been extended to the analysis of electronic/switching circuits in which the sources and/or the parameters are step-wisely changed as a result of switching. Such circuits are common in different kinds of DC-DC converters (such as Buck, Boost, Cuk, etc. converters). The proposed method gives a new approach to the analysis of the above circuits by opening the possibility of treating them in a general-analytical form, just like in regular electrical circuits having a constant configuration and constant parameters. The computation of such kinds of circuits by using the proposed method becomes very simple, since the circuit does not have to be analyzed many times, each time for a different configuration, but at once by performing a parallel computation. The theoretical presentation is accompanied by numerical examples. 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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    Towards a contextualized pedagogy for programming education in Tanzania

    Apiola, M. ; Tedre, M.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072010
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (3)

    IEEE Conference Publications

    Contextualization of curriculum and course contents has been central to development of IT education at Tumaini University in rural Tanzania. However, as the development of the IT program has progressed, pedagogical challenges have become increasingly evident. The pedagogical difficulties materialize most markedly in programming courses. We identified a number of sources of pedagogical difficulties: reliance on rote learning, group dynamics that support free riding, extrinsic motivations, and greatly varying educational backgrounds. In this paper we describe a pedagogical approach that utilizes the theories and principles of creative problem solving to overcome those difficulties. Firstly, we provided optimal challenges to cognitive development by switching to an open learning environment, and we adapted course arrangements accordingly. Secondly, we encouraged intrinsic motivation and sense of autonomy by increasing the amount of affective support. Thirdly, we encouraged reflective learning processes by introducing a new concept of coding-while-lecturing. Fourthly, we stimulated the positive aspects of group work and promoted individual learning by providing adaptable multi-level exercises. 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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    Power implications of additions in floating point DSP-an architectural perspective

    Pillai, R.V.K. ; Al-Khalili, D. ; Al-Khalili, A.J.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820976
    Publication Year: 1999 , Page(s): 581 - 586 vol.1

    IEEE Conference Publications

    This work targets experimental characterization of the architectural power implications of floating point adders that form part of DSP cores. High level models that characterize the power behavior of floating point adders are developed. Instrumented digital filter programs that emulate a DSP multiply-accumulate unit form the core of our experimental platform. The experiments substantiate the validity of our transition activity scaling based approach for the design of low power floating point adders. The worst case power reduction offered by the proposed transition activity scaled triple data path floating point adder (TDPFADD) is consistently above 50%. The corresponding reduction in power delay product is better than 70% 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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    Genetic algorithm for optimal open-loop distribution network design in competitive pool

    Filipec, M. ; Skrlec, D. ; Krajcar, S.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821904
    Publication Year: 1999 , Page(s): 977 - 982 vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    The paper presents the Computer Aided Design of Distribution Network (CADDiN) application based on geographic information system (GIS) and genetic algorithms designed to improve the planning of major investment in open-loop distribution network over the coming years. The system allows the planner to identify, from load forecast, data on the existing distribution system and all future projects, the projects to be undertaken together with the commissioning year, in such a way that the investment and maintenance costs, as well as cost of losses are minimized over a planning horizon. The application has been tested with real size distribution systems achieving optimal designs in reasonable CPU times compared with respect to the dimensions of such distribution systems 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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    Loss models of photovoltaic water pumping systems

    Lujara, N.K. ; van Wyk, J.D. ; Materu, P.N.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821902
    Publication Year: 1999 , Page(s): 965 - 970 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    The paper presents loss models of photovoltaic (PV) DC and AC motor drive water pumping systems (WPS). The DC and AC motors are fed by power electronic converters with or without maximum power tracking. The models are developed with the objective of maximizing the conversion efficiency from the solar irradiation to the potential energy of water by taking into account the variations in the pumping head at a given insolation. The efficiency of the array, the pump and the motor are found to be the most critical parameters for the performance of the systems. In addition, matching of the drive system and the load with the insolation characteristic of the solar array is found to be critical, since maximum system efficiency occurs at a specific head, which varies as the insolation changes 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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    Feasibility of using stochastic adaptive congestion control in computer networks

    Ngwenya, D.W. ; Hancke, G.P.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401461
    Publication Year: 2007 , Page(s): 1 - 8
    Cited by:  Papers (1)

    IEEE Conference Publications

    The paper presents a novel approach for congestion control and avoidance in computer networks. The approach is based on stochastic search, as opposed to systematic-like search employed by existing mechanisms. Our approach forms basis for more informed heuristics and promises to be more adaptive. We employ the Weibull distribution density function to continuously define the search space. In this paper we develop a single simple heuristic, based on the approach, and evaluate its performance in terms of congestion window evolution, response time and throughput. View full abstract»

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    Linear model of a closed three-shaft Brayton cycle

    van Niekerk, C.R. ; van Schoor, G. ; Pritchard, J.F.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406855
    Publication Year: 2004 , Page(s): 1079 - 1084 Vol.2

    IEEE Conference Publications

    A linear model of a closed three-shaft Brayton cycle is developed. The model is intended to give an understanding of the dominant dynamic behavior in a nuclear power system that utilizes a closed three-shaft Brayton cycle. The insights gained from the model can be used for system design as well as for the design of control algorithms [S.T. Glad et al. (2001)] [B.Hendrisson et al., (2001)]. Linear models of the turbines and compressors are developed, followed by models of the shafts and the volumes inside the circuit. Thereafter, the system equations are derived from the component models and put into state space format. Finally, a time domain comparison is made between the linear system model and the responses predicted by the thermal-fluid analysis software program, Flownex. View full abstract»

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    A flexible Reed-Solomon codec

    du Preez, A. ; Swarts, F. ; Agdhasi, F.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820772
    Publication Year: 1999 , Page(s): 93 - 98 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    We report on the implementation of a flexible Reed-Solomon codec using a field programmable gate array (FPGA) for use in a mobile communication system employing adaptive coding. The number of correctable errors can be changed in real time. A modified Euclidean algorithm is used with the number of correctable errors as an input parameter. The very high-speed integrated circuit hardware description language (VHDL) design can generate a codec for any Galois field size and field generator View full abstract»

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    Sensitivity of chromatic dispersion to geometrical imperfections in photonic crystal fibers

    Cherif, R. ; Zghal, M.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401468
    Publication Year: 2007 , Page(s): 1 - 5

    IEEE Conference Publications

    Small geometrical imperfections to the ideal cross section of index-guiding photonic crystal fibers (PCFs) are introduced in order to investigate their impact on the chromatic dispersion properties. Moreover, to validate our numerical analysis, the impact of real photonic crystal fiber's profile perturbations on chromatic dispersion is pointed out. This study is performed along 60 m fiber length. The analysis has been performed using the finite element method which assures high solution accuracy. View full abstract»

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    Performance evaluation of an OFDM system employing Viterbi decoded QPR in AWGN channel conditions

    Bestbier, D.C. ; Linde, L.P.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146837
    Publication Year: 2002 , Page(s): 217 - 220 vol.1

    IEEE Conference Publications

    Orthogonal frequency-division multiplexing (OFDM) has been shown to be a spectrally efficient modulation technique with inherent frequency diversity potential. Furthermore, by employing quadrature partial response (QPR) in an OFDM system, an even higher spectral efficiency can be obtained than with quadrature phase shift keying (QPSK) subcarrier modulation. Unfortunately, this is obtained at the cost of BER performance loss when compared to QPSK. However, this loss can be regained by using Viterbi decoding in the receiver. The paper presents a performance evaluation of an OFDM system employing Viterbi decoded QPR under additive white Gaussian noise (AWGN) channel conditions as an alternative to QPSK modulated OFDM. View full abstract»

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    Electronics on the Web [education]

    Joubert, T.-H.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821959
    Publication Year: 1999 , Page(s): 1239 - 1240 vol.2

    IEEE Conference Publications

    Web-based instruction is not only useful in distance education, but can also be productively used as an augmentation of classroom-based contact teaching-especially where large classes are concerned. The design and implementation of a Web-based construction site for teaching electronics to engineering students is presented in this paper View full abstract»

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    Optimal location of network devices using a novel inherent network topology based technique

    Sikiru, T.H. ; Jimoh, A.A. ; Agee, J.T.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071982
    Publication Year: 2011 , Page(s): 1 - 4
    Cited by:  Papers (3)

    IEEE Conference Publications

    A new approach for the identification of the best node for the injection of bulk power is proposed. The proposed approach can also be used to determine the minimum numbers of static var compensator devices that can ensure the operation of power system network within the specified voltage limits. The proposed approach is based on the inherent topology of networks and application of singular value decomposition technique. The results of numerical examples show that buses with the smallest singular values can serve as indicators of the best locations for static var compensators and best node for injection of bulk power without the need for additional transmission lines. 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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    Wireless sensor network gateway

    Steenkamp, L. ; Kaplan, S. ; Wilkinson, R.H.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308112
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (2)

    IEEE Conference Publications

    Using wireless sensor networks is an effective way of gathering data and also opens up new sensing opportunities. Wireless sensor networks can be more useful if the data can be effectively retrieved from the sensor network. This paper describes the development of a gateway node for a wireless sensor network, implemented in TinyOS, using the AT91RM9200 ARM evaluation kit from Atmel. This node enables the user to remotely retrieve data from-, manage- and configure the network. View full abstract»

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    Customized, locally developed microwave low noise amplifiers

    Boshnakov, I. ; Howie, D.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.563015
    Publication Year: 1996 , Page(s): 913 - 914 vol.2

    IEEE Conference Publications

    In the competitive military market, technical specifications are still the dominant criteria when designing components for front end receiver applications. Achieving system specifications that are superior to the competitors can result in component specifications that cannot be met using standard vendor catalog components. This paper discusses the approach used for development of customized low noise amplifiers (LNAs) for such applications, and the system level advantages thereof View full abstract»

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    Loss reduction in generalised multilevel converters

    Gitau, M.N. ; Konga, C.K. ; v.d.Westhuizen, J.G.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308152
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (2)

    IEEE Conference Publications

    Capacitor-switching operations found in magnetic-less DC-DC converters lead to significant capacitor power loss while capacitor voltage unbalance leads to high peak currents in the capacitors and switches. Power loss leads to premature failure of capacitors and is inversely proportional to both capacitance and switching frequency. A given reduction in losses then requires a corresponding increase in one of these parameters. This paper will show that by increasing the size of specific capacitors, it is possible to reduce significantly switching state transition capacitor losses and voltage unbalance without the need to increase the size of the capacitor bank by the same proportion. A method to identify capacitors that will lead to significant switching transition loss reduction when their sizes are increased is proposed. View full abstract»

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    A pulse-coupled-multilayer perceptron hybrid neural network for condition monitoring

    Rughooputh, H.C.S. ; Rughooputh, S.D.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821861
    Publication Year: 1999 , Page(s): 749 - 752 vol.2

    IEEE Conference Publications

    Studies of the visual cortex of cats highlight the role of temporal processing using synchronous oscillations for object identification. In this paper, a modified Eckhorn pulse coupled neural network model, the Computer-Model Cortex Neural Network, is used as a preprocessor to a neural network classifier for the condition monitoring of power transformers 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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    Indicative RES-E targets for the year 2010 and their fulfillment in slovenia

    Zlatar, I. ; Kozan, B. ; Gubina, A.F.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401450
    Publication Year: 2007 , Page(s): 1 - 5

    IEEE Conference Publications

    To reduce the reliance on imported fossil energy sources and combat climate change, to foster domestic technology development and harmonize the national support policies for renewable energy sources (RES) in its Member States, the European Commission introduced the Directive 2001/77/EC, defining renewable portfolio standards for the Member States. The indicative target for Slovenia is the 33,6 % contribution of RES in total gross electrical energy consumed by 2010. In this study, we review the mid-term possibility of achieving the Slovenian objectives, considering factors crucial for forecasting hydropower production. It is apparent that in order to achieve the RES-support policy goals and to break the spell of their weather-dependency, the support schemes in Slovenia need to be re-assessed and appropriately amended. View full abstract»

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    Software architecture for real-time sensor analysis and control of the friction stir welding process

    Kruger, G.H. ; van Niekerk, T.I. ; Blignault, C. ; Hattingh, D.G.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406716
    Publication Year: 2004 , Page(s): 461 - 466 Vol.1

    IEEE Conference Publications

    The friction stir welding (FSW) process requires advanced automation to ensure consistent and reliable joints. This has been realized by the development of an experimental set-up by the integration and online monitoring of accurate sensors with reliable modular control software. With increasing productivity and quality requirements imposed by manufacturers, machine flexibility and scalability are becoming increasingly pertinent. On-line process monitoring facilitates the `adaption' of machines able to respond to changing process parameters and conditions. Modular open software architectures allow flexibility in machine application. This paper introduces a fresh approach for the integration of the latest automation technology into an experimental setup equipped with an advanced sensory system. A new method of capturing sensory data and the implementation aspects of the software architecture for a micro-kernel based real-time embedded operating system is introduced. Agile automation of the FSW process is thus realized by advanced monitoring and control View full abstract»

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    Critical design parameters for a low altitude long endurance solar powered UAV

    Wilkins, G. ; Fourie, D. ; Meyer, J.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308105
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    The paper presented provides theoretical findings of the critical solar UAV parameters required for prolonged flight. The parameters being, battery energy density, wing surface area, total UAV weight and solar surface area. The findings are based on two individual models, a solar and an aerodynamic model, which are combined to form a solar powered UAV model. View full abstract»

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    Network transient responses to varying HVAC line length along a HVDC transmission corridor

    Oyedokun, D.T. ; Folly, K.A.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072157
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    This paper deals with the complex network transient responses to AC and DC faults in transmission network with a fixed HVDC transmission line and varying HVAC transmission lines. The rotor angle stability and management of the reactive power are investigated in order to define the network transient responses. The simulations are carried out using a multi machine power system model using DigSILENT software package. The results indicated that the network transient response cannot be generalized but defined into two separate categories namely AC and DC. During the HVDC transmission line fault, the overall rotor angle stability of the is enhanced with the increase in length of the HVAC transmission line. View full abstract»

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    Validation within safety critical systems engineering from a computational semiotics point of view

    Doeben-Henisch, G. ; Wagner, M.F.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401588
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (2)

    IEEE Conference Publications

    Software controlled Safety Critical Systems are increasing in importance in all areas of application. Combining efficient agile development processes with powerful but complex modeling and formal methods imposes grand challenges on software designing organizations. Especially the semiotic dimension which relates stakeholders and engineers in an engineering process is evoking such challenges. Focusing on these processes as basis for domain modeling and as point of reference for validation the authors outline a simulation based approach to overcome the semantic gap. But they know, that this still can only be a preparatory step for much more detailed semiotic analyses. View full abstract»

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    Information security management - a practical approach

    Dey, M.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401528
    Publication Year: 2007 , Page(s): 1 - 6

    IEEE Conference Publications

    Information security is an important issue in today's business. Information security management can no more be done by merely a set of hardware and software. Rather, it requires a complete end-to-end system. Such a system is called Information Security Management System (ISMS). It requires special focus and participation from all levels of employees with full commitments and responsibilities in establishing such a system and implementing it within the organization. ISO security standards and government compliance regulations guide and enforce organizations about certain requirements and norms. Organizations need to build an ISMS by combining all the bits and pieces as per their business needs. This paper illustrates a practical approach, as a ready reference, to build an ISMS in a business organization. View full abstract»

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    The design of low-cost modular instructional equipment in electrical and electronic engineering

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

    DOI: 10.1109/AFRCON.1992.624541
    Publication Year: 1992 , Page(s): 541 - 544
    Cited by:  Papers (2)

    IEEE Conference Publications

    The author considers some conceptual dilemmas and practical problems that arise in the attempt to develop a range of low-cost instructional apparatus with which to support a program to enrich the undergraduate electrical and electronic engineering curriculum. He illustrates these by specific examples drawn from a program under way at the University Cape Town and reports informally on some of the results to date View full abstract»

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    Comparison of two terrestrial atmospheric turbulence suppression algorithms (March 2007)

    Walters, B.D. ; Clarke, W.A.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401539
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    This paper describes the problem of capturing video through turbulent atmosphere (also referred to as heat shimmer or heat scintillation) and describes some of the existing methods used in an attempt to counteract the problem. Within this problem of imaging through turbulent atmosphere there is a distinct lack of comparisons between methods and a reliable metric for digital images. This paper contributes through the selection of two algorithms which are implemented, tested and compared, one a power spectrum restoration approach from the early 1990's and a newer image registration and fusion based method. The results show the ability of the old power spectrum method to stabilize the image although local object motion presents a problem, as well as the computational complexity of the image registration method. View full abstract»

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    Development and implementation of a 1.5 MW inverter and active power filter for the injection of regenerated energy in a Spoornet substation

    Fuchs, H.D. ; Henning, P.H. ; Mouton, H.T.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406863
    Publication Year: 2004 , Page(s): 1119 - 1124 Vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    This work discusses the implementation of a 1.5 MW system that injects the regenerated energy, caused by the braking action of electric trains, back into the Eskom supply. At present this energy is dumped into resistor banks and goes to waste as heat. For the intervals that the train is not regenerating energy, the system operates as an active power fitter. An overview of the system is provided as well as further details on the series-stacked inverter, injection transformer, measurement system and protection in the system. Simulation results show the operation of the system. View full abstract»

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    Characterization of broadcasting waves disturbances on the Tunisian telephone local loop network (LLN)

    Ghazel, A. ; Abhallah, F.B.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821934
    Publication Year: 1999 , Page(s): 1127 - 1130 vol.2

    IEEE Conference Publications

    In this paper, we present the results obtained concerning the characterization of electromagnetic disturbances on the telephone LLN caused by broadcasting nearby emissions. In this study, we propose an in site measurement methodology that permits the identification of the EMI coupling mode, the sensitive parts of the LLN and the effects on the telephone services. We demonstrate that the coupling occurs especially at the overhead line parts and at some types of user's terminal sets. An experimental susceptibility study of terminal sets is proposed, This analysis is a first step for the design of compensation solutions View full abstract»

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    Design of a sinewave inverter for alternative energy

    Malengret, M.
    AFRICON '92 Proceedings., 3rd AFRICON Conference

    DOI: 10.1109/AFRCON.1992.624426
    Publication Year: 1992 , Page(s): 95 - 98
    Cited by:  Papers (1)

    IEEE Conference Publications

    The authors describes the principle and design criteria adopted for a small economical, portable, robust inverter used for outdoor or remote area power supply (RAPS). Sine-weighted pulse-width-modulation (PWM) techniques applied to a push-pull inverter with a front-end filter are used. The front-end filter, using a cross-coupled choke on the low 12 V side, makes it a current fed inverter and hence suitable for starting motors. The topology offers a sinusoidal flux in the main step-up transformer, and thus a good efficiency at low loads. The cost is similar to that of push-pull center tap quasi-square inverters View full abstract»

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    Some research issues in cognitive radio networks

    Bansal, G. ; Hossain, J. ; Kaligineedi, P. ; Mercier, H. ; Nicola, C. ; Phuyal, U. ; Mamunur Rashid, M. ; Wavegedara, K.C. ; Hasan, Z. ; Khabbazian, M. ; Bhargava, V.K.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401589
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (8)

    IEEE Conference Publications

    The cognitive radio (CR) technology will allow a group of potential users to identify and access available spectrum resources provided that the interference to the users for whom the band has been licensed is kept below a prescribed level. However, this research area is at a very immature stage because various research challenges have to be addressed and solved. In this paper our objective is to present an overview of some research issues for CR networks. Specifically, we present some research and development in CR networks with focus on i) information- theoretic aspects, ii) spectrum sensing, iii) link adaptation, iv) advanced transceiver design, and v) admission control. We also discuss some important research problems related to these specific topics that needs to be addressed before deployment of CR systems in practice. View full abstract»

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    A Web based interactive database and CORBA tutorial

    Falb, J. ; Radinger, W. ; Goeschka, K.M.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146875
    Publication Year: 2002 , Page(s): 425 - 430 vol.1

    IEEE Conference Publications

    With Web based open and distance learning, students appreciate the possibility to learn and train when and where they want-even from home. Based on a database, CORBA middleware and Web frontend, we implemented an interactive database and CORBA tutorial to allow for efficient, interactive student training. It also supports the testing of the student's application in a distributed environment together with a real-life database. The students can concentrate on their main tasks and need not spend time nor effort on learning complicated tools or environment configurations. Consequently, they get familiar with complex e-commerce technologies in a convenient way. View full abstract»

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    Improving the accuracy and overall value of stator winding insulation assessments for operational generators, through laboratory based insulation research tests on stator bars

    van der Merwe, H. ; Rasekhi, P. ; Volk, N.R.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563154
    Publication Year: 1996 , Page(s): 447 - 450 vol.1

    IEEE Conference Publications

    The Technology Research and Investigations division of Eskom's Technology Group (T-R-I) is currently investigating the technical and logistical merit of performing offline quadratic-rate partial discharge tests on the stator winding insulation of its hydro- and turbo-generators. A series of laboratory based insulation research studies on stator bars have been conducted to gain a better understanding of the various partial discharge phenomena involved. Results thus far obtained from these tests have provided valuable insight into the discharge activity of operational generators View full abstract»

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    An adaptive reluctance motor vector control scheme based on a load angle observer

    Abdel-Raof, O. ; Tahoun, S.M.R. ; Khater, M.M. ; El-Shanawany, E.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820901
    Publication Year: 1999 , Page(s): 441 - 446 vol.1

    IEEE Conference Publications

    In this paper an algorithm based on the reluctance motor (RM) stator current angle is introduced. The algorithm investigates four cases. Two of these cases are mainly with optimizing power factor and efficiency while the other two are concerned with torque optimization. An observer based on the RM load angle and speed error is used to discriminate between transient and steady state conditions. A comparison between the two proposed torque optimization methods is carried out featuring the advantages of cage-less RM designs. An experimental drive system was implemented to verify the simulation results, Simulation and experimental results are found to be in good agreement View full abstract»

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    An active resonant snubber for high power IGBT converters

    du T.Mouton, H. ; Combrink, F.W. ; Enslin, J.H.R.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821832
    Publication Year: 1999 , Page(s): 615 - 620 vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    This paper introduces a new active resonant snubber topology suited to high power converters. The main feature of this snubber is that the peak current rating of the auxiliary switches is small compared to that of the main switches. The basic operation of the snubber is analyzed. This is followed by an experimental evaluation of the basic operating principles View full abstract»

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    Performance of a Hidden Markov channel occupancy model for cognitive radio

    Barnes, S.D. ; Maharaj, B.T.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072020
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (4)

    IEEE Conference Publications

    This paper investigates the effect that various training algorithms have on the performance of a primary user (PU) channel occupancy model for cognitive radio. The model assumes that PU channel occupancy can be described as a binary process. A two state Hidden Markov Model (HMM) has thus been chosen and it is shown that the performance of the model is influenced by the algorithm employed for training the model. Traditional training algorithms are compared to certain evolutionary based training algorithms in terms of the resulting prediction accuracy and convergence time achieved. The performance of the model is important since it provides secondary users (SU) with a basis upon which channel switching and future channel allocation may be performed. Further simulation results illustrate the positive effect that our model has on channel switching under both heavy and light traffic density conditions. View full abstract»

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    Performance enhancement of synchronous reluctance machine using split winding and capacitance injection

    Ogunjuyigbe, A.S.O. ; Jimoh, A.A. ; Nicolae, D.V.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401551
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (1)

    IEEE Conference Publications

    This paper reports the performance enhancement of synchronous reluctance machine using split stator winding and direct capacitance injection. Capacitance is injected into the machine through an additional three phase winding that is magnetically coupled to the main winding. The machine was modeled as a coupled circuit to examine the effect of the capacitance injected on the machine parameters. The condition for unity power factor at different load angles is examined. A typical capacitance value at which unity power factor is achieved was also obtained. View full abstract»

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    Stochastic adaptive control for robotic manipulator with control input constraints

    Negm, M.M.M.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820912
    Publication Year: 1999 , Page(s): 457 - 461 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    An adaptive controller is synthesized to control the motion of an n-degrees of freedom direct drive robotic manipulator. The design of the adaptive controller is based on minimum variance control with model reference which depends on the nominal values of the position and angular velocity of the manipulator joints. The parameters of the adaptive controller are estimated on line using the least squares algorithm. In the controller the end effector velocity of the manipulator is monitored in a servo loop, and the position and angular velocity of each joint of the manipulator are compelled to track their nominal values. This controller comprises an n-input vector for the actuator torque, and a 6-output vector for the linear and angular end effector velocities. The actuators of the direct drive manipulator are taken to be permanent magnet motors. Their dynamics and constraints are considered in the proposed controller. Digital computer simulations are made to demonstrate the tracking performance, robustness and applicability of the adaptive controller View full abstract»

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    Education and training of microelectronic engineers: why and how?

    Joubert, T.-H. ; du Plessis, M. ; Snyman, L.W. ; Theron, E.A.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563125
    Publication Year: 1996 , Page(s): 293 - 296 vol.1

    IEEE Conference Publications

    In this paper an undergraduate training program for engineers with practical microelectronic experience is presented. The emphasis in this program is on the design of devices and integrated circuits, and the reason for this is expounded. A discussion of the incentives for producing such engineers for the South African context is also furnished View full abstract»

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    Advanced beamforming techniques for acoustic source localization

    Mukwevho, T. ; Jordaan, J. ; Noel, G.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308363
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper tackles the issue of acoustic source localization using an array of microphones. From the conventional method to advanced beamforming, the algorithms are presented from a theoretical point of view. The advantages and drawbacks of each method are then discussed. Finally, simulation results are presented. View full abstract»

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    A particle swarm optimization approach for model independent tuning of PID control loops

    Pillay, N. ; Govender, P.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401521
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (2)

    IEEE Conference Publications

    The paper proposes a model independent tuning technique that yields optimal proportional-integral-derivative parameters for a range of typical process control loops. The proposed tuning technique utilizes the particle swarm optimization algorithm to generate optimal tuning parameters. The PSO tuning method is applied to typical process models. Comparisons are made between the proposed PSO technique and other conventional methods. View full abstract»

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    Guided modes in slab chirowaveguides

    Rokushima, K. ; Matsumoto, K. ; Wei Yu Feng ; Wu Jun Xian
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.563016
    Publication Year: 1996 , Page(s): 915 - 918 vol.2

    IEEE Conference Publications

    A rigorous analysis of guided modes in chirowaveguides is presented. The numerical examples clarify that not only surface waves but also leaky waves exist owing to the chirality of the medium View full abstract»

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    Design of magnetic-commutational wind energy generator for autonomous installations

    Mkrttchian, V.S. ; Shahinyan, A.G. ; Alexeevskij, V.V.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821900
    Publication Year: 1999 , Page(s): 955 - 958 vol.2

    IEEE Conference Publications

    For the small autonomous energy installations using the energy of the wind or small rivers it is not possible in regard of daily and seasons-related fluctuations, to provide constant volleying (rotation) speed and rotary installations power. In such cases using traditional generators of general purpose usually applied in industry is not quite justified and expedient. For the above-mentioned cases, a special purpose generator should be used, in which energy transformation is performed by using magnetic current commutation obtained during the rotation of the conductor magnetic anchor. The wind energy generator has revealed certain problems with discontinuities and disruption of automatic adjustment that can be eliminated using the sliding mode characterized by reduced order of mathematical support and feedback from discontinuities View full abstract»

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    Integrated fiber-wireless networks: What, why and how

    Ng'oma, A. ; Hejie Yang ; George, J.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072190
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    Recent popularization of video-centric handheld devices including smart phones and computer tablets has led to a sharp increase in the demand for wired and wireless data capacity and coverage towards the edge of modern communication networks. Since these devices are operated mostly from inside buildings, in-building coverage and capacity have also become critical components of wireless networks. But poor propagation of wireless signals inside buildings leads to significant performance degradation of wireless systems in terms of both coverage and capacity. As a result, a high density of antennas is needed to provide the required performance. Due to its inherent large bandwidth, optical fiber is ideally suited to provide flexible backbone infrastructure of high-capacity wireless networks. By employing analog radio-over-fiber signal transmission techniques, highly transparent fiber-wireless networks, which are ideal for multi-standard wireless system operation can be realized. We have demonstrated multiple simple techniques that may be used solve many technical challenges faced when analog signal transport is employed. Using simple and practical solutions, we have experimentally demonstrated ultra high-capacity radio-over-fiber systems operating at >; 30 Gb/s. View full abstract»

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    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406839
    Publication Year: 2004 , Page(s): 1002

    IEEE Conference Publications

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    Evolutionary computing methodologies for constrained parameter, combinatorial optimization: Solving the Sudoku puzzle

    Almog, J.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308284
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (2)

    IEEE Conference Publications

    Three evolutionary computing algorithms are applied to a constrained parameter, combinatorial optimization problem; the Sudoku puzzle. These methodologies include, quantum simulated annealing, cultural genetic algorithm and a hybrid between simulated annealing and genetic algorithm. The results obtained from these techniques indicate that the most effective of these optimization techniques is quantum simulated annealing with an effective accuracy of solving 64 out of 100 simulations in under 6 000 iterations, with an average running time of approximately 40.2 seconds. While classical, logic based search algorithms tend to outperform these evolutionary computational algorithms (in both complexity and time) for simple, `unique-solution' problems, it is found that the evolutionary based algorithms surpasses these classical methodologies when solving higher dimensional, more complex puzzles. View full abstract»

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    Influence of new over - head power lines construction on the operation of the relay protection system

    Frlan, K. ; Rubesa, R. ; Marusic, A.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401498
    Publication Year: 2007 , Page(s): 1 - 6

    IEEE Conference Publications

    One of the basic ways to improve the safety of either a part or the whole of the power system (PS) is construction of new overhead power lines. Since such interventions in the system are rare nowadays for economic, as well as ecological reasons, every significant alteration requires detailed analyses of the influence of line construction on the entire power system. In this paper the influence of the construction of new lines on the relay protection system has been described. Power system has been modeled by using the CAPE software and relay protection operation has been analysed. The first part of this paper describes the power system before reconstruction. Accuracy of the software model has been tested by comparison with the real faults in the network recorded by numerical relays. Distribution of fault current in the current and new system configuration has been shown by analysing the single-phase high-resistance fault, and functionality of the relay protection in both instances has been analysed. View full abstract»

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    A prototype for achieving digital forensic readiness on wireless sensor networks

    Mouton, F. ; Venter, H.S.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072117
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    The field of wireless sensor networking is still a new and upcoming one and, unfortunately, still lacking in terms of digital forensics. All communications between different nodes (also known as motes) are sent out in a broadcast fashion. These broadcasts make it quite difficult to capture data packets forensically whilst retaining integrity and authenticity of the data packets. This paper examines whether and how one can add a digital forensic readiness layer to an existing IEEE 802.15.4 wireless sensor network without any modification to the existing wireless sensor network. This paper also provides demonstrations of a working prototype to show that a digital forensic readiness layer can be added to an existing wireless sensor network, if the prototype adheres to a list of requirements in order to achieve digital forensic readiness in a wireless sensor network environment. This is done by performing several demonstrations which resemble real world wireless sensor network scenarios in order to show that the prototype does indeed add a layer of digital forensic readiness to the existing wireless sensor network. View full abstract»

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    Piezoelectric sensor array with evaluation electronic for counting grains in seed drills

    Meyer zu Hoberge, S. ; Hilleringmann, U. ; Jochheim, C. ; Liebich, M.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072063
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    A special application area of the sensor system presented here, is the detection of grain in seed drills. With the highly precise measurement of the seed, the crop yield can be strongly improved. Under the extreme environmental conditions inside of the seed drills, each single grain of very different seed species must be safely detected. Because of the touching piezoelectric measuring principle, the mounting contact mode of the sensor is either in the distributor head or in each of the seed hoses of the seed drill. Up to 15 thousand grains must be counted per second. For the detection of these high grain frequencies, a novel design of the sensor element was developed. A special evaluation electronic converts the analog sensor signals into binary pulses, which can be recognized as interrupts and counted by a microcontroller. View full abstract»

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    A broadband microwave amplifier design by means of immittance based data modelling tool

    Kilinc, A. ; Pinarbas, H. ; Sengul, M. ; Yarman, B.S.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159965
    Publication Year: 2002 , Page(s): 535 - 540 vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    In this paper a practical broadband microwave amplifier design algorithm is introduced utilizing the immittance data-modelling tool. In the course of design, first, the optimum input and output terminations for the active device are produced employing the real frequency technique. Then, these terminations are modelled utilizing the new immittance-modelling tool to synthesize the front-end and back-end matching networks. An example is included to exhibit the implementation of the proposed design algorithm to construct a single stage BJT amplifier over a wide frequency band. It is expected that the proposed design algorithm will rind applications to realize wideband microwave amplifiers put on MMIC for mobile communication. View full abstract»

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    Double concatenated space-time trellis codes

    Byers, G.J. ; Takawira, F.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146823
    Publication Year: 2002 , Page(s): 143 - 148 vol.1
    Cited by:  Papers (3)

    IEEE Conference Publications

    Two double concatenated coding structures are proposed which employ two convolutional codes and a space-time trellis code (STTC) as constituent codes. These are a serial concatenation of a parallel concatenated convolutional code (PCCC) with an STTC and a serial concatenation of a serially concatenated convolutional code (SCCC) with an STTC. The decoding of these two systems is described and their frame error rate (FER) performance is evaluated by simulation. The proposed systems are shown to outperform simple concatenated STTCs in rapid fading channels and achieve equivalent performance in quasi-static fading channels. View full abstract»

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    Development of a mathematical model for VARS transmission in electric power systems

    Anderson, G.O. ; Ogwu, F.J.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160040
    Publication Year: 2002 , Page(s): 941 - 945 vol.2

    IEEE Conference Publications

    The paper gives detailed analyses to determine the increase in production cost due to the transmission of VARS. On the basis of that and with due consideration to the cost of VARS compensation equipment, a mathematical model is developed to determine the economically justified transmission distance for VARS in electric power systems. Standard voltages and line parameters are used for computation. MATLAB computer programming is used to obtain the numerical results. The developed mathematical model and the numerical results could be useful to electric power systems engineers. View full abstract»

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    Energy management system (EMS) on the Botswana Power Corporation electrical network

    Masawi, F.
    AFRICON '92 Proceedings., 3rd AFRICON Conference

    DOI: 10.1109/AFRCON.1992.624556
    Publication Year: 1992 , Page(s): 601 - 604

    IEEE Conference Publications

    The increase in energy requirements in Botswana grew at an average annual rate of 8% in the 1985/86-1990/91 period from 680 GWh in 1985/86 to just over 1000 GWh in 1990/91. To cope with the growing complexity of system operations the Botswana Power Corporation (BPC) implemented a centralized computer control system at the National Control Centre based in Gaborone, the capital city of Botswana. The author describes the BPC EMS system with an emphasis on its major features such as production planning and control, the computer system configuration, the data acquisition subsystem, and the comunications and man-machine interface subsystem. Its functional overview is presented, and its high-performance, actual operating experience, and future system expansion possibilities are described View full abstract»

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    Development of a MV IGBT based solid-state tap changer

    Fourie, R. ; Mouton, H.D.T.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308128
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (3)

    IEEE Conference Publications

    This paper proposes an alternative connection topology for tap changers. Power electronic switches are implemented instead of conventional mechanical tap changers. This topology has the advantage of using less taps than the latter conventional method. The main focus is on improving the response time to sudden voltage changes. A practical implementation is presented to prove the feasibility of the design. View full abstract»

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    Speed control of a DC drive based on optimal performance

    Mohamed, E.A. ; Negm, M.M. ; Said, A.I. ; Awad, A.S.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.562964
    Publication Year: 1996 , Page(s): 638 - 653 vol.2

    IEEE Conference Publications

    A simple robust preview control system theory is synthesized for DC motor drive speed control. It proceeds to find future values of desired and disturbance signals which are needed for improving robustness and control system performance. The dynamic equation of a separately excited DC motor is introduced as the basis of a constant field current system. Simulation results are used to investigate the effectiveness of the above technique. Experimental results prove the effectiveness of the proposed controller View full abstract»

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    Frequency management in South Africa

    Hibbard, S.M.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563084
    Publication Year: 1996 , Page(s): 79 - 82 vol.1

    IEEE Conference Publications

    In dealing with the topic of frequency spectrum management in South Africa the author has approached the topic from four points of view, namely: an indication of which bodies are currently responsible for frequency management at a national level; an indication of the current status of and recent developments within the frequency management environment, with a bias towards telecommunications; an indication of short term future expectations for frequency management; and a view of the future regulatory environment and management in a broader context within this framework View full abstract»

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    Feedback-linearised control of a solar power platform with nonlinear measurements

    Agee, J.T. ; Jimoh, A.A.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401568
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Patents (1)

    IEEE Conference Publications

    The paper presents the design and simulation results of the input-state feedback-linearised control of a polar- axis solar tracking platform, capable of hosting ten 300 W solar photovoltaic panels. The controller reduced the settling time of the open-loop platform system from 105 seconds to 2 seconds. Compared with a linear controller we had designed for the same system, the new controller also minimized system accelerations. 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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    Measuring SET effects in a CMOS operational amplifier using a built-in detector

    Espinosa-Duran, J.M. ; Velasco-Medina, J. ; Huertas, G. ; Velasco, R. ; Huertas, J.L.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401472
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (4)

    IEEE Conference Publications

    This paper studies the effects produced by radiation single event transient (SET) injected in the transistors of a custom operational amplifier, in order to evaluate their sensitivity to the radiation transient faults. A BID (built-in detector), was included in the circuit in order to amplify and detect the SETs effect. The circuit was designed using a non-rad- hard AMS-CMOS 0.8 mum process. In this case, simulation results allow the identification of the operational amplifier most sensitive transistors and the operating conditions during which the worst effects in the operational amplifier response were produced. View full abstract»

  • Freely Available from IEEE

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    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406618
    Publication Year: 2004 , Page(s): 2

    IEEE Conference Publications

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    New developments in the management of power quality performance in a regulated environment

    Koch, R.G. ; Balgobind, P. ; Tshwele, E.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160022
    Publication Year: 2002 , Page(s): 835 - 840 vol.2
    Cited by:  Papers (3)

    IEEE Conference Publications

    This paper reviews recent developments in utility power quality, management in South Africa. Anew (and more comprehensive) regulatory framework is discussed in the context of experience with previous performance-based requirements. This framework will significantly change! the way in which power quality is addressed by all stakeholders (i.e. utilities, customers, and equipment suppliers) in South Africa. The role of proposed revisions to the NRS-048 Power Quality Standard are discussed with regard to this framework. View full abstract»

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    Fuzzy logic traffic management for ATM networks

    Scheffer, M.F. ; Kunicki, J.S.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563093
    Publication Year: 1996 , Page(s): 124 - 129 vol.1

    IEEE Conference Publications

    Asynchronous transfer mode gives network users the possibility to accommodate heterogeneous traffic with characteristics vastly different from conventional telephone traffic. These networks are not fully described by formal traffic models and assumptions, such as Poissonian sources. On the other hand fuzzy logic methods are capable of extracting the inherent characteristics of a system without the need for a priori assumptions as to network characteristics View full abstract»

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    Organizing laboratory training in electric drives

    Mircevski, S.
    AFRICON '92 Proceedings., 3rd AFRICON Conference

    DOI: 10.1109/AFRCON.1992.624488
    Publication Year: 1992 , Page(s): 336 - 339

    IEEE Conference Publications

    The courses on electric drives at the Faculty of Electrotechnical Engineering at Cyril and Methodius University in Skopje, Macedonia is described. Attention is given to the teaching programs, the laboratory training conditions and concept, and the laboratory equipment 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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    On performance of residue number system coded differential space-time-frequency coding

    Akol, R.N. ; Takawira, F.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401439
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    Space-time-frequency (STF) coding has emerged as a technique for transmitting high data rate over wideband mobile channels. Most of the proposed architectures in the literature maximize diversity gains from one diversity domain and frequency diversity is predominantly dependent on the intrinsic frequency-selective nature of the fading channel In this paper we propose differential space-time-frequency (DSTF) modulation scheme. The available bandwidth is divided into several orthogonal subbands by a frequency encoder and redundancy is added to maximize coding (frequency) gains. For improved non-coherent detection at the receiver, iterative decoding employing hard decision-feedback of differentially encoded space-time block code on each carrier is concatenated with an outer frequency encoder. It is shown through analytical expressions that with appropriate code design, the proposed DSTF coding scheme can maximize the diversity gains over space, time, and frequency domains. 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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    Modeling and analysis of a multibus reticulation network with multiple DG. Part III. economic dispatch

    Davidson, I.E.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406798
    Publication Year: 2004 , Page(s): 815 - 819 Vol.2

    IEEE Conference Publications

    For pt.I see ibid., vol.2 p.805-10. For pt.I see ibid., vol.2 p.811-14. A significant growth in the utilization of autonomous- and distributed power sources deployed at subtransmission (132 - 22 kV) and reticulation levels (<22 kV) in stand-alone or grid connection notations has been seen in many electricity industries across the world. With electricity industry reform, an open access regime is a standard policy governing the transmission grid, thus providing for full competition at generation and distribution end of the electricity delivery value chain. It has become necessary to investigate the technical and economic impact future connections of distributed generators will have on electric power distribution networks, and evaluate some of these effects of power sector deregulation. This work presents the modeling and analysis of a multibus reticulation network model with multiple distributed generation (DG) injection. Results for economic evaluation of a multibus network using economic dispatch models are presented and discussed. View full abstract»

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    Analysis of bus voltage regulation and OLTC performance on mismatched parallel-connected transformers

    Madzonga, L.S. ; Munda, J.L. ; Jimoh, A.A.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308082
    Publication Year: 2009 , Page(s): 1 - 5

    IEEE Conference Publications

    This paper analyzes the regulation of bus voltage when master-follower or master-slave tap change control method is used when two mismatched-transformers are operated in parallel. Bus voltage regulation at a distribution substation relies on the use of the AVR relay that controls the OLTC. The circulating current method yields expected performance regarding bus voltage regulation when mismatched transformers are operated in parallel. When the master-follower/slave method is used, the standard voltage set-point of 103% results in low voltages being experienced by the customer at the end of the feeder. The simulations done on the network suggests that the voltage set point of each AVR relay be determined with the consideration of the upstream and downstream AVR relay settings. View full abstract»

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    Reliability management in a nuclear power plant

    Kokol, P. ; Novak, B. ; Kunej, A.
    AFRICON '92 Proceedings., 3rd AFRICON Conference

    DOI: 10.1109/AFRCON.1992.624471
    Publication Year: 1992 , Page(s): 271 - 274

    IEEE Conference Publications

    Considering the potential efficiency of reliability-centered maintenance in the nuclear power industry, a pilot project concerning electrical components was started in the Krsko nuclear power plant in Slovenia. In this project the reliability management was automated with a software system called REMASOS (reliability maintenance software system) which runs effectively and efficiently on low-cost personal computers View full abstract»

  • Freely Available from IEEE

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    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406720
    Publication Year: 2004 , Page(s): 484

    IEEE Conference Publications

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    Combination of diffuse and local connections in the cortex

    Remmelzwaal, L.A. ; Tapson, J. ; Ellis, G.F.R.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072107
    Publication Year: 2011 , Page(s): 1 - 4

    IEEE Conference Publications

    We present a simple neural network model that combines local and diffuse connections. It represents the interaction between ascending or monamine systems, and the cortex in the human brain. We show that this simple model allows the use of salience (cognitive significance) as an input and response in the neural network. Results for single and multiple-trial learning show that salience can drive the learning process to a high degree. View full abstract»

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    Estimation of SRTT using techniques from the practice of SPC and change detection algorithms

    Ngwenya, D.W. ; Hancke, G.P.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406702
    Publication Year: 2004 , Page(s): 397 - 402 Vol.1
    Cited by:  Papers (2)  |  Patents (1)

    IEEE Conference Publications

    We have employed principles from change detection algorithms and statistical process control (SPC) to improve the estimation of the average of the round-trip time (RTT). Two mechanisms are proposed. The first is based on SPC principles. The other is based on an intuition derived from the log-likelihood ratio concept. Data employed to test the mechanisms are obtained by pinging several nodes on a campus network. Both methods improved the ability to track the change in the mean and take appropriate action View full abstract»

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    A time step choice algorithm for transient analysis of circuits

    Constantinescu, F. ; Gheorghe, A.G. ; Nitescu, M.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308136
    Publication Year: 2009 , Page(s): 1 - 4

    IEEE Conference Publications

    A new error and a new time step choice algorithm are proposed. A comparison with the SPICE results is given for a linear circuit, showing that the proposed algorithm rejects a smaller number of time steps. View full abstract»

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    An object based approach for distributed automation

    Riedl, M. ; Diedrich, C. ; Naumann, F. ; Simon, R.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406892
    Publication Year: 2004 , Page(s): 1253 - 1260 Vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    Design methods in the area of automation are dominated by the function block approach. These blocks represent a kind of object with an internal behaviour. The blocks interact via Input and output variables with their environment. In order to improve the engineering and the system design, other approaches like method invocations coming from computer science have to be considered. One promising approach among others is the usage of ports for the interaction of objects. This article describes an approach for a distributed, object-oriented automation system, based on objects interacting via the port concept. View full abstract»

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    Evaluating the contribution in the harmonic distortion level based on Digital Fault Recorder (DFR) analysis

    Musasa, K. ; Siti, W.M. ; Jordaan, J.A.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072127
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    The analog recorded information from Digital Fault Recorder (DFR) analysis is useful information for analyzing the distortion level in the electrical network. This paper develops a methodology for tracking of individual harmonic sources and evaluating the distortion level in localized substations where the DFR is installed. To solve it using Fast Fourier Transform, the captured data are processed on-site to compute the harmonics. The computed harmonics (magnitude) are transmitted to the master station computer where the system wide harmonic flow is constructed. View full abstract»

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    Advanced Level Robotics/Automatics University New Adjoint (ALRAUNA) Program

    Mandic, I.
    AFRICON '92 Proceedings., 3rd AFRICON Conference

    DOI: 10.1109/AFRCON.1992.624430
    Publication Year: 1992 , Page(s): 111 - 114

    IEEE Conference Publications

    The author discusses the proposed ALRAUNA (Advanced Level Robotics/Automatics University New Adjoint Program) at FEMENA, (Faculty of Electrical Engineering, Mechanical Engineering, and Naval Architecture), University of Split, Split, Croatia. The objective of the proposed program is to solve the bottleneck problem of the education of qualified engineers and technicians in modern robotic work cells, production lines, and automated factories. The ALRAUNA program includes job competencies, course outlines and objectives, and laboratories for courses in applied physics, electromechanical devices, electrical and electronic devices, hydraulics, pneumatics, controllers, computers, robots, sensors, vision systems, robotic interfacing, and workcell integration. The ALRAUNA graduate student has to be a technical specialist in robotics/automatics and processing equipment who can set up automatic machines that work together as part of a total automated system. In his area of specialization he can install, set up, troubleshoot, integrate, program, modify, test, operate, and repair various automatic components and systems View full abstract»

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    Thin FC film for sidewall passivation in SCREAM process for MEMS

    Vrtacnik, D. ; Resnik, D. ; Aljancic, U. ; Mozek, M. ; Penic, S. ; Amon, S.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401632
    Publication Year: 2007 , Page(s): 1 - 5

    IEEE Conference Publications

    SCREAM process for releasing micromechanical MEMS structures using plasma polymerized fluorocarbon thin film for trench sidewall passivation is reported. The developed process is designed as a one mask process, and all etchings and depositions are fabricated in the same etching system (standard capacitive coupled RIE), as one-step-one-run process. View full abstract»

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    Towards automatic Digital Surface Model generation using a Graphics Processing Unit

    van der Merwe, D. ; Meyer, J.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308102
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    Digital Surface Models (DSM) are widely used in the earth sciences. It provides information for various geological studies and other applications. There are a number of methods for automatic DSM generation, each of which has its own strengths and weaknesses, none of which are perfect. Even though there are plenty of algorithms to date which can generate the DSMs, it is a computationally complex calculation and does tend to take some time to complete. In order to achieve faster DSMs, an algorithm was implemented on a graphics processing unit. This platform greatly improves the processing speed but does have some drawbacks; namely, no support for double precision floating point values, limited memory and algorithms has to be adapted to be usable in a stream processor environment. A speed performance increase of 900% was obtained while having a negligible decrease in accuracy. The GPU does offer a more efficient platform for computationally extensive digital surface modelling applications. View full abstract»

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    Modified quasi-one-junction SQUID and read-out system as a comparator for high speed analog-to-digital conversion

    Powell, I.A. ; Perold, W.J.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821951
    Publication Year: 1999 , Page(s): 1203 - 1208 vol.2

    IEEE Conference Publications

    We have designed and simulated a comparator, based on the quasi-one-junction superconducting quantum interference device (SQUID) and a non-symmetrical two-junction SQUID read-out system. This comparator can be utilized to construct an n-bit analog-to-digital convertor with only n comparators. The theoretical input bandwidth is in the GHz range View full abstract»

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    A rapid technique for stator resistance extraction using key features of pseudorandom modified PWM fed induction motor impulse responses

    Benil, L. ; Burton, B. ; Hatley, R.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406869
    Publication Year: 2004 , Page(s): 1155 - 1159 Vol.2

    IEEE Conference Publications

    This paper explains how the electrical impulse response of a VSI fed induction motor can be extracted online from normal working data if the normal PWM signals are slightly modified to introduce a small pseudorandom binary sequence (PRBS), from time to time when measurements are required. It also explains how generic templates can be fitted to the measured impulse responses to obtain adaptive estimates of certain electrical motor parameters. A case study presents simulated and measured results of online rotor speed and stator resistance estimations based on the impulse response method. A novel technique of direct parameter extraction based on certain key points on the impulse response curve is developed to rapidly, yet accurately predict online rotor speed and stator resistance, (under various loads from standstill to full speed), which can be used for sensorless thermal condition monitoring and protection. The paper also discusses possible implementations for line operated machines equipped with standard soft-starter hardware. View full abstract»

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    The possible applications of fuzzy logic for the treatment of conflicts in the dispositional tasks of railway traffic control centers

    Heray, T. ; Rozsa, G. ; Koczy, L.T.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401624
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    The handling of traffic conflicts of trains is rather complicated if full dynamic models are used. Often it is senseless to take into consideration all details of the motion equations and environmental parameters especially as the main parameters, like maximum speed of the trains involved are not exactly known. Also, a large number of noise type variables are always available. The paper proposes the use of the Mamdani type fuzzy rule based reasoning algorithm for handling railway traffic conflicts. The essential point is the granulation of all important parameters into a relatively small number of categories labeled by terms such as small, large, etc. This way the possible decisions for a concrete traffic conflict situation get various fuzzy weights after accumulation of all the fired rules. The final (non-fuzzy) decision is taken by choosing the option with the largest weight. A simplified example is presented for a delay and overtaking type conflict. View full abstract»

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    Error correction of frequency-selective fading channels with spectral nulls codes

    Ouahada, K. ; Ferreira, H.C. ; Snyders, A.J. ; Vinck, A.J.H. ; Swart, T.G.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401560
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (2)

    IEEE Conference Publications

    In this paper, we investigate a prior error correction technique for frequency selective fading channels. Spectral nulls codes with nulls at submultiple frequencies are used to avoid fades at the corresponding frequencies. Coincide the spectrum null at the corresponding fading frequency and playing with its wideness, will minimize the bit errors caused by the channel. View full abstract»

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