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    A novel LCD backligth with mixed white and colorful LEDs

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

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

    IEEE Conference Publications

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

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

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

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

    IEEE Conference Publications

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

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    Multiple access interference (MAI) canceller enhanced RAKE receiver for asynchronous CDMA system in multipath channels

    Chitamu, P.J.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820804
    Publication Year: 1999 , Page(s): 239 - 244 vol.1
    Cited by:  Patents (1)

    IEEE Conference Publications

    We propose and study a receiver structure for an asynchronous CDMA system which incorporates a MAI canceller in a RAKE receiver structure. The strong MAI components are first estimated along with the channel impulse responses and separate operations of MAI cancellation and RAKE combining performed. Results show that for a CDMA channel loading of about 17%, the proposed receiver structure has a better BER performance than when either the MAI canceller or the RAKE receiver is used on its own by over 2 dB for the MAI canceller and by over 4 dB for the RAKE receiver at 10 dB Eb/N0 View full abstract»

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    Uplink MC-DS-CDMA using ZCZ sequences for frequency-selective block-fading channels

    Basilio, D.J. ; Linde, L.P. ; Maharaj, B.T.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308119
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    In this paper, a time and frequency (TF) domain spreading multicarrier direct sequence code division multiple access (MC-DS-CDMA) scheme employing zero correlation zone (ZCZ) sequences, designed specifically for quasi-synchronous uplink transmissions, is proposed to exploit frequency and temporal diversity in frequency-selective block-fading channels. This is in contrast to previously proposed schemes designed only to exploit frequency diversity in frequency-selective slow fading channels. Almost optimal quadriphase ZCZ sequences are employed to minimize multi-user interference (MUI) in the uplink channel. Joint detection is employed at the receiver using the optimal maximum likelihood (ML) detector and sub-optimal minimum mean square error (MMSE) detector. When using the ML detector, the proposed system showed a performance improvement of 2.7 dB at a BER of 10-4 over a previously proposed scheme designed only to exploit frequency diversity. View full abstract»

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    Point-to-point rural telephone system

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

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

    IEEE Conference Publications

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

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

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

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

    IEEE Conference Publications

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

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

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

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

    IEEE Conference Publications

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

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    Investigating the validity of the Czarnecki three phase power definitions

    Rens, A.P.J. ; Swart, P.H.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160019
    Publication Year: 2002 , Page(s): 815 - 821 vol.2

    IEEE Conference Publications

    Nonsinusoidal conditions in modern power systems require special definitions to quantify power. A clear physical interpretation of different conditions, leading to different phenomena, is essential to enable engineers to relate power measurements to meaningful physical manifestations in the power network with the objective of tariff implementation and the design of compensation strategies. L.S. Czarnecki originated a number of unique power definitions in the frequency domain that conform very well to these requirements. Unfortunately an important, but hitherto neglected deficiency appears to be present in the Czarnecki definitions: under practical conditions, the summation of power in three-phase networks with distorted waveforms yields erroneous results. This paper investigates this important inherent deficiency of the Czarnecki power theory. View full abstract»

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    What will customers demand of a new entrant telecommunications operator?

    Kennedy, I.G. ; Chitamu, P.J. ; Van Olst, R.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146881
    Publication Year: 2002 , Page(s): 457 - 460 vol.1

    IEEE Conference Publications

    As part of its business plan, a new entrant operator (NEO) that is planning to enter an existing telecommunications marketplace will carefully analyse the demographics and demand patterns of its potential customers. The NEO will source the components of the network to meet this demand. This paper models the temporal and spatial characteristics of the likely demand. View full abstract»

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    Implementation of a primary tapped transformer in a high frequency isolated power converter

    Joannou, A.J.L. ; Pentz, D.C.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072058
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    On load, transformer primary tap changing is not common in high frequency converters. This paper investigates a new converter topology to drive primary tapped transformers. The ideas that have been introduced previously are simply implemented into existing converter topologies which have been modified to accommodate a primary tapped transformer. The effects of efficiency with variation of source voltage and duty cycle are studied. It is shown that this topology can maintain a load voltage for a much wider source voltage variation without major sacrifices in efficiency. View full abstract»

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    Why electronic and not electromechanical ELCBs ?

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

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

    IEEE Conference Publications

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

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    The use of screen printed electrodes for the sensing of cell responses

    Brischwein, M. ; Herrmann, S. ; Vonau, W. ; Berthold, F. ; Grothe, H. ; Motrescu, E.R. ; Wolf, B.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401543
    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (4)

    IEEE Conference Publications

    Impedance sensors in thick film technology have been tested as a tool for testing cell-mediated effects. The screen printed Pt electrodes have a width of 250-400 mum. Electrodes and the surrounding ceramic chip substrate could be homogeneously grown with L-929 and Hela cells. The performance of a screen printed interdigitated electrode structure (IDES) was compared with that of thin film structures with the same layout geometry. The thick film impedance sensors allowed to correctly record the morphological response of confluent Hela cell layers to stimulation with histamine. A thick film conductivity sensor also revealed impedance values which were dependent on cell growth on the electrode surface, even at a very low frequency range of ap1Hz. View full abstract»

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    Control for systems in the presence of actuator and sensor hysteresis

    Xinkai Chen ; Ozaki, T.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308174
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper studies the output control for a linear plant containing uncertain hysteresis nonlinearities both in actuator and sensor devices, where the hysteresis is represented by Prandtl-Ishlinskii model. A new adaptive control scheme is developed to compensate the uncertainties in the plant, the actuator and the sensor, and to generate an estimate of the plant output. The proposed control law ensures that all the signals in the closed-loop system are uniformly bounded. Furthermore, asymptotic zero tracking of the error between the estimated output and the desired output is guaranteed. The effectiveness of the proposed algorithm is shown by computer simulation. View full abstract»

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    Optimal pricing of telecomm services in a developing country: A game theoretical approach

    Sumbwanyambe, M. ; Nel, A.L. ; Clarke, W.A.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072082
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    Pricing is an important feature in preventing the misuse of any resource (specifically public resources) in a telecommunication network. The free-rider, tragedy of the anti-commons and tragedy of the commons problems can arise in the provision of public resources, when users of the resource have to contribute towards the cost of production. Selfish users in a group have the tendency to misrepresent preferences, so as to minimize their individual contributions and maximize their utilities, preventing the free rider and tragedy of the commons problems in telecommunications networks is crucial to prolonging the existence of a free or subsidized public resource. In this paper we develop a game theoretical approach to mitigating the free rider and tragedy of the commons problems in telecom networks. View full abstract»

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

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

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

    IEEE Conference Publications

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

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    Experience in using MALTLAB Power System Toolbox (PST) for transient stability study of an AC/DC interconnected power system

    Folly, K. ; Limbo, B.S.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401463
    Publication Year: 2007 , Page(s): 1 - 4
    Cited by:  Papers (1)

    IEEE Conference Publications

    This paper discusses the experience of the authors in using Matlab power system toolbox for the transient stability studies of an AC/DC interconnection power system. The modified two-area power system model with HVDC Link is used in the investigation. It is shown that as the AC line became weaker (as compared to the DC line), the transient stability of the interconnected AC/DC system is negatively affected. The use of power system stabilizer (PSS) was critical in maintaining the stability of the system. View full abstract»

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    Research solar power boat - data management and online visualization

    Leiner, R.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401548
    Publication Year: 2007 , Page(s): 1 - 5

    IEEE Conference Publications

    The solar power boat of the Faculty of Electrical Engineering and Information Technology, HTWG-Konstanz, University of Applied Sciences, Konstanz, Germany is driven by an electrical motor whose energy is solely provided by photovoltaic cells. Since long-time performance of photovoltaic cells and batteries in a marine application is unknown, an information-management-system (IMS) was developed to collect all relevant data from cells, batteries, motor and environment. Periodically the data is sent via internet to the main data store at the institute where it is processed and made available in a web page. Thus real-time data can be observed online as well as graphically displayed as a function of time. Communication on board is done via CAN-Bus. For the skipper, real-time data is also displayed in numeric and graphical form. 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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    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»

  • Freely Available from IEEE

    [Blank page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406775
    Publication Year: 2004 , Page(s): 704

    IEEE Conference Publications

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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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    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»

  • Freely Available from IEEE

    [Breaker page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406722
    Publication Year: 2004 , Page(s): 491

    IEEE Conference Publications

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    The role of open ims testbeds in complex service delivery platforms

    de Gouveia, F.C. ; Magedanz, T. ; Good, R. ; Ventura, N.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401492
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (3)

    IEEE Conference Publications

    Network convergence and the multimedia service provisioning platforms within next generation networks (NGN) are subjects of huge complexity and the required architecture is extremely expensive to implement. Network operators will find it difficult to commit the necessary capital expenditure unless the NGN architecture has been thoroughly tried and tested. To ensure early adoption of this convergence platform, low cost testbeds are needed to bring together various parties to research and develop the necessary architectures. The IP multimedia subsystem (IMS), defined by the 3rd Generation Partnership Project (3GPP) represents today the global service delivery platform (SDP) standard for providing multimedia applications in NGN. Knowing that the full potential of the IMS can only be revealed by the early non-discriminant provisioning of IMS know-how and related technologies to the different market players the Fraunhofer Institute FOKUS launched the "Open Source IMS Core" in November 2006, which is based on extensions to the SIP express router (SER) that cope with the SIP extensions specified by 3GPP. This paper describes the Open IMS Playground and the activities in progress and cooperation works between FOKUS and the University of Cape Town for establishing joint works on open issues within IMS research and development. View full abstract»

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    From theoretical and empirical constraints to synthetic experiments on symbol-based communication

    Loula, A. ; Ribeiro, S. ; Queiroz, J.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401501
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    Here we present an Alife experiment for the investigation of the emergence of self-organized symbol-based communication involving distributed interactions between artificial creatures. The set-up, design and synthesis of our creatures, along with the digital ecosystem, are theoretically based on Peircean pragmatic philosophy of sign and empirically informed by neuroethological evidence. View full abstract»

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    Antenna amplitude distributions for improved wireless power transmission efficiency

    Shaposhnikov, S.S. ; Vaganov, R.B. ; Voitovich, N.N.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159970
    Publication Year: 2002 , Page(s): 559 - 562 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    Here are discussed the methods and algorithms of the amplitude distribution synthesis needed for the increase of the wireless power transmission (WPT) efficiency. It is shown that the WPT efficiency is increased not only of the uniform or the taper distribution but and when the field intensity is raised at the edges of the radiating apertures. In this case the receiving antenna is illuminated uniformly enough and at the same time the level of the near side lobes is essentially decreased. Peculiarities of the requirements for the field are described. Algorithms of the phase and amplitude distribution are found. 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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    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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    The diffusion of a new technology into the marketplace implementing UMTS

    Engelbrecht, D. ; Pretorius, M.W.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406816
    Publication Year: 2004 , Page(s): 897 - 904 Vol.2

    IEEE Conference Publications

    One of the biggest challenges for the telecommunications environment has always been the introduction of a new technology into the market. Introducing a new technology in the market differs greatly from introducing a product as it is not tangible, which necessitates a different approach to the enabling of customers on a new technology. New technologies are generally expensive and therefore there is always a certain resistance in accepting these new technologies. In structuring the diffusion process to the customer at an early stage makes the acceptance of the new technology much easier and less painful. Through tapping into a worldwide base of technology sharing, a company can benefit tremendously from new and innovative solutions that can be utilised in order to apply a technology in the South African market. One such technology is UMTS (Universal Mobile Telecommunication System). 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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    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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    Four dimensional modem employing complex spreading sequences

    Marx, F.E. ; Linde, L.P.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820800
    Publication Year: 1999 , Page(s): 221 - 226 vol.1

    IEEE Conference Publications

    In this paper a description and analysis of a four dimensional direct sequence spread spectrum (DS-SS) modem structure (Linde and Marx, 1999) employing complex spreading sequences (CSS), is presented. A description of the the four dimensional DS-SS transmitter as well as the receiver is given. The synchronization loops, including the four dimensional decision-directed Costas carrier recovery loop (DD-CGRL) and four dimensional decision-directed complex delay-locked-loop (CDLL) (De Gaudenzi and Luise 1991) are analysed and presented. The whole system is simulated and the simulation results as well as the performance in AWGN, which is comparable with a conventional BPSK SS modem, are shown View full abstract»

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

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

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

    IEEE Conference Publications

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

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    Software development for DSP implementation of GMSK modulation for GSM transceiver

    Youssef, N. ; Ghazel, A. ; Tabbane, S. ; Zhili, M.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820838
    Publication Year: 1999 , Page(s): 321 - 326 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    This work deals with software radio. It presents an implementation of a GMSK transmitter and receiver algorithms for the GSM system on a fixed-point 16 bit-33MIPS Analog Devices DSP. By an optimal software design that takes the maximum advantages from DSP architecture facilities, good real time experimental performances have been obtained for the GMSK modem implemented modules View full abstract»

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    Cancellation and error correction for narrowband interference with spectral nulls codes and OFDM modulation

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

    DOI: 10.1109/AFRCON.2007.4401559
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (2)

    IEEE Conference Publications

    Distance preserving mappings (DPM) is a relatively new technique finding its way to a wide use in the coding field. New codes mapping convolutional code outputs onto spectral nulls codewords have the purpose of generating a code with a certain spectrum specification and error correction capabilities, which can be exploited by the Viterbi decoder. Combining this class of new codes with an OFDM modulation scheme is actually a tool to reduce electromagnetic compatibility interference (EMC) in selected subbands or to cancel the narrowband interference (NBI) potentially caused by, amongst others, HF radio transmissions. Taking into consideration the fact that a narrowband noise source is almost similar to a modulated OFDM carrier, and also the periodicity of the nulls in our spectrum, we are able to cancel the narrowband signal and its sideband interferences without using traditional techniques of cancellation, which is based on filtering. Shaping our spectrum at the transmitter is a technique, which can be exploited at the receiver to suppress any narrowband signal interference, which is regarded as noise. We will present in this paper the technique of cancellation and the coding gain that can be obtained when comparing to the uncoded data. View full abstract»

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    Modeling and analysis of a multibus reticulation network with multiple DG. Part I. Electrical losses

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

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406796
    Publication Year: 2004 , Page(s): 805 - 810 Vol.2

    IEEE Conference Publications

    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 paper presents the modeling and analysis of a multibus reticulation network model with multiple distributed generation (DG) injection. Results for steady-state dynamic performance and optimum location of generator for minimum network losses are presented. 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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    Fusing theory and practical in a curriculum for engineering students - A case study

    Swart, J. ; Sutherland, T.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401497
    Publication Year: 2007 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    Engineering students at the Vaal University of Technology are exposed to both theoretical and practical instruction within their specified disciplines. This provides the students with greater learning opportunities, which is a core academic function of a university of technology. The department of Electronic Engineering comprises one of eight departments within the Faculty of Engineering and Technology that emphasizes the importance of practical instruction for engineering students. This department focuses primarily on finding solutions to industrial problems in the power electronics and telecommunications world. This paper will attempt to highlight the importance of fusing theory and practical in a curriculum for engineering students. Two different approaches exist in this regard, namely presenting the theory before the practical and the practical before the theory. Both approaches were included in a module, Radio Engineering III, which serves as the case study for this paper. It comprises five different theory sections and 10 practical assignments. Most of the engineering students enrolled for this module successfully completed the practical work, which was designed with both approaches in mind. A post-practical survey revealed that the students felt that the practical work done in the laboratory was relevant to the theory work done in the classroom. It also revealed that students enjoyed the practical work, acquiring needed skills relevant to their engineering discipline. View full abstract»

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    A novel technique for non-volatile data storage using avalanche degradation

    Schoeman, J.F. ; du Plessis, M.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146872
    Publication Year: 2002 , Page(s): 411 - 414 vol.1

    IEEE Conference Publications

    A novel bipolar EEPROM is presented. Data can be stored in bipolar transistors or diodes by using avalanche degradation to alter junction characteristics. The relative ease of manipulating breakdown voltages makes it easier to design devices to operate with low programming voltages. Various two and three junction devices are analysed for non-volatile storage characteristics. View full abstract»

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    Using parallel-interconnected Viterbi decoders to correct insertion/deletion errors

    Swart, Theo G. ; Ferreira, H.C. ; dos Santos, M.P.F.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406688
    Publication Year: 2004 , Page(s): 341 - 344 Vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    We present a new insertion/deletion correction scheme for standard convolutional codes that makes use of multiple interconnected parallel Viterbi decoders. Whenever an insertion or deletion error occurs, the connections between different Viterbi decoders ensure that decoding proceeds from the decoder that is in synchronization. In this way, a larger Viterbi decoder is created that can correct insertion and/or deletion errors by extending the Viterbi algorithm to encompass all parallel decoders. Further, we show how the performance can be improved by inverting certain bits during the encoding of the convolutional codes, thus lowering the frequency of occurrence for repeating sequences, which is detrimental to synchronization 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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    PID control of a nonlinear half-car active suspension system via force feedback

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

    DOI: 10.1109/AFRCON.2011.6071979
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (4)

    IEEE Conference Publications

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

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    Watermarking for JPEG image using error correction coding

    Hailing Zhu ; Clarke, W.A. ; Ferreira, H.C.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406657
    Publication Year: 2004 , Page(s): 191 - 196 Vol.1

    IEEE Conference Publications

    Compression is the most common process that limits the robustness of watermarking. We propose a watermarking method for JPEG compressed color images in the semi-decompression domain, using Reed-Solomon (RS) codes. The watermark embedding and recovery processes can be applied without decompressing the compressed file completely. There is no perceptible degradation between the watermarked image and the original image. Experimental results show that the scheme is robust against some distortion attacks and JPEG lossy compression with different compression rates View full abstract»

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    Design of a power factor correction ac-dc converter

    Ekemezie, P.N.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401519
    Publication Year: 2007 , Page(s): 1 - 8
    Cited by:  Papers (5)

    IEEE Conference Publications

    The need to keep EMI emissions by electronic power supplies below the limit specified by international standards have dictated that any new power supply design must include active power factor correction at the front end. The modern trend in power supply designs is towards digital control. This paper reports an effort to design a power factor correction AC-DC converter that is geared towards digital control. The power factor correction circuit employs zero voltage transition arrangement to minimize switching losses. Calculations that led to the selection of the circuit components are presented. Interface requirements between the power converter stage and the digital control processor are tackled. Average current mode control method is employed in the controller. The complete design has been tested by means of Powersim power electronics simulation software. The resulting input voltage and current waveforms show that the design is successful. View full abstract»

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    Design and development of an on-line vending system for selling prepaid electricity via the Internet

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

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406801
    Publication Year: 2004 , Page(s): 833 - 838 Vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    The vending of prepaid electricity is finding widespread use in South Africa. STS (Standard Transfer Specification) specifies the way that tokens are used in the vending of prepaid electricity. This paper describes the development and implementation of an on-line vending system based on the Internet, aimed at enhancing the current off-line CVS (Common Vending System) specification that is used to generate the tokens. The proposed enhancements allow existing and readily available TCP/IP network infrastructure to be used as a transport mechanism for the sale of tokens. The physical security of the system is also improved, since it is no longer necessary to provide vendors with security modules at the point of sale. The proposed on-line system is compatible with the large number of installed EDs (Electricity Dispensers). This paper further describes the PKI (Public Key Infrastructure) required to implement the system, as well as the set of interactive exchanges required for the communication over the Internet. View full abstract»

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    Estimating radiating current from digital PCB's with attached wire

    de Beer, A.S.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072044
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper shows the problematic aspects when estimating radiating current from digital PCB's with attached wires. Variances in the digital waveform, trasmission lines vs. lumped circuits, antenna ground interaction and antenna terminal impedance predictions were difficult to include in a simple lumped circuit model. View full abstract»

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    Multi-hop routing protocol for an intelligent transport application

    Morrison, D.W. ; Wolhuter, R.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401592
    Publication Year: 2007 , Page(s): 1 - 9

    IEEE Conference Publications

    The rapid growth of vehicular traffic in many countries around the world has caused chronic congestion of traffic networks in many cities. To manage traffic networks more effectively intelligent transport systems (ITS) are required, but these systems require a communication infrastructure to operate. The availability of communication infrastructure is often a problem, especially in third world countries. The work presented in this paper looks at how ad hoc wireless networks can contribute towards such infrastructure. Using components from existing routing protocols, an efficient tree-based ad hoc routing protocol is developed. It is also shown how this protocol can be optimised for use in a large communication network, as would be required by ITS systems. View full abstract»

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    Automatic licence plate recognition system

    Aghdasi, F. ; Ndungo, H.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406631
    Publication Year: 2004 , Page(s): 45 - 50 Vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    A machine vision system designed to recognize Botswana license plates is presented. The system has an average processing time of about 2.41 seconds. The techniques used to perform the detection and recognition are: colour filtering; Niblack binarisation; blob selection; segmentation; template matching; neural networks; Euler number; positional checks View full abstract»

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    Airborne satellite antenna mount and tracking systems

    Heev, S.D.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406676
    Publication Year: 2004 , Page(s): 289 - 295 Vol.1

    IEEE Conference Publications

    Communication mobile satellite antennas (MSA) are relatively large and heavy, especially airborne high gain antenna (HGA) systems for Inmarsat-H and HSD aircraft Earth stations (AES). Over the past decade, steering airborne antenna systems, which comprise a mechanical assembly, a control electronic system, a microwave electronic package and an antenna assembly (arrays and steering elements), have reduced considerably in physical size and weight. These reductions, brought about by greater EIRP from satellite transponders coupled with GaAs-FET technology at the receiver front end leading to higher G/N RF amplifiers, have initially made the fitting of shipborne antennas on trucks and airplanes a reality. A little later, airborne and vehicle-borne MSA were developed on the basis of these shipborne antennas. The MSA systems are required to be always pointed towards the satellite, in spite of vehicle motion. Therefore, the mount system is one of the main requirements, from the technical and rational viewpoints, in designing MSA systems. Several types of mount system are used, including mechanical and electrical among others, especially those concerned with shipborne MSA systems. In the case of airborne and vehicle-borne MSA, electrical pointing systems are preferable 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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    A projection-based joint probabilistic data association algorithm

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

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406621
    Publication Year: 2004 , Page(s): 13 - 17 Vol.1

    IEEE Conference Publications

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

  • Freely Available from IEEE

    1999 IEEE AFRICON - 5th AFRICON CONFERENCE IN AFRICA


    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821826
    Publication Year: 1999 , Page(s): iii - xiv

    IEEE Conference Publications

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    Performance analysis of MMSE ST-MUD of DS-CDMA with a correlated vector channel model

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

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146826
    Publication Year: 2002 , Page(s): 161 - 166 vol.1

    IEEE Conference Publications

    Space-time multiuser detection (ST-MUD) of DS- CDMA is studied in the context of a frequency selective Rayleigh fading vector channel model. The fading correlation between the antenna elements, and the multipath receiver architecture, necessitates a new technique for the computation of the bit error rate (BER). A simplified expression for the output signal-to-interference-plus-noise-ratio (SINR) is derived to this end, and a simulation of this SINR is used to compute the BER of the desired user. View full abstract»

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    Design and implementation of a topology control scheme for Wireless Mesh Networks

    Mudali, P. ; Nyandeni, T.C. ; Ntlatlapa, N. ; Adigun, M.O.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308242
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (5)

    IEEE Conference Publications

    The wireless mesh network (WMN) backbone is usually comprised of stationary nodes but the transient nature of wireless links results in changing network topologies. Topology Control (TC) aims to preserve network connectivity in ad hoc and mesh networks and an abundance of theoretical results on the effectiveness of TC exist. Practical evaluations of TC schemes that provide gradual transceiver power adjustments for the WMN backbone are however in their infancy. In this paper we investigate the feasibility of power control in a popular WMN backbone device and design and evaluate an autonomous, light-weight TC scheme called PlainTC. An indoor test-bed evaluation shows that PlainTC is able to maintain network connectivity, achieve significant transceiver power savings and reduce MAC-level contention but that no significant reductions in physical layer interference were realised. The evaluation has also highlighted the danger of associating power savings with network lifetime. Further larger-scale experiments are required to confirm these results. 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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    Neural network application in identification of decompositions of complex logic functions

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

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146806
    Publication Year: 2002 , Page(s): 59 - 64 vol.1

    IEEE Conference Publications

    An artificial neural network analysis is used to determine the disjunctive decompositions that yield the least intermediate field. The method, which can be adapted to various implementation primitives, is shown to effectively identify optimal decompositions. 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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    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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    Low density parity check irreducible Goppa codes

    Kubwalo, P.F. ; Ryan, J.A.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401460
    Publication Year: 2007 , Page(s): 1 - 8

    IEEE Conference Publications

    In this paper, whose earlier version was presented at SAMSA 05 conference, we present some of the results obtained in the on-going research on low density parity check (LDPC) irreducible Goppa codes. The objective of the research is to find irreducible Goppa codes with sparse parity check matrices to which LDPC decoding can be applied. If such codes are found then they would permit efficient encoding and decoding algorithms. We use two methods to come up with a sparse parity check matrix. The first method involves changing the basis of the splitting field of the Goppa polynomial. In the other method, we build the parity check matrix using low weight codewords in the dual code of the Goppa code. View full abstract»

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    A scanning tunneling microscope control system with potentiometric capability

    Bredekamp, A.H. ; Tapson, J.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820754
    Publication Year: 1999 , Page(s): 61 - 66 vol.1
    Cited by:  Patents (1)

    IEEE Conference Publications

    This paper describes the design of a scanning tunneling microscope (STM) control system and the addition of a high current, high frequency scanning tunneling potentiometry (STP) stage. This combination of STM and STP allows for the extraction of topographic and also potentiometric information in two dimensions on a sub-micron scale View full abstract»

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    The role of natural language in social information engineering

    Englmeier, K. ; Murtagh, F. ; Mothe, J. ; Pereira, J. ; Rosenberg, D.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072069
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    In this paper we present work-in-progress - a technology platform for Social Collaboration in the context of Personalized Information Extraction. In particular, we consider elements of user-centered software engineering as it converges on the development of folksonomies. Results from our work-in-progress demonstrate to what extent non-IT users can apply natural language when managing their IT-based processes addressing information integration. We concentrate on the language model that supports the development of process-related folksonomies in the context of retrieving and merging textual information from different sources concerning legal documents. Findings in our work-in-progress underpin the conjecture that the computational nature of natural language overcomes the inherent problem of ambiguity when applied in a collaboration context that the users are aware of. View full abstract»

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    Bit error probability performance of MIMO-OFDM in multi-tone interference

    Esli, C. ; Deliç, H. ; Koca, M.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401607
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    We consider an orthogonal space-frequency block coded (OSFBC) orthogonal frequency-division multiplexing (OFDM) system under multi-tone interference and multi-path fading environment. An approximate analytic expression for the bit error probability of OSFBC-OFDM system with a block code matrix for four transmit antennas is derived and the derivation methodology for other code matrices is summarized. The bit error rate simulations are performed for QPSK signals and compared with the theoretical results. The influences of the total energy of multi-tone interference and the fraction of interfered bandwidth are investigated. 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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    Rate-compatible pruned convolutional codes and Viterbi decoding with the Levenshtein distance metric applied to channels with insertion, deletion, and substitution errors

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

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

    IEEE Conference Publications

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

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    Optimization of resources for H.323 endpoints and terminals over VoIP networks

    Nlend, S. ; Swart, Theo G. ; Clarke, W.A.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072160
    Publication Year: 2011 , Page(s): 1 - 5

    IEEE Conference Publications

    We suggest a method of optimizing resource allocation for real time protocol traffic in general, and VoIP in particular, within an H.323 environment. There are two options in the packet network to allocate resources: aggregate peak demand and statistical multiplexing. Statistical multiplexing, our choice for this case, allows the efficient use of the network resources but however exhibits greater packet delay variation and packet transfer delay. These delays are often the result of correlations or time dependency experienced by the system's queue due to the variations observed in different point processes that occur at a point of time. To address these issues, we suggest a queuing method based on the diffusion process approximated by Orstein-Ulenbeck and the non-validated results of Ren and Kobayashi. View full abstract»

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    Particle size distribution determination using acoustic information

    Swanepoel, F. ; Weber, D.M. ; Metzner, G.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820840
    Publication Year: 1999 , Page(s): 327 - 330 vol.1

    IEEE Conference Publications

    A desire to increase the efficiency of the comminution process in mineral processing systems has led to the need of determining the size distribution of ore particles at various stages in the system. This paper presents a method to achieve this from the acoustic signal generated when the particles impact on a cantilever bar. The bar is modeled as a linear system which is excited by impulses (impact of particles). The response of the bar is deconvolved from the acoustic signal to obtain an impulse whose amplitude is proportional to the energy of the impact. The feasibility of various transducers and feature extraction techniques are investigated 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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    Simulator of an optical communication system

    Martins, M.J. ; Pereira, M. ; Fernandes, R. ; Goncalves, G.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401458
    Publication Year: 2007 , Page(s): 1 - 5

    IEEE Conference Publications

    The need for higher bandwidth in a global scale for the transmission of real-time video, will change the role of optical communication systems from the high bit-rate international and intercontinental digital networks to local area networks, using also the immunity of such systems to electromagnetic interference. However the proficiency of students of electrical engineering in optical systems is hampered by the cost and maintanence of university and high school optical labs. The computer simulator can constitute an answer for a portable, safe and low cost optical lab. This paper presents the framework of a functional simulator of an optical communication system. The blocks of such systems are represented by behavioural multilevel models with input, output and internal parameters. View full abstract»

  • Freely Available from IEEE

    [Blank page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406605
    Publication Year: 2004 , Page(s): 0_2

    IEEE Conference Publications

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    Analog-digital systems descriptions for signal processing and control application

    Zagursky, V. ; Gertners, A.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820785
    Publication Year: 1999 , Page(s): 159 - 163 vol.1

    IEEE Conference Publications

    The paper deals with two comparatively simple, but common, approaches to deal with real analog-digital systems (ADS). The first description is based on the decomposition of the static input-output characteristic, which is used to get properties for a wide class of nonlinearities, and it allows to calculate the output signal for any input signal. To deal with dynamics, coefficients of a differential equation are used. As a result, the behaviour of the object, which contains a nonlinear static part and linear dynamic part, can be described with a small set of parameters only and each of them can be estimated experimentally. The second description is based on a linear inertial stochastic model, which takes account of nonlinear and inertial conversion effects by introducing equivalent noise. This makes it possible to remain within the class of linear operators in normalizing the total dynamic response to allow for nonlinear properties of ADS. The simulation and experimental results confirmed the usefulness of the both descriptions utilizing the same coefficients of the differential equation estimated experimentally View full abstract»

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    Design, analysis and development of a multistage axial-flux permanent magnet synchronous machine

    Braid, J. ; van Zyl, A. ; Landy, C.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159993
    Publication Year: 2002 , Page(s): 675 - 680 vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    An axial-flux topology, together with the use of the strong coercive forces of today's rare-earth permanent magnets, combine to form machines suitable for high torque, low speed applications. A 3 kW single- and 6 kW double-stage machine was developed for the investigation into the improvement of the power-to-mass ratio in a multistage configuration. Producing torques of 36 Nm and 70 Nm respectively at 750 rpm, highlights their suitability for such applications, one being a direct in-wheel drive for an electric vehicle. View full abstract»

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    A soft approach to building recognition

    Levitt, S. ; Aghdasi, F.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820954
    Publication Year: 1999 , Page(s): 537 - 542 vol.1

    IEEE Conference Publications

    We examine different approaches to the task of building recognition. It is demonstrated that vagueness, uncertainty and imprecision affect any approach to this task. We address these factors by presenting a new soft approach to building recognition in the form of our fuzzy recognition system, called FuzzBuRS 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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    Simulating trade with renewable energy

    Kadar, P.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406849
    Publication Year: 2004 , Page(s): 1043 - 1047 Vol.2

    IEEE Conference Publications

    A triple face market simulator was developed in 2002 modelling the physical network, the market regulation and the financial processes of the deregulated electricity market (MEKSZ - Hungarian energy trade simulator). With the help of this tool different bidding, buying and trading strategies can be tested for power plants, distribution companies, large customers and traders. In the paper we introduce two simulation cases: effect of the small gas engines (recent case) and the operation of wind farms (planned). View full abstract»

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    Aperture theory and the equivalence theorem

    Booysen, A.J.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821915
    Publication Year: 1999 , Page(s): 1035 - 1040 vol.2

    IEEE Conference Publications

    It is shown that the conventional aperture theory formulation is mathematically incorrect and that in many standard textbooks image theory is incorrectly applied to equivalent sources in aperture problems. A rigorous new formulation is derived which yields exact results if the aperture fields are known exactly 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»

  • Freely Available from IEEE

    Presenting and principal authors (photos)


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

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160045
    Publication Year: 2002 , Page(s): 968 - 971

    IEEE Conference Publications

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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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    Effect of a dynamic force compensation in a low voltage vacuum circuit breaker

    Miedziński, B. ; Kowalski, Z. ; Jarosz, J.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160018
    Publication Year: 2002 , Page(s): 807 - 810 vol.2

    IEEE Conference Publications

    The paper presents and discusses the investigated results of performance of a LV circuit breaker under short circuit conditions in a case when a contact dynamic repulsive force is self-compensated by the load. View full abstract»

  • Freely Available from IEEE

    [Blank page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406790
    Publication Year: 2004 , Page(s): 782

    IEEE Conference Publications

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    University of Stellenbosch satellite ground station operation and future plans

    Barry, R.M. ; Nel, F.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146800
    Publication Year: 2002 , Page(s): 25 - 28 vol.1

    IEEE Conference Publications

    The purpose of this paper is to provide an overview of the past and current operations of the satellite ground station at the University of Stellenbosch. Future plans for upgrades to the station are also discussed. View full abstract»

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    Speed sensorless control of a converter-fed DC motor

    Jahmeerbacus, M.I. ; Oolun, M.K. ; Bhurtun, C. ; Soyjaudah, K.M.S.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820906
    Publication Year: 1999 , Page(s): 453 - 456 vol.1
    Cited by:  Papers (2)

    IEEE Conference Publications

    This paper presents a speed sensorless control scheme for a DC motor driven by a DC-DC converter. The proposed system is based on the computation of the motor speed from the converter output line parameters. The performance of the designed system is also evaluated View full abstract»

  • Freely Available from IEEE

    [Breaker page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406838
    Publication Year: 2004 , Page(s): 1001

    IEEE Conference Publications

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    An animal powered electricity generator for stand alone applications

    van Niekerk, H.R. ; Hancke, G.P.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821897
    Publication Year: 1999 , Page(s): 939 - 942 vol.2
    Cited by:  Patents (1)

    IEEE Conference Publications

    The paper presents an electricity generating system for remote, stand alone applications, which utilises a draught animal as the primary energy source. The features of a prototype generating system, comprising of a mechanical speed multiplier and a permanent magnet generator, are described. Preliminary results indicate that a minimum continuous power output of 200 W can be obtained View full abstract»

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    Controlling the design process for minimal life cycle cost

    Wahl, M.G. ; Bruck, R.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401487
    Publication Year: 2007 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper focuses on the area between design and management. This area is critical, because during the design phase many decisions are made that strongly influence the manufacturing process and thus finally the price. A continuous source of tension is the fact that engineers and managers sport different ways of approaching their work: Managers think in processes, whereas engineers prefer thinking in structural hierarchies. In this paper we describe the design process and, as an example, a standard management approach. Further on, we de-scribe a set of cost factors that finally go into the cost models that allow a cost estimation at an early design stage. At the end of the paper, we present a tool that is capable of dealing with cost estimations based on imprecise data, which are typical for the design phase of a product's life. View full abstract»

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    Brushless DC motor characterisation and selection for a fixed wing UAV

    Gabriel, D.L. ; Meyer, J. ; Du Plessis, F.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072087
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    The aim of the paper is to present a method for evaluating brushless DC motors (BLDC) for fixed wing Unmanned Aerial Vehicles (UAVs). Selection of a BLDC motor, which operates in its efficient region for a UAV platform's specifications, will affect the endurance capabilities of the UAV platform. A four-constant model is presented as a means of modelling and predicting the characteristics of BLDC motors. Further, physical testing of each motor is performed on a constructed motor test bench. Validation of the model's results is compared to physical testing. The methods presented provide a means of accurately characterising a given BLDC motor. This data can be used to design the additional components used in the UAV's propulsion system. View full abstract»

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    Hybridisation of MoM and GMT for the numerical analysis of electromagnetic sources radiating in the vicinity of persons with implanted cardiac pacemakers

    Jakobus, U. ; Ruoss, H.-O. ; Geisbusch, L. ; Landstorfer, F.M.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821916
    Publication Year: 1999 , Page(s): 1041 - 1044 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    An iterative combination of the MoM (method of moments) and the GMT (generalised multipole technique) is presented for the analysis of electromagnetic sources radiating close to a human body with implanted cardiac pacemaker. The metallic parts (source and pacemaker) are treated by MoM, while the influence of the smooth dielectric body is taken into account by GMT View full abstract»

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    A statistical method to minimize electrical energy losses in a local electricity distribution network

    Fourie, J.W. ; Calmeyer, J.E.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406768
    Publication Year: 2004 , Page(s): 667 - 673 Vol.2
    Cited by:  Papers (12)

    IEEE Conference Publications

    A focus area of energy management research is the reduction of electrical energy losses occurring in an electricity distribution network. These losses are the technical and nontechnical losses. Reducing these losses ensure that the cost of electricity to customers will be reduced and in turn the efficiency of the distribution network will be improved. The model developed minimizes the nontechnical electrical energy losses of an electrical distribution network. This model simulates the electrical distribution network and includes different parameters that calculate the estimated technical losses of the electricity distribution network. The model is used as a base for developing a strategy that minimizes the electrical energy losses of an electrical distribution network. 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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    Transport telematics and road pricing

    Knipping, O.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820668
    Publication Year: 1999 , Page(s): 13 - 14 vol.1

    IEEE Conference Publications

    The past decades have seen governments providing the transport infrastructure in all European countries. This paper examines the theoretical implications of a private road network instead of a public one and the essential role of transport telematics in order to develop a successful private road infrastructure 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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    RoboCup Junior: A vehicle for S&T education in Africa?

    Ferrein, A. ; Marais, S. ; Potgieter, A. ; Steinbauer, G.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072136
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    One of the challenges of the 21st century is to prepare learners for the rising technological challenges in jobs and daily life. In order to be able to do so curiosity and motivation of the learners have to be stimulated. There exist initiatives such as the First Lego League or RoboCupJunior to spark interest in youngsters for science and technology. In a playful way, the children get into contact with technology and become more interested in these fields. In this paper we report on the experiences of the South African RoboCupJunior Rescue team AmaJukuJuku that participated in the 2010 RoboCupJunior in Singapore. From the first-hand experiences of this group of learners with a disadvantaged learning background, we show the positive effects and argue that such initiatives are helpful and important, particularly in the African context. We propose a scheme how such initiatives could be undertaken in the whole of Africa. View full abstract»

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    A comparative study on fault detection and correction techniques on active magnetic bearing systems

    Gouws, R. ; van Schoor, G.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401494
    Publication Year: 2007 , Page(s): 1 - 10

    IEEE Conference Publications

    In this paper, the authors distinguish between three real-time fault detection, correction and identification schemes for vibration forces on the rotor of a rotational active magnetic bearing (AMB) system. Historical fault data obtained from a fully suspended 250 kW water cooling AMB pump was used in the design process of the three schemes. The real-time schemes perform three main tasks: 1) fault detection, 2) fault diagnosis and error correction and 3) fault identification. Displacement and current masking were performed during the fault detection stage and the vibratory amplitudes and frequencies were extracted by means of the Wigner-Ville distribution. Pattern recognition techniques, statistical diagnosis and fuzzy logic were used to calculate fault features during the fault diagnosis and error correction stages. During the fault identification stage, data fitting, fuzzy logic and ISO standards were used to calculate the type, parameters, vibratory level and zone of the vibration force. A comparison between the experimental results obtained from a double radial AMB test rack was performed to demonstrate the effectiveness of the proposed schemes in the real-time detection, correction and identification of vibration forces on the rotor of a rotational AMB system. The three real-time schemes were able to correct and minimize vibration forces to a stable working condition. 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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    Development of a gaming strategy for soccer robots using optimal methods

    Du Plessis, W. ; Craig, I.K.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146810
    Publication Year: 2002 , Page(s): 81 - 84 vol.1

    IEEE Conference Publications

    The purpose of this paper is to develop a software gaming strategy for soccer robots in the MiroSot league of the FIRA organisation. The paper describes the development of the strategy from the first principles of robot control to the implementation of a global playing strategy. View full abstract»

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    An evaluation of configuration parameters affecting network coding on the data link layer in a wireless network

    van Wyk, J.L. ; Helberg, A.S.J. ; Grobler, M.J.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072133
    Publication Year: 2011 , Page(s): 1 - 5

    IEEE Conference Publications

    Network Coding, introduced in [2], promises significant theoretical capacity gains in multicast networks. Practical implementations in underlay networks are however quite complex in practice and performance is subject to many network variables. In this paper we model a network coding function at the data link layer of an 802.11g wireless node and evaluate the network coding performance for certain well known network coding topologies. We evaluate the throughput in a simulated ad hoc wireless network using the OPNET® Modeler and show the effect of various network parameters on the fraction of network coded data. 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»

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    Projection statistics for power system state estimation

    Els, S.L. ; Els, A.D. ; Jordaan, J.A. ; Zivanovic, R.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821867
    Publication Year: 1999 , Page(s): 783 - 786 vol.2

    IEEE Conference Publications

    This paper presents the use of projection statistics method to detect and downweight leverage points that appear in power system state estimation. A 14-bus system is used to compare the difference between a state estimator using projection statistics and one not using projection statistics View full abstract»

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    On the importance of systems-oriented education in engineering

    Yurtseven, M.K. ; Buchanan, W.W.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146877
    Publication Year: 2002 , Page(s): 437 - 441 vol.1

    IEEE Conference Publications

    This paper addresses one of the important dilemmas in engineering education: how to educate engineering students in the area of systems thinking or systems approach. A framework is presented in which the authors describe how the systems-oriented topics can be integrated into an engineering program to enable students to design "messy" socio-technical systems from a systems point of view. View full abstract»

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