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    Energy consumption of air conditioners at different temperature set points

    Wang, N. ; Zhang, J. ; Xia, X.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072174
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    Energy saving in air conditioners is a primary concern in building projects, since a large proportion of the energy consumption in building service equipment is caused by air conditioners. The energy-saving research in air conditioners focuses mostly on the chiller system and the associated control strategies. For air conditioners in buildings, the thermal control strategy to adjust the temperature set point is very easy to implement and very effective in energy saving. In this paper an energy consumption calculation model of a data center in South Africa is presented to estimate the energy consumptions of air conditioners when the temperature set points are 22°C and 23°C. View full abstract»

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    Formalizing certain tasks for processor architecture verification

    Shah, A.K. ; Al-Mazyad, A. ; Ramani, A.K.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308179
    Publication Year: 2009 , Page(s): 1 - 4

    IEEE Conference Publications

    Present day verification is a time consuming task. With processor architecture complexity increasing by the day, managing the complete verification process has become a major challenge. Besides, a small bug in the final product may ruin all the efforts. This problem has resulted in the popularity of verification and other related technologies. For example formal verification is now considered as an important part of any verification process. Similarly other technologies and methodologies are gaining acceptance. However, despite all these tools and technologies, verification still remains the main bottleneck and challenge in the overall process for the development of a modern processor. This problem can be looked from a different angle. We believe that a proper strategy is equally important for the verification efforts to succeed. The strategy will be easier once we formalize certain aspects of the process. This paper is an attempt to formalize some of the important aspects, ideas and methodologies towards the verification of processor architecture. 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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    Two hardware implementations of the group operations necessary for implementing an elliptic curve cryptosystem over a characteristic two finite field

    Potgieter, M.J. ; van Dyk, B.J.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146831
    Publication Year: 2002 , Page(s): 187 - 192 vol.1
    Cited by:  Papers (2)

    IEEE Conference Publications

    Two FPGA (field-programmable gate array) implementations of the elliptic curve scalar multiplication operation are presented. The main design objective influencing all implementation decisions was complete scalability. Scalability refers to being able to change both the field size and the elliptic curve parameters without reprogramming the hardware. Measures were taken during the design process to ensure near-optimal performance for the set of algorithms used despite the scalable nature of the hardware. A new field multiplication algorithm is used in one of the implementations, improving performance by approximately 50%. View full abstract»

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    A comparison of glass cap and pin, silicone rubber and EPDM rubber insulators over a four day period at Koeberg Insulator Pollution Test Station

    Vosloo, W.L.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821860
    Publication Year: 1999 , Page(s): 743 - 748 vol.2
    Cited by:  Papers (5)

    IEEE Conference Publications

    Three 22 kV insulators with similar creepage lengths (glass, silicone rubber and EPDM rubber, the last two having identical profiles) were energised at Koeberg Insulator Pollution Test Station. Data are presented for a humid four day period, including leakage current and weather data. The interaction of the environment and the insulators is discussed View full abstract»

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    The prediction of insulator leakage currents from environmental data

    Vosloo, W.L. ; Holtzhausen, J.P.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159978
    Publication Year: 2002 , Page(s): 603 - 608 vol.2
    Cited by:  Papers (4)

    IEEE Conference Publications

    The leakage currents of various insulators were monitored together with environmental data at a coastal test site. In addition the daily maximum surface, conductivity was measured. In this paper it is shown how, using multiple regression, the leakage current can be predicted from the measured weather and environmental parameters. View full abstract»

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

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

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

    IEEE Conference Publications

    Studies of the visual cortex of cats highlight the role of temporal processing using synchronous oscillations for object identification. In this paper, a modified Eckhorn pulse coupled neural network model, the Computer-Model Cortex Neural Network, is used as a preprocessor to a neural network classifier for the condition monitoring of power transformers View full abstract»

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    Wire antenna model of the human body exposed to the low frequency electromagnetic field

    Roje, V. ; Poljak, D.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821917
    Publication Year: 1999 , Page(s): 1045 - 1048 vol.2

    IEEE Conference Publications

    A simplified model of the human body immersed in an electromagnetic field is considered. The body is represented by a cylindrical scatterer placed vertically on a perfect ground, according to the wire antenna theory. The Pocklington type integral equation with exact kernel is solved by the boundary element method. Modifying the Green's function the influence of the body loss is discussed View full abstract»

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    Neural stator flux estimator with dynamical signal preprocessing

    Grzesiak, L.M. ; Ufnalski, B.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406866
    Publication Year: 2004 , Page(s): 1137 - 1142 Vol.2
    Cited by:  Papers (6)

    IEEE Conference Publications

    This work presents a novel method of stator flux estimation for induction motor, using artificial neural networks. Proposed estimation scheme can be employed in any vector controlled drive, e.g. DTC (direct torque control) or SFOC (stator field oriented control) drive. It does not exploit pure integration, therefore there is no problem with drift and initial conditions. Moreover, it does not require any stator resistance adaptation algorithm. A multilayer perceptron is trained off-line to approximate stator flux space vector. The approximation space is spanned by stator voltages and currents preprocessed with different low-pass filters. The performance of the SFOC drive with the above stator flux estimator has been investigated in simulation. The results seem to be very promising. Developed estimator is quite insensitive to the stator resistance variations. View full abstract»

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

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

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

    IEEE Conference Publications

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

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    Development of research capacity in HVDC technology in southern Africa

    Ijumba, N.M. ; Britten, A.C. ; Rajpal, L. ; Pillay, L.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406787
    Publication Year: 2004 , Page(s): 765 - 768 Vol.2

    IEEE Conference Publications

    High voltage direct current (HVDC) schemes are increasingly being applied world-wide to deliver large amounts of power over long distances. Two of such schemes are in Africa. It is envisaged that in the next 5-10 years, the continent will an additional HVDC scheme, delivering power to the southern Africa region, from central Africa. Many of the utilities in the SADC region have limited skills and experience in HVDC technology. So it is essential to build capacity in this field, to enable the utilities to manage the technology. The HVDC centre was established at the University of KwaZulu-Natal for the purpose of capacity building through research and training. This paper discusses the development and management of the centre with regard its develop objectives. View full abstract»

  • Freely Available from IEEE

    [Blank page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406766
    Publication Year: 2004 , Page(s): 660

    IEEE Conference Publications

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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»

  • Freely Available from IEEE

    [Breaker page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406807
    Publication Year: 2004 , Page(s): 853

    IEEE Conference Publications

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    Active microstrip antenna for mobile system communication

    Wnuk, M. ; Kolosowski, W. ; Amanowicz, M. ; Rozanski, G.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821925
    Publication Year: 1999 , Page(s): 1087 - 1091 vol.2

    IEEE Conference Publications

    Recent years have seen a rapid development of mobile communications systems. Therefore, protection of the user, and especially his head, against non-ionizing electromagnetic radiation generated by mobile telephones is an urgent problem, Presented in this paper is the performance of newly developed microstrip antennas with reduced radiation towards the user's head, View full abstract»

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    Mechatronic and computational intelligence

    Schroder, D.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401513
    Publication Year: 2007 , Page(s): 1 - 6

    IEEE Conference Publications

    In this paper we present identification methods for nonlinear mechatronic systems. First, we consider a system consisting of a known linear part and an unknown static nonlinearity. With this approach, using an intelligent observer, it is possible to identify the nonlinear characteristic and to estimate all unmeasurable system states. The identification result of the nonlinearity and the estimated system states are used to improve the controller performance. Secondly, the first approach is extended to systems where both, the linear parameters and the nonlinear characteristic are unknown. This is achieved by implementing the intelligent observer as a structured recurrent neural network. View full abstract»

  • Freely Available from IEEE

    [Blank page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406808
    Publication Year: 2004 , Page(s): 854

    IEEE Conference Publications

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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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    Neurocontrol of turbogenerators with adaptive critic designs

    Venayagamoorthy, G.K. ; Wunsch, D.C. ; Harley, R.G.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820927
    Publication Year: 1999 , Page(s): 489 - 494 vol.1

    IEEE Conference Publications

    This paper presents the design of a neuro-controller for a turbogenerator using a novel technique based on adaptive critic designs (ACD). This adaptive critic design based neuro-controller augments/replaces the traditional automatic voltage regulator (AVR) and the turbine governor of the generator. Simulation results are presented to show that neural network controllers with the ACD have the potential to control turbogenerators when system conditions and configuration changes View full abstract»

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    Modeling and analysis of a multibus reticulation network with multiple DG. Part III. economic dispatch

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

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

    IEEE Conference Publications

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

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    Optimised asynchronous self-timing for superconducting RSFQ logic circuits

    Gerber, H.R. ; Fourie, C.J. ; Perold, W.J.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406739
    Publication Year: 2004 , Page(s): 551 - 556 Vol.1
    Cited by:  Papers (2)

    IEEE Conference Publications

    Rapid single flux quantum (RSFQ) logic is a digital circuit technology that in recent years has presented itself as an alternative to semiconductors in the application of ultra high speed, very low power applications. The optimal timing of digital circuits operating at hundreds of GHz is still a complex problem for both RSFQ and semiconductor technologies. The fact that most RSFQ gates require a clock signal to function makes this even more complex. Various RSFQ timing schemes have been adapted from semiconductor design methodologies, and some have been designed specifically for RSFQ. Currently, synchronous clocking schemes outperform other schemes, but with the scale of RSFQ circuits ever increasing, the proper use of timing schemes are becoming more crucial. This paper describes a new asynchronous self-timing scheme where the details of clock distribution and clocking are built into the logic gates. Tests were done on the newly developed asynchronous logic gates and an asynchronous full adder was implemented and tested View full abstract»

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    Effect of the current controller of a converter driven synchronous generator on the transient stability of a power system

    Khomari, M. ; Folly, K.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308109
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper investigates the impact of the voltage source converter (VSC) current controller of a converter driven synchronous generator on the transient stability of a power system. The transient disturbance which the power network is exposed to is that of a three-phase short circuit. The transient response of the power system is firstly observed with system controllers' i.e. Automatic voltage regulator (AVR) and speed governor and without system controllers while the current controller was inactive. The transient response of the power network is then analyzed under similar power system control scenarios with the VSC current controller engaged. The results highlight how the VSC current controller improves on the power systems transient stability. View full abstract»

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    Pedagogical outlines for OLPC initiatives: A case of Ukombozi school in Tanzania

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

    DOI: 10.1109/AFRCON.2011.6072084
    Publication Year: 2011 , Page(s): 1 - 7
    Cited by:  Papers (3)

    IEEE Conference Publications

    One-to-one computing initiatives in developing countries have been criticized for ignoring pedagogical considerations and for lacking tight integration with the local educational context. Ukombozi primary school in Iringa, Tanzania, faced the same situation in 2009, when we received 100 laptop computers for pupils to use. Through a collaborative effort of local and foreign teachers we designed and tested a pedagogical approach which starts from the local educational context, and builds on theoretical literature and documented experiences of using one-to-one computing in the classroom. We developed student-centered, exploratory, and creative practices for classroom pedagogy, and we experimented on using individual (one-to-one) laptops as a support tool. We identified a number of challenges, too, and propose further research directions that extend one-to-one computer-assisted learning to other school subjects, also. This paper is aimed at educators who work and develop education in similar challenging environments, as well as educational technology researchers who wish to gain alternative views about pedagogical design. View full abstract»

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    The solid-state transformer concept: A new era in power distribution

    van der Merwe, J.W. ; du T.Mouton, H.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308264
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (10)

    IEEE Conference Publications

    This paper considers the solid-state transformer concept as a viable alternative to the line frequency transformer in distribution circuits. The benefits of the concept are presented in terms of improvements to problem areas currently experienced on distribution networks as well as envisaged future or fringe benefits. Some barriers to universal acceptance of the concept are also identified, with the effects of these barriers analysed and discussed below. View full abstract»

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    Measuring SET effects in a CMOS operational amplifier using a built-in detector

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

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

    IEEE Conference Publications

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

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    New hardware implementation of parallel 1D FFT

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

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146802
    Publication Year: 2002 , Page(s): 35 - 40 vol.1
    Cited by:  Patents (1)

    IEEE Conference Publications

    In this paper, we propose a new technique for the parallel implementation of 1D FFT. The paper allocates one two-port memory unit for each butterfly-processing unit. The two output words of the ith memory module are connected permanently to the inputs of the ith butterfly processor. The interconnection network used uses a limited number of two-way switches. This layout cancels completely the transposition operation required in all the existing implementations. The address generating system is very simple and results in conflict-free addressing. The proposed system reduces the total processing time and leaves the results in the different memory modules arranged in the natural order that saves another transposition operation normally used with existing systems. View full abstract»

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    Loss reduction in generalised multilevel converters

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

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

    IEEE Conference Publications

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

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    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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    Earth current memory sensor for use in power distribution lines

    Nderu, J.N. ; Soeda, M. ; Yamasaki, J.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159984
    Publication Year: 2002 , Page(s): 635 - 638 vol.2

    IEEE Conference Publications

    This paper discusses an earth current memory sensor (for use in power distribution lines) that we have suggested, constructed and evaluated. The sensor employs a semi-hard magnetic material to record whether there has been an earth current in a given earthing conductor or not, and an amorphous magnetostrictive metal wire to retrieve the information stored in the memory (semi-hard material). So far we have achieved a sensitivity of 6 A. The sensor permanently stores the information of an earth current, making it possible to retrieve the information even long after the earth current has ceased. Furthermore, the sensor is fairly cheap to be viable for installation on each and every distribution line pole without significantly increasing the cost. View full abstract»

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    Energy optimization based path selection algorithm for IEEE 802.11s Wireless Mesh Networks

    Mhlanga, M.M. ; Olwal, T.O. ; Mutanga, M.B. ; Adigun, M.O.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072125
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (2)

    IEEE Conference Publications

    It is everyone's dream to have network connectivity anywhere at all times. This dream can only be realized provided there are feasible solutions that are put in place for the next generation of wireless works. Wireless Mesh Networks (WMNs) configures itself and because of its cost effectiveness, it is therefore seen as a solution for the next generation networks. However, this field still has a lot of limitations and the main constrain is that the energy of the nodes is very limited, especially when the network is deployed in rural areas where electricity is a scares resource. This research therefore presents an energy optimization based path selection algorithm for IEEE 802.11s WMNs which is aimed at addressing the above mentioned constrains. As a newly proposed standard specifically designed for WMN, the IEEE 802.11s does not consider energy conservation as a priority in its protocol. As a result, the main goal for this research is that paths with enough energy for transmission in the network must be selected when transmitting packets. Our simulation results obtained from the experiments prove that there is a substantial increase with regard to the network's operational time when energy is considered by the protocol used in IEEE 802.11s. View full abstract»

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

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

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

    IEEE Conference Publications

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

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    Space-time-polarization diversity in multiple-input multiple-output communication systems

    Kilic, Y. ; Koca, M. ; Anarim, E.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308186
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    In this work, we consider the use of multiple antenna signaling technologies, specifically space-time block coding (STBC) and spatial multiplexing (SM) schemes, in multiple-input multiple-output (MIMO) communication systems employing dual polarized antennas at both ends. The use of dual-polarized antennas theoretically double the number of virtual antennas used in the system. On the other hand, the correlation effects and the cross-polar discrimination (XPD) deteriorates the system performance. In our work, we consider these effects and present performance analysis of a 2 times 2 system with dual-polarized antennas for both STBC and SM cases. We also present simulation results for both multi-antenna signalling techniques together with hybrid approaches under various XPD and correlation scenarios. Both the theoretical analysis and the simulation results show a significant performance gain by joint utilization of space, time and polarization diversity in comparison to uni-polarized systems with the same number of antennas. View full abstract»

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    Intelligent static VAr compensator control for supply loading optimization

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

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

    IEEE Conference Publications

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

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    A novel DC-DC converter for low voltage ratio conversion

    van der Linde, R. ; Hofsajer, I.W. ; Ferreira, J.A.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160003
    Publication Year: 2002 , Page(s): 723 - 728 vol.2

    IEEE Conference Publications

    A new DC-DC converter topology for low voltage ratio conversion is presented. The standard boost converter is the topology of choice for low voltage ratio conversion applications where galvanic isolation is not a requirement. The standard boost has low switch utilization and poor efficiency, especially at high current and high switching frequencies. The new topology presented incorporates the principle of an autotransformer in order to reduce the stress on the switching devices. The operating modes of the converter and design equations are presented. The new converter is compared with the standard boost converter. View full abstract»

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

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

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

    IEEE Conference Publications

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

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    Loss models of photovoltaic water pumping systems

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

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

    IEEE Conference Publications

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

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    Load modeling

    Coker, M.L. ; Kgasoane, H.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821844
    Publication Year: 1999 , Page(s): 663 - 668 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    Load characteristics have a significant effect on the performance of a power system. Load flow, transient and voltage stability results are known to be highly dependent upon the load characteristics assumed. This paper deals with the calculation of representative static and dynamic load models based on component based methods for computer simulation packages 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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    Sensors signal processing using neural networks

    Golovko, V. ; Grandinetti, L. ; Kochan, V. ; Laopoulos, T. ; Sachenko, A. ; Turchenko, V.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820846
    Publication Year: 1999 , Page(s): 339 - 344 vol.1
    Cited by:  Papers (4)

    IEEE Conference Publications

    The authors proposed to use neural networks (single- and multi-layer perceptrons) for the prediction of measurement channel components (including sensors). This allows one to improve the processing quality of measurement information and the design of intelligent sensing instrumentation systems. The hardware and software of such systems, computer power distribution and processing algorithms are considered View full abstract»

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    Solid state opening switch requirements for standard inductive storage pulse forming networks

    van der Merwe, J.B. ; du T.Mouton, H.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821856
    Publication Year: 1999 , Page(s): 725 - 730 vol.2

    IEEE Conference Publications

    The commutation of energy from an inductive energy storage pulse forming network (PFN) to a load requires high power opening switches. The problems associated with this are numerous as requirements reach far into the tens of kA and kV. This paper examines the relationship between standard storage topologies and their opening switches, and draws attention to the possible problems one could encounter 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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    Effect of converter DC fault on the transient stability of a Multi-Machine Power System with HVDC transmission lines

    Oyedokun, D.T. ; Folly, K.A. ; Chowdhury, S.P.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308120
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (2)

    IEEE Conference Publications

    This paper deals with the effect of DC faults on the transient stability of a multi-machine power system with two transmission line configurations; HVDC and a hybrid HVAC-HVDC transmission line. The faults are located at the DC terminals of the HVDC converter station. In order to carry out this study, two case studies are presented. In the first case study a double HVDC transmission line is used to transmit 2000 MW to an area of the power system called Pookland which has a total load demand of 2440 MW. In case two, a parallel hybrid HVAC-HVDC transmission line is used to transmit the same amount of power to Pookland. In both cases, the impact of a short term converter DC fault on the transient stability of the entire system was investigated. This was done by studying the response of the rotor angle of G2 in Pookland, G3 in the Bing Coal plant and the voltage profile at the terminals of the generators to the DC fault at the HVDC converter station. Amongst other results, it was established that in case 1 which has a double HVDC transmission line, the rectifier side (in the Bing coal plant) has less rotor angle oscillations when compared to the inverter side (in Pookland), but the rectifier side took longer than the inverter side for the rotor angle of the generators to stabilize. In case 2, the voltage at G2 in Pookland took six times the amount of time it took G3 in the Bing coal plant to stabilize while the voltage in the Bing Coal plant dipped by 0.35 pu (smaller than case 1 which dipped by 0.4 pu). In conclusion, the converter DC fault had a smaller impact on the transient stability of the multi-machine power system when the hybrid HVAC-HVDC transmission line was adopted. View full abstract»

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    Flexible AC transmission systems simulation and control

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

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

    IEEE Conference Publications

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

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

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

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

    IEEE Conference Publications

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

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    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»

  • Freely Available from IEEE

    2004 IEEE AFRICON - 7th AFRICON Conference in Africa - Title Page


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406606
    Publication Year: 2004 , Page(s): 0_3

    IEEE Conference Publications

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    Power line telecommunications option in rural KwaZulu-Natal

    Mhlongo, T.E. ; Afullo, T.J.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406895
    Publication Year: 2004 , Page(s): 1263 - 1268 Vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    Since its introduction in the early 1990's, use of the Internet has exploded. Access to the Internet is fast becoming a need, not just a want, for most homeowners. Ethernet and phone line solutions provide fast, reliable service but require snaking cable to each connection. Network nodes must be identified and placed during construction of new homes. Considerable renovation is required to retrofit older homes or to place additional nodes. Wireless networks provide nodes everywhere. They are ideal for hand-held or battery-operated devices, but the addition of RF conversion hardware makes this an inherently costlier solution. Additionally, wireless networks suffer from security concerns and competing standards. Power line networking uses power lines existing in the home. Nodes are already available throughout the household, making it a low-cost solution. Each room in a residence possesses one, two, or more outlets. Any device requiring power will already be attached to the power line network making it convenient and accessible to low-tech users. Home network users seek three major factors in any solution: ease-of-use, low cost, and ubiquitous node availability. Power line networking delivers all three. So, while it is true that power line networking faces some technical hurdles, it remains a compelling choice. This work starts by describing the power line as a communication medium and then the problems encountered in the power line communication channel in terms of frequency response and noise characteristics. A transmission technique (OFDM) that avoids power line noise and uses the common modulation formats is also explained. Finally, traffic projections are also estimated based on Brady's measurements. View full abstract»

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    Implementation of arbitrarily high order hierarchical vector basis functions for the finite element analysis of a rectangular waveguide

    Lezar, E. ; Davidson, D.B.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401502
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (3)

    IEEE Conference Publications

    In any computational field there is an ever-present drive for better computational efficiency. This also holds true in the field of computational electro-magnetics where the finite element method (FEM) is regularly used. To improve the efficiency of a solution, various higher order basis functions are often employed. Two closely related sets of basis functions are considered, namely those implemented by Webb [1] and those of Slone [2] which are given as a correction to Webb's original basis functions. To facilitate the comparison between these two sets of basis functions, an efficient representation scheme is devised which allows for generation of these basis functions to any order. This representation is then used to perform a direct comparison between the results for the eigen-analysis of a rectangular PEC waveguide in two dimensions. View full abstract»

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    Fieldbus device description using tag-based trees

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

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146845
    Publication Year: 2002 , Page(s): 263 - 268 vol.1

    IEEE Conference Publications

    Fieldbus systems are generally static configured systems. However, the configuration processes are often complex and would take advantages of technologies providing flexibility, adaptability, etc. Specifically, fieldbus technologies are often incompatible to each other. A technology bringing on the one hand a homogeneous interface between different fieldbusses and, on the other hand providing a simple addressing mechanism and plug-and-play capability could bring advantages to fieldbus systems. Therefore, an alternative data format offering the aforementioned features is presented in this paper. This data format, called tag-based trees, is strongly related to XML and XML DOM trees, and basically provides a generic data format, which is suitable for almost all types of data. Moreover, it also gives the opportunity for fieldbus networks to provide semantics to the system by enriching the data with an appropriate structure describing the meaning of the data. Hence, it is also possible to provide a kind of interpretation instructions to the data consumer. View full abstract»

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    Build user daily activity model and model structure changing

    GuoQing Yin ; Bruckner, D.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071996
    Publication Year: 2011 , Page(s): 1 - 5
    Cited by:  Papers (1)

    IEEE Conference Publications

    Because of the activity dynamic it is a challenged work to build daily activity model of user. The goal of the paper is to build daily activity model of the user with high accuracy. At first the raw data derived from motion detector will be “translated” to state data, then use state split and merge to build the basic model. Thirdly in order to increase accuracy of the model the count of the state data increased by changing the parameter of the translator. Here we get another two activity models with higher accuracy. The changing of the count of the state data caused to the structure changing of the build activity model. We merge the states from same route of activity models, compare different models and find out the same activity trends of the user. On the other hand from the models with higher accuracy the hidden activity will be detected. View full abstract»

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    Adaptive CIR prediction of time-varying channels for OFDM systems

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

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

    IEEE Conference Publications

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

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    Finding an optimal PV panel maximum power point tracking method

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

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406864
    Publication Year: 2004 , Page(s): 1125 - 1129 Vol.2
    Cited by:  Papers (20)

    IEEE Conference Publications

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

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    Experimental setup for multiparametric characterization of photovoltaic panels

    Lay-Ekuakille, A. ; Trotta, Amerigo ; Miduri, F. ; Carella, R. ; Alonso, D.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308114
    Publication Year: 2009 , Page(s): 1 - 4

    IEEE Conference Publications

    Photovoltaic panels (PVs) are growing in terms of development and utilization all over the world. Different manufacturers deliver photovoltaic panel characteristics according to the locations where they are tested. Since there are different technological materials used in the manufacturing of PVs, the present research represents an effective method of prediction of the energy produced by the photovoltaic systems and an acceptable method of their characterization by using an experimental setup. The prediction of the energy produced by a photovoltaic system is generally made through software which uses algorithms that describe the trend of the efficiency of the panels depending on the temperature, the radiation and, in more particular cases, depending on the incident spectrum features. View full abstract»

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    Adaptive robust controller design of uncertain nonlinear time-delay dynamical systems

    Hansheng Wu
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071969
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    The problem of adaptive robust stabilization is considered for a class of uncertain nonlinear dynamical systems with multiple nonlinear delayed state perturbations and external disturbances. In the paper, the upper bound of the nonlinearity and uncertainty, including delayed states, is assumed to be a linear function of some parameters which are still assumed to be unknown. Here, it is not required that the nonlinear terms including delayed states are linear norm-bounded in the states. In particular, it is not assumed that the uncertaities and external disturbances have to satisfy the matching conditions. A class of continuous memoryless adaptive robust state feedback controllers is synthesized for such uncertain nonlinear time-delay systems. The standard adaptive backstepping design approach is properly modified to allow the use of our adaptive robust control technique for uncertain nonlinear time-delay dynamical systems. By making use of Lyapunov-Krasovskii functional method, it is also shown that the proposed memoryless adaptive robust control schemes can guarantee the uniform asymptotic stability of uncertain nonlinear time-delay systems. 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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    Quality of service in telecommunications - the customer's perspective

    Afullo, T.J.O.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406641
    Publication Year: 2004 , Page(s): 101 - 106 Vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    In today's competitive telecommunications environment, customer satisfaction is key to gaining market share. Improving service quality results in improved customer satisfaction. A telecommunications service provider's survival depends on its ability to prepare for changes in customer needs, as well as changes in regulation and technology. But the increasing expectations of customers and the introduction of many new services and technologies is making it difficult to comprehend and meet customer requirements. Therefore, while the quality of service (QoS) required by the customer is the vital input to both the service provider and the regulator, the QoS achieved and that perceived are equally important. In this paper, we highlight standard procedures for determining quality of service. Then, we present typical results for the UK and Singapore, as well as customer survey results for Botswana View full abstract»

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    DC motor control via high order differential feedback control

    Nyabundi, S.A. ; Qi, G. ; Hamam, Y. ; Munda, J.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308165
    Publication Year: 2009 , Page(s): 1 - 5
    Cited by:  Papers (1)

    IEEE Conference Publications

    In practice, there are many motor systems whose models are usually unknown or partially unknown. However, the majority of control schemes focus on model-dependent techniques. To cope up with unavailable dynamics, a model-free controlling problem for a DC motor system is investigated in this study. A robust higher-order differential feedback controller (HODFC), which does not depend on the model of the controlled DC motor system, is applied. The controller only utilizes the information of the measured output and the given objective as well as the extracted differentials of those via higher-order differentiator (HOD). Simulation results show that HODFC successfully controls the uncertain DC motor system, and can drive its trajectories to desired steady states subject to unknown bounded disturbance. Stability, convergence and robustness of PID, fuzzy and HODFC control schemes for the closed-loop system behavior are compared. From the performance comparisons, the robust HODFC control system yields favorable control performance superior to that of PID and fuzzy control systems. Moreover, it not only has a learning ability similar to that of fuzzy control but also a simple control structure as PID control. View full abstract»

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    Adaptive inverse quadratics interpolation with applications to vector fitting and the hankel transform of spectral domain green’s functions

    Knockaert, L. ; De Zutter, D.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401441
    Publication Year: 2007 , Page(s): 1 - 5

    IEEE Conference Publications

    In this contribution we discuss the translation- invariant interpolation of univariate functions by means of inverse quadratics radial basis functions. For the implementation we use an adaptive interpolation process which is a variant of a recently introduced adaptive residual subsampling method. It is shown that the interpolation process with the inverse quadratics kernel also provides an excellent pre-processing interface when used in conjunction with the popular vector fitting algorithm. This results in a composite algorithm, performing the sampling and modelling of the given function in a fully automatic way. It also provides a platform for calculating the Hankel transform of spectral domain Green's functions. View full abstract»

  • Freely Available from IEEE

    Message from the Vice Chancellor, University of Botswana

    OtIhogile, B.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406610
    Publication Year: 2004 , Page(s): 0_7

    IEEE Conference Publications

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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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    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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    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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    A theory for the systems engineering process

    Erasmus, L.D. ; Doeben-Henisch, G.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071989
    Publication Year: 2011 , Page(s): 1 - 5
    Cited by:  Papers (2)

    IEEE Conference Publications

    A theory for describing the systems engineering process using formal mathematical structures is presented in this paper. This abstraction of the systems engineering process makes it possible to concentrate on the operations and structures involved in the process without the distraction of the narrative word. An important aspect in the formulation of this theory is the inclusion of people as part of it. Further development of the theory will lead to the implementation of the mathematical description in simulation software to study the dynamic characteristics of and interaction of people with the systems engineering process as well as systematically validating the theory through empirical studies. View full abstract»

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    Digital chaotic coding and modulation in CDMA

    Soobul, Y. ; Chady, K. ; Rughooputh, H.C.S.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160023
    Publication Year: 2002 , Page(s): 841 - 846 vol.2
    Cited by:  Papers (1)  |  Patents (38)

    IEEE Conference Publications

    Conventional CDMA system uses PN sequences to spread user information. The number of shift registers used to generate them limit the lengths of these sequences. Good correlation properties can be achieved by Walsh codes and time-shifted version of PN sequences. The ability to predict future sequence is nevertheless possible, though difficult. Transmission therefore is not completely secured. Several other codes (Gold codes, Kasami etc) perform equally well as PN sequences, however it has been reported that these do not improve the security aspect of the system. Hence there is a need for a highly secure code that can be regenerated at the receiver and that can mimic PN sequences for spreading. In this paper, chaotic codes are investigated and their performance compared with the conventional PN sequences in an AWGN and Raleigh fading channel. The other type of spreading code which is the Walsh code uses its orthogonal property for user separation in the channel. This paper also investigates the behaviour of chaotic code in a multi-user situation. The auto and cross correlation properties of the spreading codes are also investigated. Chaotic codes are dependent on initial conditions and are continuous in nature. The undeterministic property of its amplitude from past sequences yields better security. Common modulation techniques (BPSK, QPSK) require higher SNRs to give similar performance in a multi-user environment. The use of QAM in order to improve BER whilst simultaneously inheriting secure property of chaotic codes is also investigated. View full abstract»

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    Using the oscillation test method to test for delay faults in embedded cores

    Vermaak, H.J. ; Kerkhoff, H.G.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406859
    Publication Year: 2004 , Page(s): 1105 - 1110 Vol.2
    Cited by:  Patents (6)

    IEEE Conference Publications

    Continual advances In the manufacturing processes of integrated circuits provide designers the ability to create more complex and denser architectures and increased functionality on a single chip. The increased usage of embedded cores necessitates a core-based test strategy in which cores are also tested separately. The IEEE P1500 proposed standard for embedded core test (SECT) is a standard under development which aim is to improve the testing of core-based system chips. This paper deals with the enhancement of the test wrapper and wrapper cells to provide a structure to be able to test embedded cores for delay faults. This approach allows delay fault testing of cores by using the digital oscillation test method and the help of the enhanced elements while staying compliant to the PI500 standard. View full abstract»

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    Multiband Doherty RF power amplifier

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

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

    IEEE Conference Publications

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

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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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    Join call admission control algorithm to enhance connection-level QoS in heterogeneous cellular networks

    Falowo, O.E. ; Chan, H.A.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401527
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (1)

    IEEE Conference Publications

    Next generation wireless networks will be heterogeneous where different radio access technologies (RATs) coexist. This coexistence of different RATs necessitates joint radio resource management. This paper proposes a joint call admission control (JCAC) algorithm for heterogeneous cellular networks and develop an analytical model for the JCAC. The cellular networks are integrated together and radio resources are jointly managed to support multiple classes of service. We decompose the integrated cellular networks into groups of co-located cells. In each group of co-located cells, the objectives of the JCAC algorithm are to uniformly distribute traffic load among the available RATs, prioritized handoff calls over new calls, and enhance connection-level QoS. Prioritization of handoff calls over new calls is achieved by using threshold-based bandwidth reservation method. The JCAC algorithm is modeled as a multi-dimensional Markov chain. We derive two connection-level QoS metrics, new call blocking probability and handoff call dropping probability, for the heterogeneous cellular network and then evaluate the performance of the JCAC algorithm through simulations. Results show that connection-level QoS can be significantly increased by using the JCAC algorithm in heterogeneous cellular networks. 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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    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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    Surge protection of communication equipments for power line communication: Effects on communication signal

    Sanya, T.O. ; Hove, M. ; Snyders, A.J. ; Ferreira, H.C.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072067
    Publication Year: 2011 , Page(s): 1 - 4
    Cited by:  Papers (1)

    IEEE Conference Publications

    The effect on the communication signal by Zener Diodes (ZDs) when connected as surge protection devices in coupling circuits for power line communication (PLC) against common mode and differential mode electrical surges on the power line channel is investigated. Unlike the conventional mode of providing differential mode surge protection only, common mode surge protection was introduced as well. This was done by introducing the grid grounding system to the conventional mode of protection. The results show that with common mode surge protection included, the received signal is attenuated and there is signal drop at certain critical frequency. The ZDs have no significant effect on the received signal when used in the differential mode. View full abstract»

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    Simulation of optical XOR encryption using MATLAB

    Zhang, B. ; Kahn, M.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406837
    Publication Year: 2004 , Page(s): 995 - 1000 Vol.2

    IEEE Conference Publications

    We describe an optical security device that is the exclusive-OR (XOR) encryption. In the field of electronic ciphering, one such algorithm is the exclusive-OR encryption. This encryption technique can handle only binary signals and encrypts each pixel individually. Because images consist of pixel, we can use mask bit to encrypt it. The theoretical results are verified by computer simulation. Theoretical and computer simulation indicate that XOR encryption is a safe coding method. 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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    Application of finite state machines in hybrid simulation of dc-dc converters

    Ocaya, R.O. ; Wigdorowitz, B.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401529
    Publication Year: 2007 , Page(s): 1 - 4
    Cited by:  Papers (3)

    IEEE Conference Publications

    Much attention is currently being directed at nonlinear effects such as bifurcations, sub-harmonics and chaos in conventional and hybrid power electronic converters (PECs). Traditionally, PECs have been difficult to model and simulate because of the discontinuous nature of their underlying differential equations. This work suggests a modeling and simulation framework for a PECs that employs a Matlab/Simulink based finite state machine (FSM) in the context of hybrid systems theory. The literature contains mostly abstractions on hybrid simulation and few suggestions of practice. The approach is illustrated with the boost topology. The simulations are subsequently compared and contrasted with PSpice results. View full abstract»

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    Component-oriented design of an intelligent, networked refrigerator

    Gaderer, G. ; Sauter, T.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146821
    Publication Year: 2002 , Page(s): 135 - 138 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    Fieldbus systems in home automation are still an emerging technology, although the networking of household appliances has advantages like remote control and maintenance, but also energy management We demonstrate how the controller of an off-the-shelf refrigerator can be redesigned to make the device network-aware. In this case study, the appliance has been equipped with an EIB interface. Both hard- and software have been designed in a modular way according to functional components. This concept gives the possibility to replace control algorithms by more sophisticated ones and to establish a coordinated consumption of electrical energy to avoid expensive load peaks. 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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    Comparison of the communication time of a high gain versus a low gain monopole-like low profile antenna on a 3-unit CubeSat

    Khotso, P.A. ; Lehmensiek, R. ; van Zyl, R.R.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072146
    Publication Year: 2011 , Page(s): 1 - 4

    IEEE Conference Publications

    This paper investigates the effect of the antenna pattern on the communication time between a ground station and a low earth orbit satellite with passive attitude control, i.e. the antenna is nadir pointing. Two low profile antennas that fit on a 3-unit CubeSat are considered, namely a high gain patch and a low gain monopole-like patch antenna. The communication system is for high speed S-band communication. View full abstract»

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    A review of mobile phone usage in enclosed areas and RF safety guideline

    Simba, A.Y. ; Watanabe, S. ; Hikage, T. ; Nojima, T.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308075
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    The use of mobile phones in metallic enclosed environments such as elevators, train cars and even airplanes has attract a lot of attention in recent years. In these environments, most of the radio frequency (RF) energy from mobile phones remains inside due to the lack of escape routes, resulting in possibility of the field levels exceeding limits described in the international RF safety guidelines. This has resulted in an anxiety on possible health effects of passengers in these environments. In this review paper, size of the passengers (child vs. adult human model), method of investigation (theory vs. numerical), passenger position, elevator structure etc., are briefly discussed to determine how they affect the RF exposure. We also discuss few experimental investigation related to this problem for the passenger using a mobile phone near a metallic wall. Our objective is to provide an understanding of the SAR characteristics of the mobile phone user in such environment and how these characteristics are affected by the aforementioned factors. View full abstract»

  • Freely Available from IEEE

    [Front cover]


    AFRICON 2007

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

    IEEE Conference Publications

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    Optimal block differential space-frequency codes for MIMO-OFDM

    Kruger, A.E. ; Maharaj, B.T.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308141
    Publication Year: 2009 , Page(s): 1 - 5

    IEEE Conference Publications

    This paper proposes an optimal block differential space-frequency scheme for multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems. A rather general channel model is assumed, where the channel is frequency-selective and remains constant for only a single OFDM block. We achieve resilience against this fast fading environment by differentially encoding blocks of the transmitted signals in the frequency domain within each OFDM block so that differential decoding can be performed over blocks of subcarriers within each single OFDM block. This, coupled with an optimal subcarrier grouping allocation method, results in a computationally efficient differential modulation scheme that performs well for a wide variety of channel environments. The results demonstrate a 5 dB difference in performance between the scheme with the proposed optimal subcarrier grouping and a scheme without any subcarrier grouping. View full abstract»

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    Pedestrian detection for underground mine vehicles using thermal images

    Dickens, J.S. ; van Wyk, M.A. ; Green, J.J.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072167
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (2)

    IEEE Conference Publications

    Mine vehicles are a leading cause of mining fatalities. A reliable anti-collision system is needed to prevent vehicle-personnel collisions. The proposed collision detection system uses the fusion of a three-dimensional (3D) sensor and thermal infrared camera for human detection and tracking. In addition to a thermal camera, a distance sensor will provide depth information and allow the calculation of the vehicle and pedestrian velocities. The results of subsystem tests show that a simple temperature range is sufficient for segmentation and a neural network shows the best classification results in terms of speed and accuracy. Results of initial tests performed on two different 3D sensors show a significant disadvantage to the use of time of flight cameras in a mine environment. View full abstract»

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    Evaluation of current harmonic distortion in wind farm application based on Synchronous Active Front End converters

    Fioretto, M. ; Raimondo, G. ; Rubino, L. ; Serbia, N. ; Marino, P.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072064
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    Worldwide, request of renewable energy and power rating of wind farm is strongly increasing in parallel. This, makes more difficult the design of the power electronics converter that interfaces the grid to the renewable energy resource. Synchronous Active Front-End (SAFE) is considered one of the most efficient topology that successfully manages the hard trade-off between high power size and power quality requirements at the Point of Common Coupling (PCC). In this paper the authors present a mathematical approach to estimate the harmonic distortion of converter current at the PCC due to SPWM modulation. This, shows the advantages in terms of current spectrum of the SAFE topology. Moreover, it represents a strong tool in the converter design, as it allows to design converters parameters in order to respect power quality standards requirements. Finally, numerical simulation results validate the study. View full abstract»

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    On the use of high bit rate transceivers for low duty cycle wireless sensor networks

    Mahlknecht, S. ; Bock, M.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406888
    Publication Year: 2004 , Page(s): 1235 - 1238 Vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    In most wireless sensor network applications reducing the energy consumption of each node has highest optimisation priority to allow sensor nodes to operate for an extended period of time. The radio transceiver plays an especially important role in this regard, because it typically consumes most of the nodes energy. Up to now only low bit rate radio transceivers (up to 115 kbps) were proposed for the use in sensor applications which leads to a sub optimal node efficiency. In This work the use of commercially available high bit rate (≥ 1 Mbps) transceivers for low duty cycle, ultra low power wireless sensor networks is proposed. Using state of the art high bit rate transceivers with an efficient MAC protocol such as the recently proposed CSMA-MPS can save considerable energy at the physical layer. View full abstract»

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    Enabling wireless broadband technologies and services for the next billion users

    Mekuria, F.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072115
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (2)

    IEEE Conference Publications

    As wireless devices and the useful services they can deliver become more pervasive and affordable; the need for wireless broadband technologies meeting the demands of emerging market countries is growing. In this paper the technology choice in wireless broadband access and service architecture is discussed with reference to three important wireless broadband technologies and relevant parameters such as service activation, authentication and delivery, cost effectiveness and sustainability. The main focus of the article is towards wireless broadband technology deployment in developing countries and rural communities for providing innovative wireless broadband services. View full abstract»

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    An assessment of the proposed TSO model for South Africa's new electricity industry

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

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406809
    Publication Year: 2004 , Page(s): 855 - 859 Vol.2

    IEEE Conference Publications

    Transmission network and system operations remain a monopoly institution under electricity industry deregulation. This can be attributed to the need for efficiency and effectiveness. The unbundling of the electricity value delivery chain and introduction of competition amongst generators and distribution companies raises challenges to the operation of this vital sector of the industry. Various models for transmission network and system operations peculiar to specific industry environments have been proposed by policymakers involved in electricity deregulation. In the wider industry context, the success of these models depends on the operational framework from which their roles and functions are derived, in addition to the appropriate regulatory incentive schemes. An assessment of the proposed transmission and system operations (TSO) model for the new deregulated electricity industry in South Africa is presented in This work. The functions and regulatory regime undertaken for assessing transmission and system operations performance under deregulation are discussed. View full abstract»

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    Input-output linearizing and decoupling control of a nonholonomic power wheelchair

    Nyabundi, S.A. ; Qi, G. ; Hamam, Y. ; Munda, J.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308161
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    While nonholonomic powered wheelchairs (NPWs) have made advances over the past three decades, the control algorithms remain virtually unchanged since 1980's. The simple proportional integral (PI) controller is antiquated, and does not perform well in the presence of disturbances, sensors uncertainties, nonlinearities and load variations. The practical interest is driven by the fact that today's wheelchairs need to be operated under tighter performance specifications. At the same time more and more constraints, stemming for example from environmental and safety considerations, need to be satisfied. Often these demands can only be met when nonlinearities and constraints are explicitly considered in the controller. A new approach to trajectory tracking control for wheelchair systems containing uncertain, nonsmooth nonlinearities is proposed. The method is based on decoupling theory and system input-output feedback linearization technique by which the system stability and convergence of velocity tracking errors to zero are rigorously examined. The effectiveness and efficiency of the proposed controller is demonstrated through simulation studies. The study would result in better driving performance, smoother feel, and fewer accidents or inadvertent collisions. View full abstract»

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    Optimal placement and tuning of power system stabilisers

    Lakmeeharan, K. ; Coker, M.L.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821869
    Publication Year: 1999 , Page(s): 793 - 798 vol.2

    IEEE Conference Publications

    Power system stabilisers (PSSs) have been widely used to damp low frequency electromechanical oscillations in power systems. Interconnections within the South African Power Pool introduce the possibility of inter-area oscillations affecting the ESKOM system. This paper details a systematic procedure for the placement and tuning of power system stabilisers to mitigate dynamic oscillations utilising standard industrial grade software View full abstract»

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    Module antenna on multilayer dielectric for base station

    Wnuk, M. ; Amanowicz, M. ; Kolosowski, W. ; Sedek, E.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821914
    Publication Year: 1999 , Page(s): 1031 - 1034 vol.2

    IEEE Conference Publications

    Module antennas consisting of 4 radiating elements realized in stripline technology for the 1.8 GHz frequency band are presented. Practical realization of radiating elements and the results of measurements are presented. The method of module dimension choice as well as its characteristics is demonstrated. The possibility of practical applications of these modules in planar array antennas is also described View full abstract»

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    Adaptive Robust Anti-windup Generalized Predictive Control (RAGPC) of Non-minimum phase systems with input constraints and disturbance

    Osunleke, A. ; Mingcong Deng ; Inoue, A. ; Yanou, A.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308188
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    This paper deals with a design problem of non-minimum phase systems with input constraints and unknown disturbance using the adaptive robust anti-windup generalized predictive control (RAGPC) scheme. In essence non-minimum phase systems are characterized by presence of dead time and invariably has unstable inverse. This effect is not desirable in control processes especially when problems of static output feedback stabilization are concerned. Consequently, robust closed-loop stability of non-minimum processes with input constraint and disturbances becomes difficult to achieve. Addressing this issue provides a good motivation for the current study. Here, we present a new scheme for controlling such systems and in overall achieving a desired robust performance. To apply the proposed design scheme to a practical system, the system has been identified adaptively and thus the control scheme is applied. The practical system considered here is a water level experimental system whose parameters are identified adaptively offline. Simulation results are presented to support the efficacy of the proposed scheme in controlling this kind of system. 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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    Direct adaptive neural control of a quarter-car active suspension system

    Pedro, J.O. ; Dahunsi, O.A. ; Baloyi, N.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071981
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper presents the design and implementation of a direct adaptive neural network (DANN) based feedback linearization controller for a two degree of freedom (2DOF), quarter-car active vehicle suspension system (AVSS). The main objective is to improve ride comfort and handling quality. The constant gain PID controller (based on Ziegler-Nichols tuning method) is used to benchmark the DANN controller during a suspension travel sinusoidal set point tracking in the presence of deterministic road disturbance. The maximum sprung mass acceleration of the DANN controller was about 2.723ms-2, for the PID, it was 2.676ms-2. The tire deflection was approximately 5mm and 4mm for the DANN and the PID controllers. The performance of the DANN controller was achieved at a marginally higher cost of the control input. View full abstract»

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    Speed control of a DC drive based on optimal performance

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

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

    IEEE Conference Publications

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

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    Advanced scalable medical video transmission based on H.264 temporal and spatial compression

    Doukas, C.N. ; Pliakas, T.A. ; Maglogiannis, I.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401517
    Publication Year: 2007 , Page(s): 1 - 4

    IEEE Conference Publications

    Medical video transmission with proper perceived quality is vital for applications in the domain of remote surgery, diagnosis, treatment and health-related education. Video transmission over wired and wireless networks can introduce delays and improper content delivery. Scalable video coding (SVC) is considered as an appropriate solution for overcoming such transmission. This paper introduces an advanced medical video transmission platform based on temporal and spatial H.264 scalable compression. The efficiency and effectiveness of the presented platform are demonstrated by experimental results. View full abstract»

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    Frequency management in South Africa

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

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

    IEEE Conference Publications

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

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    SA children take a SUN-STEP to engineering

    Myburgh, M. ; Schoonwinkel, A.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821953
    Publication Year: 1999 , Page(s): 1215 - 1218 vol.2

    IEEE Conference Publications

    The MTN-SUNSTEP programme reaches out to disadvantaged children and increases their science, electronics and technology awareness. It also reinforces the fact that electronics offer career opportunities and that mathematics and science are crucial high school subjects View full abstract»

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    An improved method for the identification of opportunities for Deterministic Network Coding

    Engelbrecht, M.J. ; Grobler, M.J. ; Ferreira, M.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072090
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    In this paper a new method for the identification of sub-topologies, suitable for the implementation of network coding in a wireless mesh network is presented. When nodes are positioned in certain locations relative to each other they create an environment where network coding opportunities can be identified for instances where certain data flows occurs between nodes in that environment. If nodes forming those sub-topologies can be informed of the occurring coding opportunities, it would improve the performance of the network. View full abstract»

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    Iron loss analysis in linear DC motor: laminated vs. solid core

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

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160000
    Publication Year: 2002 , Page(s): 711 - 714 vol.2

    IEEE Conference Publications

    Iron loss analysis in a linear DC motor is discussed. Two cases are considered: the motor core made of solid steel and a laminated core. Those two cases call for different methods of iron loss calculation, which are discussed in detail. Influence the magnetic bias, produced by the motor's permanent magnet excitation, on the iron loss is discussed. Iron loss calculated for both versions of the core is compared and design recommendations are made. View full abstract»

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    Modelling and measurement of magnetic fields around a railway track

    Moresco, M.A. ; Cronje, W.A. ; Steyn, B.M.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406784
    Publication Year: 2004 , Page(s): 749 - 754 Vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    The South African railway company (Spoornet) is experiencing difficulties with some of their train wheel detection systems, due to magnetic fields generated by distorted currents flowing in the tracks. These fields interfere with the proximity sensor's operation and causes inaccurate counting of train wheels. The magnetic field distribution is determined experimentally to determine if shielding can resolve the problem. View full abstract»

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    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406628
    Publication Year: 2004 , Page(s): 30

    IEEE Conference Publications

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    Automated generation of Poisson-Voronoi tessellations in R2 for NS (Nov 2003)

    Minnaar, M. ; Ngwenya, D.W.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406857
    Publication Year: 2004 , Page(s): 1091 - 1097 Vol.2

    IEEE Conference Publications

    Stochastic point processes and geometrical objects can be used to represent communication network stations and architecture. This includes a combination of point processes, graphs and tessellations. This approach can be useful in simulation of large communication networks containing multilevel stations following an irregular point pattern. This research modeled the process using object-oriented approach. The implementation allows a Poisson point process at each level of the stations and the rules of a connected graph are realized by applying Delaunay triangles and Voronoi tessellations to the point process. A stochastic model was implemented in C++ and OTcl for NS2. Simulations were performed in MATLAB to verify the C++ code. View full abstract»

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