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    A residential energy and power conservation System Utilizing an Optimization Model

    Zhang, H. ; Xia, X. ; Zhang, J.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308303
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (2)

    IEEE Conference Publications

    This paper presents a residential energy and power conservation system that utilizes an optimization model and user side controller. The aim of this paper is to enforce a reduction in the users' current level of consumption and yet minimize any discomfort as the result. An energy usage optimization model is the foundation of this work. It computes a set of directives for a specific user based on the historical electrical devices usage data and the conservation requirement. A user side controller utilizes this directive and actively allows or denies user's access to certain appliance. This system has the following advantages: it ensures the conservation requirement is met by all of the end users; it has relatively low cost; it is highly efficient. View full abstract»

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

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

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

    IEEE Conference Publications

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

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    Loudspeaker, narrator and language influences on speech intelligibility

    Esterhuizen, H.D.
    AFRICON 2007

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

    IEEE Conference Publications

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

  • Freely Available from IEEE

    [Front cover]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406900
    Publication Year: 2004 , Page(s): 1300

    IEEE Conference Publications

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    Realization of pipelined multiplier-free FIR digital filter

    Dawoud, D.S.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820843
    Publication Year: 1999 , Page(s): 335 - 338 vol.1

    IEEE Conference Publications

    The paper introduces a high-speed multiplication-free realization for FIR filter. The realization is based on the use of a linear periodically time-varying (PTV) system and the use of radix-r recoding schemes for obtaining the filter coefficients. The paper combined and reformulated the Modified Booth multiplication algorithm and the filter operation in bit-level. As a result, two schemes are proposed. The structures can be used to build programmable FIR filter View full abstract»

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    Computer-aided process planning-an object oriented structure

    Huang, J. ; van Niekerk, T.I. ; Hattingh, D. ; Du Preez, E.F.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820950
    Publication Year: 1999 , Page(s): 531 - 536 vol.1

    IEEE Conference Publications

    Machining process planning is a complex process requiring a variety of knowledge of design and manufacturing. This paper proposes an object oriented structure for process planning in the environment of a flexible manufacturing cell View full abstract»

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

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

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

    IEEE Conference Publications

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

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    Diode laser absorption spectroscopy for teaching undergraduate physics

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

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

    IEEE Conference Publications

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

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    Point-to-point rural telephone system

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

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

    IEEE Conference Publications

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

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

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

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

    IEEE Conference Publications

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

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    Some research issues in cognitive radio networks

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

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

    IEEE Conference Publications

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

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    Qualitative and quantitative characteristics of deghosting in advanced radar systems

    Paradowski, L.R.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146799
    Publication Year: 2002 , Page(s): 19 - 24 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    Deghosting, i.e. elimination of false targets during data processing in multi-sensor tracking of jamming targets, is a crucial process for effective use of air defence systems. It is particularly important for radar systems operating in passive mode because of their excellent properties against present-day electronic warfare techniques and tactics (especially jamming equipment and anti-radiation missiles). A deghosting algorithm based on bearing association/compounding strategy is outlined. A method of deghosting effectiveness evaluation using the ghost eliminator operating characteristic (reference to the receiver operating characteristic from statistical theory of signal detection) is presented. Such an approach enables to compare performances of various deghosting procedures in different operational conditions or scenarios. 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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    UAV Collision Avoidance: A Specific Acceleration Matching control approach

    Patel, A. ; Winberg, S.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072176
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    The potential uses for Unmanned Aerial Vehicles (UAVs) is vast. However, much of their potential can only truly be unlocked by giving them a higher level of autonomy. This paper focuses on an autonomous Collision Avoidance System using Specific Acceleration Matching, which is termed the `CASSAM' in this paper. This approach is being studied as it may prove an effective means to increase the level of autonomy of UAVs. The paper presents the design of the CASSAM first by modelling the UAV dynamics and then by designing suitable control algorithms. Simulation results in 2D show that it is a viable option to address the UAV collision avoidance problem having effectively evaded threats with minimal control effort. View full abstract»

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    A novel hybrid neural network for identification of trace compounds

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

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820885
    Publication Year: 1999 , Page(s): 411 - 414 vol.1

    IEEE Conference Publications

    Developments in the field of neural networks have come to a stage that they can participate well in the recognition of these trace compounds. A novel neural network model is proposed for quick identification of trace compounds from their Raman images View full abstract»

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

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

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

    IEEE Conference Publications

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

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    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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    Why electronic and not electromechanical ELCBs ?

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

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

    IEEE Conference Publications

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

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

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

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

    IEEE Conference Publications

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

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    Empirical analysis of the effect of parasitics and of reverse recovery as an amplitude error on distortion in a class D audio amplifier

    Koeslag, F. ; du T.Mouton, H. ; Beukes, H.J.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308132
    Publication Year: 2009 , Page(s): 1 - 7

    IEEE Conference Publications

    An analysis of the effect of parasitics and reverse recovery on harmonic distortion in a class D audio amplifier is performed in this paper. The error sources under investigation are modelled empirically as an amplitude error, after which an existing strategy based on Newton's numerical method is implemented to simulate its effect within the audible band. The results are compared to existing timing errors to determine its degree of dominance. View full abstract»

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    A traffic simulator for advanced transport telematics (ATT) strategies

    Jimenez, T. ; Furmento, N. ; Mussi, P. ; Siegel, G.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820690
    Publication Year: 1999 , Page(s): 33 - 36 vol.1

    IEEE Conference Publications

    ATT systems are now widely deployed. The traffic simulation models need to represent ATT elements and the driver's reactions to them. We present a model for traffic simulation of systems with ATT elements and the simulator developed using this model View full abstract»

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    Fuzzy logic congestion control in IEEE 802.11 wireless local area networks: A performance evaluation

    Nyirenda, C.N. ; Dawoud, D.S.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401645
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    In 802.11 wireless local area networks, the wired and the wireless interfaces of the access point are characterized by the disparity in channel capacity. This presents a significant bottleneck for traffic flowing from the wired network to the wireless network. Therefore, the implementation of a congestion control mechanism in access points promises to be a suitable solution. Recently, a particle swarm optimized fuzzy logic congestion detection (FLCD) was proposed for IP networks. This algorithm synergistically combines the good characteristics of traditional active queue management (AQM) algorithms and fuzzy logic based AQM algorithms. Its membership functions are designed automatically by using a multi-objective particle swarm optimization (MOPSO) algorithm in order to achieve optimal performance on all the major performance metrics of IP congestion control. In this paper, we evaluate the performance of the FLCD algorithm in the wireless local area network environment. We compare its performance with that of ARED and the Droptail mechanism. Simulation results show that the FLCD algorithm helps to minimize UDP traffic delay, packet loss rates. In terms of throughput, the FLCD algorithm exhibits similar performance to the other schemes. Its UDP jitter is slightly higher than that of the Droptail mechanism but better than that of ARED. View full abstract»

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    Application of extended Huygens' principle to scattering discontinuities in waveguide

    Geschke, R.H. ; Ferrari, R.L. ; Davidson, D.B. ; Meyer, P.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159969
    Publication Year: 2002 , Page(s): 555 - 558 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    A recently proposed extended Huygens' principle for scattering objects in a waveguide is reviewed. This technique allows the coupling of a finite element discretisation with a quasi method of moments (MM) surface element approach. Perfectly conducting posts are considered as test cases. Implementational details are discussed and results for the conducting post are presented. View full abstract»

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

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

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

    IEEE Conference Publications

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

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    An adaptive thresholding method for automatic lung segmentation in CT images

    Lin-Yu Tseng ; Li-Chin Huang
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308100
    Publication Year: 2009 , Page(s): 1 - 5

    IEEE Conference Publications

    Cancer is one of the most serious health problems in the world. Lung Computer-Aided Diagnosis (CAD) is a potential method to accomplish a range of quantitative tasks such as early cancer and disease detection, analysis of disease progression, analysis of pulmonary function and perfusion, and automatic identification and tracking of implanted devices. For identifying the lung diseases, computed tomography (CT) scan of the thorax is widely applied in diagnose. The lung segmentation is the preprocessing step in most CAD systems. However, manually segmenting the lungs is tedious and taking lots of time for the large-sized CT databases. In this paper, we propose a novel lung segmentation technique that can determine the threshold for each CT slice in a patient stack and automatically do the lung segmentation. The accuracy is 98% when the method was tested on five patient stacks that contained 914 slices. View full abstract»

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    Analysing market power in the restructured electricity market using game theory

    Yan, J.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406706
    Publication Year: 2004 , Page(s): 411 - 416 Vol.1

    IEEE Conference Publications

    This paper focuses on the investigation of market power behaviour of market participants in the deregulated electricity market. The physical exercise of market power of a firm includes withholding part of its output and raising the price above its marginal cost for a certain period of time. In the simulations, different competition styles are considered. The results show that the price will increase dramatically when market participants behave strategically. Participants obtain significant profits through their strategic gaming behaviours. Market price, generators' generation and profit have been compared. We suggest that the game theoretical approach could help us to predict the strategic behaviour of the market participants, so that we can prevent or reduce the effect of market power in the market View full abstract»

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

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

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

    IEEE Conference Publications

    The paper presents the design and simulation results of the input-state feedback-linearised control of a polar- axis solar tracking platform, capable of hosting ten 300 W solar photovoltaic panels. The controller reduced the settling time of the open-loop platform system from 105 seconds to 2 seconds. Compared with a linear controller we had designed for the same system, the new controller also minimized system accelerations. View full abstract»

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    An animal powered electricity generator for stand alone applications

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

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

    IEEE Conference Publications

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

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    The Effect of Type of Transient Voltage Suppressor on the Signal Response of a Coupling Circuit for Power Line Communications

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

    DOI: 10.1109/AFRCON.2011.6072050
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    The effect of the type of transient voltage suppressor (TVS) used in coupling circuits for surge protecting PLC equipment on the signal response has been studied. The study was focused at TVS devices used in both differential and common mode surge protection. It is found that the gas discharge tube (GDT) has no effect on the communication signal, whilst TVSs that operate on avalanche breakdown attenuate the signal and they also render signal dropout at a particular frequency. Metal Oxide Varistors (MOVs) behave similarly. View full abstract»

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    Parallelising calculations in electric power distribution networks

    Neumann, Y. ; Dwolatzky, B.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160042
    Publication Year: 2002 , Page(s): 957 - 960 vol.2

    IEEE Conference Publications

    CART (Computer Aided Reticulation of Townships) is a software package used for the design of radial, electrical power distribution networks. Having many transformers and large numbers of consumers in the distribution network significantly increases computation time. A distributed, service-based platform is being developed, with parallelisation functionality for CART as the flagship service. The system will be used to parallelise CART's voltage and current calculations for use in the design of much larger networks, possibly of metropolitan scale. Eventually, more complex scenarios will be addressed, including real-time calculation and simulation of lightning and transient faults and performance testing and optimisation of existing power distribution networks. View full abstract»

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    Performance of an adaptive multi-dimensional lattice equaliser for Q2PSK over multipath channels

    Cilliers, J.E. ; Linde, L.P.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146825
    Publication Year: 2002 , Page(s): 155 - 160 vol.1

    IEEE Conference Publications

    The paper presents results on the performance of an adaptive decision feedback equaliser (DFE) for the multi-dimensional Q2PSK modulation format in static multipath channels. The modem integrates dynamic synchronisation mechanisms with an adaptive multi-dimensional lattice equaliser to mitigate the detrimental effects of intersymbol interference (ISI) caused by multipath channels. The results presented have been constrained to static channels due to the complexity of the problem addressed. The presentation incorporates both analytical as well as simulation results. View full abstract»

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    Active noise control in real-time using a TMS320C50 DSP system board

    Oolun, M.K. ; Bhurtun, C. ; Soyjaudah, K.M.S. ; Jahmeerbaccus, M.I.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146815
    Publication Year: 2002 , Page(s): 105 - 108 vol.1

    IEEE Conference Publications

    This paper presents a real-time active noise controller system, based around a TMS320C50 DSP system board. The proposed technique consists of identifying the noisy space medium where the cancellation needs to be effected using a coded interrogation technique, and subsequently cancelling the noise using a simple, yet robust prediction strategy. Software coding and implementation has been achieved, with a signal-to-noise ratio improvement of up to 16 dB. The time taken to achieve this performance is about 32 s, for a wideband noise over the range 50 to 200 Hz. Once the system has learned the noise characteristics of the medium, it offers good tracking characteristics in cancelling the noise thereafter. 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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    Emerging Behavior as driver for the sustainability of a modular, “skills-centric” production system

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

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

    IEEE Conference Publications

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

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    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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    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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    The African Speech Technology project for tele-services: achievements, state of the technology and roadmap

    Botha, E.C.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146864
    Publication Year: 2002 , Page(s): 367 - 370 vol.1

    IEEE Conference Publications

    The African Speech Technology project, sponsored by DACST's Innovation Fund, aims to develop speech and language software tools and libraries to enable the implementation of tele-services (automated information and transaction systems over the telephone). We are adapting state-of-the-art speech technology (recognition and generation) to work in five South African languages. This paper gives an overview of achievements, the state of the technology and the road ahead. View full abstract»

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    Automatic generation control performance of the Nigerian power system after deregulation

    Katende, J. ; Okafor, F.N.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406778
    Publication Year: 2004 , Page(s): 717 - 722 Vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    The current restructuring program which seeks to split the national electric power authority (NEPA) -the sole electricity supply company in Nigeria-into one transmission company, often reffered to as a Transco, and several generation and distribution companies (Gencos & Discos), is a welcome development. This paper investigates some of the technical problems associated with automatic generation control (AGC) of the Nigerian power system after deregulation. Simulation studies are presented utilizing concepts of the traditional two area power system model, but incorporating factors which represent bilateral contracts between the Gencos and the Discos, in a state space formulation. A further decomposition of the model results in a 15th order vector-matrix performance equation which is solved under some assumptions to track the relevant parameters. It is then easy to visualize the physical constraints on system operation and thus, appreciate the conclusions of the authors. 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»

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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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    Analysis of the LCDCM criterion for DS-CDMA blind multiuser detection

    de Villiers, J.P. ; Linde, L.P.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146868
    Publication Year: 2002 , Page(s): 389 - 394 vol.1

    IEEE Conference Publications

    In this paper we will see that the linearly constrained differential constant modulus (LCDCM) cost criterion is well suited for blind multiuser detection. Unlike the linearly constrained constant modulus (LCCM) cost function, it is not dependent on desired user amplitude to ensure a single optimum point. The global minimum of the LCDCM cost function will be established by proving the Hessian matrix positive definite at the single solution where the gradient function is zero. View full abstract»

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    Tapping small amounts of power from HVDC transmission lines using parallel cascaded converters

    Pietersen, D.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406773
    Publication Year: 2004 , Page(s): 691 - 696 Vol.2

    IEEE Conference Publications

    Tapping small amounts of power from HVDC transmission lines for rural electrification, has been the desire of network planners, designers and researchers for many years. This work investigates a parallel-cascaded converter topology for tapping small amounts of power from HVDC transmission lines. Further the effect of the parallel tapping station on the main HVDC transmission link during start-up of the tapping station is displayed. 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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    Towards Bluetooth multi-hop messaging

    Mallis, D. ; Coetzee, M.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072075
    Publication Year: 2011 , Page(s): 1 - 7

    IEEE Conference Publications

    Bluetooth-enabled cellphones are found in abundance today. Since cellphones are inherently mobile, they present obstacles for traditional Bluetooth multi-hop structures, namely scatternets. The main issue concerning scatternets is mobility and the overhead in replacing broken node links. This research proposes an approach for Bluetooth multi-hop message transport in crowded areas where mobility is considered to be walking speed. Here, opportunities for piconet links are plausible. Message transport by means of piconet message hopping is achievable by means of a novel algorithm and procedures presented. View full abstract»

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    Conceptual framework that supports environment-aware positioning and improved QOS for Location Based Services

    Dahunsi, F.M. ; Dwolatzky, B.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308149
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    Location based services (LBS) enables mobile users to have access to information based on their current geographical location. LBS are an important aspect of the ubiquitous wireless world and are paving the way to provide users with customizable services anywhere and at anytime. It is worth noting that there are different accuracy requirements for different LBS and not all location methods can provide the required accuracy due to error sources. Mobile network operators need to know which location method is best suited for the required accuracy of LBS based on the dynamically varying factors that affects the location method. The sources of the errors include geographical sources, wireless environment sources, measurement bias, geometric sources, etc. This paper proposes the development of a framework that will allow mobile network operators to compare different location methods to ensure the provision of improved quality of service to the mobile user and optimized usage of infrastructure. This framework takes into consideration the error sources of the location methods based on specific geographic area. View full abstract»

  • Freely Available from IEEE

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    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406692
    Publication Year: 2004 , Page(s): 360

    IEEE Conference Publications

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

    Polarity reinforcement: Sentiment polarity identification by means of social semantics

    Waltinger, U.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308104
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    We propose a combination of machine learning and socially constructed concepts for the task of sentiment polarity identification. Detecting words with polarity is difficult not only due to limitations in current sentiment dictionaries but also due to the colloquial terms that are often used. Current approaches disregard the dynamics of language, i.e. that new words are often created comprising different polarities. In fact, the online community is very creative in coining terms about certain subjects such as ldquotweetuprdquo (a request by a user to meet with friends via Twitter) or ldquowhackrdquo (Street slang, meaning bad). Our approach utilizes a user generated dictionary of urban term definitions as a resource for polarity concepts. Therefore, we are not only able to map newly created words to their respective polarity but also enhance common expressions with additional features and reinforce the polarity, strengthening our initial finding. We empirically show that the use of polarity reinforcement improves the sentiment classification. View full abstract»

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    A silicone based hydrophobic coating for high voltage insulators

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

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

    IEEE Conference Publications

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

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    Static VAr compensators components and design considerations

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

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

    IEEE Conference Publications

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

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    Power and spectrally efficient multi-dimensional WCDMA modem employing CPM

    Basilio, D.J. ; Linde, L.P. ; Maharaj, B.T.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401572
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    This paper introduces a multi-dimensional quadrature phase shift keying (MD-QPSK) structure for a direct sequence spread spectrum (DSSS) modem that employs constant envelope linear root-of-unity (CE-LRU) filtered generalized chirp-like (GCL) complex spreading sequences (CSS's) and code- position-modulation (CPM). The resulting MD-QPSK CPM modem exhibits a spectrally efficient minimum (Nyquist) bandwidth output power spectral density (PSD). In addition, the transmitter output signal power is virtually constant. It is shown that the MD-QPSK CPM modem's data transmission rate is larger than other proposed WCDMA systems that use these unique CSS's, with a negligible difference in spectral occupancy. 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»

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

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

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

    IEEE Conference Publications

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

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    Enhancing performance of Bayes classifier for the hardened password mechanism

    Pavaday, N. ; Soyjaudah, K.M.S.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401574
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    In pattern recognition, Bayes classifier is considered a powerful tool in the decision making process as its gives the lowest probability of committing a classification error. This has been highlighted in a number of previous works. The diversity in algorithm parameters, criteria used and number of users involved as well as the evaluation method makes the task of comparing their results and selecting an appropriate system a very thorny one. The purpose of this paper is four fold: to study the different approaches reported using a true password, to establish how normalization and using a single variance/mean impact on the results, using a maximum number of features does necessarily improve performance and finally demonstrate that performance optimization is feasible through careful selection of features and approach taken. View full abstract»

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    A dictionary approach to fault diagnosis of analog circuits

    Marin, C.V. ; Constantinescu, F. ; Nitescu, M.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072155
    Publication Year: 2011 , Page(s): 1 - 5
    Cited by:  Papers (2)

    IEEE Conference Publications

    This paper deals with dictionary approach for single soft faults diagnosis in analog circuits. A method for selecting the optimum set of test frequencies is proposed. The first step uses circuit sensitivity analysis to choose the optimum frequency ranges. Then the optimum set of frequencies is selected using the entropy criterion. View full abstract»

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    FPGA transceiver for space environment

    Jezierski, C. ; Modelski, J.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072187
    Publication Year: 2011 , Page(s): 1 - 4

    IEEE Conference Publications

    FPGA structures have the advantage over analog solutions in weight, dimensions and power consumption. Four elements of digital transceiver were implemented in FPGA: scrambler, Reed-Solomon coder, RS decoder and FIR filter. They were simulated in Quartus, Simulink and Modelsim environments. Finally the blocks were linked together into one fully digital transmitter and receiver. The modulator and demodulator were designed with IPcores from Altera. The whole design was implemented and tested on Altera Stratix-II DSP Development Board. 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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    Reconfigurable mobile agents optimizing end-to-end connectivity in heterogeneous networks

    Ogbeide, S. ; Murgu, A.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072152
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    The advancement of technology towards Next Generation Networks (NGNs) has promised the mobile network a very high speed connection with increase in network resources and support heterogeneity (manifested by the presence of different access networks). This will no doubt enhance global roaming, mobility, scalability and performance of the entire network as users of mobile devices will have unrestricted access to different network providers (NP). However, these users' constant changes in location are characterized by some of the outputs or internal states growing without the network bounds. It became necessary to incorporate some new connectivity paradigms in the networking that will have the ability of determining when and how to adapt to these changes during runtime. This project considered a cooperative framework which is able to coordinate the complexity of the managed systems based on reconfigurable mobile network agents (RMNA) to autonomously decentralize processing and control, hence effectively responding to shortage of network resources and reducing the amount of traffics around the managing station. View full abstract»

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    Automated component-handling system for education and research in mechatronics

    Vermaak, H. ; Jordaan, G.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401627
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (2)

    IEEE Conference Publications

    Mechatronic practitioners are engaged in the assembly and maintenance of complex machines, plants and systems in the engineering sector or in organisations which purchase and operate such mechatronic systems. Mechatronics, often described as the synergy of mechanical, computer systems and electronic technologies, is increasingly being singled out as a core focus by both the education and business sectors. This international trend is also evident in South Africa and Engineering Faculties now have to provide students with the opportunity not only to acquire theoretical knowledge in Mechatronics but also to develop skills in implementing and designing mechatronics systems. View full abstract»

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    A comparison between measured leakage current and surface conductivity during salt fog tests [power line insulator applications]

    Schwardt, W.H. ; Holtzhausen, J.P. ; Vosloo, W.L.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406749
    Publication Year: 2004 , Page(s): 597 - 600 Vol.1

    IEEE Conference Publications

    This paper deals with an insulator pollution monitoring relay (IPMR), designed to measure and monitor pollution on high voltage insulators. The IPMR determines the pollution severity by measuring the surface conductivity on the test insulator. The paper reports on how the IPMR was used to measure surface conductivity on the lest insulator while a salt fog test was performed on typical power line insulators. The leakage currents were measured on the test insulators and the data was captured together with the surface conductivity values. The results discuss whether the IPMR is capable of the early detection of an instantaneous pollution event. The results are also utilised to compare the relationship between measured surface conductivity and leakage current values thus predicting flashover View full abstract»

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    White space and digital dividends: The case for dynamic spectrum access in South Africa

    Ferreira, M. ; Helberg, A.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072105
    Publication Year: 2011 , Page(s): 1 - 5

    IEEE Conference Publications

    In this paper we present the current state of affairs surrounding the analog switch-off and corresponding digital dividend as pertaining to South Africa. Analog switch-off and digital dividends has enjoyed much attention lately due to the constantly increasing data requirements of wireless devices and the alarming decrease of available spectrum for deployment of new wireless technologies. An estimated 300 MHz of spectrum will be made available after analog switch-off. To this end the main contributions of this paper is to detail the state of affairs surrounding analog switch-off, the possibilities for the digital dividend and Spectrum Opportunities that exist in South Africa. View full abstract»

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    A low-cost electric power wheelchair with manual and vision-based control systems

    Romero, B. ; Camacho, A. ; Varona, J. ; Delgado, C. ; Velazquez, R.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308554
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper presents the design, implementation and experimental platform of a low-cost intelligent wheelchair for the motor-disabled. The first prototype developed is an electric power wheelchair which cost is one third of the commercially available ones and is capable of both manual and autonomous operation. Manual operation relies on a joystick and is intended for people that, in spite of their disability, are well capable of maneuvering the wheelchair. Autonomous operation relies on a mobile robotics inspired computer vision system to navigate through corridors, halls, indoors/outdoors, among other structured environments and is indented for the severely impaired, such as the tetraplegics. Besides from being an affordable-to-everyone device, its current application is museum guidance: based on a location-aware interactive storytelling platform, the wheelchair guides the user among the museum's rooms while providing audio information. View full abstract»

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    A static synchronous series compensator model for EMTDC

    Huang, F.-W. ; Rigby, B.S. ; Harley, R.G.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160039
    Publication Year: 2002 , Page(s): 933 - 939 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    This paper presents a detailed simulation model of an SSSC for the simulation package EMTDC. The model includes a detailed representation of a three-level, 24-pulse voltage source inverter as well as the SSSC controls around it. The SSSC simulation model is first benchmarked against known results from the literature and then used to analyse the potential for an SSSC to cause network resonance. View full abstract»

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    A closer look on today's home and building networks

    Kastner, W. ; Palensky, P. ; Rausch, T. ; Roesener, C.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406889
    Publication Year: 2004 , Page(s): 1239 - 1244 Vol.2
    Cited by:  Papers (2)  |  Patents (3)

    IEEE Conference Publications

    This article discusses popular control networks in the area of home and building automation (LonWorks, EIB, BACnet). The comparison includes technical aspects (platforms, security, network management, etc.) and general conditions for development (tools, starter kits, costs, licence policies, etc,). Finally, we identify possible drawbacks and "white spots" on the way to totally integrated and networked buildings. View full abstract»

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    Electronic tap changers for use with ultra-light rural distribution lines

    Meyer, A.S. ; Van Coller, J.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821890
    Publication Year: 1999 , Page(s): 909 - 912 vol.2

    IEEE Conference Publications

    The use of cost-effective ultra-light medium voltage power lines for remote rural communities is proposed. This will require the development of an electronic on-load tap changer to cope with the excessive voltage drops. The tap changer will be used with typical rural distribution transformers and a novel feature will be that it will contain intelligence so that the tap position can be determined not only from the voltage but also from the current 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»

  • Freely Available from IEEE

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    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406771
    Publication Year: 2004 , Page(s): 682

    IEEE Conference Publications

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    Spiral antenna with external feeding for planar applications

    Gschwendtner, E. ; Loffler, D. ; Wiesbeck, W.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821910
    Publication Year: 1999 , Page(s): 1011 - 1014 vol.2
    Cited by:  Papers (9)  |  Patents (1)

    IEEE Conference Publications

    Spiral antennas are conventionally fed in the center of the spiral. For planar integration of the spiral antenna this conventional feeding structure is not possible. This contribution investigates the possibility of feeding an archimedean spiral antenna with two transmission lines connected to the outer radius of the spiral at opposite sides. Experimental results show that an operation bandwidth of 3:1 with radiation characteristics corresponding to the center-fed spiral is possible View full abstract»

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    Error propagation significance of Viterbi decoding of modal and non-modal ternary line codes

    Ouahada, K.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072016
    Publication Year: 2011 , Page(s): 1 - 5

    IEEE Conference Publications

    The state machine representation of ternary line codes helped making use of the Viterbi decoder (VD), which is considered to be the maximum likelihood decoding algorithm. Viterbi decoding algorithm provides 2 dB gain between soft and hard decisions decoding. Since Viterbi decoding algorithm is usually designed for linear convolutional codes, we expect error propagation when applied to ternary line codes. These codes have gain the trellis structure from their state machine representation. 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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    Optimization of resources for H.323 endpoints and terminals over VoIP networks

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

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

    IEEE Conference Publications

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

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    An image watermarking method based on the singular value decomposition and the wavelet transform

    Dili, R.B. ; Mwangi, Elijah
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401580
    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (3)

    IEEE Conference Publications

    A robust image watermarking scheme in which a binary image is embedded in the singular values of selected DWT blocks in the horizontal and vertical sub-bands of a 1-level decomposition of a gray-scale image is proposed. The embedded blocks are selected by a secret key to enhance imperceptibility. A watermarked image that is perceptually indistinguishable from the original is obtained. The watermarking retrieval is non-blind and requires the use of parameters extracted during the watermarking process. The performance of the proposed algorithm is tested by comparing the retrieved watermark to the original watermark. Computer simulation results show that the algorithm is robust to common signal processing attacks such as Gaussian noise, cropping, and low pass filtering. It is also resistant to JPEG compression. View full abstract»

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    Application of price sensitivity measurement method to assess the acceptance of electricity tariffs

    Sendegeya, A. ; Lugujjo, E. ; Da Silva, I.P. ; Sòˆder, L. ; Amelin, M.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308301
    Publication Year: 2009 , Page(s): 1 - 5

    IEEE Conference Publications

    Understanding the way customers respond to price changes is vital for any business. The price sensitivity measurement (PSM) analysis is widely used by marketers and researchers to assess customers' price sensitivity. This paper applies the concept of PSM analysis to assess electricity consumers' tariff perceptions, attitude to tariff changes and generally acceptance of tariffs. The method is tested using field survey data obtained from low demand consumers (households and small businesses) in urban and rural areas of Uganda after tariff increase. The results indicate that the new tariff approved by the regulator is within the range of tariffs possibly expected and likely to be accepted by consumers, but higher than the tariffs which consumers consider to be worthy. Also it is realized from the results that in Uganda, tariff expectations of rural consumers are different from the urban counterparts, the former expect lower tariffs with high degree of price sensitivity. Households show a higher degree of price sensitivity than commercial consumers. Conclusively, the information obtained from PSM can be used by utilities to make a preliminary assessment of consumers' expectations and/or acceptance levels of a certain range of tariffs during tariff review. 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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    Multi-variable series infinite impulse response least squares algorithm

    Havelka, J. ; Marusic, A. ; Kuzle, I.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401586
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    The comparison is discussed between the multi- variable LSQ algorithm and newly developed LSQ IIR algorithm; the operation characteristics of both algorithms are analyzed. The obtained analyses results indicate the advantages of LSQ IIR algorithm over the LSQ one. The LSQ IIR algorithm is used in extracting fundamental components of voltage and current waveforms from which the amplitudes and phases of each component are obtained. View full abstract»

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    Program for pH and conductivity measurements and determination of salt concentration in the ion exchange process for desalination of water

    Dube, N.M. ; Tzoneva, R.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146816
    Publication Year: 2002 , Page(s): 109 - 114 vol.1

    IEEE Conference Publications

    Procedures, algorithms and programmes for acquiring of pH and conductivity measurements for input and output flows of the cation load column and for calculation of the ion exchange process input and output variables are described. The programmes are a part of a developed system for monitoring and control of an ion exchange pilot plant at Peninsula Technikon, Cape Town. 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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    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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    Sustainability of biofuel in developing countries: case study Thailand and Tanzania

    Oonsivilai, A. ; Oonsivilai, K.A.G.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308156
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    The growth of energy demand together with the consequent increase of the cost of oil is great threats in developing countries economy. Alternative and sustainable energy such as biofuel seems to be a quick solution to this problem. The emerging industry is facing a lack of feedstock supplies, so it needs initiatives in crop cultivation technologies and competitive sourcing of appropriate feedstock which can alter the biofuel economics in developing countries. Some of biofuel production supply fall in food crops such as: cassava; maize; sorghum; etc., which is another critical need in developing countries. Since the biofuel production needs to be stable supply for the industry and also cost effective, a decision on which crop to put online with fuel production in developing countries while optimizing income is expressed in this paper. In this paper, several alternatives influenced by the geographical location of the country, economy and demand are analyzed and results are presented. View full abstract»

  • Freely Available from IEEE

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    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406769
    Publication Year: 2004 , Page(s): 674

    IEEE Conference Publications

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    A bitemporal multilevel secure database system

    Meanrach, W. ; Chittayasothorn, S.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401491
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    Multilevel database security is a security management which provides clearance levels for users. It also provides classification labels for the data. Most multilevel secure database systems employ the mandatory access control as proposed by Bell and La Padula. Most research works apply the multilevel secure technique to conventional relational databases. This research project proposes an extension to the mandatory access control so that it suits our application requirements. Moreover, the support of bitemporal database features is also included. Both valid time and transaction time are added to the already complex multilevel secure relational database. Integrity rules for this new model are introduced and finally, an extension to the SQL language is proposed to be used on the data model. 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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    Comparison of two terrestrial atmospheric turbulence suppression algorithms (March 2007)

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

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

    IEEE Conference Publications

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

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    Propagation measurements and modeling for terrestrial line-of-sight links at 19.5 GHz

    Naicker, K. ; Mneney, S.H.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406640
    Publication Year: 2004 , Page(s): 95 - 100 Vol.1
    Cited by:  Papers (2)

    IEEE Conference Publications

    With the rapid growth of the telecommunications market, the hunger for greater bandwidth and higher data rates has become unrelenting. Together with the congestion of the frequency bands below 12 GHz, frequency planning has become increasingly difficult. The use of the upper portion of the k-band for terrestrial communication systems is inevitable due to the better spectrum availability of this frequency region and the inherent ability to provide higher data rates. The frequency band from 18 GHz to 20 GHz has been identified as a suitable candidate for short-haul line-of sight (LOS) links. As a consequence, a 6.73 km terrestrial LOS link centered at 19.5 GHz has been recently established between the Howard College and Westville campuses of the University of KwaZulu-Natal (UKZN). In this paper, the research into the modeling and measurement of the proposed LOS link is discussed View full abstract»

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    Higher order adaptive arithmetic coding using the prediction by partial match algorithm

    Soyjaudah, K.M.S. ; Jahmeerbacus, I. ; Oolun, M.K. ; Bhurtun, C.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146829
    Publication Year: 2002 , Page(s): 177 - 180 vol.1

    IEEE Conference Publications

    Arithmetic coding completely bypasses the traditional coding paradigm that replaces an input symbol by a specific code. Arithmetic coding represents a stream of input symbols by a single codeword. The modelling paradigm is a key aspect in effective data compression. We present an adaptive higher order arithmetic coding scheme using the prediction by partial match (PPM) algorithm as well as a framework for the comparison of the different compression techniques. Simulation study conducted with this framework shows that compressive effectiveness and implementing complexity increases as the order increases but above a certain order there is no gain in compression with increasing costs. 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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    Dual pump fibre optical parametric amplifier based on four-wave mixing in a highly nonlinear fibre

    Kipnoo, E.R. ; Waswa, D. ; Muguro, K. ; Leitch, A.W.R.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072118
    Publication Year: 2011 , Page(s): 1 - 3

    IEEE Conference Publications

    In this study, the influence of highly nonlinear fibre (HNLF) in Fibre optical parametric amplifier (FOPA) gain has been done using numerical simulations. Results shows that nonlinear coefficient, γ affect the gain flatness of a FOPA. It was also found that amplifier gain increase with increase in fibre length. These results help in improving the transmission capacity of long haul system and dense wavelength division multiplexing (DWDM). View full abstract»

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    Moment-method analysis of waveguide diaphragms of arbitrary shape

    Konditi, D.B. ; Sinha, Sachendra N.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159961
    Publication Year: 2002 , Page(s): 517 - 524 vol.2

    IEEE Conference Publications

    This paper presents a moment-method analysis of waveguide diaphragms/irises of arbitrary shape. The "generalised network formulation" for aperture problems has been used for formulating the problem in terms of an operator equation. Triangular patch modelling, using suitably defined basis functions, has been used to solve the operator equation. Various pertinent parameters have been evaluated and numerical results validated. The validated results are found to be in good agreement with the published data. Thereafter, data generated for new problems have also been given. 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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    AFRICON, 2004. 7th AFRICON Conference in Africa

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

    IEEE Conference Publications

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    Performance evaluation of a simplified multi-function current transformer for high frequency power converters

    Pentz, D.C. ; van der Merwe, F.H.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072059
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    A multi-function current transformer introduced some years ago is revisited in an effort to improve its manufacturability. The original current sensor has the ability to accurately represent load and phase-arm currents in single phase full-bridge dc-dc-converter topologies under normal operating conditions. In the event of a phase-arm fault the shoot-through current can also be detected and the information used in the protection scheme. This sensor is however very complex to manufacture and this work presents a simplified version of the sensor, which still gives the most important information with a far less complex structure. This paper briefly discusses the original current sensor, proposes a simplified sensor and evaluates the new sensor in terms of performance. View full abstract»

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    Simulator of an optical communication system

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

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

    IEEE Conference Publications

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

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    75 Hz uninterruptible power supply for the Apollo high voltage direct current transmission terminal

    Venter, F.P. ; Oberholzer, G. ; Marshall, D.A. ; Parsons, M. ; Huempfner, R.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821873
    Publication Year: 1999 , Page(s): 813 - 818 vol.2

    IEEE Conference Publications

    The original power supply to the high voltage direct current (HVDC) converter bridges used in the Apollo terminal, is via motor generator sets. The frequency of the output voltage is 75 Hz, making it a special application. The availability and reliability of the motor generator sets have reduced due to its age, impacting the safe and reliable operation of the HVDC scheme. Uninterruptible power supplies (UPSs) were installed to replace the motor generator sets. The application of the UPSs is unique due to the 75 Hz output voltage criteria View full abstract»

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    MIMO channel synchronization using Golay Complementary Pairs

    Groenewald, J.M. ; Maharaj, B.T.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401609
    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (1)

    IEEE Conference Publications

    The use of Golay Complementary Pairs to synchronize a multiple-input multiple-output (MIMO) channel is presented in this paper. The Golay code's correlation properties make it ideal for this purpose. Golay codes have been used for synchronization before and has also been suggested for possible use in MIMO channels. However we have not seen it implemented and physically tested in the past. This paper shows the generation, simulation and implementation of such a code scheme on field programmable gate array (FPGA) and investigates it's performance on a MIMO channel. The results show excellent correlation of better than 90dB and almost perfect synchronization hence confirming that Golay codes or its complementary pair is a good candidate for MIMO synchronization. View full abstract»

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    On placing the reflection plane in numeric inductance calculations of thin-film superconducting structures using the method of images

    Fourie, C.J. ; Perold, W.J.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159958
    Publication Year: 2002 , Page(s): 499 - 504 vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    Determining the inductance of thin film superconducting structures accurately is extremely important in sub-Terahertz superconducting logic circuits. For numeric analysis, both the structure and ground plane need to be sufficiently segmented. The method of images significantly reduces the number of segments, but the selection of the position of the reflection plane is critical. The influence of the position of the reflection plane on inductance is investigated, and results presented. A study of segmentation and filamentation is also made, and these results used to calculate the inductance of a complex three-dimensional structure. View full abstract»

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    On accuracy of double-screw-drive robotic forceps

    Ishii, C. ; Nakakuki, T. ; Nishitani, Y.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308372
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    Recently, robotic surgical assistance systems are in clinical use in the field of minimally invasive surgery. We have developed a multiDOF robotic forceps manipulator using a novel omnidirectional bending technique, so far. The developed robotic forceps can bend without using wires. Without wires, it has high rigidity, and it can bend at 90 degrees in any arbitrary direction. The purpose of this paper is to evaluate the performance of the developed robotic forceps and to demonstrate its validity. Tracking control experiment for examining the accuracy of the DSD forceps was conducted, and an analysis of the accuracy was performed. 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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    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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    Optimal pricing of telecomm services in a developing country: A game theoretical approach

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

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

    IEEE Conference Publications

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

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