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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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    Realization of multi-level partial response modem in reconfigurable logic

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

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146827
    Publication Year: 2002 , Page(s): 167 - 172 vol.1

    IEEE Conference Publications

    Hardware realization is an important issue in communications system design. The use of high density reconfigurable logic instead of traditional DSP based solutions is investigated. The case of a multi-level partial response modem is discussed. The practical logic structures of the internal modem components including equalizer, Viterbi decoder and FIR filters are presented. Results of the hardware implementation are also 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.2004.1406806
    Publication Year: 2004 , Page(s): 852

    IEEE Conference Publications

  • Freely Available from IEEE

    [Breaker page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406843
    Publication Year: 2004 , Page(s): 1015

    IEEE Conference Publications

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    Wavelet transform for medical image compression

    Yelland, M.R. ; Aghdasi, F.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820829
    Publication Year: 1999 , Page(s): 303 - 308 vol.1

    IEEE Conference Publications

    MRA (Multiresolution Analysis), with its relationship to subband filtering and the ability to analyse a signal locally, is suited to the compression of discrete signals. Encoding the MRA, using EZW (Embedded Zerotrees of Wavelets) and extensions is generally well established. The application of the technique to medical imaging, specifically mammograms, is examined View full abstract»

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    Optimal MAC structures in an FPGA

    du Plessis, W.P.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146858
    Publication Year: 2002 , Page(s): 333 - 336 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    Field programmable gate arrays (FPGA) are rapidly gaining popularity for signal processing applications. Multiplication, addition and multiply-accumulate (MAC) are the most important building blocks in signal processing. This paper compares a number of structures to find the optimum configurations for minimum delay, size and cost in an FPGA. View full abstract»

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    Proposal for high accuracy linearity test of triangular waveform generators

    Alegria, F.C.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401583
    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (2)

    IEEE Conference Publications

    This paper addresses the possibility of testing, with high accuracy, triangular waveform generators using a procedure inspired on the ramp Vernier test of analog to digital converters. This allows the use of a low cost data acquisition board to efficiently measure the nonlinearity of a triangular waveform. The idea is to use the waveform generator under test to produce the stimulus signal for the testing of the data acquisition system and then use the results of that test to correct its nonlinearity. This removes the influence of the acquisition system's nonlinearity on the estimation of nonlinearity of the waveform generator. View full abstract»

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    Improving three-phase induction machines power factor using single phase auxiliary winding fed by an active power filter

    Muteba, M.C. ; Jimoh, A.A. ; Nicolae, D.V.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401570
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Patents (1)

    IEEE Conference Publications

    This paper presents a three-phase induction machine that employs a single phase auxiliary winding, which is only magnetically coupled to the stator main winding, and controlled by an active power filter. The active filter consists mainly of a two leg PWM voltage source inverter, which together with the auxiliary winding serves to supply leading reactive power to the machine. With sufficient ampere-turn capability of the auxiliary winding and an adequate control algorithm, the computer simulation results show that it is possible to obtain nearly unity power factor operation at the terminals of the main winding over a range of load conditions including rated load. The simulated power factor of this scheme is compared with the measured result for a typical practical induction motor. 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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    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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    Evaluating Viterbi decoded Reed-Solomon block codes on a Complex Spreaded DS/SSMA CDMA system. Part II: channel model, evaluation platform and results

    Staphorst, L. ; Linde, L.P.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406687
    Publication Year: 2004 , Page(s): 335 - 340 Vol.1

    IEEE Conference Publications

    For pt.I see ibid., p.329-34. In recent years, the Viterbi algorithm (VA) has been shown to be an efficient trellis decoder for binary and non-binary linear blocks. In our simulation study, the performance of VA decoded non-binary Reed-Solomon (RS) block codes, employed in a wideband code division multiple access (CDMA) system, operating in multipath fading channel conditions, was considered. A RAKE receiver-based direct sequence spread spectrum multiple access (DS/SSMA) quadrature phase shift keying (QPSK) system is employed. It uses complex spreading sequence (CSS), such as Frank-Zadoff-Chu (FZC), double sideband (DSB) constant envelope linearly interpolated root-of-unity (CE-LI-RU) filtered general chirp-like (GCL), analytical bandlimited complex (ABC) and quadriphase (QPH) sequences. The paper first describes a novel complex multipath fading channel simulator model. Next, the realistic multiuser multipath fading performance evaluation platform is described. Lastly, simulated bit error rate (BER) performances are presented for uncoded systems and systems employing VA decoded non-binary RS block codes under realistic multipath fading channel conditions. The effects of multiuser interference (MUI) and of channel state information (CSI) on the decoding performance of the VA are also considered View full abstract»

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    Improved AC-DC transfer uncertainties at the NML using the PHIT/PTB thin film multijunction thermal converters

    Temba, M.L. ; Costa, A.B.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821857
    Publication Year: 1999 , Page(s): 731 - 732 vol.2

    IEEE Conference Publications

    The authors describe how thin-film multijunction thermal converters have been used to improve the AC-DC transfer uncertainties from ±15 ppm of the single junction thermal converters to ±3 ppm in the audio frequency range at South Africa's National Metrology Laboratory (NML) View full abstract»

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    Conscious learning semiotics systems to assist human persons (CLS2H)

    Doeben-Henisch, G. ; Abrami, G. ; Pfaff, M. ; Struwe, M.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072043
    Publication Year: 2011 , Page(s): 1 - 7

    IEEE Conference Publications

    Challenged by the growing societal demand for Ambient Assistive Living (AAL) technologies, we are dedicated to develop intelligent technical devices which are able to communicate with human persons in a truly human-like manner. The core of the project is a simulation environment which enables the development of conscious learning semiotic agents which will be able to assist human persons in their daily life. We are reporting first results and future perspectives. View full abstract»

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    Design principles for 2D local mapping using a laser range finder

    Corregedor, A.R. ; Meyer, J. ; Du Plessis, F.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072083
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper presents a guide on how to obtain a local map from a SICK LMS291 laser range finder (LRF). The type of local map produced is a feature map, where the objects (or features) in the world are represented by line segments. Much research has been done on local maps and how they are created with a LRF. However, there is usually a fundamental link missing on the hardware setup (and software commands) to allow a local map to be produced in a real world situation from a SICK LMS291 LRF. A design principle is therefore produced, which consists of two main aspects. The first aspect is a hardware setup, which uses off the shelf components to allow the SICK LMS291 LRF to operate at a baud rate of 500 000 baud. At a rate of 500 000 baud the LRF is able to return the highest possible resolution scan of its environment. The second aspect are the steps to implement a line extraction algorithm, which allows one to fit line segments to offline data sets and to data points extracted from the LRF in real time. View full abstract»

  • Freely Available from IEEE

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    AFRICON, 2004. 7th AFRICON Conference in Africa

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

    IEEE Conference Publications

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    Laboratory study of long, low current power frequency arcs: initial results

    Britten, A.C. ; Kohimeyer, R.E. ; Mathebula, M.E.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159986
    Publication Year: 2002 , Page(s): 645 - 648 vol.2

    IEEE Conference Publications

    The paper describes the quenching behaviour of physically long, low current, medium voltage (1-20 kV) 50 Hz arcs. The circuit devised to generate the arcs is described, together with the parameters of the multi-tap reactor used to limit the prospective short-circuit currents. The results presented include examples of the voltage-time waveforms and the dynamic volt-current characteristics. The latter characteristics are compared with those reported by Cobine. Initial criteria are proposed for predicting arc stability or quenching; these are based on the excursions of the volt-time characteristic towards the static load line. The need for further analysis of the Eskom data is stressed. View full abstract»

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    Why electronic and not electromechanical ELCBs ?

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

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

    IEEE Conference Publications

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

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    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 advanced real-time research and teaching tool for the design and analysis of control

    Stylo, A. ; Diana, G.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820939
    Publication Year: 1999 , Page(s): 511 - 516 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    Currently, the relatively low-level development tools available at most tertiary institutions greatly limit the scope of real-time control projects which can be tackled at an undergraduate level. Although more sophisticated tools are available on the market, their prices are prohibitive. This paper presents a low-cost, integrated environment which allows for rapid prototyping of advanced control algorithms designed in Simulink on an affordable DSP based processing platforms in real-time View full abstract»

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    Optical buffering and switching in packet switched optical networks

    Geldenhuys, R. ; Leuschner, F.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146844
    Publication Year: 2002 , Page(s): 259 - 262 vol.1

    IEEE Conference Publications

    Optical packet switching provides the advantages of transparency and the efficient use of the bandwidth provided by WDM on optical transport networks. There are however various impediments to deploying this technology in an all-optical fashion: optical buffering is inefficient, and all-optical signal processing has not been implemented in networks. It is possible to utilise optical signal processing for all-optical header processing and all-optical switching, and proof of concept experiments have been done to verify this. View full abstract»

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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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    Baseband digital synthesis and analysis for high-frequency software radio applications

    van Rooyen, G.-J. ; Lourens, J.G.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146865
    Publication Year: 2002 , Page(s): 371 - 376 vol.1

    IEEE Conference Publications

    Software-defined radio (SDR) employs digital modulation and demodulation techniques to solve traditionally analogue communications problems. To achieve this, the SDR must be capable of synthesising and analysing high-frequency analogue signals. However, sampling frequencies are limited by the capabilities of digital-to- analogue and analogue-to-digital converter technology. This paper presents quadrature synthesis and analysis techniques that cause the sampling rate, filtering frequencies and processing requirements to become functions of the signal bandwidth rather than the highest signal frequency component. A new investigation of the inaccuracies inherent to quadrature mixing is presented, and new techniques for digital compensation are suggested. It is shown that these proposed techniques allow all mixing artefacts to be suppressed to the level of the system's quantisation noise. View full abstract»

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    An integrated security model for WLAN

    Odhiambo, O.N. ; Biermann, E. ; Noel, G.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308183
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    IEEE802.11 wireless local area networks (WLAN) are widely deployed as extension to corporate wired LAN infrastructures. The implication of including WLAN as part of the computing infrastructure means more critical information and data is carried over the air. The threats of intrusion and denial of service is real since wireless networks have broadcasted traffic. IEEE 802.11 defines WEP, WPA and WPA2 security protocols as possible countermeasures. The most recent model defined by IEEE, the WPA2, emphasizes data confidentiality, integrity and authentication but pays little attention to availability issues. Management and control frames in WPA2 are still sent in clear making the model vulnerable to DoS attacks. The failure recovery processes requires reauthentication and reassociation a fact which makes the model easily exploited by various DoS attacks. WPA2, defines a hybrid network that implements both WEP and TKIP together with WPA2 which creates a vulnerability called security level roll back attack thus making the strong confidentiality and integrity measures in WPA2 be as weak as WEP. In this paper, we propose an integrated security model (ISM) that incorporates a drop policy to defend against DoS attacks. We assume the use of CCMP to provide confidentiality and integrity and use EAP-TTLS/802.11x with RADIUS to provide authentication. We use simulation in OPNET to show that our security model performs better to provide improved security in terms of confidentiality, integrity, authenticity and availability. View full abstract»

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    Radiation efficiency of broadside conductor-backed CPW-fed twin slot antennas on two-layer dielectric substrate

    Jacobs, J. ; Joubert, J. ; Odendaal, J.W.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159964
    Publication Year: 2002 , Page(s): 531 - 533 vol.2

    IEEE Conference Publications

    Radiation efficiency of twin slots fed by coplanar waveguide on a conductor-backed two-layer substrate with high-low dielectric permittivities is investigated. It is shown that radiation efficiency can be significantly increased compared to the radiation efficiency of a single slot when the slots are appropriately spaced. Radiating slot feed lines are explicitly accounted for. View full abstract»

  • Freely Available from IEEE

    Copyright


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406607
    Publication Year: 2004 , Page(s): 0_4

    IEEE Conference Publications

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    The value of supplemental instruction in conceptual learning

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

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

    IEEE Conference Publications

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

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    Optimization of the compressed air-usage in South African mines

    Hassan, A. ; Ouahada, K. ; Marwala, T. ; Twala, B.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072145
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (2)

    IEEE Conference Publications

    The critical electricity supply in South Africa has necessitated the implementation of demand-side management (DSM) projects. Load shifting and energy efficiency projects were introduced on mining sectors to reduce the electricity usage during day peak time. As the compressed air networks is using a large amount of mines' electricity, we investigate in this paper the possibility of improving and optimizing the compressed air usage at two different mines to reduce the electricity consumption on the compressed air system. View full abstract»

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    Experiences in data collection for the training of an automatic speech recognizer in Sepedi

    Manamela, M.J.D. ; Botha, E.C.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146866
    Publication Year: 2002 , Page(s): 377 - 381 vol.1

    IEEE Conference Publications

    This paper reports on the process, experiences and statistics of collecting Northern Sotho (Sepedi) telephone speech data for the training of an automatic speech recogniser. A toll-free telephone speech recording platform was used for the data collection. An analysis of the collected speech data together with observations made during supervised calls are included before discussing preliminary results. 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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    Real-time simulation and laboratory measurements of a system to study fault tolerance of adjustable speed drives

    Palhad, C. ; Rigby, B.S.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072014
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    Due to the complexity of modern industrial drive systems, studying drive performance under voltage dip conditions must realistically be conducted using the actual drive hardware. This paper describes the development of a test system to examine a new approach for studying drive performance under voltage dip conditions using hardware-in-loop connection of the drive controllers to a real-time digital simulation of the plant. Detailed comparative studies are presented to verify real-time models of the component parts of a specific study system against laboratory measurements. View full abstract»

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    Cascade disruption of generation - a special focus on African grid volnurebilities

    Viljoen, M. ; de Kock, J.A.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072149
    Publication Year: 2011 , Page(s): 1 - 4
    Cited by:  Papers (1)

    IEEE Conference Publications

    Large scale network disruption often lies at the heart of regional blackouts, and often disrupts entire communities in terms of their normal activities and well being. Disruptions caused by cascading failure of generating units are potentially devastating to the continued operation of large power systems, and deserving of dedicated attention. This paper deals with this form of power system disruption in the context of Southern Africa. The case in Africa, unlike networks integrated into super grids, requires a special approach in terms of resilience. The devices of last resort are often limiting or unproven, and forms a theoretical back-up only. 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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    Nonlinear model identification of fuel cell power plant

    Jurado, F.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406788
    Publication Year: 2004 , Page(s): 769 - 774 Vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    Probably, fuel cell will be a dominant distributed energy resource. The computational burden required for the simulation is highly dependent on the complexity and accuracy of each model. The factory need often to provide the user a reliable low-complexity prototype model of the fuel cell, sufficiently accurate for the above application. In This work the nonlinear autoregressive exogenous (NARX) approach is used to analyse the dynamics of this fuel cell. View full abstract»

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

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

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

    IEEE Conference Publications

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

  • Freely Available from IEEE

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    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406876
    Publication Year: 2004 , Page(s): 1186

    IEEE Conference Publications

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    Intelligent static VAr compensator control for supply loading optimization

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

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

    IEEE Conference Publications

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

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

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

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

    IEEE Conference Publications

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

  • Freely Available from IEEE

    Copyright


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406762
    Publication Year: 2004 , Page(s): 0_4

    IEEE Conference Publications

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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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    On stability of linear systems with time-varying delay: generalized Lyapunov equation

    Runyi Yu
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820970
    Publication Year: 1999 , Page(s): 569 - 574 vol.1

    IEEE Conference Publications

    This paper presents some delay independent stability criteria for linear systems with time-varying delay. The main result is stated in terms of the so-called generalized Lyapunov equation. Optimization and simplification of the main result are discussed in detail. Comparison with some other criteria in the literature is examined through analysis and examples View full abstract»

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    Nonlinear artificial line models for power BAW resonators

    Constantinescu, F. ; Gheorghe, A.G. ; Nitescu, M. ; Florea, A.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072051
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (2)

    IEEE Conference Publications

    The linear artificial transmission line model developed in 1986 by Morris and Hutchens is extended for nonlinear piezoelectric materials. Two new physical circuit models are proposed, one of them taking into account a mechanical nonlinearity while the other considers an electrical nonlinearity. Both nonlinearities are described by third degree polynomials. The measurements of the amplitude-frequency effect and of the frequency characteristic of the second harmonic reflected power have been compared with simulation results. The good agreement for AlN resonators with mechanical nonlinearity suggests that it can be the origin of their nonlinear behavior. 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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    A time step choice algorithm for transient analysis of circuits

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

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

    IEEE Conference Publications

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

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

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

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

    IEEE Conference Publications

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

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    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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    Virtual wired control networks: a wireless approach with Bluetooth

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

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146846
    Publication Year: 2002 , Page(s): 269 - 272 vol.1
    Cited by:  Patents (1)

    IEEE Conference Publications

    One of the most compelling challenges of the next few years is the integration of different types of wired and wireless networks into a system that enables the intercommunication between devices ranging from control and monitoring devices to consumer electronic equipment. This paper discusses the possibilities of integrating state-of-the-art wireless technology into common control networks. Given a suitable architecture an algorithm is proposed, that self-installs wireless control nodes into existing fieldbus networks. As a case study, the BlueLon project is presented. It tries to integrate Bluetooth technology into the distributed fieldbus system of LonWorks. View full abstract»

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    Design of a dual-loop frequency synthesizer

    Sinha, S. ; du Plessis, M.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406732
    Publication Year: 2004 , Page(s): 525 - 529 Vol.1

    IEEE Conference Publications

    Due to higher costs, bulkiness and larger power consumption, it is no longer desirable to implement wireless transceivers with discrete elements. The paper describes the design of an essential component in wireless transceivers, the frequency synthesizer. The synthesizer is implemented using the dual phase locked loop (PLL) architecture. The synthesizer generates signals in the 2.4-2.5 GHz range with a 1 MHz resolution. Using the 0.35 mum CMOS process, post-layout simulations showed a phase noise of -82 dBc/Hz at an offset of 10 kHz and reference sidebands at -60 dBc, both these parameters with respect to a 2.45 GHz carrier View full abstract»

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    Model predictive control of an electric arc furnace off-gas procedure combined with temperature control

    Oosthuizen, D.J. ; Craig, I.K. ; Pistorius, P.C.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820888
    Publication Year: 1999 , Page(s): 415 - 420 vol.1

    IEEE Conference Publications

    Model predictive control (MPC) of an electric arc furnace (EAF) off-gas process combined with temperature control is investigated. A more predictable process, safer working environment, cleaner emission gases and reduced energy wastage are some of the advantages obtained by controlling relative furnace pressure, CO-emission and temperature View full abstract»

  • Freely Available from IEEE

    Message from the technical programme chair

    Helberg, A.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406613
    Publication Year: 2004 , Page(s): 0_10

    IEEE Conference Publications

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    Mobile banking: A comparative study of South Africa and Nigeria

    Bankole, O. ; Cloete, E.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072178
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    This study identifies factors that influence user acceptance of m-banking in South Africa and Nigeria. This research is aimed at examining the relative differences/similarities of mobile banking usage in South Africa and Nigeria. Several studies on the acceptance of m-banking have produced various results across different countries. This can be accredited to the dissimilar socio-cultural composition of such countries. The user acceptance of m-banking in a country is determined by distinct characteristic factors which are unique to that country. This study employed quantitative and qualitative data gathering and analysis processes. The result showed that SMS alert for account transactions is the most used m-banking service in both countries. The research indicates that culture has an indirect impact on the user acceptance of m-banking. Factors such as awareness, convenience and literacy level were also revealed to influence the acceptance of m-banking in both countries. 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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    On-line remote and automatic switching of consumers’ connection for optimal performance of a distribution feeder

    Popoola, O. ; Jimoh, A. ; Nicolae, D.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401520
    Publication Year: 2007 , Page(s): 1 - 6

    IEEE Conference Publications

    Load balancing on phases is performed using a conventional trial and error approach. With this approach, service interruption is unavoidable; hence rearrangement of consumers load distribution points on phases cannot be performed frequently. Also phase voltage and current imbalances might improve using this approach but the change does last for too long. To get the secondary distribution to operate at its optimal performance, a technique in the form of remote and automated technology is needed. This paper contributes such a technology at the low voltage side of the distribution network. The proposed static transfer switching technology is based on the open-transition switch that enables transfer or arrangement of consumer loads in a three-phase system within milliseconds and supervisory control system for effective co-ordination, computational and control of other intelligent units. View full abstract»

  • Freely Available from IEEE

    [Back cover]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406758
    Publication Year: 2004 , Page(s): 652

    IEEE Conference Publications

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

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

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

    IEEE Conference Publications

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

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

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

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

    IEEE Conference Publications

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

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

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

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

    IEEE Conference Publications

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

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    SELDI-TOF-MS pattern analysis for cancer detection as a base for diagnostic software

    Radlak, M. ; Klempous, R.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401485
    Publication Year: 2007 , Page(s): 1 - 6

    IEEE Conference Publications

    Cancer is one of the twenty-first century disease affecting thousands of people around the globe every year. The biggest problem is that there is currently no non-invasive method for detection, while early detected can be cured avoiding death of a person. SELDI-TOF-MS can be used but resulting data are very noisy. Therefore methods for data preprocessing and classification are reviewed and their effectiveness measured. Finally requirements of diagnosis software are discussed. View full abstract»

  • Freely Available from IEEE

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    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406624
    Publication Year: 2004 , Page(s): 20

    IEEE Conference Publications

  • Freely Available from IEEE

    [Blank page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406890
    Publication Year: 2004 , Page(s): 1246

    IEEE Conference Publications

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    Modeling and analysis of a multibus reticulation network with multiple DG. Part II. Electrical fault analysis

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

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406797
    Publication Year: 2004 , Page(s): 811 - 814 Vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

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

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    Estimating the viral load response time after HIV chemotherapy

    Jeffrey, A.M. ; Xia, X.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146809
    Publication Year: 2002 , Page(s): 77 - 80 vol.1
    Cited by:  Papers (2)

    IEEE Conference Publications

    HIV therapy is considered to be effective if it can suppress the viral load to below 50 copies per ml of plasma in less than 6 months. This response time to therapy can be estimated towards the development of an on/off control strategy for the chemotherapy of HIV as well as to aid clinicians in therapy and measurement scheduling. 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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    An implementation of generalised convolution for image processing

    Levitt, S.P. ; Dwolatzky, B.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146854
    Publication Year: 2002 , Page(s): 311 - 316 vol.1

    IEEE Conference Publications

    Generalised convolution is a ubiquitous image processing operation in which a local operator is applied to an image in order to transform it in some manner. We present an extensible and flexible C++ implementation of generalised convolution in the image domain that is based on the Strategy design pattern. Our implementation facilitates the coding of different local operators. View full abstract»

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    A queueing model for CDMA cellular networks using soft capacity

    Narrainen, R.P. ; Takawira, F.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820783
    Publication Year: 1999 , Page(s): 147 - 152 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    CDMA cellular radio networks are well known for their time-varying interference dependent capacity. However, many papers in the literature have used a single moment approach and assumed an average fixed value of CDMA capacity in mathematical analyses. In this paper we propose an analysis that takes into account the time-varying nature of CDMA capacity. We assume, from the central limit theorem, that the system interference is Gaussian and propose an expression for the system capacity. We then present a traffic model for a power controlled DS-CDMA network where only handoff calls are queued. Network performance is computed in terms of the carried traffic, the queue length and the probability of blocking new and handoff calls View full abstract»

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    Cryogenic CMOS-based control system

    van Niekerk, P.C. ; Fourie, C.J.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401493
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (1)

    IEEE Conference Publications

    This article describes the design and evaluation of a CMOS-based control system for use in cryogenic vacuum environments. A control system, with accompanying software, was designed to interface superconductive digital and sensor circuits in a cryocooler to portable computers at room temperature. It is designed to operate as close as possible to the superconductors to reduce thermal noise. The controller connects via a fibre optical RS-232 interface to any USB connector on a computer at a data rate of 1 Megabaud. The interface to the superconductor electronics consists of 16-bit ultra low-noise ADCs and DACs. Extensive research and testing was done on all components - both active and passive - to validate operation at 60 K. An integrated temperature control system was designed to ensure a stable temperature environment. Results are shown and discussed. 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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    Identifiability of run-of-mine ore grinding mill circuit parameters

    le Roux, J.D. ; Craig, I.K.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072076
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    A nonlinear phenomenological model of a grinding mill is used to determine five run-of-mine (ROM) grinding milling circuit parameters. The five parameters are fraction of fines and fraction of rocks in the ore fed to the mill, rock and steel abrasion factor and power needed for a ton of fines produced. The model is analyzed according to an identifiability procedure to identify the system data needed to calculate the parameter values. It is shown that a minimum of 18 measurements for a single-stage closed circuit and a minimum of 16 measurements for a single-stage open circuit are needed to determine the five milling circuit parameters. For the closed circuit, the time signals of 8 quantities in the mill will be sufficient to determine all five parameters since the other 10 measurements are time derivatives of these signals. The measurements require the holdup quantities of states within the mill. Since these measurements are not readily available in real-time at plants, it may be difficult to estimate the parameters on-line. 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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    FPGA-implemented carrier based SPWM multilevel controller

    Ebersohn, G. ; Gitau, M.N.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406873
    Publication Year: 2004 , Page(s): 1175 - 1178 Vol.2

    IEEE Conference Publications

    Multilevel converters were originally developed for high voltage high current applications. These topologies have several advantages to offer that include voltage blocking requirements for the individual components in the switch matrix, lower EMI generation, lower THD, better output waveform as well as higher efficiency for a given quality of output waveform. However, all these benefits comes with the price of added controller and circuit complexity. The aim of This work is to show a total digital solution to the generation of control signals for a seven level diode clamped multilevel inverter. 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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    Adaptive decision-taking of protection systems in networks with dispersed power generating sources

    Halinka, A. ; Sowa, P. ; Szewczyk, M.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072134
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    Incorporating renewable energy sources into the power system is connected with a number of new challenges, i.e. for the power system protections. Thus, several problems have been identified in addition to the factors which occur in such systems without the connected i.e. wind farms. Taking the presence of wind farms into account, the selectivity and the speed of decisions of distance protection will probably be very limited. One of the possible solutions will be creating protection systems which use data from the selected area of the power system network to increase the correctness of decision-taking by adapting settings of protection functions to the changing conditions. This paper will discuss the proposal of such a solution as well its simulation results. View full abstract»

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    250 kW transformer-less voltage dip compensator

    Visser, A.J. ; Mouton, H.D.T.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821882
    Publication Year: 1999 , Page(s): 865 - 870 vol.2
    Cited by:  Papers (3)  |  Patents (1)

    IEEE Conference Publications

    Voltage dips cause serious problems for sensitive equipment in industrial applications. The possibility of applying a transformerless dip compensator is investigated as a cost-effective solution to overcome this hazard. This is achieved by means of a power electronic multi-level converter placed in series with the supply View full abstract»

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    The exponential stability of the vibration of two connected flexible arms by direct strain feedback control

    Baozhu Guo
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820903
    Publication Year: 1999 , Page(s): 447 - 452 vol.1

    IEEE Conference Publications

    Two uniform Euler-Bernoulli beams connected by a spring which models the vibration of two flexible arms is considered. It is shown that the direct strain feedback control which makes the closed-loop system of a single beam exponentially stable also works for current case when the spring mass is less than a fixed value. The closed-loop system is shown to be a Riesz system and the general condition for the exponential stability of the system is presented View full abstract»

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    A holistic test procedure for security systems software: An experience report

    Dhlamini, S.M. ; Mwakabaga, T. ; Kachienga, M.O.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401471
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    This paper presents a comprehensive holistic software test procedure for security systems applications. The method evaluates the functional requirements of a security system. Based on the functional requirements and the hardware solution that satisfies the requirements, a test procedure was developed. The test procedure evaluates the correctness, robustness, efficiency, portability, integrity, verifiability and validation and ease of use. An impact assessment is done to assess the cost effectiveness, compatibility and reusability of the software with existing hardware. The study found that the impact of software on the business process is the most important test for any new software prior to deployment. View full abstract»

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

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

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

    IEEE Conference Publications

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

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    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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    Performance of a synchronous balanced QPSK CDMA system using complex spreading sequences in AWGN

    Staphorst, L. ; Jamil, M. ; Linde, L.P.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820799
    Publication Year: 1999 , Page(s): 215 - 220 vol.1
    Cited by:  Papers (2)

    IEEE Conference Publications

    Due to the availability of potentially large sets of sequences with good correlation characteristics, the interest in the implementation of complex spreading sequences (CSS) in code division multiple access (CDMA) systems, has increased dramatically. In this paper, the bit error rate (BER) performance of a synchronous balanced quadrature phase shift keying (QPSK) CDMA system employing different classes of CSS, is presented View full abstract»

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    Low-complexity constrained LMMSE estimator for the sparse OFDM channels

    Golovins, E. ; Ventura, N.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401614
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    In this article the constrained linear minimum mean squared error (CLMMSE) algorithm is presented for the multipath channel response estimation in the OFDM systems using equispaced and equipowered pilot subcarriers. It relies on tracking of the channel correlation and signal-to-noise ratio and has a low computational complexity due to the transform-domain processing and no matrix inversions required. The proposed algorithm exhibits a substantial performance improvement for the sparse channels (9 dB in MSE and 1.4 dB in BER), whereas for channels with the dense impulse responses its accuracy is equivalent to the LMMSE scheme with the robust design parameters. View full abstract»

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    Two moment analysis of channel reservation in cellular networks

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

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

    IEEE Conference Publications

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

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    An investigation into the measurement techniques to compile an insulator pollution severity application map for South Africa

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

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159975
    Publication Year: 2002 , Page(s): 585 - 591 vol.2
    Cited by:  Papers (4)

    IEEE Conference Publications

    The Insulator Pollution Severity Application Map (IPSAM) for South Africa is being developed to identify pollution severity levels throughout the country. Directional Dust Deposit Gauges (DDDG's) and Equivalent Salt Deposit Density Gauges (ESDD's) are installed at various sites to measure the aggressiveness of the environment. A Geographic Information System (GIS) map was developed to accurately determine the location of pollution monitors progressively inland from the coast in order to study the effect of distance from the sea. A weather tower is used for the installation of pollution monitors to study the effect of height above ground level. View full abstract»

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    Efficient frequency domain univariate Parzen approximation and applications

    Esterhuizen, G. ; du Preez, J.A.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146850
    Publication Year: 2002 , Page(s): 287 - 292 vol.1

    IEEE Conference Publications

    This paper introduces a frequency domain approximation to the univariate Parzen probability density function estimator. It is applied to construct an efficient semi-parametric density function estimator and density function distance measure that operates directly from sample data. The complexity of the techniques are constant with respect to the number of data samples and only depends on a pre-determined factor controlling the accuracy. View full abstract»

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    Facial component features for facial expression identification using Active Appearance Models

    Wilfred, O.O. ; Geum-Boon Lee ; Jung-jin Park ; Beom-joon Cho
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308126
    Publication Year: 2009 , Page(s): 1 - 5

    IEEE Conference Publications

    Statistical methods of shape and appearance are powerful tools used in computer vision for near-correct interpretation of images. In this paper, we present a method for classifying facial expressions based on the extracted features of facial components. The face, the window to the inner self of an individual can be analyzed for outright expressions like sadness, happiness, anger, surprise, disgust and fear. The facial region is detected; pre-processing is done on the image by using Active Appearance Model (AAM) to extract the vital feature on the facial components. Six classes are formed based on the different expressions and the model from the AAM procedure used to compare with the query image/face. Mahalanobis distance algorithm is used to classify the image in question into the best-fit class. Japanese Female Facial Expression (JAFFE) public database is used to evaluate our method with over 200 images of still images used in our experiment. A higher classification rate observed. View full abstract»

  • Freely Available from IEEE

    [Breaker page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406709
    Publication Year: 2004 , Page(s): 429

    IEEE Conference Publications

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    Exploitation of stream processing on graphical Processors in Inertial Navigation

    Roets, S.F. ; Meyer, J. ; Du Plessis, F.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308388
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper focusses on implementing an inertial navigation system (INS) on a graphics processor unit (GPU). The GPU allows simultaneous processing of large amounts of data and multiple use of the algorithm at the same time. Using the stream processing abilities of the GPU an investigation is launched into the simultaneous running of several navigation algorithms (INS's) with different sensor error models for each INS algorithm. The simultaneous processing of several INS systems allows for faster simulation times and data analysis. Aiding an error perturbed INS with a Kalman filter (KF) is considered when tuning the KF to obtain the optimally tuned KF from n amounts of KF's. View full abstract»

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

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

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

    IEEE Conference Publications

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

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    Effective Earth radius factor characterization for line of sight paths in Botswana

    Afullo, T.J. ; Odedina, P.K.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406664
    Publication Year: 2004 , Page(s): 227 - 231 Vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    The ITU has adopted new methods for predicting the deep-fading distribution due to multipath propagation for the average worst month over UHF and SHF terrestrial line-of-sight links. These methods employ refractivity gradient statistics available from world maps, and are recommended for application in all regions of the world. In this regard, significant progress in the global climatological modeling of the main propagation effects in clear-air and precipitation conditions have been reported (Olsen, R.L. and Tjelta, T., IEEE Trans. Anten. and Propag., vol.47, no.1, 1999; Olsen, Proc. 3rd Regional Workshop on Radio Communications in Africa, 1999), with an attempt to relate the results to the African continent. D.C. Baker and A.J. Palmer (see Trans. SAIEE, vol.93, 2002) have proposed a model for the cumulative distributions of the fraction of times of occurrence for certain values of the k-factor for South Africa. They have assumed, based on earlier reports, that a normal distribution for the pdf of the k-factor is appropriate. We develop an empirical model for the k-factor distribution based on radiosonde data for Botswana. We model the distribution for the months of February, May, August and November, as per ITU-R practice, at height ranges of 0-500 m and 0-200 m above ground level 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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    Adaptive Robust Anti-windup Generalized Predictive Control (RAGPC) of Non-minimum phase systems with input constraints and disturbance

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

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

    IEEE Conference Publications

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

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    Speed control of a DC drive based on optimal performance

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

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

    IEEE Conference Publications

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

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    Frequency management in South Africa

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

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

    IEEE Conference Publications

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

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    Non-priority QoS guarantee for next generation routers

    Salami, O. ; Chan, H.A. ; Dlodlo, M.E.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401564
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    Virtual Output Queuing (VOQ) is a proffered queuing strategy that solves the head of line blocking (HoL) issue in routers implementing input queuing (IQ). Also, VOQ can achieve 100% throughput with an effective scheduler. However, most schedulers for VOQ are deterministic algorithms, which either provide QoS guarantee or do not. Even though these algorithms have high performance, they schedule packets arbitrarily or with priority thereby starving some traffic. These algorithms may become inadequate in future networks where data rate continues to increase and traffic with different QoS requirements co-exist. This paper recommends a probabilistic QoS guarantee for routers using VOQ. Probabilistic QoS guarantees for network traffic ensure fairness and prevent traffic starvation. A probabilistic scheduling algorithm termed Iterative Probabilistic Scheduling (IPS) is proposed. IPS guarantees probabilistic QoS with a basic mathematical operation as its scheduling policy. From simulation, it achieves a high throughput performance and does not starve traffic. IPS was used at the first stage of the Multi-stage Queuing and Scheduling (MQAS) architecture. MQAS is a two-stage queuing architecture with VOQ at the input and Output Queuing (OQ) at the output of the router. View full abstract»

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    Zeros and the output-zeroing problem in a LTI system with single state delay

    Tokarzewski, J. ; Sokalski, L.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401459
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    The concept of invariant zeros in a linear time- invariant system with state delay is considered. The problem of zeroing the system output is discussed and a general formula for output-zeroing inputs is provided. View full abstract»

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    Dual-Repeat-Punctured Turbo Codes on AWGN channels

    Pillay, N. ; Hongjun Xu ; Takawira, F.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308225
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    Turbo codes (TC) is a powerful branch of error-control coding that has exhibited performances close to the Shannon limit, whilst offering a reasonable level of computational complexity. Repeat-punctured turbo codes (RPTCs) exploit the fact that the use of larger interleavers correspond to better bit-error rate (BER) performances for the conventional turbo code, and makes use of repetition and puncturing to improve the performance of the conventional turbo code for moderate to high signal-to-noise ratios (SNRs). Motivated by turbo codes and repeat-punctured turbo codes, we study the use of a new scheme, dual-repeat-punctured turbo codes (DRPTC) in the additive white Gaussian noise (AWGN) channel. DRPTCs primarily make use of repetition and puncturing and the structure of the conventional turbo code to yield a more superior performance. The decoding in principle follows the technique of turbo decoding but needs some changes to yield the performance improvement. Simulation results for the AWGN channel is presented together with the analytical union bounds derived from transfer-function bounding techniques, and the codeword distance-spectrum for the proposed scheme is presented and evaluated. View full abstract»

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    On-line remote and automatic switching of consumers’ connection for optimal performance of a distribution feeder

    Popoola, O. ; Jimoh, A. ; Nicolae, D.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401536
    Publication Year: 2007 , Page(s): 1 - 6

    IEEE Conference Publications

    Load balancing on phases is performed using a conventional trial and error approach. With this approach, service interruption is unavoidable; hence rearrangement of consumers load distribution points on phases cannot be performed frequently. Also phase voltage and current imbalances might improve using this approach but the change does last for too long. To get the secondary distribution to operate at its optimal performance, a technique in the form of remote and automated technology is needed. This paper contributes such a technology at the low voltage side of the distribution network. The proposed static transfer switching technology is based on the open-transition switch that enables transfer or arrangement of consumer loads in a three-phase system within milliseconds and supervisory control system for effective co-ordination, computational and control of other intelligent units. View full abstract»

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    A thyristor controlled series capacitor design for research laboratory application

    Rigby, B.S. ; Ndlovu, C.K. ; Harley, R.G.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821889
    Publication Year: 1999 , Page(s): 903 - 908 vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    This paper discusses the theory of operation of the thyristor controlled series capacitor (TCSC), and describes the design of a prototype, laboratory-scale TCSC to meet a specific range of capacitive reactance values suited to a research laboratory application. Simulated and measured results of the designed TCSC are presented to verify the soundness of the approach View full abstract»

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    Comparison of theoretical models with practice for ADSL

    vanWyk, J.H. ; Linde, L.P.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406846
    Publication Year: 2004 , Page(s): 1023 - 1026 Vol.2

    IEEE Conference Publications

    Asymmetric digital subscriber line (ADSL) is becoming a relatively matured technology as many telecommunication service providers offer this technology to customers. The actual throughput of ADSL is highly dependent on the number of simultaneous users within a cable grouping. In order to guarantee throughput to any user at any time, one must be able to predict the circumstances under which throughput cannot be guaranteed any more. To guarantee high reliability of these predictions, a reliable theoretical model of the system is required. A comparison is made between the theoretical model and the practical scenario to determine the accuracy of the theoretical model. It was found that the theoretical model closely resembles the practical scenario, which makes QoS estimation possible using a theoretical model, rather than a trial-and-error method. View full abstract»

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    Direct adaptive neural control of a quarter-car active suspension system

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

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

    IEEE Conference Publications

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

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