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    Performance improvement of spread spectrum spatial-domain watermarking scheme through diversity and attack characterisation

    Bangaleea, R. ; Rughooputh, H.C.S.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146851
    Publication Year: 2002 , Page(s): 293 - 298 vol.1
    Cited by:  Patents (10)

    IEEE Conference Publications

    We present a spatial-domain-watermarking scheme for data hiding and copyright protection of still images using the attack characterisation approach. A small number of bits are embedded onto an image in the spatial domain using a method similar to the direct sequence spread spectrum. Perceptual analysis is used to guarantee the imperceptibility of the watermark and proper scaling of the raw mask values maximises the robustness of the watermark, while keeping it imperceptible to the human senses. We add two types of watermarks: reference and robust. The reference watermark is used to assess the way, in which the marked signal has been modified, so that the robust watermark can be optimally extracted. The watermarking system requires two keys; one for generating the pseudo-noise sequence for spread spectrum modulation and another for embedding the two watermarks in a checkerboard arrangement, where the use of the key introduces spatial uncertainty about the location of the watermark bits. This approach has been implemented for a spatial diversity of 64 and 256. Simulation results reveal the effectiveness of the new approach. View full abstract»

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    Implementation of a modern microprocessor based voltage quality recorder

    van Wyk, W.F.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.563037
    Publication Year: 1996 , Page(s): 1024 - 1028 vol.2
    Cited by:  Patents (2)

    IEEE Conference Publications

    This paper presents a low-cost solution for an instrument capable of recording most of the voltage anomalies that constitute poor quality of supply. The most common and severe power supply quality anomalies were implemented. Special attention is given to the hardware and embedded software of the instrument View full abstract»

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    Enhancement of GMM speaker identification performance using complementary feature sets

    Lerato, L. ; Mashao, D.J.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406669
    Publication Year: 2004 , Page(s): 257 - 261 Vol.1

    IEEE Conference Publications

    This paper describes a way of enhancing speaker identification (SiD) performance using N-best list method which utilises complementary feature sets. The SiD process is first done by training the Gaussian mixture model (GMM) classifier using parameterised feature sets (PFS) to form speaker models. During testing, the likelihood of a talker, given a set of speaker models is measured. The performance of the SiD system is normally degraded as the population of speakers increases. This paper addresses this problem by using linear prediction cepstral coefficients (LPCC) to complement the errors obtained from the PFS and the final identification is performed on smaller population. Results obtained using 2-best list show performance improvement View full abstract»

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    Scheduler performance evaluation and the effect of aggregation on QoS in a DiffServ enabled network

    Smit, J.J. ; Ferreira, H.C.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406685
    Publication Year: 2004 , Page(s): 323 - 328 Vol.1

    IEEE Conference Publications

    Various network traffic models exist that describe network traffic behaviour, but no model describes differential traffic treatment to such an extent to be able to relate the impact different rates has on the various traffic classes. With computer network simulation, we evaluate four different standardized PHBs, namely EF, AF1, AF2 and BE. The PQ, SFQ, SCFQ, WFQ, WF2Q+ and LLQ scheduling mechanisms are analysed to find their performance in relation to EF traffic as well as the effects of different traffic aggregation schemes on them. The QoS factors we focus on are: one-way delay, queue lengths and inter-packet delay variation. Network topologies are large and are defined by various parameters, thus our simulations are performed using acceptable bounded properties View full abstract»

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    The transfer and commercialisation of technology from south africa to foreign markets in the financial services industry

    Lubbe, F.H. ; Brent, A.C.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401518
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    International technology transfer (ITT) processes are complex, risky, and fail often. When financial services organisations have the opportunity to transfer their business model and core technologies to a foreign market, comprehensive technology and market research are compulsory. Numerous applicable theories and models in technology transfer were reviewed to develop such a model. Interviews with key individuals and focus group sessions were used to rank factors that affect the success of ITT in the financial services industry; more specifically the direct short term insurance industry. These success factors were implemented in the developed market evaluation model where the user is required to enter evaluation values for each factor. The evaluation model then delivers a value that represent the market potential. This model can be used to evaluate between one and many potential markets. Two factors an organisation must always be aware of is the influence stakeholders have on the ITT process and what ITT strategy is employed. View full abstract»

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    The method of lines as special moment method

    Dreher, A.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821918
    Publication Year: 1999 , Page(s): 1049 - 1052 vol.2

    IEEE Conference Publications

    A simple mathematical relation between the method of lines (MoL), a semianalytical finite-difference procedure, and a moment method based solution of an integral equation in the spectral domain is presented. Implicit basis and weighting functions as well as nodes and path of the integration procedure are identified and discussed View full abstract»

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    Identifying fault location in distribution systems with high Distributed Generation penetration

    Calderaro, V. ; Piccolo, A. ; Galdi, V. ; Siano, P.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308089
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (3)

    IEEE Conference Publications

    This paper presents a method to built a Petri Net (PN) to identify fault location in distribution systems with high penetration of distributed generation (DG). The design of PN is based on the composition of single PN, modeling protection systems and current detectors. A case study considering a typical Italian distribution grid is shown. The results highlight that the proposed method can remove a lot of complexity in data analysis also in presence of misoperation of protection systems. View full abstract»

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    Direct and indirect feed-in for inductive power transfer systems with multiple loads

    Gleissner, M. ; Sollner, M. ; Schmidt, H.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072094
    Publication Year: 2011 , Page(s): 1 - 5
    Cited by:  Papers (1)

    IEEE Conference Publications

    Direct and indirect feed-in for an inductive power transfer system with multiple loads are compared. The system is described by an equivalent circuit model. The transfer behavior is simulated by use of this model and verified by measurements. Additionally, a method to determine the optimal ratio of windings for high transfer efficiency is presented. The advantages of indirect feed-in and series compensation are demonstrated. View full abstract»

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    Effect of variation in modelling of generator saturation on electromechanical modes

    Kaberere, K. ; Petroianu, A. ; Folly, K.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308173
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    Several industrial-grade power system simulation tools are commercially available in the market. They are expensive to acquire and time-consuming to learn. As a result, very few institutions (utilities, academic/research organizations) can afford to use more than one power system simulation tool. The simulation tools differ in their components modelling. Different simulation tools can give different results for the same system model. Understanding the reasons for the discrepancies in the results is not a trivial task. In this paper, we investigate the effect of variations in modelling generator saturation. We carried out an eigenvalue analysis of a single machine infinite bus (SMIB) system using PSS/E, PowerFactory, EUROSTAG, SSAT, and MatNetEig. The simulation results show that the effect of saturation on the local modes is erratic and there is a need for further research on saturation representation in power system stability simulation tools. View full abstract»

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    Rural area survey and proposal for telecommunications service provision

    Mbatha, S.J. ; Afullo, T.J.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406636
    Publication Year: 2004 , Page(s): 71 - 76 Vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    Telecommunication service provision in rural areas is a very demanding enterprise, due to inadequate infrastructure and scattered settlements. On the other hand, since the rural areas are also developing, albeit with varying needs, telecommunications services also need to develop. In order to service such areas, we consider using an ATM network because of its capability to accommodate or combine voice, data and video communication in one network and reduce the use of multiple networks. We investigate the feasibility of ATM implementation in a rural area as a wide area network. In particular, we focus on different ATM classes of services 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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    Modelling and PD control of a novel reconfigurable robotic machining manipulator

    Ernesto, H. ; Pedro, J.O.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072144
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    Robotic machining is being applied in the manufacture of a broad spectrum of products and in a diverse industrial sectors ranging from aerospace, automotive to fashion. This paper presents a conceptual design, modelling and proportional-derivative (PD) control of a four degree-of-freedom (DOF) robotic machining manipulator (RMM) for use in a reconfigurable manufacturing system (RMS). The conceptual design of the RMM is introduced, followed by its mathematical modelling, and then the PD controller for the multi-input/multi-output (MIMO) system is designed for position tracking in absence of a dither signal. The simulation results justify the application of the PD controller through the set point tracking performances. View full abstract»

  • Freely Available from IEEE

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    AFRICON, 2004. 7th AFRICON Conference in Africa

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

    IEEE Conference Publications

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    Antenna amplitude distributions for improved wireless power transmission efficiency

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

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

    IEEE Conference Publications

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

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    Compatibility criteria for digital radio systems in nonlinear channels

    Amanowicz, M. ; Gajewski, P.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.563046
    Publication Year: 1996 , Page(s): 1066 - 1070 vol.2
    Cited by:  Papers (3)

    IEEE Conference Publications

    The electromagnetical compatibility (EMC) criteria for radio systems engineering are discussed with multiple channel reuse for frequency, time and code division multiple access (FDMA, TDMA and CDMA) schemes in a mobile environment. The BER is usually used as a measure of digital signals transmission quality. In nonlinear radio-channels with multipath propagation, the dynamic BER is used to evaluate the communication range R, which is the basic parameter of cellular radio. The intrasystem interference level is a parameter, which mostly limits the channel reuse in cellular systems. To fulfil the EMC condition, the interference influence should be optimized. We discuss the structural solutions based on the co-channel reuse distance as well as the signals orthogonality, especially for direct sequence CDMA systems View full abstract»

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    Spiral antenna with external feeding for planar applications

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

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

    IEEE Conference Publications

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

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    A business case for the sharing of processing power between 2.5G mobile phones

    Gazendam, A.D. ; Kaka, Y.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406690
    Publication Year: 2004 , Page(s): 349 - 352 Vol.1

    IEEE Conference Publications

    Current 2.5G mobile phones, and the coming wave of mobile phones conforming to the specifications of 3G and beyond, have great potential to be utilized as nodes in what is referred to as "wireless grids". Many modern mobile phones have processing power comparable to that of personal computers of a few years ago. This attribute, in combination with the vast numbers of mobile phones being sold every year and their various connectivity options, make mobile phones interesting candidates for distributed processing nodes. The ad-hoc networking benefits of Bluetooth and "always-online" characteristic of GPRS are networking benefits that could well compensate for relatively low user-level data rates of 2.5G networks when compared to that of conventional computer networks. The programming options provided by Java, Microsoft and Symbian environments on modern mobile phones enable development of the client-side software necessary for the wireless grid View full abstract»

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    Hybrid cascaded multilevel inverter with improved DC-link voltage control for grid connected systems

    Wanjekeche, T. ; Nicolae, D.V. ; Jimoh, A.A.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071994
    Publication Year: 2011 , Page(s): 1 - 7

    IEEE Conference Publications

    A lot of research has been done on balancing of DC capacitor voltage for multilevel converter with little success in converters with higher levels (more than five). Under normal operating conditions, the average DC capacitor can be controlled by slightly shifting sinusoidal modulating waves of phase shifted hybrid PWM technique, however this cannot be easily realized during transient operation or when there is phase to phase imbalance in the output switching pattern. This paper presents investigation of a DC - link voltage balance with the use of balance circuit for upper and lower DC capacitors in a single phase diode clamped inverter composed of two three level legs. Combined with the individual voltage control, a complete voltage controller is developed for a cascaded nine level hybrid model. Mathematical modeling of the whole system is also presented. Robustness of the proposed algorithm under varying operating conditions and modulation indices is verified by simulation results. View full abstract»

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    A data acquisition and processing system

    Klempous, R. ; Lysakowska, B. ; Nikodem, J.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820960
    Publication Year: 1999 , Page(s): 549 - 552 vol.1

    IEEE Conference Publications

    The main use made of a SCADA system by the operator is data acquisition and processing (DAP). We demonstrate the multilevel structure of such a system and describe the main properties of DAP systems. We demonstrate that DAP is a technical and information problem. There are two examples given illustrating the practical application of the DAP system: a traffic control system and a gas distribution network View full abstract»

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    Efficient functional built-in test for RF systems using two-tone response envelope analysis

    Barragan, M.J. ; Vazquez, D. ; Rueda, A. ; Huertas, J.L.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308070
    Publication Year: 2009 , Page(s): 1 - 5
    Cited by:  Papers (1)

    IEEE Conference Publications

    This paper presents a novel and low-cost methodology that can be used for testing RF blocks embedded in complex SoCs. It is based on the detection and spectral analysis of the two-tone response envelope of the block under test. The main non-linearity specifications of the block under test can be easily extracted from the envelope signal. The analytical basis of the proposed methodology is demonstrated, and a proposal for its implementation as a built-in test core is discussed. Finally, practical simulation examples show the feasibility of the approach. 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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    Application of spreadsheet in beam bending calculations

    Uziak, J. ; Gandure, J. ; Martin, L.D.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071988
    Publication Year: 2011 , Page(s): 1 - 5

    IEEE Conference Publications

    The paper presents the application of an Excel spreadsheet as an educational tool for the beam bending calculations. It describes the advantages of using the spreadsheet in engineering education. It also describes the spreadsheet which uses Macaulay's method for beam calculations. The spreadsheet can be applied to both statically determined and indeterminate beams. It calculates the reactions (both forces and moments), shear force and bending moment as well as deflections for any of four typical beam end-fixing conditions (simply supported, cantilever, propped and built-in). The dimensions of the beam, the loads and their location are given by the user. The spreadsheet works as a menu driven program and is designed to be user-friendly. The paper therefore makes a case for the use of spreadsheets in beam bending calculation to improve students understanding and performance in this topic. View full abstract»

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    Integrated conformal four-beam antenna array with wide angular coverage fed by compact 4×4 Butler matrix

    Wincza, K. ; Gruszczynski, S.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071962
    Publication Year: 2011 , Page(s): 1 - 4
    Cited by:  Papers (1)

    IEEE Conference Publications

    The paper presents the design of an integrated conformal four-beam antenna array. The goal was to design an integrated conformal multibeam antenna array that is capable to generate four independent beams which ensure wide angular coverage. Moreover, it was desirable that the designed multibeam conformal antenna featured sidelobe level comparable to a four-beam planar antenna array. To achieve that, a relatively small radius of the antenna array has been selected, and the phase compensation technique, in which additional phase delays introduced in outer channels compensate the curvature of the antenna structure, has been applied. A fully integrated four-beam conformal multibeam antenna array designed in a multilayer microstrip technology has been manufactured and measured, in which a compact 4×4 Butler matrix, additional phase shifters and a compensated multilayer crossover have been integrated constituting its feeding network. View full abstract»

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    Application of evolutionary computation in power electronics

    Fivaz, J. ; Cronje, W.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160004
    Publication Year: 2002 , Page(s): 729 - 734 vol.2

    IEEE Conference Publications

    An overview is given of possible evolutionary programming applications in power electronics CAD/E. Evolutionary programming is discussed in terms of the procedures and advantages. An overview of the requirements and concerns in power electronics CAD/E is given. Then the possible ways of applying evolutionary programming to address the concerns are discussed. View full abstract»

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    The measurement and assessment of corona power losses on 400 kV transmission lines

    Loxton, A.E. ; Britten, A.C.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159980
    Publication Year: 2002 , Page(s): 613 - 616 vol.2

    IEEE Conference Publications

    This paper presents the results of measurements of conductor corona losses on two open-circuited 400 kV transmission lines, one 85 km long and the other 143.2 km long. The results are compared with those obtained under test conditions in a local corona cage. From these it is shown that the loss predictions from the cage excitation functions (for the relevant conductors and conductor surface gradients) agree tolerably with the losses measured in both wet and dry conditions on the two lines. The overall errors and uncertainties in the CVT, CT and wattmeter measurements are also assessed. View full abstract»

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

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

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

    IEEE Conference Publications

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

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    Superconducting COSL building blocks for implementation in ultra-high speed logic circuits

    Rabie, F.J. ; Perold, W.J.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821950
    Publication Year: 1999 , Page(s): 1197 - 1202 vol.2

    IEEE Conference Publications

    Complementary output switching logic (COSL) is used to define building blocks for ultra-high speed (~20 GHz) logic circuits. The family consists of the standard logic functions OR, NOR, AND, NAND and XOR. The building blocks include a new single gate inverter and various latch functions. Changes in the layout of the COSL gates are proposed to improve the uniformity of current distribution in the gates, which will, in turn, prevent unwanted field concentrations View full abstract»

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    Developing location based services in Parlay/OSA

    Masenya, L. ; Hanrahan, H. ; Dwolatzky, B. ; Van Olst, R.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406878
    Publication Year: 2004 , Page(s): 1193 - 1196 Vol.2

    IEEE Conference Publications

    Open standards have the potential to greatly simplify the way a utility's infrastructure is developed. Moreover the software development process of applications based on that infrastructure is improved. To facilitate the development of location based services (LBS), Parlay/OSA is used as an open standard development platform for such services. It supports application programming interfaces for accessing different network architectures that can be used by LBS services to query for location of a mobile. The Parlay/OSA framework also addresses security concerns. For LBS services to be complete, a geospatial database must be used to provide information based on location. An extension to the Parlay/OSA gateway is thus proposed to encapsulate the necessary APIs for querying geospatial databases. View full abstract»

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    Radar remote sensing potential for Southern Africa

    Inggs, M.R.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563085
    Publication Year: 1996 , Page(s): 83 - 88 vol.1

    IEEE Conference Publications

    This paper introduces the field of remote sensing using radar and explains some of the ways in which this relatively new technology can be applied to the development of Southern Africa. Active and passive radar sensors are discussed. The need for remote sensing user training in radar techniques is stressed, as well as the need for a local airborne sensor. The difference between airborne and satellite sensors is discussed. An update of radar remote sensing activities in Southern Africa is given. The existing large body of satellite data is mentioned as a good starting point for environmental applications View full abstract»

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    ML estimator based on the EM algorithm for subcarrier SNR estimation in multicarrier transmissions

    Descure, J.-G. ; Bellili, F. ; Affes, S.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308116
    Publication Year: 2009 , Page(s): 1 - 5
    Cited by:  Papers (1)

    IEEE Conference Publications

    In this paper, considering multicarrier transmissions, we present a maximum likelihood estimator of the subcarrier signal-to-noise ratio (SNR) based on the expectation-maximization (EM) algorithm. This new estimator is applicable to any linearly-modulated signal. It is a non-data-aided (NDA) method since no a priori knowledge is assumed about the transmitted data. The channel gains and phase distortions on the different subcarriers are assumed to be constant during the observation window, and the signal is assumed to be corrupted by additive white Gaussian noise (AWGN). The performances of our estimator are empirically assessed using Monte-Carlo simulations, showing that the new algorithm reaches the corresponding Crameacuter-Rao lower bounds (CRLBs) over a wide SNR range. View full abstract»

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    Power system topology assessment and pre-estimation in an object oriented environment

    Peharda, D. ; Hebel, Z. ; Barta, A.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401478
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    Electrical power system engineers often face a challenge of software implementation of heuristic knowledge about power systems. This knowledge can be structured in a rule form. This is different from analysis and calculations knowledge which usually comes in form of algorithms and formulae. Object oriented environment enables power system engineers to transparently implement rules in objects, thus allowing more heuristic knowledge to be implemented without the use of complex models or algorithms. Technology has simplified the coding paradigm, thus allowing electrical engineers with little experience in programming to work on the development of the software. View full abstract»

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    Validation of PIM DM and PIM SM protocols in the NS2 network simulator

    Bartczak, T. ; Zwierzykowski, P.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308360
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    Multicast transmission offers efficient network resource utilization, but, at the same time, it is also a demanding and complex technology. Multicast protocols are far more sophisticated than their unicast counterparts. As a result, building one's own simulation environment is a difficult, time-consuming and error-prone endeavor. Hence, there is a need for ready-made network simulation tools supporting these protocols. One of such tools is the open source NS2 simulator. However, the results obtained from this simulator are not reliable without prior testing and a validation of the application. This work concentrates on validation of the PIM SM and the PIM DM protocols implementation in NS2. The NS2 implementation was tested using a wide range of techniques commonly used in software engineering filed. View full abstract»

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    Xpertfinder - message analysis for the recommendation of contact persons within defined topics

    Heeren, F. ; Sihn, W.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146803
    Publication Year: 2002 , Page(s): 41 - 46 vol.1

    IEEE Conference Publications

    Personal acquaintance represents an essential basis for the exchange of information between employees. Recommendation of contact persons is a method that fosters the build-up of acquaintanceship in order to support the exchange of information. The subject of the present paper is a new recommendation technique, which automatically and continuously detects contact persons within relevant topics and represents them anonymously. For the detection of contact persons, various indicators are drawn up, e.g. authorship for the source of textual information and addresses for contact information. The emphasis of the paper is on the description of the data processing concept using Latent Semantic Analysis as well as the effectiveness of that method for document classification. View full abstract»

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    Improvement of the Ulco network voltage regulation using a phase shifting transformer

    Sithole, S. ; Mbuli, N. ; Pretorius, J.H.C.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072034
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    In networks feeding loads that vary from low levels during low loading and extremely high levels during high loading conditions, with lines providing supply to these loads being very long, voltage regulation within the acceptable range can be a challenge. In a case where such lines to the load centers constitute parallel corridors with different impedance characteristics, and therefore different loading properties, problems of regulating voltages within acceptable limits may be experienced. The previous paper [1, 2, 3, 4] proved that by changing the phase angle of the network connected in parallel, the voltage can be regulated. These voltages can be increased or decreased depending on the angle change. The Ulco network has the described characteristic and was used as a case study to observe network voltages during different loading conditions. This network experience overvoltages during lightly loaded conditions and undervoltages during heavily loaded conditions. The phase shifting transformer is one of the devices broadly used in power systems to change the power flows by changing the phase angle. This paper provides the analyses of peak and off-peak loading of the Ulco network voltages. The phase shifting transformer is then used to mitigate against voltage limit violation. View full abstract»

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    Simulating a wind energy synchronous generator with skin-effect

    Okoro, O.I. ; Chikuni, E.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401537
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    This paper presents the MATLAB simulation of a synchronous generator for wind energy generation. Park's equations for a synchronous generator in rotor reference frame are modified to independently account for any Skin-effect on the d-axis and the q axis. The proposed skin-effect model is used to compare with the conventional model. The error involved underscores the need for the analysis, especially in wind energy generation where intermittent load variations call for the exact dynamic behavior of the system. View full abstract»

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    Radiation hazards: standards, measurement and prediction

    Smith, A.G. ; Meyer, F.J.C.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563140
    Publication Year: 1996 , Page(s): 371 - 376 vol.1

    IEEE Conference Publications

    This paper discusses non-ionizing radiation hazards (RADHAZ) in an introductory way. The following aspects of RADHAZ analysis are addressed: standards against which fields are evaluated to be potentially dangerous or not, measurements that can be used to determine compliance to the standards, numerical methods that can be used to predict fields in order to determine safe regions around potentially hazardous transmitters View full abstract»

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    A process framework for customising software quality models

    Sibisi, M. ; van Waveren, C.C.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401495
    Publication Year: 2007 , Page(s): 1 - 8
    Cited by:  Papers (1)

    IEEE Conference Publications

    The quality objective of many software organisations is to deliver software products that meet and or exceed customer expectations. The key to achieving this is to capture these expectations at the beginning of the project by clearly defining all quality requirements. The characteristics particularly defined in ISO/IEC 9126-1 (2001) provide the framework for specifying quality requirements. The ISO/IEC 9126-1 quality model is intended to be applicable to any type of software product or intermediate product. Before application this model needs to be tailored to a specific software and specific need. Since these characteristics cannot be directly measured this makes it difficult to directly prioritise and choose the most relevant characteristics and sub-characteristics. Hence a process framework that will link these characteristics and sub- characteristics to user needs is required. This will in turn help customise software quality models like ISO/IEC 9126-1 (2001) and other general software quality models. A process framework for customising software quality models is proposed in the text and it is further shown how this framework was applied in a real working environment in an attempt to quantitatively validate it. The results collected in the study showed that the framework could be used reliably in customising a generic software quality model at characteristic level only. The deviations at sub-characteristic level were due to unclear questions in the generated Generic Quality Questionnaire that resulted in misunderstandings. And the metrics used to create these questions were not fully tested for validity and reliability due to time constraints. Enhancements are discussed in the study and it is further shown how reliability can also be achieved at sub-characteristic level. View full abstract»

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    Optimization of quality of service requirements for real-time applications using Cross Layer Design

    Sentongo, V. ; Chan, H.A.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308125
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    The evolution of the Next Generation heterogeneous Networks relies on the improved services that these networks can provide to real-time applications. Applications running on wired networks work seamlessly with the Open Systems Interconnect (OSI) protocol stack implementation. Its modularity eases functionality and improves performance of these applications. However, the channel conditions for wireless networks are constantly varying. This affects the performance of real-time wireless applications running on wireless networks. Therefore, the operation of the OSI protocol stack is not as effective as it is when used with its wired counterpart. This research paper proposes a Cross Layer Design architecture that can be used to extend the functionality of the OSI protocol stack allowing cross layer communication between non-adjacent layers of a wireless application. It proposes a means of improving end-user delay and per-user throughput of Voice over Internet Protocol (VoIP). The proposed method entails execution of cross-talk between the transport and MAC layers of the protocol stack through cross layer clients appended to each layer and controlled by a local host called a cross layer manager. View full abstract»

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    Microprocessor control of hybrid energy systems

    van der Linde, H.A. ; Clark, I.
    AFRICON '92 Proceedings., 3rd AFRICON Conference

    DOI: 10.1109/AFRCON.1992.624458
    Publication Year: 1992 , Page(s): 217 - 220
    Cited by:  Papers (1)

    IEEE Conference Publications

    Remote area power supplies in the form of a hybrid system can be a very effective alternative in that the different components can be complementary. The authors describe a project whose aim was to develop a dedicated microprocessor control system to effectively manipulate a hybrid energy system so that available energy is efficiently utilized while at the same time the life span of battery banks is extended. The system was referred to as a Hybrid Energy System Manager (HESM). The HESM was connected to simulated and real energy sources and loads, and subjected to a series of tests. The results were very gratifying in that it performed as expected View full abstract»

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    Chaotic attractor of the controlled He´non map

    Changpin Li ; Xiaohua Xia ; Guanrong Chen
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406721
    Publication Year: 2004 , Page(s): 485 - 489 Vol.1

    IEEE Conference Publications

    The paper considers the Heacutenon map controlled by simple sine functions. A new chaotic attractor is found in this controlled Heacutenon map, and its basic properties are discussed in terms of its Lyapunov exponents. The chaotic behavior is also numerically analyzed for a range of control parameters View full abstract»

  • Freely Available from IEEE

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    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406748
    Publication Year: 2004 , Page(s): 596

    IEEE Conference Publications

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    Continuous representation of unevenly sampled signals - An application to the analysis of heart rate variability

    Tkacz, E.J. ; Kostka, P.S. ; Budzianowski, Z. ; Oleksy, W.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072162
    Publication Year: 2011 , Page(s): 1 - 7

    IEEE Conference Publications

    Various methods for the continuous representation of unevenly sampled physiological signals, especially of heart rate and heart rate variability have been published over the past two decades. Due to the mathematical difficulties of analyzing unevenly spaced event series or unevenly sampled signals, all of the previously described techniques are impeded by some severe limitations which result from either representing the signal based on an assumed and often insufficient physiological model of signal generation, or from simplifications in the selected signal processing tools. Though the described methods have their merits and allow sufficient description of heart rate in some special applications, there has been no systematic investigation into a continuous representation of unevenly sampled physiological signals which is free from any limitations or simplifying assumptions and which would allow an objective comparison of the known methods and the determination of the respective errors in order to decide which technique is the best suited for a specific application. In this paper a continuous representation of the point event series describing the temporal sequence of heart beats is presented which does not impose any limiting assumptions on the data analysis. The results obtained were validated through simulations in both time and frequency domains, and compared with the established techniques to allow the determination of errors at the specific times where the heart beats occur, as well as within the intervals between these sample points. View full abstract»

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    Hybrid BFSK/MPSK modulation employing GAC codes

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

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820768
    Publication Year: 1999 , Page(s): 71 - 74 vol.1

    IEEE Conference Publications

    In this paper a hybrid binary frequency shift keying/multiple phase shift keying (BFSK/MPSK) modulation technique employing generalised array codes (GAC) and trellis decoding is proposed. The performances of the GAC employing the hybrid BFSK/MPSK are compared with those employing BPSK, MPSK schemes and the corresponding uncoded MPSK scheme View full abstract»

  • Freely Available from IEEE

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    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406643
    Publication Year: 2004 , Page(s): 114

    IEEE Conference Publications

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

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

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

    IEEE Conference Publications

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

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    Optimizing the industrial system utility interface by means of AC/DC boost converters

    Carpinelli, G. ; Marino, P. ; Testa, A. ; Vasca, F.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563159
    Publication Year: 1996 , Page(s): 473 - 478 vol.1
    Cited by:  Papers (5)

    IEEE Conference Publications

    The problem of voltage disturbance compensation in an industrial power system is considered. Reference is made to a case-study where a transformer feeds an AC/DC boost power converter, a capacitor VAr compensator and a balanced AC load. The transformer supplying voltages are supposed to be affected by flicker, slow variations and unbalance. The proposed perturbation compensation consists in suitably controlling the boost power converter which so acts as both a rectifier and static VAr compensator. The power converter sizing is discussed and the controller design presented. The effectiveness of the proposed compensation is shown via simulations obtained by means of the SIMULINK implementation of the power system dynamic model 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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    Towards automatic Digital Surface Model generation using a Graphics Processing Unit

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

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

    IEEE Conference Publications

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

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    A new structure of single parity check product codes

    Hongjun Xu ; Takawira, F.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406635
    Publication Year: 2004 , Page(s): 67 - 70 Vol.1

    IEEE Conference Publications

    The paper proposes a new structure of single parity check (SPC) product codes, which are inherently embedded with an interleaver. The complexity of decoding of the new SPC product codes is the same as that of existing single parity check product codes using a message passing algorithm. Simulation results and bound analysis demonstrate a significant BER performance improvement compared to the existing single parity check product codes for a high code rate at medium SNR View full abstract»

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    Comparison and optimisation of CSMA/CA back-off distribution functions for a low earth orbit satellite link

    Cawood, A.D. ; Wolhuter, R.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401598
    Publication Year: 2007 , Page(s): 1 - 8

    IEEE Conference Publications

    This paper presents a comparison of several random number distributions for use in the back-off random variable, in a CSMA/CA protocol. These distributions are optimised for the specific case of a low earth orbit (LEO) satellite communicating with several ground stations, where the propagation time from satellite to different stations is diverse. The results of using these different distributions are presented, with a proposed Boolean- type distribution shown to be optimal. The results are confirmed using OMNeT++ simulations. 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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    Projection statistics for power system state estimation

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

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

    IEEE Conference Publications

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

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    Data compression in distributed virtual environments

    van der Elst, H. ; van Schalkwyk, J.J.D.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.563056
    Publication Year: 1996 , Page(s): 1115 - 1118 vol.2

    IEEE Conference Publications

    The development of large-scale virtual environments is the new grand challenge in computing. New breakthroughs in 3D computer graphics and networking enable us to perceive and share virtual worlds in new and familiar ways. There is a natural desire to make these environments both large and detailed. This brings up many problems in efficiently managing the flow of large amounts of data between users. We are looking at ways to complement current work in the field of network traffic redundancy. Traditional and new data compression techniques can effectively be used to reduce the flow of information between participating hosts, especially at a local level View full abstract»

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    Estimation of polluted insulators flashover time using artificial neural networks

    Farag, A.S.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563113
    Publication Year: 1996 , Page(s): 226 - 234 vol.1

    IEEE Conference Publications

    Artificial neural networks (ANN) algorithms have been applied successfully on a very wide range of applications in power systems. In high voltage engineering. ANN have been applied efficiently and effectively for pattern recognition of partial discharges. A major field of ANN application is function estimation, because of the useful properties of ANN such as adaptivity and nonlinearity, they are well suited to function estimation tasks. The equation describing the function is unknown since the only prerequisite is a representative experimental sample of the function's behavior. In this paper, the prerequisite training data are available from experimental studies performed on models of polluted insulators under power frequency voltages representing different pollution levels ranging from light to severe pollutions. Extensive detailed studies and tests have been carried out to determine the ANN parameters to give the best attainable results and to assess the effect of the presence of inadequate data in the training set on modeling accuracy. In this paper, a new approach using ANN as function estimator is engaged to model accurately the relationship t=f(V.L.Rp). It is found that, when training is complete, the ANN is capable of estimating the flashover time very efficiently and effectively even when the inadequate data are incorporated in the training set. The present study clearly indicates the efficacy of ANN as function estimators in the insulator flashover studies View full abstract»

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    Flexible network for Internet access in rural areas

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

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

    IEEE Conference Publications

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

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    Vector based higher-order 3D finite element simulation of microwave cavities

    Davidson, D.B. ; Geschke, R.H. ; Meyer, F.J.C.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821919
    Publication Year: 1999 , Page(s): 1053 - 1058 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    Finite elements (FE) for microwave device simulation are reviewed, with specific emphasis on vector elements. The FE analysis of microwave cavities, and the resulting generalised eigenvalue equation, is discussed. Results for two benchmark cavity analysis problems are shown. Applications are briefly outlined. The paper concludes with an overview of current work, including sparse linear algebra and incorporating the FE code within the advanced FEKO code suite View full abstract»

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    Non iterative channel estimation and equalisation strategy for burst π/4 DQPSK transmission

    Chitamu, P.J. ; Mgombelo, H.R.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563144
    Publication Year: 1996 , Page(s): 392 - 396 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    An inverse linear transversal equaliser algorithm (ILTE) which uses a non-iterative channel estimation and equalisation strategy is presented. It is shown to be more efficient in terms of computational load requirements as compared to the least mean squares (LMS) or recursive least squares (RLS) approaches or the linear solution using direct matrix inversion or solutions employing matrix decomposition algorithms such as Cholesky decomposition. The computational load of the ILTE approach is shown to be less than 1% that required when the taps are derived using iterative techniques such as LMS or RLS and of less than 5% that required when using direct matrix inversion to solve the equalisation linear equation problem. The significance of the results is seen when the technique is applied in distributed ad-hoc type digital radio networks where a channel has to be estimated and equalised on a packet-by-packet basis without buffering the received packets. Examples of equalisation of typical minimum and non-minimum phase three-ray channels using the technique are presented and show a good error rate performance with the PI/4 DQPSK detector. The ILTE method, which is based on inverse filter modelling, is compared with linear solution based on Cholesky decomposition and shown to perform much better in both minimum and non-minimum phase channels 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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    A low cost fence impact classification system with neural networks

    de Vries, J.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406647
    Publication Year: 2004 , Page(s): 131 - 136 Vol.1
    Cited by:  Papers (1)  |  Patents (2)

    IEEE Conference Publications

    Due to a high rate in live stock theft and farm intrusions, securing property is a problem in South Africa. Research is necessary to investigate possible improvements. By analyzing the acoustical vibrations that are generated on a game farm or security fence during entry, intrusions can be detected. Owners of protected property can receive an early warning. Different type of intrusions can be distinguished since they generate different vibrations. A point sensor is used to detect vibrations generated at a distance from the sensor. This proposed system is part of a more elaborate farm information system and is not intended to function as a stand-alone security system View full abstract»

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    A simulation study and analysis of certain properties of spectral null codes

    Ouahada, K. ; Ferreira, H.C.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072018
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    The technique of spectral shaping and the design of codes providing nulls at certain frequencies, as the case with spectral null codes, have enhanced digital signaling over communication channels like for digital mass recorders and metallic cables. The special structure of these codes help in investigating and analyzing certain of their properties. The possibility of links between these codes and other error correcting codes are also presented and discussed. Interesting results have shown a special structure of spectral null codes and their link to Low density parity check error correcting codes. View full abstract»

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    Power line telecommunications option in rural KwaZulu-Natal

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

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

    IEEE Conference Publications

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

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    The diffusion of a new technology into the marketplace implementing UMTS

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

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

    IEEE Conference Publications

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

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    A control system analysis for a potential small geostationary satellite for South Africa

    Thopil, G.A. ; Steyn, W.H.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401553
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    The availability of an indigenous communications satellite helps in driving down communication and entertainment costs of services obtained through such a satellite. The design and implementation of a small GEO satellite will also act as a stepping stone for missions of greater complexity and stringent specifications [2]. This paper presented is based on a simulation study with real world and worst case scenarios modelled as accurately as possible keeping in mind the trade-off between computational burden and accuracy. An overall control system analysis comprising of the Attitude Control and Determination system is performed, keeping actuator failure in mind. An analytical Orbit Control evaluation is also performed which gives an estimate of the propellant requirement for an average GEO lifetime of 10 years. View full abstract»

  • Freely Available from IEEE

    [Breaker page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406623
    Publication Year: 2004 , Page(s): 19

    IEEE Conference Publications

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

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

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

    IEEE Conference Publications

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

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    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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    Off-line identification of an open-loop automatic voltage regulator using pseudo-random binary sequence perturbations

    Vermeulen, H.J. ; Strauss, J.M.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821870
    Publication Year: 1999 , Page(s): 799 - 802 vol.2
    Cited by:  Patents (1)

    IEEE Conference Publications

    The accuracy of power system stability simulations is determined by the validity of the model topologies and parameter values used for the subsystems such as the automatic voltage regulator (AVR), etc. This paper presents the results of a laboratory investigation to determine the parameters of an AVR off-line using pseudo-random binary sequence (PRBS) perturbations applied at the AVR reference voltage input View full abstract»

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    Position control using variable structure control

    Kang'ethe, S.M. ; Hinga, P.K.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563117
    Publication Year: 1996 , Page(s): 251 - 254 vol.1

    IEEE Conference Publications

    This paper discusses the application of variable structure control to a typical position control laboratory plant. It analyses the choice of the sliding mode and relates it to the equivalent control regime. Practical and simulation results are discussed of the effect of the parameters studied when applied to a typical position control servosystem View full abstract»

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    Integrated management intelligence system for customized throughputs

    Onunka, C. ; Nnadozie, R.C.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072004
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    The much desired components of an effective intelligent management system require a business intelligence system and methodology to enable effective management decision making skills. The development of low-cost data acquisition; storage systems and the wide availability of fast wide area networks have made data more accessible for managers and individuals to make an integrated intelligent management decision in an organization or manufacturing environment. This paper demonstrates that the right use of data for improved throughputs opens more interesting opportunities which are maximized by managers and decision makers in managing an enterprise. View full abstract»

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    Classroom simulation of an electricity market

    Dingley, C.E. ; McDaniel, T.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160030
    Publication Year: 2002 , Page(s): 881 - 886 vol.2

    IEEE Conference Publications

    This paper describes an experiment in which 36 final year under-graduate electrical engineering (power) students acted as participants in the simulation of an electricity market. The market structure simulated was along the lines of the Pool used in England and Wales between 1990 and 2001 and (with modifications) in California, Australia and South Africa (only within Eskom at this stage). The aims of this simulation were twofold: (i) to introduce students to the commercial aspects of electricity supply and to the technicalities of one particular market type; and (ii) to gain further insight into the operation of this market structure and to obtain comparative data on the performance of certain variations on the basic market structure. View full abstract»

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    Radiation to transmission lines with varying load and ground conditions

    Stuart, T.E.W. ; Reader, H.C. ; van der Merwe, J.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821936
    Publication Year: 1999 , Page(s): 1135 - 1138 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    A transmission line above both an ideal and a lossy ground is illuminated by a plane wave, while its terminations are varied. The intention of this study, for EMI purposes, is to explore the minimisation of power induced in the loads, both by simulation and measurement. The simulations are performed in the time domain and the frequency domain, while measurements are made in the frequency domain with a network analyser. Great care is needed for the measurement procedures View full abstract»

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    An AC-to-AC converter based voltage regulator

    van Schalkwyk, C. ; Beukes, H.J. ; du T Mouton, H.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160002
    Publication Year: 2002 , Page(s): 719 - 722 vol.2
    Cited by:  Papers (5)

    IEEE Conference Publications

    This paper presents an AC voltage regulator based on a pulse width modulated AC-to-AC converter and a step-down transformer. The regulator is aimed at electrification of small rural communities and compensates for the voltage variations ranging from +10% to 40% of the nominal. The fast dynamics associated with a pulse width modulated converter is a significant benefit when compared to more conventional techniques, for instance the use of tap changing, transformers. View full abstract»

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    New cellular array for the hardware implementation of very high speed digital filter

    Dawoud, D.S.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.562985
    Publication Year: 1996 , Page(s): 753 - 758 vol.2

    IEEE Conference Publications

    A new pipeline sequential processor system is proposed. The system takes the form of a cellular array the basic element of which is a sequential synchronous full adder. The proposed system is used to build a very high speed digital filter. The execution time of any term Ai .Xi (i=0, 1, …, N) of the digital filter equation is the time of three clock cycles. The time is constant and completely independent on the word length. The basic element of the proposed array consists of two flip-flops. The analysis of the logic capabilities of the flip-flop showed that it is possible to implement any of the sixteen possible functions of two variables directly in the flip-flop. The next state of the flip-flop represents the result of the logic function. The two flip-flops of the basic element are used to realise the function of the single-bit full adder, one to form the sum S and the other to form the carry Ci, where: S=X⊕Y⊕Ci-1, and Ci=X.Y+(X¯+Y¯).Ci-1 The complete hardware of the basic element, the cellular array and that of the digital filter are given. The new cellular array results in great saving in the computation time compared with the conventional techniques. A comparison is given between this new hardware and the conventional ones based on the time-hardware product as a criterion. The comparison proved that the new hardware reduces the time-hardware product View full abstract»

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    A nonlinear torsional vibration model of a propeller shaft with a crack-induced parametric excitation and a hookes joint type of kinematic constraint

    Alugongo, A.A.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072181
    Publication Year: 2011 , Page(s): 1 - 7

    IEEE Conference Publications

    In this paper, a model for analyzing torsional vibration of a ground vehicle propeller shaft system has been proposed. The model takes into account dynamics of a Hooke's joint and a crack-induced parametric excitation. By considering torsional vibration and Energy of the propeller, a Lagrangian approach has been used to derive the equation of motion yielding a highly nonlinear 3-DOF system with four coupled inertias. Subsequently, nonstationary response of the system has been characterized by a wavelet technique. The system vibration response in various scenarios has been evaluated and reported. Obtained results concur with existing literature. By analysis it is demonstrated that, the model is good for investigating nonlinear vibration of a typical propeller shaft system used in light ground vehicles. View full abstract»

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    Towards a converged network: Video streaming over WiMAX vs. HSDPA in the rural environment

    Odhiambo, M.O. ; Amimo-Rayolla, P.O. ; Kurien, A.M.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308196
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    As the telecommunications industry evolves towards a converged IP-Core network the role of cellular/wireless broadband technologies in achieving Long Term Evolution (LTE) must be greatly evaluated. This would in effect provide lessons for improvement and blueprints for final adoption in NGN (Next Generation Networks). The emergence of BWA (broadband wireless access) as a reliable player, in some cases a substitute for fibre/ADSL, maybe attributed to poor or non-existent copper/fibre, largely inefficient telecommunications management and/or ineffective telecommunications policies in mostly underserviced areas. In this paper, video streaming over existing 3G high-speed packet networks is evaluated against WiMAX as alternatives to fibre/ADSL. Simulation results show WiMAX was found to be a viable and better alternative barring capital expenditure (CAPEX) and operational expenditure (OPEX) considerations. HSDPA was found to achieve rates per user equipment (UE) that meet QoS needs for codec streaming Q-levels of 16 and 64 kbps. The 16 kbps codec rarely requires extensive preroll buffer requirements. However, WiMAX was found to perform better by at least three times for throughput and capacity. View full abstract»

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    Defining ‘project governance’ for large capital projects

    Bekker, M.C. ; Steyn, H.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401604
    Publication Year: 2007 , Page(s): 1 - 13
    Cited by:  Papers (1)

    IEEE Conference Publications

    During the past decade corporate governance has received ample attention. Lately the principles of governance have been applied to other management disciplines, especially project management. This evolution of the concept of project governance resulted in various uses and applications of the term, causing confusion among academics and practitioners in various industries. Especially for large capital projects the formal definition of the term 'project governance', and agreement on the content of a project governance model, have been largely neglected. This paper reports on exploratory work to define the concept of governance for large capital projects. An international Delphi survey, that involved credible practitioners as well as academics, was conducted to better define the term 'project governance'. Finally, the paper introduces a framework for project governance. View full abstract»

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    Simplified waveform measurement in a microwave power amplifier

    Elkhazmi, E.A. ; McEwan, N.J. ; Ali, N.T.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821930
    Publication Year: 1999 , Page(s): 1115 - 1116 vol.2

    IEEE Conference Publications

    Voltage and current time waveforms in a microstrip-based microwave power amplifier are measured using capacitive and inductive probes with a small spatial extent and essentially pure response to voltage and current. Their transfer functions are inverted by elementary analogue filtering of waveforms scaled to low frequency by a sampling oscilloscope View full abstract»

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    Design flow for CMOS based Class-E and Class-F power amplifiers

    Bozanic, M. ; Sinha, S.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308187
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper presents the design flow for an integrated power amplifier. The flow is presented as a software routine. For a given set of amplifier specifications and CMOS process parameters, the routine computes the passive component values for a class-E or class-F based power amplifier. The routine includes the matching network for standard impedance loads. The routine also provides its user with a spiral inductor search algorithm, which can be used to generate layouts of inductors with Q-factors optimised at a desired frequency. For a typical power amplifier design case where several amplifiers are designed for application over different channels, the routine presented in this paper contributes by streamlining the design flow. The operation of the software routine was demonstrated by simulations in Austriamicrosystems 0.35 mum single-supply process for a 14 dBm, 2.4 GHz power amplifier design. View full abstract»

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    Development of a generic tension control system

    Van Blerk, B.D. ; Diana, G.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.563006
    Publication Year: 1996 , Page(s): 864 - 868 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    This paper describes the development of a generic tension control system (GTCS) test bed that is to be used to train people and demonstrate the principles of tension control. In order to correctly size the motors, the associated power electronics and sensors required by the GTCS, a system model has to be developed in order to assess the performance and requirements via simulation in SIMULINK. The simulation results are presented and it is shown how the system components were sized View full abstract»

  • Freely Available from IEEE

    Table of contents


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406616
    Publication Year: 2004 , Page(s): i - xxii

    IEEE Conference Publications

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    Low density parity check irreducible Goppa codes

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

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

    IEEE Conference Publications

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

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    Controlled switching of shunt capacitors

    de Grijp, M.H.B. ; Hopkins, R.A.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.563008
    Publication Year: 1996 , Page(s): 874 - 879 vol.2
    Cited by:  Papers (4)

    IEEE Conference Publications

    During field measurements on shunt capacitor banks several characteristics were investigated. For these measurements Eskom utilised its mobile transient measuring facility which is equipped with a 12 bit, Nicolet 500 system, a fibre optic system for measurement signal transmission and resistive/capacitive voltage dividers. For inrush current limitation during shunt capacitor bank energising a series damping network or a pre-insertion impedance is common practice. Reduction of transient phenomena is determined by a suitable choice of damping network element parameters or pre-insertion impedance. By precisely controlling the instant of closing it is possible to almost entirely to eliminate or reduce to a minimum, the impact of the inrush current phenomena. The inrush currents are of a moderate nature, but the substation busbar voltage can exhibit significant transients. In the case of back-to-back capacitor bank energising the impact on the circuit breaker itself is of major interest. Inrush currents of significant nature can flow. In most instances this can lead to unexpected and abnormal wear of circuit breaker contact systems. It is recommended for each new shunt capacitor bank application to consider the combination of a series damping network and controlled closing. Such a combined scheme offers an effective solution to different switching situations occurring in practice. A consideration of what represents a critical or noncritical switching application for either the network or the circuit breaker itself then becomes the basis whether or not to apply controlled switching View full abstract»

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    Intelligent static VAr compensator control for supply loading optimization

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

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

    IEEE Conference Publications

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

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    A detailed analysis of the effect of dead time on harmonic distortion in a class D audio amplifier

    Koeslag, F. ; du Mouton, H.T. ; Beukes, H.J. ; Midya, P.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401640
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (4)

    IEEE Conference Publications

    This paper presents an analytical method for determining the effect of dead time on harmonic distortion in a class D audio amplifier. The analysis is based on the well established double Fourier series, providing accurate analytical solutions to the pulse width modulated spectra under natural sampling. The proposed analytical model differs from that of previous work in the sense that the precise contribution of each separate component can be determined, i.e. the fundamental component, baseband, carrier and sideband harmonics. View full abstract»

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

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

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

    IEEE Conference Publications

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

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    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»

  • Freely Available from IEEE

    [Blank page]


    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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    The effect of customer premises wiring on the performance of ADSL and VDSL

    van Wyk, J.H. ; Linde, L.P.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146839
    Publication Year: 2002 , Page(s): 227 - 232 vol.1

    IEEE Conference Publications

    The loop plant is the only part of the telephone network that has stayed structurally almost the same for the best part of a century. Due to the increasing demand for broadband services, the time has come for a powerful upgrade of the entire outside loop plant, which includes upgrading the network to optical fibre. Initial provisioning of new services, such as asymmetric digital subscriber line (ADSL) and high-bit-rate digital subscriber line (HDSL), has to take place on the existing loop plant, because of the high costs associated with optic fibre for the so-called 'last mile'. Very-high-bit-rate digital subscriber line (VDSL) paves the way to a total fibre solution, introducing a hybrid copper/fibre solution for delivering high speed broadband services at up to 52 Mbps asymmetric and 26 Mbps symmetric. This paper investigates the possible effect that current premises wiring might have on the performance of ADSL and VDSL services. Basic channel modelling principles are applied for a twisted-pair transmission line. A number of scenarios are investigated and compared, and recommendations regarding future customer premises wiring are made. 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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    RF-MEMS dielectric charging: Dependence on dielectric film polarization procedures

    Papaioannou, G. ; Papapolymerou, J. ; Pons, P. ; Plana, R.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401447
    Publication Year: 2007 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    The paper demonstrates the advantages arising from the simultaneous assessment of RF-MEMS capacitive switches and MIM capacitors. The application of simple capacitive-voltage characteristics and thermally stimulated depolarization current methods, respectively, allow the discrimination of the contribution of injected charges induced space charge polarization and the dipolar polarization. The proposed method allows the direct determination of device degradation sources and can be used for the dielectric material improvement. View full abstract»

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

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

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

    IEEE Conference Publications

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

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    Double concatenated space-time trellis codes

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

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

    IEEE Conference Publications

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

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    Smart demand response scenarios

    Meisel, M. ; Leber, T. ; Ornetzeder, M. ; Stachura, M. ; Schiffleitner, A. ; Kienesberger, G. ; Wenninger, J. ; Kupzog, F.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072138
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (3)

    IEEE Conference Publications

    Automated demand response has the potential to be an essential future tool for maintaining the balance of supply and demand in electrical energy systems with a very high density of generation from renewable sources. Although this scenario can become true in the near future, only very few actual implementations of automated demand response can be found in Europe. This paper is tackling this by analyzing current demand response implementations, placing them into a matrix of different aspects and strategies, with the goal to provide a systematical basis of current application scenarios of demand response, highlighting barriers and starting points for further development decisions. Recommendations for important and possible near future application scenarios of demand side energy management concepts in Austria are the result of this analysis by a multidisciplinary team of researchers. This paper describes related and important future work for Austria in demand response in context of a defined scenario kit. Aspects and strategies of each scenario are described in the following subsections. 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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    Subjective quality assessment of 3D videos

    Umar, A.S. ; Swash, R.M. ; Sadka, A.H.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071968
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    Colour plus depth map based stereoscopic video has attracted significant attention in the last 10 years, as it can reduce storage and bandwidth requirements for the transmission of stereoscopic content over wireless channels such as mobile networks. However, quality assessment of coded 3D video sequence can currently be performed reliably using expensive and inconvenient subjective tests [1]. The main goal of many subjective video quality metrics is to automatically estimate average user or viewer opinion on a quality of video processed by the system. However, measurement of subjective video quality can also be challenging because it may require a trained expert to judge it. Many subjective video quality measurements are described in ITUT recommendation BT.500. Their main idea is the same as in Mean Opinion Score for video sequences which are showed to the group of viewers and then their opinion is recorded and averaged to evaluate the quality of each video sequence. Optimization of 3D video systems in a timely manner is very important, it is therefore necessary that reliable subjective measures are calculated based on statistical analysis. This paper investigates subjective assessment for four standard 3D video sequences. Subjective tests are performed to verify the 3D video quality and depth perception of a range of differently coded video sequences, with packet loss rates ranging from 0% to 20%. The subjective quality results are used to determine more accurately the objective quality assessment metrics for 3D video sequences such as the Average PSNR, Structural similarities (SSIM), Mean Square Error (MSE) etc.The proposed measure of 3D perception and 3D quality of experience (QoE) is shown to correlate well with human perception of quality on a publicly available dataset of 3D videos and human subjective scores. The proposed measure extracts statistical features from depth and 3D videos to predict the human perception and 3D QoE. View full abstract»

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    Reduction of cogging forces in linear synchronous motors

    Cruise, R.J. ; Landy, C.F.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821834
    Publication Year: 1999 , Page(s): 623 - 626 vol.2
    Cited by:  Papers (13)

    IEEE Conference Publications

    Cogging forces in linear synchronous motors are due to the interaction between the edges of the permanent magnet and the teeth of the primary core. Various techniques can be employed to reduce the cogging force, namely, the optimisation of the magnet length, the use of semi-closed slots, the variation of the air-gap length and skewing. Finite element methods (FEM) are used to assess the various different schemes View full abstract»

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

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

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

    IEEE Conference Publications

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

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    Foundation Fieldbus H1 physical layer diagnosis improvement

    Kafoori, K.E. ; Motamedi, S.A. ; Ziaei, A.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308122
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    Fieldbus networks have been widely used for process controlling, automation and many other applications. These types of network designed to work reliably and timely. But fieldbuses usually works under harsh conditions which can degrade the expected features. Quality of communication on the links can be decreased in these environments and cause to physical layer malfunction. In order to detect such degradations, physical layer diagnostic systems have been developed. In this paper present systems have been investigated and tried to improve them. For improvement, two suggestions have been offered; moving the system and using new diagnostic parameter. We have examined the performance of previous and proposed diagnostic parameters for the first time and found significant improvements. View full abstract»

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    Maximising user acceptance as the underlying strategy for the development of an interactive website for South Africa's citizens

    Van Olst, R. ; Wray, C.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071974
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper describes the development of an interactive GIS website for the Gauteng City-Region Observatory (GCRO), using User- and Usage-centric design methodologies. User acceptance was tested with the Technology Acceptance Model (TAM) to ensure that the targeted users of the website would benefit from the information presented within the website and find the technology easy to assimilate. View full abstract»

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