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    Lightning protection in the Republic of Kenya

    Akello, R.J.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.562972
    Publication Year: 1996 , Page(s): 687 - 692 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    This paper outlines the history of lightning protection in The Republic of Kenya. It addresses itself to the proneness in terms of Mean Thunder Days (MTDs) and the Flash Density (Flashes per km2 per year), losses incurred in the period 1960-1980, protection of schools and residential buildings, protection of storage and transport facilities for petroleum products and of electrical and electronic equipment. Subtle aspects in the Kenyan Standard are referred to whenever necessary View full abstract»

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    Optimal power flow for the high voltage network of the Kenya Power System

    Murlithi, M.G.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563100
    Publication Year: 1996 , Page(s): 162 - 168 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    Economy and reliability of service are important considerations in power system operation and planning. These two aspects of a power system can be adequately satisfied by formulating a suitable optimal power flow problem and finding an appropriate solution methodology. The solution to an optimal power flow problem locates a feasible operating point that gives the least value of a desired objective parameter (e.g. fuel cost, real power loss) subject to satisfying system constraints like voltage levels, real and reactive power flow on transmission lines and transformer tap settings. A suitable optimal power flow solution thus ensures an economical and secure operating point. The solution can be obtained using several nonlinear programming techniques which include the steepest descent method, quadratic programming method (QPM) and the gradient projection method (GPM) among others. In this paper, the optimization problem is solved using the steepest descent method and targets the Kenya Power System View full abstract»

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    Development of a research framework for prepayment metering reliability

    Koert, A.J. ; Lings, R.J.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.563032
    Publication Year: 1996 , Page(s): 996 - 1001 vol.2

    IEEE Conference Publications

    Eskom's Technology Research and Investigations Division (TRI) undertakes research for the ultimate benefit of Eskom's mission. Due to the scale of Eskom's electrification programme (over 1 million completed household connections and a target of 300000 per annum) the reliability of the watthour meter located on the customers premises is critical to the success of this programme. Eskom has conducted metering research for the last 5 years. Past research experience, coupled with an increasing household connection rate and a downward push on costs, demands a review of the approach to electricity metering research. This revised approach, which spans the period 1996-1998 is the subject of this paper View full abstract»

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    On accuracy of double-screw-drive robotic forceps

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

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

    IEEE Conference Publications

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

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

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

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

    IEEE Conference Publications

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

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    Design and implementation of an autonomous hybrid vehicle

    Smith, K. ; Corregedor, A. ; Murcott, C. ; Andrews, B. ; Holte, S. ; Furrutter, M. ; Evans, M. ; Carroll, J. ; du Plessis, F. ; Meyer, J.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072096
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (3)

    IEEE Conference Publications

    This paper outlines the design strategy for the University of Johannesburg's (UJ's) hybrid vehicle entry into the South African Solar Challenge (SASC) 2010. The SASC is a biennial event focused on alternative energies and showcasing various automotive technologies. The SASC is broken up into different classes; UJ entered in the Greenfleet Technology class. This paper presents the design principles and strategies used to implement a working prototype vehicle which is hybrid (propelled by multiple energy sources) and autonomous (able to operate without human assistance). Various specifications of the vehicle structure and systems (brakes and steering) are discussed in the context of these two goals. A description of physical considerations outlines the different design decisions made in order to provide the vehicle with its autonomous and hybrid capabilities; the design and implementation of these systems are also described. The autonomy system allows the vehicle to follow the path of a lead vehicle. The energy management system implemented on the vehicle dynamically optimises the amount of fuel used by the internal combustion engine of the vehicle. The vehicle produced at UJ was able to participate in the SASC 2010 and win the Greenfleet Technology class. The vehicle platform has allowed the development and demonstration of hybrid energy systems and autonomous control. View full abstract»

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    Design of a wideband orthomode transducer

    de Villiers, D.I.L. ; Meyer, P. ; Palmer, K.D.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308555
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    The design of an offset ridge quad-ridged waveguide (QRWG) orthomode transducer (OMT) is presented. By offsetting one of the ridges in the direction of propagation, a much wider single mode operating bandwidth can be achieved than that achievable in a traditional symmetric QRWG OMT's. This wide single mode operating bandwidth ensures that no higher order modes are excited at the feeds of the OMT, which in turn eliminates unwanted resonances often observed in traditional QRWG OMT's. The performance of the OMT is similar to that of traditional types, with reflections below -20 dB and cross coupling below -40 dB across most of the desired 1.7:1 bandwidth. View full abstract»

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    Investigating the validity of applying artificial neural networks to localise harmonic distortion sources [power quality management]

    Cronje, W.S.T. ; Rens, A.P.J.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406757
    Publication Year: 2004 , Page(s): 645 - 650 Vol.1

    IEEE Conference Publications

    Power system equipment is designed to operate under sinusoidal conditions. Damage and even failure of equipment can result from the presence of a harmonically distorted supply waveform. The level of harmonic distortion on modern power systems is a concern as more non-linear devices are used in sophisticated energy conversion. Harmonic mitigation techniques are most effective when the location of the harmonic distortion source is known. Tariff systems cannot allocate distortion costs amongst the utility's consumers when the relative distortion contributions cannot be assigned to distinct sources. A reliable localisation technique is therefore required. In this paper, the application of artificial neural networks as a possible aid in the localisation of distortion sources, is investigated and demonstrated View full abstract»

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    Investigating the validity of the Czarnecki three phase power definitions

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

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

    IEEE Conference Publications

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

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    Linear model of a closed three-shaft Brayton cycle

    van Niekerk, C.R. ; van Schoor, G. ; Pritchard, J.F.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406855
    Publication Year: 2004 , Page(s): 1079 - 1084 Vol.2

    IEEE Conference Publications

    A linear model of a closed three-shaft Brayton cycle is developed. The model is intended to give an understanding of the dominant dynamic behavior in a nuclear power system that utilizes a closed three-shaft Brayton cycle. The insights gained from the model can be used for system design as well as for the design of control algorithms [S.T. Glad et al. (2001)] [B.Hendrisson et al., (2001)]. Linear models of the turbines and compressors are developed, followed by models of the shafts and the volumes inside the circuit. Thereafter, the system equations are derived from the component models and put into state space format. Finally, a time domain comparison is made between the linear system model and the responses predicted by the thermal-fluid analysis software program, Flownex. View full abstract»

  • Freely Available from IEEE

    Author index


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406898
    Publication Year: 2004 , Page(s): 1287 - 1298

    IEEE Conference Publications

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    A generic LDAP CORBA connector

    Radinger, W. ; Jandl, M. ; Szep, A. ; Goeschka, K.M.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146807
    Publication Year: 2002 , Page(s): 65 - 70 vol.1

    IEEE Conference Publications

    In general, telecommunication systems should provide a simple interface for third party integration. Unfortunately, the interfaces are often too complex, mainly due to the distribution of these systems. Therefore, we implemented a generic LDAP CORBA connector to bridge between these two technologies and to provide a simple, standardized interface. We achieve this by including the mapping information in the CORBA interface definition file. Thus, changes on the application have no direct impact on the connector, only the mapping information has to be updated, which is nested in the interface description's comment lines. Consequently we achieve robustness due to separation of concerns. View full abstract»

  • Freely Available from IEEE

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    AFRICON, 2004. 7th AFRICON Conference in Africa

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

    IEEE Conference Publications

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    Training electrical engineers at Moi University: the 8-4-5 BTECH curriculum

    Afullo, T.J.O.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563087
    Publication Year: 1996 , Page(s): 95 - 100 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    The curriculum for the training of electrical engineers at the Department of Electrical & Communications Engineering, Moi University, Kenya, is discussed in this presentation. The paper discusses the introduction of the 8-4-5 Educational system in Kenya, the rationale behind this, and the emphasis on a practical graduate engineer with the inherent capability to adapt to local demands and to new challenges of the future. It also discusses the challenges facing the Universities as they grapple with this new programme View full abstract»

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    Building envelope shape design using a shape grammar-based parametric design system integrating energy simulation

    Granadeiro, V. ; Duarte, J.P. ; Palensky, P.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072140
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    The envelope shape is considered the most salient design characteristic in a building and also impacts its energy performance. And although energy efficiency in design is gaining momentum, the value of architectural attributes should not be underestimated. Design rules of thumb are useful guidelines to achieve better energy performance but they do not substitute energy simulation results, particularly in more complex projects. However, in the early design stages, when the envelope shape is defined, energy information is normally inexistent, due to modeling for energy simulation being a time-consuming task, frequently overlooked at this phase, when the design is still uncertain regarding many parameters. This paper presents a methodology to assist design decisions regarding the building envelope shape taking into account its implications on the energy performance of the building. Basically, this methodology involves a design system, an editable (flexible) system to generate various envelope shape designs, with integrated energy simulation, to calculate the energy consumption values of each generated design. Design systems encoded into shape grammars are more adequate for the architecture field, given their ability to guarantee stylistic coherence, but they are hard to implement. This methodology converts a grammar into a parametric design system and is illustrated with its application to the grammar for Frank Lloyd Wright's prairie houses. Output examples of the application are also presented. Results show the validity of the proposed methodology and the addition of optimization techniques is identified as the obvious next step. View full abstract»

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    Applying soft magnetic materials to conductive surfaces to realise a novel conformal HF antenna concept

    Dresel, J. ; Clark, A.R. ; Fourie, A.P.C.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821922
    Publication Year: 1999 , Page(s): 1069 - 1074 vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    This paper presents a novel conformal HF antenna concept. Soft magnetic materials are used to suppress currents on conductive surfaces in order to realise conformal HF antennas. The concept is verified by comparing predicted HF antenna characteristics to measured results. The efficiency of the conformal HF antenna is compared to a tuned whip and loop antenna. The conformal antenna shows superior performance above 15 MHz 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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    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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    Design of an auto-braking regulator for a small wind generator

    Fredericks, A.F. ; deVries, I.D.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401565
    Publication Year: 2007 , Page(s): 1 - 5

    IEEE Conference Publications

    Wind generators require braking mechanisms to prevent serious damage in high wind speeds. This paper proposes an, automated, electronic solution to existing mechanical methods that are expensive and reduce reliability. The "soft" automatic braking system brakes the generator, by slowly decreasing the phase to phase resistance of the generator, allowing the generator to decelerate steadily until it is fully braked. Regulation is achieved by monitoring the charging voltage of the battery, braking the system when the battery is fully charged and releasing it when below fully charged. Synchronous rectification is also incorporated and results in an increase of output power from the system, by approximately 10%. High wind speed can also be sensed by monitoring the charging current or the current through the MOSFETs and the generator can be braked if necessary. View full abstract»

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    Energy consumption of air conditioners at different temperature set points

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

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

    IEEE Conference Publications

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

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    Use of spatial interpolation technique for determination of geoclimatic factor and fade depth calculation in Southern Africa

    Odedina, P.K. ; Afullo, T.J.O.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401597
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    Different authors have adopted various techniques to resolve the clear-air radio-propagation effect problems. These authors have presented different modeling techniques based on the radio propagation variables of the region in question. These variables are determinable from the local radio propagation data of the region in question. This paper uses the radiometeorological data collected in Durban, South Africa and in Maun, Botswana to determine the geoclimatic factor (K) variable. This is then used in implemented link designs to calculate the fade depth and worst month for these two locations. View full abstract»

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    Example of undervoltage load shedding implementation

    Klaric, M. ; Kuzle, I. ; Tesnjak, S.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401446
    Publication Year: 2007 , Page(s): 1 - 6

    IEEE Conference Publications

    After deregulation of power systems, large problems with voltage stability incurred due to the large transits of power transmitted to large distances. Systems are very stressed and often work on their limits. Therefore, single contingency is sometimes enough to cause system collapsing. One of the most economic methods to prevent larger scale voltage collapse is undervoltage load shedding (UVLS). In this article, implementation of UVLS scheme is tested in New England Test System and then modeled in part of Croatian power system. Simulation of system behavior is presented as well. View full abstract»

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    Sampling in the radial configuration with jitter of Gaussian Fields

    Kazakov, Vladimir A. ; Rodriguez, D.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401465
    Publication Year: 2007 , Page(s): 1 - 6
    Cited by:  Papers (3)

    IEEE Conference Publications

    The optimum sampling-reconstruction procedure of Gaussian fields with jitter is described on the basis of the conditional mean rule when the quantity of samples is limited. Jitter is only presented in some samples. Moreover, the jitter of each sample is independent and can have the same or different distribution law. The statistical average is applied to the conditional mean rule with regard to the random position of samples in order to analyze jitter effects in Gaussian fields when samples are in a radial configuration. The surfaces of the optimum error reconstruction functions are calculated in the whole space domain. The applied method provides the possibility of considering to each sample with its own type of jitter probability density function. View full abstract»

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

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

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

    IEEE Conference Publications

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

  • Freely Available from IEEE

    Message from the technical programme chair

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

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

    IEEE Conference Publications

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    Simulation criteria for ultra high voltage power systems

    Trabulus, S. ; Inan, A.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821843
    Publication Year: 1999 , Page(s): 659 - 662 vol.2

    IEEE Conference Publications

    Due to increasing energy requests, ultra-high-voltage power systems are coming more to the fore. In this paper, power systems of 1000 kV are especially taken into account. New simulation technologies are required to be able to understand the behavior of 1000 kV power systems and to guide the development of 1000 kV equipment. The paper explains two related subjects: a simulation method for evaluating the unbalanced voltage and current conditions that occur in nontransposed transmission lines; and a modeling method that can analyze the surge behavior of low attenuation 1000 kV lines View full abstract»

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    Modelling of the absolute capacitance of a planar inductor for EMI mitigation purposes

    Hofsajer, I.W. ; Crosato, M.O.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406858
    Publication Year: 2004 , Page(s): 1099 - 1104 Vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    Due to the large surface area of the conductors of planar magnetic components, they exhibit a large intra and interwinding capacitance. In addition they have a large absolute capacitance to the surroundings. In order to predict the behaviour of the magnetic component with respect to the parasitic absolute capacitance, it is necessary to be able to accurately model it. This is difficult as the conductor of the magnetic component, which can be considered to be one of the plates of the capacitor, is not an equipotential surface. The absolute capacitance is a distributed effect along the length of the winding. In this paper an equivalent model of the absolute capacitance of the structure is derived. The model is verified experimentally through direct capacitance measurements on the planar structure under operating conditions. View full abstract»

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    A less conservative method for average consensus with multiple time-varying delays

    Hui Yu ; Xiaohua Xia ; Tiecheng Zhang
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072031
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    In this paper, average consensus problem of multiagent systems with switching topology and multiple time-varying delays are investigated in undirected networks. Based on Lyapunov stability theory combined with linear matrix inequalities (LMIs) techniques, some novel forms in terms of LMIs are obtained via taking relationship among the terms in the Newton-Leibniz formula into account. Since some free weighted matrices are employed to express this relationship and appropriate ones are selected by means of LMIs, this method is less conservative and more general. Finally, simulation examples are given to demonstrate the effectiveness of our theoretical results. View full abstract»

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    DC motor control via high order differential feedback control

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

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

    IEEE Conference Publications

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

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    Towards 3-dimensional face recognition

    Eriksson, A. ; Weber, D.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820880
    Publication Year: 1999 , Page(s): 401 - 406 vol.1
    Cited by:  Papers (3)  |  Patents (6)

    IEEE Conference Publications

    This paper describes a system for recognizing human faces from a stereo image pair out of a large database with one image pair per person. The faces are stored as image meshes which contain the position and disparity for 40 feature points extracted from the image pair. Texture information, described by the outputs of a set of Gabor wavelets is stored for each feature point. The Gabor wavelets are also used in the disparity estimation process to resolve a 3-D representation of the face. The recognition is conducted by examining how well the stored meshes can be projected onto the image pair to be tested, using camera calibration data. This is important as recognition is independent of pose, camera geometry, distance from camera and lighting conditions View full abstract»

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    Optimization of SiO2-Si3N4 antireflective coating on P+NN+ photodiode

    Resnik, D. ; Vrtacnik, D. ; Amon, S.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821940
    Publication Year: 1999 , Page(s): 1153 - 1156 vol.2

    IEEE Conference Publications

    Optimization of anti-reflective coating on planar 1.8 mm2 area monocrystalline silicon photodiode was performed. Thermally grown SiO2 and LPCVD Si3N4 of different thicknesses were fabricated on the top of p+nn+ structure. Short circuit current density Jsc, open circuit voltage Voc and spectral response were measured as a function of both layers thickness and the results are discussed. Considerable improvement, particularly of Jsc was achieved with matched thicknesses of the two layers over single layer. It is shown that by tailoring the thickness of individual layers, spectral response can be efficiently varied along the wavelength axes View full abstract»

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    Algebraic attacks on cipher systems

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

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406830
    Publication Year: 2004 , Page(s): 969 - 974 Vol.2

    IEEE Conference Publications

    Recently, algebraic attacks have emerged as a new type of cryptographic attack on block ciphers. These attacks involve the formulation of a system of nonlinear equations that describe the secret keybits in terms of the input and output bits of the block cipher, which is then solved. Courtois and Pieprzyk have shown that that the AES-Rijndael block cipher can be written as an overdefined system of 8000 multivariate quadratic (MQ) equations with 1600 binary (2002). The estimated complexity for solving these equations requires O(2230) steps. Recently, Murphy and Robshaw (2002) have shown how to embed Rijndael in a new extended 128-bit cipher, called BES (big encryption system). Within this simplified framework AES encryption can be described by a small and extremely sparse multivariate quadratic (MQ) system over GF(28). Key recovery requires the solution of a sparse MQ systems over GF(28) in approximately O(2108) steps. This work presents a comparison of these two similar algebraic attacks and a detailed overview of the XL algorithm for solving MQ equations. View full abstract»

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    A genetic algorithm for impedance matching

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

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159972
    Publication Year: 2002 , Page(s): 567 - 570 vol.2

    IEEE Conference Publications

    A genetic algorithm is used as the basis for a new impedance matching algorithm. The new algorithm obtains similar results to published techniques in most cases despite not requiring transformers. View full abstract»

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    Path loss analysis between the north and the south of mauritius with some existing models for digital television broadcasting for summer season at UHF bands

    Armoogum, V. ; Soyjaudah, K.M.S. ; Mohamudally, N. ; Fogarty, T.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401524
    Publication Year: 2007 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    After the official launching in October 2005 of digital terrestrial television (DTT), plans were made to carry out field measurements across the island. Field strength, carrier-to-noise ratio and bit-error-rate were measured at two antenna heights (4 m and 6 m) both in the north and south of Mauritius at UHF bands (470 to 862 MHz). In this paper, we compare the measured path loss obtained for the sub-urban northern area with that for the rural southern area and then with four propagation models, that is, free-space, Lee, Hata and extended COST-231. Firstly, for both areas, the results show that the path loss is not constant at various locations for a constant distance around the respective base station showing that the terrain of Mauritius is irregular. Moreover, for the same antenna height, the path loss is higher in the south than in the north by 5 dB to 20 dB depending upon the distance from the station. The effects of the slow fading effect (shadow) and fast fading effect are more pronounced in the south than in the north, causing higher probability of signal errors. Secondly, we found that Lee and free space models are not in agreement with the values obtained for both regions. However, observations show that Hata and extended COST 231 models give better agreement and hence, can be used to model areas in Mauritius. View full abstract»

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    Performance evaluation of Viterbi decoded binary and non-binary linear block codes in flat fading channels

    Staphorst, L. ; Linde, L.P.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146830
    Publication Year: 2002 , Page(s): 181 - 186 vol.1

    IEEE Conference Publications

    In recent years, much attention has been given to the decoding of linear block codes by means of trellis decoding algorithms, such as the Bahl-Cocke-Jelinek-Raviv (BCJR) and Viterbi algorithms. Not only do these algorithms support soft in. put decoding, but also the application of channel state information for improved decoding performances in fading channel environments. This paper presents a performance evaluation, based on an extensive simulation study, of Viterbi decoded binary Hamming and non-binary Reed-Solomon block codes under flat fading channel conditions with varying Doppler frequencies and line-of-sight signal strengths. Special attention is given to the influence of channel state information on the bit error rate performance. 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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    Demand-side solutions for extending the capacity of rural reticulation networks using Written-pole technology

    Boake, I. ; Hennessy, T.D.J. ; Roesel, J.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563150
    Publication Year: 1996 , Page(s): 425 - 430 vol.1

    IEEE Conference Publications

    This paper investigates the use of Written-pole technology to eliminate the disadvantages of conventional induction machines as they are applied in rural reticulation networks. The intended purpose of this exercise is to extend the “lifetime” of these networks. The concerns and considerations pertaining to reticulation planning as well as the potential problems which may be encountered on these networks are discussed. Written-pole technology ('permanent magnet' synchronous motor) is justified as a feasible alternative to conventional induction machines based on the following considerations: the lower start-up current, the high power factor, the higher efficiency and additional benefits such as dip ride-through capabilities. The thermal limit of a reticulation line, the voltage regulation limit at the end of a reticulation line and the power quality of the line are used as the comparison criterion View full abstract»

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    The South African airborne SAR initiative

    da Silveira, M. ; Taute, B.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563134
    Publication Year: 1996 , Page(s): 341 - 344 vol.1

    IEEE Conference Publications

    Satellite synthetic aperture radar (SAR) data has already provided valuable unique information to a number of applications in South Africa. Airborne SAR data can provide additional information to assist in the interpretation of remote sensing data. This paper reports on the current developments and future initiatives in the field of airborne SAR remote sensing in South Africa View full abstract»

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    Correcting adjacent errors using permutation code trees

    Heymann, R. ; Swart, T.G. ; Ferreira, H.C.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072122
    Publication Year: 2011 , Page(s): 1 - 5
    Cited by:  Papers (1)

    IEEE Conference Publications

    Permutation codes are M-ary codes which can be used, in combination with M-ary FSK, to correct errors in Power Line Communications (PLC). It has been shown in [1] that permutation code trees can be used to correct a single substitution or synchronization error per codeword, without the use of markers. In this paper, we show that, due to the structure of the permutation code tree, adjacent errors can also be corrected if the codebook is adapted. 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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    Comparative analysis of reliability evaluation of a real distribution network in South Africa

    Awodele, K.O. ; Zikalala, V.L. ; Van Harte, M.A.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072161
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper describes the evaluation of a sub transmission network within Eskom Distribution by performing comparative analysis using analytical methods: Failure Mode and Effects Analysis (FMEA) and Network Reduction techniques and a reliability assessment tool (DigSILENT Powerfactory version 14.0.511). The analysis used in this paper first compares the results of the analysis of the existing networks using FMEA and DigSILENT. The future network configuration is evaluated using a Network Reduction technique and DigSILENT. The results obtained for the existing network and future expansion network demonstrated the advantages and disadvantages of using the different techniques. The differences observed are discussed in the paper. View full abstract»

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    An investigation into the methodology to develop an insulator pollution severity application map for South Africa

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

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406774
    Publication Year: 2004 , Page(s): 697 - 703 Vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    The development of an insulator pollution severity application map (IPSAM) for South Africa is being investigated. This work discusses the results that were obtained from directional dust deposit gauges (DDG's) and equivalent salt deposit density gauges (ESDD's) across South Africa. An investigation into the effect of distance-from-seacoast on pollution severity levels is discussed. Correlations between DDG and ESDD and between DDG and corrosion test results are also included. View full abstract»

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    A contribution to the IEEE STD. 1451.2-1997 revision and update

    Ramos, H.G.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401453
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    After a technical overview of the IEEE 1451 family of standards, detailed descriptions of implemented smart transducers interface modules (STIM) and transducer interface modules (TIM) either using 10-wire transducer independent interface (TII) or USB are presented. These experimental research results aim to be a small contribution for the IEEE STD. 1451.2-1997 revision and update. View full abstract»

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    Bushing monitoring using MLP and RBF [power insulators]

    Dhlamini, S.M. ; Marwala, T.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406752
    Publication Year: 2004 , Page(s): 613 - 618 Vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    This paper examines the use of artificial neural networks (ANN) for monitoring bushings. The first ANN uses a multiplayer perceptron (MLP) while the second uses radial basis activation functions (RBF). In this approach, a decision can be taken to remove or leave a bushing in service, based on analysis of bushing parameters using RBF and MLP. The results show that the RBF converges to a solution faster than the MLP. Furthermore, the MLP is found to be the best tool of the two for analyzing large amounts of non-parametric non-linear data View full abstract»

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    Validation within safety critical systems engineering from a computational semiotics point of view

    Doeben-Henisch, G. ; Wagner, M.F.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401588
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (2)

    IEEE Conference Publications

    Software controlled Safety Critical Systems are increasing in importance in all areas of application. Combining efficient agile development processes with powerful but complex modeling and formal methods imposes grand challenges on software designing organizations. Especially the semiotic dimension which relates stakeholders and engineers in an engineering process is evoking such challenges. Focusing on these processes as basis for domain modeling and as point of reference for validation the authors outline a simulation based approach to overcome the semantic gap. But they know, that this still can only be a preparatory step for much more detailed semiotic analyses. 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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    PWM current rectifier-five NPC level inverter cascade. Application to the PM synchronous machine

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

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

    IEEE Conference Publications

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

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    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»

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    Static and dynamic force characteristics of paramagnetic shields in linear synchronous motors

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

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821836
    Publication Year: 1999 , Page(s): 631 - 634 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    A small-scale prototype of a linear synchronous motor has been designed, built and tested. Present studies include the investigation of the shielding properties of a paramagnetic material as well as its use as a stabiliser during asynchronous operation. It has been found through finite element methods that a 3 mm copper shield provides the greatest static inductive force. Aluminium has been used however, as it is a more economically viable material than copper. Dynamic tests have shown that a paramagnetic shield provides a damping action during transients View full abstract»

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    Optimization model for loss minimization in a deregulated power distribution network

    Davidson, I.E. ; Ijumba, N.M.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160031
    Publication Year: 2002 , Page(s): 887 - 894 vol.2
    Cited by:  Papers (4)

    IEEE Conference Publications

    Power sector deregulation and its impact on power systems performance is investigated. The introduction of distributed generation in networks by independent power producers (IPPs) is bound to have a significant effect on network losses, voltage profile and loading limits. Earlier studies showed that the contribution to network losses by additional generating sources depends on the location of the generator. This paper presents an optimisation model to achieve loss minimization through constrained power flows and optimal siting of distributed generators in a multi-bus distribution network. The main objective is to minimize the line losses subject to generation revenue, transmission constraints (P, Q, V) and consumer demand. Calculated results of technical loss computation and network performance, and those obtained from software simulation are compared and discussed. 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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    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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    Graphical preprocessing of orderings used in disjunctive decomposition detection

    Ngwira, S.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820973
    Publication Year: 1999 , Page(s): 575 - 580 vol.1

    IEEE Conference Publications

    A graphical analysis is presented to predict the input variable subsets that give efficient disjunctive decompositions of complex combinatorial logic functions. The subsets obtained match substantially with the optimum orderings from an exhaustive search for disjunctive decompositions, thus, the technique can serve as a preprocessor before exhaustive search algorithms View full abstract»

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

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

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

    IEEE Conference Publications

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

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

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

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

    IEEE Conference Publications

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

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    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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    Field experience with PRBS perturbation of a 133 MVA hydro-generator

    Strauss, J.M. ; Vermeulen, H.J. ; Coker, M.L.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160017
    Publication Year: 2002 , Page(s): 803 - 806 vol.2

    IEEE Conference Publications

    Research has shown that the parameters of automatic voltage regulators (AVRs) and synchronous generators can be estimated from on-line measurements acquired while perturbing the automatic voltage regulator reference signal with a pseudo-random binary sequence (PRBS) signal. The technique has, however, been tested mainly for small round rotor machines under laboratory conditions. This paper presents field experience in applying PRBS perturbations to a 133 MVA hydro-generator to obtain data for verification of the technique for larger generators. View full abstract»

  • Freely Available from IEEE

    Psychoanalytical model for automation and robotics

    Dietrich, D. ; Bruckner, D. ; Zucker, G. ; Mùˆller, B. ; Tmej, A.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308065
    Publication Year: 2009 , Page(s): 1 - 8
    Cited by:  Papers (10)

    IEEE Conference Publications

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    South African Power Systems Studies Institute (SAPSSI)

    Lakmeeharan, K. ; Lings, R.J.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821868
    Publication Year: 1999 , Page(s): 787 - 792 vol.2

    IEEE Conference Publications

    The South African Power Systems Studies Institute (SAPSSI), a joint project between ESKOM and EPRI, was formally launched on the 3rd of November 1997, with the following strategic intent: “The enhancement of skills in power systems analysis, planning, control and operation, in the South and Southern African Electrical Supply Industry, to meet the challenges of the future, through formal training and human resource development, supported by appropriate technology transfer, applied research and consultancy,” This paper deals with the formation and operation of SAPSSI over the last two years, and its role in the emerging Southern African Power Market View full abstract»

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    Capture and imperfect power control in spread-ALOHA systems with lognormal shadowing

    Mpako, V.M.W. ; Takawira, F.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820806
    Publication Year: 1999 , Page(s): 245 - 250 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    This paper investigates the performance of a spread slotted ALOHA system with power control errors that lead to the capture effect. This paper is motivated by the apparent uncertainties in the performance of a spread-ALOHA system with unequal received power at the base stations. The assumption made by Schwartz and Yeh (1982) that the sum of lognormal random variables is also lognormal, is used in determining an expression for the probability of capture. This paper shows that the analytical expression for capture gives the same throughput curves as lognormal power control errors. It is further shown that higher throughputs at heavy loads are obtained when there are imperfections in power control View full abstract»

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    Load flow analysis with a neuro-fuzzy model of an induction motor load

    Muriithi, C.M. ; Ngoo, L.M. ; Nyakoe, G.N.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308308
    Publication Year: 2009 , Page(s): 1 - 4

    IEEE Conference Publications

    In the conventional load flow study, the active and reactive powers of all load buses are generally specified. Although the constant power model is applicable for approximate studies, it may not be suitable for the motors because the reactive power is very sensitive to the voltage variations while the active power is dependent upon the torque being driven. This paper proposes to solve the load flow equations using a neuro-fuzzy model of an induction motor. Both the active and reactive powers of the motor are estimated at each iteration using neuro fuzzy techniques. The efficiency is estimated using the IEEE 30 bus system. The results indicate that the inclusion of induction motor loads has an effect on the convergence characteristic of the active and reactive power mismatches of the modified load flow. View full abstract»

  • Freely Available from IEEE

    [Blank page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406806
    Publication Year: 2004 , Page(s): 852

    IEEE Conference Publications

  • Freely Available from IEEE

    1999 IEEE Africon. 5th Africon Conference in Africa (Cat. No.99CH36342)


    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820664
    Publication Year: 1999

    IEEE Conference Publications

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

    University student exchange programmes

    Liew, A.C. ; Mendis, F.V.C.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563074
    Publication Year: 1996 , Page(s): 32 - 37 vol.1

    IEEE Conference Publications

    This paper discusses the establishment of a student exchange programme between two universities, with particular reference to the exchange of undergraduate engineering students. The many issues involved with the management of such a programme are considered in detail View full abstract»

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    Small wind turbine power curve comparison

    Simic, Z. ; Vrhovcak, M.B. ; Sljivac, Damir
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308281
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (2)

    IEEE Conference Publications

    This paper focus is on the small wind turbines resource potential estimation. Assessment is done for seven selected small wind turbines and one measured set of wind speed data with the micropower optimization modeling tool HOMER. Goal was to investigate how estimated energy production and economical parameters are sensitive to the selection of small wind turbine. Selected turbines have similar rated power, but different blades diameter and aerodynamic characteristics. Energy production was quantified for one year with hourly resolution. Results from all different wind turbines were compared on the power production base, and on the economical base. Two sensitivity cases related to the wind speed and installation lifetime were also simulated. Results are showing significant importance of the small wind turbine selection for the both total energy production and economical feasibility. This makes small wind turbine characteristics such as reliability and power curves testing very important. View full abstract»

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    A budget supercomputer: implementation and application

    Wicomb, L.P. ; van Zyl, R.R.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406699
    Publication Year: 2004 , Page(s): 383 - 384 Vol.1

    IEEE Conference Publications

    This paper presents an overview of the implementation and current application of the Peninsula Technikon's first cluster-based supercomputer. The cluster consists of 18 off-the-shelf, diskless PC's and 1 controller/master high-end PC. The approach taken for implementing this budget supercomputer is discussed View full abstract»

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    QoS management of a cost-effective ATM protocol for distributed multimedia

    Ghinea, G. ; Kisimov, V. ; Neishlos, H.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563090
    Publication Year: 1996 , Page(s): 106 - 111 vol.1

    IEEE Conference Publications

    This paper describes the design and simulation of a dynamic quality of service (QoS) based call admission protocol for distributed multimedia over ATM networks. The protocol incorporates the innovative idea of an extended QoS. This is a composite term which takes account of not only classic QoS multimedia measures, but also of the human aspect of the interaction through human receptivity. A session pricing policy has also been elaborated and its effect on user behaviour and network resource allocation studied 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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    A digital image watermarking scheme based on localised wavelet coefficients' dependency

    Buse, R.D. ; Mwangi, Elijah
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308153
    Publication Year: 2009 , Page(s): 1 - 4

    IEEE Conference Publications

    A wavelet based robust image watermarking scheme in which a binary image is embedded in the horizontal and vertical quadrants of a wavelet transformed image is proposed. The algorithm exploits the inter-coefficients relationship within a DWT block of a predetermined size. Only one wavelet coefficient is perturbed slightly in order to embed a single bit of the watermark and also to produce a watermarked image of high perceptual quality. The embedded DWT coefficients block is selected by the use of a secret key in order to enhance the security of the scheme. The retrieval process is blind and only requires the knowledge of the key. Results, obtained by MATLAB simulation have been used to confirm the feasibility and effectiveness of the proposed algorithm against common attacks such as lossy image compression, low pass filtering, additive white Gaussian noise, and image cropping. 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»

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    Mobile robot navigation in unstructured environments using machine vision

    Scott, D. ; Aghdasi, F.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820778
    Publication Year: 1999 , Page(s): 123 - 126 vol.1

    IEEE Conference Publications

    The aim of this investigation is to develop and evaluate a stereo vision system specifically for navigation and position estimation. The system must be capable of automatically modeling an environment and providing an accurate estimate of its own position within the environment. Specific areas in current vision algorithms are identified as candidates for improvement. The application of recent image processing tools such as wavelets and neuro-fuzzy logic to the proposed vision system is investigated. A combination of stereo matching techniques, photogrammetry and position estimation is used in an attempt to produce a system ideally suited to gathering detailed information about an unfamiliar environment for the purpose of navigating an autonomous mobile robot View full abstract»

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    Unconstrained MPC and PID evaluation for motion profile tracking applications

    Tsoeu, M.S. ; Esmail, M.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072037
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    Motion profile tracking control forms an integral part of most industrial applications ranging from manufacturing, where planned motion robots perform assebly tasks, medical applications for position patients and moving scanners across patient bodies and unmanned vehicle applications such as automated parking. In all these applications, the challenges are keeping the tracking error as low as possible, using as low a control effort as can be afforded. Numerous control methods ranging from PID, to Sliding Mode Control (SMC) have been researched in this regard, some with great success. With the objectives and aspects of motion profile tracking, specifically a desired trajectory that is known apriori, it is intuitive to assume that Model Predictive Control (MPC) which is heavily rooted on the use of future information would be a good candidate for such applications. In this paper we test optimally tunned MPC and PID controllers for motion profile tracking applications, and draw comparisons based on Pareto optimality. Optimal controller tunning is performed and simulation as well of experimental tests of some of the pareto optimal points are undertaken for comparisons. The results for PID control are reasonable and MPC gives unanticipated outcomes. View full abstract»

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    New developments in the management of power quality performance in a regulated environment

    Koch, R.G. ; Balgobind, P. ; Tshwele, E.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160022
    Publication Year: 2002 , Page(s): 835 - 840 vol.2
    Cited by:  Papers (3)

    IEEE Conference Publications

    This paper reviews recent developments in utility power quality, management in South Africa. Anew (and more comprehensive) regulatory framework is discussed in the context of experience with previous performance-based requirements. This framework will significantly change! the way in which power quality is addressed by all stakeholders (i.e. utilities, customers, and equipment suppliers) in South Africa. The role of proposed revisions to the NRS-048 Power Quality Standard are discussed with regard to this framework. View full abstract»

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    Internetworking optimisation

    Bajenescu, T.I.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.563047
    Publication Year: 1996 , Page(s): 1071 - 1074 vol.2

    IEEE Conference Publications

    An approach for designing and optimising local and wide-area data communications networks is presented. Because analytical techniques incorporating these technologies into operational networks have received little attention, a unique approach based on a network engineering process of analysis and design is presented. The process includes three interrelated phases: network analysis, network design, and network management. Each phase is part of a feedback control process that iteratively progresses towards a network optimum View full abstract»

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    Jitter peaking investigation in charge pump based clock and data recovery circuits

    Samii, F. ; Abrishamifar, A. ; Atani, R.E.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401483
    Publication Year: 2007 , Page(s): 1 - 6

    IEEE Conference Publications

    Jitter transfer function of a clock and data recovery circuit (CDR) must satisfy difficult specifications versus of loop bandwidth and jitter peaking. This paper describes the method of setting poles and zero in third order CDR circuit to keep jitter peaking below a certain value required by specific optical standards. The results are validated by MATLAB simulations for a 10 Gb I s clock and data recovery circuit with an approximately 1MHz bandwidth. View full abstract»

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    Generalized analysis of electrical circuits by using hypernion matrixes

    Berkovich, Y. ; Shenkman, A.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401600
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    In this paper a novel method for circuit analysis is proposed. It is based on using symbolic analysis in matrix form, which is especially appropriate for repetitive similar calculations of the same circuit. The method, which applies hyper-complex numbers (hypernions), was first developed by the authors for analyzing the non-sinusoidal operation of electrical circuits. Now, the method has been extended to the analysis of electronic/switching circuits in which the sources and/or the parameters are step-wisely changed as a result of switching. Such circuits are common in different kinds of DC-DC converters (such as Buck, Boost, Cuk, etc. converters). The proposed method gives a new approach to the analysis of the above circuits by opening the possibility of treating them in a general-analytical form, just like in regular electrical circuits having a constant configuration and constant parameters. The computation of such kinds of circuits by using the proposed method becomes very simple, since the circuit does not have to be analyzed many times, each time for a different configuration, but at once by performing a parallel computation. The theoretical presentation is accompanied by numerical examples. View full abstract»

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    The link between project management and strategic management: Realising strategy success

    Britz, J. ; Buys, A.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401637
    Publication Year: 2007 , Page(s): 1 - 8

    IEEE Conference Publications

    Successful strategy implementation is very important to every leader of a company or division. This is, after all, one of their most important functions. Many such leaders are frustrated about the poor execution of their great ideas and in some cases may even lose their jobs, because they fail to implement their strategies. However, on the other hand, some companies are very successful in implementing their strategies year after year. This paper investigates why some companies fail and why some companies are so successful in implementing their strategies. The value that project management principles add to the implementation process is determined and a revised model, based on project management principles, is developed to assist leaders with the implementation of their strategies. View full abstract»

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    A dictionary approach to fault diagnosis of analog circuits

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

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

    IEEE Conference Publications

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

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    Digital spatial domain multiplexing of interferometric optical fibre sensor systems for distributed real time condition monitoring of engineering structures

    Bridge, B. ; Hu, Y. ; Chen, S. ; Khalid, A.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821939
    Publication Year: 1999 , Page(s): 1147 - 1152 vol.2

    IEEE Conference Publications

    The potential of large scale fibre optic sensor arrays for distributed and real time monitoring of engineering structures is discussed. It is shown that novel spatial multiplexing techniques augmented by special signal processing algorithms, whilst being more robust than systems based on other multiplexing techniques, can also achieve higher multiplexing capacity, measurement speed and cost effectiveness View full abstract»

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    The design of low-cost modular instructional equipment in electrical and electronic engineering

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

    DOI: 10.1109/AFRCON.1992.624541
    Publication Year: 1992 , Page(s): 541 - 544
    Cited by:  Papers (2)

    IEEE Conference Publications

    The author considers some conceptual dilemmas and practical problems that arise in the attempt to develop a range of low-cost instructional apparatus with which to support a program to enrich the undergraduate electrical and electronic engineering curriculum. He illustrates these by specific examples drawn from a program under way at the University Cape Town and reports informally on some of the results to date View full abstract»

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

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

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

    IEEE Conference Publications

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

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    Design of a dual-loop frequency synthesizer

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

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

    IEEE Conference Publications

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

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    A DSP based controller for high dynamic bandwidth power electronic applications

    Du Toit, J.A. ; Enslin, J.H.R.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.562968
    Publication Year: 1996 , Page(s): 665 - 670 vol.2

    IEEE Conference Publications

    Developments in power electronics and control have led to a wide variety of control algorithms for drive and power quality applications. These new control algorithms are computationally intensive and are more practical to implement on microprocessor based controllers. This field of study is still heavily under investigation with many new algorithms being developed. A flexible controller capable of handling these algorithms in real time is therefore necessary. This paper presents such a digital signal processing based controller and implements an active power filter to show the operation of the new controller View full abstract»

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    Combined field integral equation formulation for broad wall radiating slots of arbitrary shape

    Konditi, D.B.O. ; Dharmadhikary, V.V. ; Koech, E.K. ; Makiche, J.K.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308211
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    In this paper CFIE formulation is presented to analyze broad wall slots of arbitrary shape partially filled with homogeneous dielectric materials. The ldquogeneralized network formulationrdquo for aperture problems is formulated in terms of linear operator equations and expanded in RWG functions in a Galerkin sense. The approach uses a simultaneous representation of the equivalent surface current densities. Representative aperture shapes have been considered such as rectangular, elliptic, and cross-shaped. Numerical results are presented, which are in good agreement with the published data. View full abstract»

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    A bioinspired 2-DOF throwing robot

    Frank, H. ; Frank, T. ; Mittnacht, A. ; Sichau, C.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071965
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    A bio-inspired throwing robot with two degrees of freedom (DOF) was developed for a science center. It has a rotary axis to turn the robot like a human his body and a second rotary axis to throw objects like a human with his arm. With this kinematic, the robot is capable to throw objects into predefined positions within a given 3D-space. The goal of this robot is to demonstrate visitors in the science center robotic throwing with a simple kinematic. In experiments the visitors can learn how the angle of throwing and the speed of throwing determines the trajectories of thrown objects. Student-classes who want to spend more time for the robot can also calculate such trajectories. Therefore, the required mathematical models for this robot are also presented in this paper. View full abstract»

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    Design of a sinewave inverter for alternative energy

    Malengret, M.
    AFRICON '92 Proceedings., 3rd AFRICON Conference

    DOI: 10.1109/AFRCON.1992.624426
    Publication Year: 1992 , Page(s): 95 - 98
    Cited by:  Papers (1)

    IEEE Conference Publications

    The authors describes the principle and design criteria adopted for a small economical, portable, robust inverter used for outdoor or remote area power supply (RAPS). Sine-weighted pulse-width-modulation (PWM) techniques applied to a push-pull inverter with a front-end filter are used. The front-end filter, using a cross-coupled choke on the low 12 V side, makes it a current fed inverter and hence suitable for starting motors. The topology offers a sinusoidal flux in the main step-up transformer, and thus a good efficiency at low loads. The cost is similar to that of push-pull center tap quasi-square inverters View full abstract»

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    Multiconverter controller design for an infrared heater grid

    Adonis, M. ; Mte, K.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308139
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    Power control methods are introduced for the regulation of a multiple-input-multiple-output (MIMO) dc-dc converter. The sliding-mode control and the synergetic mode control techniques are contrasted. These two methods are studied for the stability that each portrays to a disturbance. The advantages and disadvantages of each scheme is studied. Simulation results are used in order to predict the most stable control scheme. The simulation and experimental results reinforced the argument for the efficacy of the desired control implementation. View full abstract»

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

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

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

    IEEE Conference Publications

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

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    Optimum step size determination for FDPM-based CIR estimator for OFDM systems

    Oyerinde, O.O. ; Mneney, S.H.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071970
    Publication Year: 2011 , Page(s): 1 - 5

    IEEE Conference Publications

    Fast Data Projection Method (FDPM) subspace tracking algorithm has been demonstrated to exhibit high convergence rate towards orthonormality. This was shown to be the fastest among all competing algorithms of the same order of computational complexity. However, its convergence rate depends largely on the selection of its step size. Coincidentally, this is the only parameter needed to be specified for the algorithm, making its structure simple in comparison with other algorithms. In the original article, only the region in which the step size could be selected in order to ensure stability is given. However, in this article an optimum step size is determined through computer simulation for the FDPM algorithm in the context of channel impulse response (CIR) estimator for Orthogonal Frequency Division Multiplexing (OFDM) Systems. View full abstract»

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    Acceleration of nonparametric time-varying phasor estimation

    Jordaan, J.A. ; van Wyk, M.A. ; van Wyk, B.J.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401619
    Publication Year: 2007 , Page(s): 1 - 6

    IEEE Conference Publications

    In this paper we present an acceleration procedure for an application of a robust nonparametric signal modelling technique for tracking time-varying phasors of voltage and current in power systems. A first degree polynomial is used to approximate these voltage and current signals locally on a sliding window of fixed length. The least-squares criterion and non-quadratic criteria (quadratic-squares-root, quadratic- tangent and quadratic-constant) was used to fit the linear function to the data, and methods to speed up the procedures was introduced. The paper concludes with the presentation of the representative testing results. View full abstract»

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    Test bench for multi-MW grid side wind power converter

    Wegener, R. ; Notzold, K. ; Uphues, A. ; Griessel, R. ; Soter, S.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072173
    Publication Year: 2011 , Page(s): 1 - 5
    Cited by:  Papers (2)

    IEEE Conference Publications

    This paper deals with an integrated full power test bench for the grid side of a wind power converter. The speciality is the high side voltage and current measurement to use the stray inductance as an additional filter element. The presented test bench is enhanced for fault ride through measurement capabilities with a full power grid simulator. View full abstract»

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    Mounting DE-Series MOSFETs - a comparison of two recognised techniques

    Swart, J. ; Pienaar, C.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401496
    Publication Year: 2007 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    MOSFET devices have developed significantly to become the number one choice for high-power applications in power electronics and electronic communication. Commercially available devices now operate into the VHF range, boasting output powers of up to 300 W. The IXYS RF manufactured IXZ210N50L RF power MOSFET falls into this category of MOSFET devices. It is optimised for linear operation and suitable for broadcast and communication applications. This paper presents two proposed techniques, from the manufactures, for mounting this device with regard to high-power applications. These two techniques (A and B) are contrasted with regard to thermal efficiency, cost and simplicity. The MOSFET drain current is adjusted from 0.5 to 4.5A in both techniques with corresponding heat sink temperatures being measured using the PICO TC-08 temperature logger. The results revealed that technique B has a slightly lower on-state resistance when compared to technique A. However, technique B has a more complex mount and a higher cost. The change in on-state resistance is due to a rise in the junction temperature resulting from the drain current increase. View full abstract»

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    Particle size distribution determination using acoustic information

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

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

    IEEE Conference Publications

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

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    Received noise on powerline communications where the in-building wiring acts as an antenna

    Emleh, A. ; Ferreira, H.C. ; Vinck, A.J.H. ; Snyders, A.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072100
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    The powerline channel is considered as a challenging channel due to the heavy load and noise impairments. In this paper we investigate an important type of measurement with regards to the powerline communications channel, where the low voltage wiring inside a house is considered as a receiving antenna for interference. Several types of measurements are presented using the corresponding broadband PLC channel as a communication medium. Impulsive and interference noise play a major role in the contamination factors on a powerline channel. The results include the different measurements of noise in the frequency domain. Extensive tests and measurements have been used to ascertain which specific external interference, after filtering by the coupling circuit, does affect the entire PLC system being used in a house. View full abstract»

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    Hybrid concatenated super-orthogonal space-time trellis codes applying iterative decoding

    Oluwafemi, I.B. ; Mneney, S.H.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071975
    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    Hybrid concatenated code is a combination of parallel and serial concatenated codes. In this paper, two hybrid concatenated super-orthogonal space-time trellis code (SOSTTC) applying iterative decoding is proposed for flat fading channels. The encoding operation is based on the concatenation of convolutional codes, interleaving and super-orthogonal space-time trellis codes. The first concatenated scheme consists of a serial concatenation of a parallel concatenated convolutional code with a SOSTTC while the second consist of parallel concatenation of two serially concatenated convolutional and SOSTTC codes. The decoding of these two schemes is described and their bit error rate (BER) and frame error rate (FER) performance evaluated by computer simulation in Rayleigh fading channels. The proposed topologies are shown to perform better than existing concatenated schemes with constituent code of convoluntional and space time codes in literatures. View full abstract»

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    Capacity analysis of an indoor industrial environment using a dual-polarized MIMO system at 2.4 GHz and 5.2 GHz

    Nair, L.R. ; Maharaj, B.T.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401557
    Publication Year: 2007 , Page(s): 1 - 5

    IEEE Conference Publications

    The results of a multiple-input-multiple-output (MIMO) measurement campaign, using an 8x8 dual-polarized system, conducted in a semi-industrial environment at 2.4 GHz and 5.2 GHz are presented. Capacities in this environment are compared with respect to: array orientation, antenna polarization and center frequency. It was found that array orientation and antenna polarization did not have a significant influence on the channel capacity attained. When the effect of center frequency was analyzed, based on the eigenvalues, it was found that slightly higher capacities were obtained at 5.2 GHz than at 2.4 GHz. The capacities achieved in this environment were found to be between 40% and 85% of the maximum capacity that can be attained ideally. View full abstract»

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

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

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

    IEEE Conference Publications

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

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    Development of an electrochemical sensor array for determination of food analytes

    Jawaheer, S. ; Rughooputh, H.C.S. ; White, S. ; Cullen, D.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146871
    Publication Year: 2002 , Page(s): 407 - 409 vol.1

    IEEE Conference Publications

    With modern techniques of sensor fabrication and the processing power of modern microelectronic, sensors can be conferred a degree of miniaturisation and integrated into a small portable devices to allow in situ real-time monitoring. We report here the development of a multi-analyte electrochemical sensor array tailored to monitor the quality of fruits of economical importance to tropical countries. The array sensor has the ability to simultaneously monitor a range of food quality indicator analytes offering a robust analytical output. For this work, one-shot array sensors were mass fabricated using screen-printing (thick film) technology. View full abstract»

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