Cart (Loading....) | Create Account
Close category search window
 
Skip to Results

Search Results

1,723 Results returned
Skip to Results
  • Save this Search
  • Download Citations Disabled
  • Save To Project
  • Email
  • Print
  • Export Results
  • Full text access may be available. Click article title to sign in or learn about subscription options.

    Realization of multi-level partial response modem in reconfigurable logic

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

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

    IEEE Conference Publications

    Hardware realization is an important issue in communications system design. The use of high density reconfigurable logic instead of traditional DSP based solutions is investigated. The case of a multi-level partial response modem is discussed. The practical logic structures of the internal modem components including equalizer, Viterbi decoder and FIR filters are presented. Results of the hardware implementation are also presented. View full abstract»

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

    A Web based interactive database and CORBA tutorial

    Falb, J. ; Radinger, W. ; Goeschka, K.M.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146875
    Publication Year: 2002 , Page(s): 425 - 430 vol.1

    IEEE Conference Publications

    With Web based open and distance learning, students appreciate the possibility to learn and train when and where they want-even from home. Based on a database, CORBA middleware and Web frontend, we implemented an interactive database and CORBA tutorial to allow for efficient, interactive student training. It also supports the testing of the student's application in a distributed environment together with a real-life database. The students can concentrate on their main tasks and need not spend time nor effort on learning complicated tools or environment configurations. Consequently, they get familiar with complex e-commerce technologies in a convenient way. View full abstract»

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

    Microprocessor control of hybrid energy systems

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

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

    IEEE Conference Publications

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

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

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

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

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

    IEEE Conference Publications

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

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

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

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

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

    IEEE Conference Publications

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

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

    The new subsensitive instrument-active transducers

    Molchanov, P.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821938
    Publication Year: 1999 , Page(s): 1143 - 1146 vol.2

    IEEE Conference Publications

    The new standards of transducers - active transducers (AT) have been introduced. The principle of AT theory is developed on the basis of the nonlinear charge model. A Volterra functional series is used to calculate parameters of AT. Particular attention have been devoted to the microwave AT for control applications. An experimental AT for temperature and moisture telemetering control has been described to confirm the theoretical assumptions View full abstract»

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

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

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

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

    IEEE Conference Publications

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

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

    An adaptive thresholding method for automatic lung segmentation in CT images

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

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

    IEEE Conference Publications

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

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

    "The Importance of Being Certified": the role of conformance testing and certification of communication systems in building automation and control devices

    Fischer, P. ; Palensky, P.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406886
    Publication Year: 2004 , Page(s): 1223 - 1227 Vol.2
    Cited by:  Papers (3)

    IEEE Conference Publications

    This work describes the importance of conformance testing and certification of communication systems in building automation and control devices, especially in Europe. Conformance testing in Europe involves a number of parties and is a serious issue. One of the most important aspects is to use devices with standardized communication systems and standardized building automation and control functions. A strict framework of the European regulation bodies defines the roles and duties of manufacturers and the respective test laboratories. Conformance testing of the communication of a building automation and control device is much more than a pure communication test. View full abstract»

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

    Catering for electromagnetic compatibility requirements in the project plans of products

    Venter, F.A.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821935
    Publication Year: 1999 , Page(s): 1131 - 1134 vol.2

    IEEE Conference Publications

    This paper addresses the main issues that one needs to take into account when drafting project plans for new products, where EMC requirements have to be incorporated. It is also shown why these guidelines must be implemented as early in the product development cycle as possible. Some practical problems with introducing EMC requirements during the final project stages are also be given View full abstract»

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

    A structural model of semiotic alignment: The classification of multimodal ensembles as a novel machine learning task

    Mehler, A. ; Lucking, A.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308098
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    In addition to the well known linguistic alignment processes in dyadic communication - e.g., phonetic, syntactic, semantic alignment - we provide evidence for a genuine multimodal alignment process, namely semiotic alignment. Communicative elements from different modalities ldquoroutinize intordquo cross-modal ldquosuper-signsrdquo, which we call multimodal ensembles. Computational models of human communication are in need of expressive models of multimodal ensembles. In this paper, we exemplify semiotic alignment by means of empirical examples of the building of multimodal ensembles. We then propose a graph model of multimodal dialogue that is expressive enough to capture multimodal ensembles. In line with this model, we define a novel task in machine learning with the aim of training classifiers that can detect semiotic alignment in dialogue. This model is in support of approaches which need to gain insights into realistic human machine communication. View full abstract»

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

    Distribute fluctuating energy to devices with storage capacity

    Hansen, J.N.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071997
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper studies the increased production of renewable energy in Denmark. Is it possible to penetrate a large amount of renewable energy? Is it possible to consume the surplus energy in a low demand situation? How is it possible to share the surplus energy seen from the consumer (green energy/cheap energy) and the distributor (avoid overload of grid), point of view. Is it possible for the consumer to control the energy even though there is no urgent need for energy? These questions could help make the electrical grid even smarter! The paper is divided into 3 areas. Transmission of fluctuating energy, Energy sharing algorithm and Control application for heat pumps. View full abstract»

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

    A use of instantaneous frequency estimators for radio signals identification

    Lopatka, J. ; Bukowski, R.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821937
    Publication Year: 1999 , Page(s): 1139 - 1142 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    Identification of digitally modulated radio signals is one of the essential problems in intelligent radio links and radio monitoring systems. FSK signals are widely used for this purpose. An estimated instantaneous frequency (IF) can be used as one of the identification parameters. LPC and DESA estimators for real signals are compared to frequency estimators obtained for complex signals. Autoregressive models are proposed as a method of precise estimation of time-varying frequency in a noisy environment. A hardware solution for radio signal acquisition in complex form is also presented View full abstract»

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

    Pedestrian detection for underground mine vehicles using thermal images

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

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

    IEEE Conference Publications

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

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

    A residential energy and power conservation System Utilizing an Optimization Model

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

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

    IEEE Conference Publications

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

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

    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»

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

    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»

  • Freely Available from IEEE

    [Front cover]


    AFRICON 2007

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

    IEEE Conference Publications

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

    Robot catching system with stereo vision and DSP platform

    Chyi-Yeu Lin ; Yi-Pin Chiu ; Chi-Ying Lin
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072132
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    The Texas Instrument DSP (TMS320DM642 EVM) is used as the implementation platform in our robot catcher system with two CCDs as source of the stereo vision. The system will separate the thrown-in target from the paired images and then calculate the centroid coordinates of each target image, thereby determining the space location of the object. The Lagrange interpolation formula and the linear function are used to simulate the ball trajectory and predict the catch position and then use the inverse kinematics to calculate the rotation angle and velocity of the 2-DOF robot arm system. After that, the control commands are sent by the RS-232 to the robot arm so as to catch the flying object at the expected location. This catcher robot system can catch the ball thrown to it from four meter away with an average success rate of 65%. View full abstract»

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

    Integration effects of multiple microstrip patch antennas into small handsets

    Peixeiro, C.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401445
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    This paper describes the integration of multiple microstrip patch antenna elements into a small handset. The antenna system has been developed for multiple-input multiple- output (MIMO) applications in WLAN systems at 5 GHz. Four square microstip patches are printed on the top area of a 45mmxl05 mm ground plane, representing the back side of a typical small handset. The small ground plane integration effects on input return loss, mutual coupling, envelope correlation and radiation pattern, are evaluated. An antenna prototype has been fabricated and tested. Good agreement has been obtained between numerical simulations and experimental results. View full abstract»

  • Freely Available from IEEE

    [Blank page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

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

    IEEE Conference Publications

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

    FPGA emulators in digital circuits education

    Zajc, B. ; Trost, A.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406727
    Publication Year: 2004 , Page(s): 509 - 512 Vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    Digital circuit emulators based on programmable devices are extensively used for research and educational purpose in the field of digital logic design. Emulation of a complex digital circuit is much faster than a gate level simulation. The circuit is also physically implemented in the emulation platform and can be embedded in the target system working at or near real-time speed. The paper presents an architecture for digital circuit emulators and the design flow used in digital circuits education. There are many student projects and diploma works which can be realized only by reprogramming the emulation system. We present some typical projects and applications implemented on our emulation systems View full abstract»

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

    Low-complexity constrained LMMSE estimator for the sparse OFDM channels

    Golovins, E. ; Ventura, N.
    AFRICON 2007

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

    IEEE Conference Publications

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

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

    A contactless torque sensor based on the magnetostriction property of amorphous iron

    Neves, M.F.S.V.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.562966
    Publication Year: 1996 , Page(s): 661 - 664 vol.2
    Cited by:  Patents (1)

    IEEE Conference Publications

    In this paper, a torque meter is described in which the sensor installed on a rotating shaft and the stationary measuring equipment are magnetically coupled, thus avoiding the need for slipping contacts. The sensor is based on the change of magnetic properties of amorphous iron alloys with mechanical stress. An experimental set-up is described, and experimental results are presented View full abstract»

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

    Converter parasitics-extraction, modelling and utilization: an overview

    van Wyk, J.D., Jr. ; Cronje, W.A. ; van Wyk, J.D.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821829
    Publication Year: 1999 , Page(s): 599 - 604 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    A general discussion concerning converter parasitics is given. Analytical equations for extraction, typical SPICE models and results are presented. Minimizing negative parasitic effects is discussed as well as possible utilization of interconnects as low-pass filters View full abstract»

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

    Perimeter Echo Algorithm for network localization

    Chinnappen-Rimer, S. ; Hancke, G.P.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308395
    Publication Year: 2009 , Page(s): 1 - 5
    Cited by:  Papers (1)

    IEEE Conference Publications

    We propose an algorithm, the perimeter echo algorithm (PEA), to accurately determine the location of sensor nodes in a wireless network. The algorithm assumes a limited number of nodes (beacons) in the network are equipped with a location finding mechanism such as GPS. Nodes on the perimeter range of a beacon echo the beacons virtual ID to all nodes within range. This approach reduces the number of messages required to achieve network localization. The advantage of PEA is reduced power consumption and reduced flooding of the network because the beacon nodes only transmit an initialisation message once within a specific range and only those sensor nodes on the edge of a transmitting node's range, re-transmits the message. View full abstract»

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

    Implementation of integrated services digital network (ISDN) in developing countries: the case of Mauritius

    Seenundun, R. ; Bhurtun, C.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820852
    Publication Year: 1999 , Page(s): 351 - 356 vol.1

    IEEE Conference Publications

    In this paper ISDN implementation in developing countries is discussed based on Mauritius as a case study. The requirements in terms of basic telecommunications infrastructures for the setting up of an ISDN network are looked into. The problems which can be encountered in the process are analysed and possible solutions are identified View full abstract»

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

    Micro-controller based Internet phone

    Kaplan, S. ; Davies, J.R.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406680
    Publication Year: 2004 , Page(s): 307 - 311 Vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    This paper describes the development of a low cost micro-controller based, stand-alone Internet telephone to be used as an alternative to conventional line telephones. Bandwidth usage has been minimized to allow for use with dial up connections. The hardware comprises of a controller board for an AWC86 SlimLinkreg web server-controller (AWC86), which comes with a real-time operating system (RTOS) and TCP/IP stack, and codec boards for G.729 annex A (G.729A) codec ICs-MAS3159Fs. Cost was the main factor in the selection of hardware. Signalling is performed by the session initiation protocol (SIP) using the session description protocol (SDP) to negotiate the attributes of the media session to be established. The G.729A frames are transported between the units using the real-time transport protocol (RTP). RTP is accompanied by the RTP control protocol (RTCP). Two phone units were developed that communicated directly with each other and not through intermediary servers View full abstract»

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

    How to motivate students in project based learning

    Pucher, R. ; Mense, A. ; Wahl, H.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146878
    Publication Year: 2002 , Page(s): 443 - 446 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    Educational thinking in higher education has undergone a rapid change. The ability to remember facts loses importance whereas the capability to solve problems becomes more and more the main focus of teaching. At the Technikum Wien Project Based Learning (PBL) was introduced in various subjects of our IT course. The basic approach of PBL originated from the University of Maastricht in the Netherlands where it is reported to be highly successful. The specific problem the authors tried to solve, deals with the motivation of students. The main motivation of students is-of course-to achieve good test results and only the lesser focus lies on the specific contents of the subject. The authors tried to develop a method, which allows the students to focus their intrinsic motivation onto the study project itself and not onto the extrinsic motivation, namely test results. View full abstract»

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

    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»

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

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

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

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

    IEEE Conference Publications

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

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

    Tolerance-based control mechanism for approximate symbolic analysis

    Kolka, Z. ; Biolek, D. ; Biolkova, V. ; Dobes, J.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072093
    Publication Year: 2011 , Page(s): 1 - 5
    Cited by:  Papers (1)

    IEEE Conference Publications

    The paper deals with an enhanced control mechanism for approximate symbolic analysis of the Simplification-Before-Generation class. A traditional approach consists in the evaluation of errors caused by simplification only for the nominal parameters of network components. The proposed procedure uses sensitivities to estimate the worst-case error due to component tolerances, i.e. the expression validity is checked over the tolerance interval of component parameters. A fast computational algorithm based on the Sherman-Morrison formula is used. The numerical cost is approximately given by two matrix inversions per one control-frequency point and one simplification step. View full abstract»

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

    Managing the deregulation and privatisation of the Nigerian electricity industry

    Odubiyi, A. ; Davidson, I.E.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146883
    Publication Year: 2002 , Page(s): 467 - 472 vol.1
    Cited by:  Papers (2)

    IEEE Conference Publications

    Power sector deregulation is a global phenomena and the Nigerian state has embarked on privatisation and deregulation with the introduction of competition in its electricity industry. Economic, environmental issues and regulatory challenges, and changing public perception have contributed to the profound changes or reform being embarked upon by developed and developing countries. This paper discusses the management process of the deregulation and privatisation of the electricity industry in Nigeria, and offers proposals to avoid pitfalls in deregulation. View full abstract»

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

    Heuristic dynamic assignment based on microsimulation with AIMSUN2

    Barcelo, J. ; Casas, J. ; Ferrer, J.L. ; Funes, G.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820670
    Publication Year: 1999 , Page(s): 21 - 26 vol.1

    IEEE Conference Publications

    Microscopic traffic simulation has proven to be a useful tool for the design and assessment of intelligent transport systems due to its ability to capture the full dynamics of the time dependent phenomena. Dynamic traffic assignment is a useful tool when a global level of dynamic analysis is necessary. Unfortunately analytical tools are not yet mature enough to provide the answers for networks of a sensible size. This paper presents a heuristic procedure based on an origin-destination microscopic simulation using time sliced origin-destination matrices to account for time variations in traffic demand. Paths from origins to destinations are updated in a timely manner depending on changes in link travel times according to changes in traffic conditions. The paper also includes some preliminary results View full abstract»

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

    Vibrating sample magnetometer for large permanent magnets

    Ribeiro, A.L.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401540
    Publication Year: 2007 , Page(s): 1 - 5

    IEEE Conference Publications

    This paper describes a vibrating sample magnetometer (VSM) intended to measure the magnetic moment of large permanent magnets. The reciprocity theorem was used to preview the pick-up coils output voltage. The finite element method was utilized to determine the magnetic field produced by a unitary current in the pick-up coils. The sensitivity of the magnetometer was determined by the measurements carried out with a well characterized sample. View full abstract»

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

    Bitstream characteristics of variable bitrate coded interactive tele-teaching video sequences

    De Wet, P.J. ; Van Schalkwyk, J.J.D.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.562954
    Publication Year: 1996 , Page(s): 586 - 591 vol.2

    IEEE Conference Publications

    Interactive tele-teaching (ITT) can serve as support for formal education, especially in South Africa, with its huge educational backlog. ITT is a possible application for video coding technology. The world is going digital, and so will video storage and transmission. The coded bistreams of different video sequences display different characteristics when digitally coded. Thus, the study of specific types of coded video sequences is imperative in order to be able to apply existing technology as efficiently as possible. The characteristics distinguishing ITT video sequences from general video, are placed under the spotlight. The article extends previous work of De Wet et al. (see COMSIG conf. proceedings, IEEE South African Symposium on Communications and Signal Processing, Pretoria, 1995, p.81-86) View full abstract»

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

    The method of lines as special moment method

    Dreher, A.
    Africon, 1999 IEEE

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

    IEEE Conference Publications

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

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

    Assessment of commercially available software tools for transient stability: experience gained in an academic environment

    Kaberere, K.K. ; Folly, K.A. ; Petroianu, A.I.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406777
    Publication Year: 2004 , Page(s): 711 - 716 Vol.2
    Cited by:  Papers (5)

    IEEE Conference Publications

    There are many power system simulation software tools for transient stability analysis that are commercially available today. The choice of the most adequate tool for a specific type of stability analysis is a difficult task, and is influenced by economical reasons. It is imperative that a comparative study of various tools be carried out to help users make informed decisions. This work evaluates DIgSILENT, PSS/E and PSCAD, which are commercial software tools used for digital simulation of power systems. As criteria for software assessment, the following features are investigated: (i) modelling capabilities - synchronous generator, generator saturation, transmission line representation, and external network, (ii) flexibility allowed to the user. A well known benchmark power system model from literature is used to validate the simulation results of the commercial tools. View full abstract»

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

    Concept for an architecture of a wireless building automation

    Stein, G. ; Kabitzsch, K.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146822
    Publication Year: 2002 , Page(s): 139 - 142 vol.1

    IEEE Conference Publications

    In several applications for automation, radio transmission could be a good alternative to wired field buses (see Rauchhaupt, L. and Hahniche, J., Proc. Fieldbus Conf. FeT'99, p.48-54,1999). The advantages are an easy, fast and low cost installation scenario in common with the possibility of flexible device placing. However, the specifics of radio require a very specialized protocol stack which affects the whole system architecture. Starting from the requirements of building automation, the paper shows a concept of an architecture for the integration of wireless devices into wired field buses. It is shown that radio transmission is well suited for open loop sensors and user terminals. But for actuators and backbones, it is a better choice to keep them on wires. View full abstract»

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

    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»

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

    An analysis of the effects of filtering on the correlation characteristics of 4-phase sequences for CDMA applications

    Jamil, M. ; Linde, L.P. ; van Wyk, D.J.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820801
    Publication Year: 1999 , Page(s): 227 - 232 vol.1

    IEEE Conference Publications

    This paper studies the construction and effects of filtering on the correlation properties of 4-phase sequences that are suitable for the use in spread spectrum multiple access communications. An introduction on the construction methods of these sequences from the set of binary sequences is presented. The effects of filtering on the correlation properties by using Nyquist and constant envelope root-of-unity (CE-LI-RU) filtering technique are also investigated. It is shown that it is possible to achieve better correlation properties by using the latter filtering method while maintaining the perfect constant envelope, which is not possible with Nyquist filtering View full abstract»

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

    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»

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

    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»

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

    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»

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

    A proposal for secure software download in SDR

    Dawoud, D.S.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406637
    Publication Year: 2004 , Page(s): 77 - 82 Vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    To promote the commercial implementation of software defined radio (SDR) terminals, a secure method of download is vital. The flexibility of the system to change from one environment to the other and the possibility of changing any cryptographic component at any time is also an important issue. In this paper we are discussing three main design metrics of SDR. A proposed protocol for changing any cryptographic component is proposed View full abstract»

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

    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»

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

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

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

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

    IEEE Conference Publications

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

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

    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»

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

    A hardware implementation of an adaptive channel coding system

    Opperman, T.A.K. ; Staphorst, L. ; Sinha, S.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401650
    Publication Year: 2007 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    This paper details the implementation of an adaptive channel coding system on a DSP. Two DSP's communicate directly over an AWGN (additive white Gaussian noise) channel. Multiple FEC (forward error correction) codes are then implemented directly onto the DSP's to provide data integrity over the channel. Taking into account the current BER (bit error rate), the system chooses an appropriate FEC code to satisfy the user specified maximum BER. Three different coding algorithms were used, namely Hamming (7,4), Reed-Solomon (7,5,3) and 1/2 rate convolution coding. The BER vs. Eb/No transfer curves obtained experimentally allowed adaptive channel coding to be achieved. View full abstract»

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

    Nonlinear model identification of fuel cell power plant

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

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

    IEEE Conference Publications

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

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

    Neural network implementation on a FPGA

    Chen, Y. ; du Plessis, W.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146859
    Publication Year: 2002 , Page(s): 337 - 342 vol.1
    Cited by:  Papers (4)

    IEEE Conference Publications

    This work implemented a feedforward neural network on a FPGA (field programmable gate array). A study was conducted to find the minimum precision required to maintain a recognition rate of at least 95% for two characters within an optical character recognition application. To reduce the circuit size, the bit serial architecture was realised to perform the arithmetic operation. This resulted in an optimal use of the FPGA resources. View full abstract»

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

    Soft-computing methods for diagnosis and design of electrical devices

    Szczepaniak, P.S. ; Rudnicki, M.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821862
    Publication Year: 1999 , Page(s): 753 - 758 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    The paper offers a modern approach to the problems of diagnosis and design arising in electrical engineering. The methods are genetic algorithms, fuzzy logic and neural networks. Two kinds of tasks are considered. First, the algorithm which enables creation of an expert system for diagnosis of technical condition of oil transformers is presented. The system is based on real results of chromatography of gases dissolved in transformer oil (DGA) and creates a set of diagnostic rules using fuzzy logic and a genetic algorithm. An alternative method based on a fuzzy controller is also mentioned. In the second part, attention is given to neural simulation of pulse magnetiser for magnetising permanent magnets. Moreover, the problem of identification of the induction motor parameters from available performance data using the equivalent circuit model and soft-computing methods is compactly presented View full abstract»

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

    Use-cases for performance evaluation of human-mind inspired control units

    Deutsch, T. ; Kohlhauser, S. ; Perner, A. ; Muchitsch, C.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072046
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    With the advent of artificial general intelligence architectures, comparison between different architectures became more complicated. Small isolated tasks like box stacking, path finding, chess, or collecting objects is sufficient for highly specialized algorithms like the ones used in artificial intelligence. The holistic control systems are designed to cope with rich, dynamic, and complex real world environments and tasks. The approaches used to design these architectures differ in many ways but all share the goal to create human like “intelligence.” Each project uses its own approach to evaluate its success which is usually tightly coupled with the target application. We propose the usage of a simulated virtual world with embodied autonomous agents. These agents should be equipped with control systems from the architectures that should be compared and exposed to situations where their performance is assessed. The situations-or test-cases-have to be designed with tests from psychology in mind. Thus in a top-down design approach, tests from psychology have to be refined and converted such that they can be implemented into the simulation. We discuss different approaches and introduce the use-cases developed for project ARS. View full abstract»

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

    Algebraic PWM strategies of a five-level NPC voltage source inverter. Application to a great power induction machine drive

    Lourci, N. ; Ameur, R. ; Berkouk, E.M. ; Manesse, G.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821851
    Publication Year: 1999 , Page(s): 697 - 703 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    In this paper, the authors study the control of a three-phase five-level NPC source voltage inverter (VSI) and its application to an induction motor drive. They elaborate a working model of this inverter, without presumption of its control by using the design methodology associated with Petri nets. They propose knowledge and control models of this converter using connection functions. As an application of this control model, they develop two algorithms of algebraic PWM strategies for this converter. They also study the performances of an induction motor drive fed by this inverter and controlled by these PWM strategies. The results obtained are full of promise for the use of this five-level inverter in high-voltage and large power applications such as electrical traction View full abstract»

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

    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»

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

    Effects of stray inductance on switching transients of an IGBT propulsion inverter and resulting gate control strategies

    Fasching, M.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563158
    Publication Year: 1996 , Page(s): 467 - 472 vol.1
    Cited by:  Patents (1)

    IEEE Conference Publications

    A 720 kVA transistor-based inverter unit for local transportation systems is described. The discussion is focused on the stray inductance of the commutation circuit (Lσ), the switching transients and a novel gate control strategy which limits transient overvoltages due to Lσ. A simple measurement of Lσ is introduced. Based on switching transients, Lσ can be calculated with a standard deviation of 4%. A closed loop control of the IGBT gates uses the collector emitter voltage as a feedback signal and adjusts the turn-off speed according to the inverter's point of operation. This guarantees an energy optimal turn-off transient without danger of transient overvoltage. Even under short circuit condition remains below a preset value View full abstract»

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

    Radio frequency identification (RFID) based conference registration system

    Nordier, L.J. ; Sinha, S.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401594
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    For the registration process at a conference to be successful, a delegate's information needs to be verified quickly and accurately. In this paper, a system using external radio frequency identification devices (RFID) to bridge the gap between digital information and user requirements at a conference, is described. The system presented in this paper is divided in two subsystems, a registration subsystem and a presentation subsystem. These subsystems are written in C++ and use a connection module, to connect to an external MySQL database, written in C. View full abstract»

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

    Performance comparison of multidimensional trellis coded modulation and convolutionally coded MC-DS-CDMA in a Rayleigh fading channel

    Akol, R.N. ; Takawira, F.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146833
    Publication Year: 2002 , Page(s): 197 - 202 vol.1

    IEEE Conference Publications

    In this paper we investigate the performance of multidimensional (multi-D) trellis coded modulation (TCM) and low rate convolutionally coded multicarrier (MC) code division multiple access (CDMA) schemes In a Rayleigh fading channel. In both systems, the output of the encoder modulates multiple band-limited DS-CDMA signals, which are then transmitted simultaneously at different carrier frequencies. Although low rate convolutional codes perform better than multi-D TCM, TCM systems are more bandwidth efficient for the same signal-to-noise ratio (SNR) and number of carriers. View full abstract»

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

    Performance measures for a telecommunications company

    Visser, J.K. ; Sluiter, E.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401479
    Publication Year: 2007 , Page(s): 1 - 8

    IEEE Conference Publications

    Performance management is part of the strategic management process in the business enterprise. This paper describes the development of a complete set of high-level performance measures for a mobile telecommunications company in Mozambique. Eighteen performance metrics were identified which, together with an implementation plan and actual flow of information, will make up the proposed performance measurement system for the company. A process is outlined to ensure that a balanced set of indicators are selected, that conflicts don't exist and that the indicators are cost effective to implement. View full abstract»

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

    A wavelet neural network for the detection of microcalcifications in multiscale enhanced digitised mammograms

    Aydin Alayhoglu, B. ; Aghdasi, F.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820874
    Publication Year: 1999 , Page(s): 389 - 394 vol.1

    IEEE Conference Publications

    The detection of microcalcification clusters (MCCs) during mammographic examination is vital for the correct diagnosis of breast cancer in asymptomatic women. Automated detection methods augment the diagnostic process by providing the radiologist with a second opinion. Detection schemes making use of a neural network classifier, with input feature vectors containing spatial, spectral and multiscale image attributes, are investigated. A wavelet-based image enhancement technique is implemented to improve the detection performance View full abstract»

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

    Interaction primitives: Describing interaction capabilities of Smart Objects in ubiquitous computing environments

    van der Vlist, B.J.J. ; Niezen, G. ; Jun Hu ; Feijs, L.M.G.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6072101
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    The design of ubiquitous computing environments introduces challenges on both infrastructure level and the level of interaction design. To support the transition from a device-oriented paradigm towards a system-oriented paradigm with increased interoperability, we need a framework to describe interactions and interactive objects in such a way that the physical and contextual meaning of the interaction is preserved. In this paper we describe a way to model interactions in terms of their essential elements, which we call interaction primitives: The smallest addressable interaction elements that have a meaningful relation to the interaction itself. By semantically describing the user interaction capabilities of devices which are meaningful to be shared with other devices, interoperability will not only become possible at infrastructure level, but may also improve user interaction in ubicomp environments. View full abstract»

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

    Multi-user class pseudo-dynamic traffic assignment model with signal control

    Camynta-Baezie, G. ; Cassir, C. ; Bell, M.
    Africon, 1999 IEEE

    Volume: 1
    DOI: 10.1109/AFRCON.1999.820691
    Publication Year: 1999 , Page(s): 37 - 42 vol.1

    IEEE Conference Publications

    A multi-user class pseudo-dynamic traffic assignment model is presented. It combines deterministic and stochastic user-equilibrium route choice models and defines two classes of drivers; the guided drivers and the unguided drivers. Three signal policies are introduced into the model and the effect of these policies on drivers are presented View full abstract»

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

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

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

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

    IEEE Conference Publications

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

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

    A decision unit inspired by cognitive sciences for future robotic applications

    Muchitsch, C. ; Perner, A. ; Bruckner, D.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071980
    Publication Year: 2011 , Page(s): 1 - 6

    IEEE Conference Publications

    The complexity of technical systems is constantly increasing. To manage the amount of data several strategies have been followed and a lot of achievements were made especially in artificial intelligence. But still the capabilities of human intelligence are unrivaled. The contribution of this article is an introduction to a decision unit based on psychoanalytical models and a description how the findings can be used in future robotic applications. The neuro-psychoanalytical theories used, cover a comprehensive model of human intelligence and presents structures for all aspects of human decision making. The psychoanalytic-inspired decision unit shows promising prospects that standard planning and control units lack in various respects. Amongst others, scenario and experience-based planning, drive-based intention models, and the 3-tier (neuro-symbolic, thing presentations, word presentations) data processing architecture, are very promising methods. In order to validate the model, a simulation environment was implemented holding various agents with the neuro-psychoanalytical decision unit. This first implementation shows the possibilities of the system and gives a great outlook for future investigations of the capabilities. 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

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

    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»

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

    Electromagnetic compatibility in open air substations

    de Grijp, M.H.B. ; Borm, C.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.563042
    Publication Year: 1996 , Page(s): 1044 - 1050 vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    An investigation was conducted into the electromagnetic compatibility (EMC) behaviour of the TRI transient measurement truck during shunt capacitor bank field tests at the Impala Substation. The measurement configuration during the measurements, the various measurement transducers and measurement cables used are analysed for their possible influence on the measurement results. Interference coupling mechanisms are discussed and different measurement methods, reducing or eliminating interference in the measurement results, are discussed. The measurement results of the shunt capacitor bank close, trip, and disconnector switching operations are examined for signs of electromagnetic interference (EMI). Specific measurements to investigate the influence of common mode currents, flowing on coaxial cable shields, on the measurement results were carried out and analysed. Several effects were observed which result from interference with the measurements and recommendations are made to prevent this occurring in future measurements. Suggestions are made for future measurements which would answer questions raised about the EMC behaviour of the measurement truck View full abstract»

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

    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»

  • Freely Available from IEEE

    [Blank page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406679
    Publication Year: 2004 , Page(s): 306

    IEEE Conference Publications

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

    A software interface for an industrial control network using the CAN protocol

    Travis, A.R.L. ; Collier, M.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.563049
    Publication Year: 1996 , Page(s): 1081 - 1082 vol.2

    IEEE Conference Publications

    The band period of a controller area network (CAN) interface written in software cannot be less than the time taken for a bit move, bit comparison and count with branch. Such an interface has been demonstrated, and baud rates of 0.5 MHz may be possible View full abstract»

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

    Electromagnetic simulations for nanoscale RF blocks

    Schilders, W.H.A. ; Silveira, L.M. ; Villena, J.F.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401507
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    Next-generation nano-scale RFIC designs have an unprecedented complexity and performance that will inevitably lead to costly re-spins and loss of market opportunities. In order to cope with this, efficient and accurate models of interconnects, integrated inductors, the substrate and devices, together with their mutual interactions, need to be developed. The key idea is that integrated devices can no longer be treated in isolation as the EM interactions due to proximity effects are becoming more relevant in the behavior of the complete system. EM simulations must also address these interactions, so new procedures and models able to be included in coupled simulation must be developed. But these simulations may become very expensive as the complexity of the system increases, so model order reduction techniques able to treat these coupling effects are necessary in order to obtain a better performance. In this work some solutions for efficient simulation of such problems are introduced. View full abstract»

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

    Estimation of polluted insulators flashover time using artificial neural networks

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

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

    IEEE Conference Publications

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

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

    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»

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

    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»

  • Freely Available from IEEE

    [Blank page]


    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406899
    Publication Year: 2004 , Page(s): 1299

    IEEE Conference Publications

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

    Feasibility of using stochastic adaptive congestion control in computer networks

    Ngwenya, D.W. ; Hancke, G.P.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401461
    Publication Year: 2007 , Page(s): 1 - 8
    Cited by:  Papers (1)

    IEEE Conference Publications

    The paper presents a novel approach for congestion control and avoidance in computer networks. The approach is based on stochastic search, as opposed to systematic-like search employed by existing mechanisms. Our approach forms basis for more informed heuristics and promises to be more adaptive. We employ the Weibull distribution density function to continuously define the search space. In this paper we develop a single simple heuristic, based on the approach, and evaluate its performance in terms of congestion window evolution, response time and throughput. View full abstract»

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

    Protective devices for live line work on high voltage transmission systems

    Govender, P.N. ; Hoch, D.A.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1159987
    Publication Year: 2002 , Page(s): 649 - 654 vol.2

    IEEE Conference Publications

    This paper presents the results of an investigation into the requirements of a surge arrester and surge diverter to protect live line workers positioned in the conductor-earth gap against switching and other surges that may be generated onto the phase conductors. The results of theoretical models of switching surges generated and the associated energy absorption requirements for such an arrester is described in detail. View full abstract»

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

    A process framework for customising software quality models

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

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

    IEEE Conference Publications

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

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

    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»

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

    Architecture and model of Profinet IO

    Poschraann, A. ; Neumann, P.
    AFRICON, 2004. 7th AFRICON Conference in Africa

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406884
    Publication Year: 2004 , Page(s): 1213 - 1218 Vol.2
    Cited by:  Papers (1)  |  Patents (2)

    IEEE Conference Publications

    This work presents the communication architecture and model for Profinet IO that has been currently released by the Profibus User Organization. Profinet IO provides the service definition and protocol specification for real time communication based on Ethernet, IP, and UDP for the field bus domain. It defines services and protocols mainly for communication between IO controllers (e.g. a PLC) and IO devices (e.g. Remote IO). It Includes a QoS architecture for real time control and alarm messages taking precedence over parameter, diagnosis, or Infrastructure messages Including other TCP or UDP based protocols. High message priorities In combination with a time division multiplexing approach with direct data link layer access provide short cycle times and low jitter. The IO device model itself is an enhancement of the Profibus DP device model. The enhancement includes a more flexible control access of one or more IO controllers in parallel to one IO device. Furthermore, address parameters and levels are enhanced too. The specification itself is according to IEC 61158 styles, which opens the possibility to be easily added in a new maintenance period of the standard. View full abstract»

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

    Bit error probability performance of MIMO-OFDM in multi-tone interference

    Esli, C. ; Delic̀§, H. ; Koca, M.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401607
    Publication Year: 2007 , Page(s): 1 - 7

    IEEE Conference Publications

    We consider an orthogonal space-frequency block coded (OSFBC) orthogonal frequency-division multiplexing (OFDM) system under multi-tone interference and multi-path fading environment. An approximate analytic expression for the bit error probability of OSFBC-OFDM system with a block code matrix for four transmit antennas is derived and the derivation methodology for other code matrices is summarized. The bit error rate simulations are performed for QPSK signals and compared with the theoretical results. The influences of the total energy of multi-tone interference and the fraction of interfered bandwidth are investigated. View full abstract»

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

    Analysis of EM coupling from AC electrified railway to nearby earth return circuit

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

    Volume: 2
    DOI: 10.1109/AFRICON.2004.1406779
    Publication Year: 2004 , Page(s): 723 - 727 Vol.2
    Cited by:  Papers (1)

    IEEE Conference Publications

    An electrified railway is an electromagnetically complex installation due to its physical size, the interaction between its constitute parts and the electromagnetic interference coupling mechanisms between these parts. The complexity of the installation requires proper management and understanding of the electromagnetic disturbance that may compromise the safety and operational integrity of the railway infrastructure. Increasingly, over riding safety requirements demand an analysis of all credible failures, due to electromagnetic interference, under normal or abnormal operation. Such analysis lends itself to the application of analytical methods to support the measurement efforts. This work reviews the physics of the electromagnetic coupling between an AC electrified railway and nearby earth return circuits. It covers the application of transmission line theory to describe the conductive and inductive coupling mechanism that exist between railway traction and nearby buried signaling conductors. View full abstract»

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

    Scalable low cost approach for future multifunction antennas

    LaManna, M.
    AFRICON, 2011

    DOI: 10.1109/AFRCON.2011.6071991
    Publication Year: 2011 , Page(s): 1 - 5

    IEEE Conference Publications

    The scalable approach for multifunctional antennas has been demonstrated to give substantial benefits in terms of reduction of non recurring and recurring costs [1]. With the availability of new wideband technologies, the present trend in multifunctional systems is to enhance the system capabilities, such as extending the operating range of frequencies, use the same antenna for radar, ECM, ESM and communication functions and perform new advanced functions, such as Non Cooperative Target Recognition (NCTR). The principle of using a scalable model for many different antennas will evolve, in the near future, in the process of standardizing the basic elements (tiles) of the antenna and its design methodologies. This will lead to conceiving low cost antennas, based on general purpose tiles, to be assembled and tailored for specific use. This paper defines the basic architecture of the scalable antenna, shows the cost advantages of the scalable approach and demonstrates the practical application of the scalable architecture to typical case studies. View full abstract»

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

    Geospatially-based software tools to support mass electrification

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

    Volume: 2
    DOI: 10.1109/AFRCON.2002.1160029
    Publication Year: 2002 , Page(s): 875 - 880 vol.2

    IEEE Conference Publications

    Over the past decade tremendous progress has been made in bringing grid electricity for the first time to over 2 million homes in South Africa. Over this time a group at Wits University has carried out research leading to the development of innovative geospatial software applications to solve some of the problems faced toy the designers of these new networks. The paper overviews a number of relevant MSc and PhD projects carried out at the University over the past decade, and discusses the contribution made to electrification in South Africa. View full abstract»

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

    Comparison of theoretical models with practice for ADSL

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

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

    IEEE Conference Publications

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

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

    A comparison of controllers for improving the time response of NiTi wires

    Velazquez, R. ; Pissaloux, E.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308412
    Publication Year: 2009 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper presents a comparative theoretical study of the performance of a set of controllers for improving the speed of actuators based on shape memory alloys (SMAs), especially on Nitinol (NiTi). To prevent overheating and thermal fatigue, these controllers take into account the maximum heating current at which a NiTi element can safely be heated. The thermal behavior of NiTi is first modeled for calculating the time response and, based on the suggested model, we show that hysteresis due to phase transformation can be neglected for rapid heating, thus simplifying the model to a linear problem. We present then the design and performance of a set of linear controllers. Simulation results show a substantial increase in actuation speed. View full abstract»

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

    Genetic algorithm for optimal open-loop distribution network design in competitive pool

    Filipec, M. ; Skrlec, D. ; Krajcar, S.
    Africon, 1999 IEEE

    Volume: 2
    DOI: 10.1109/AFRCON.1999.821904
    Publication Year: 1999 , Page(s): 977 - 982 vol.2
    Cited by:  Papers (2)

    IEEE Conference Publications

    The paper presents the Computer Aided Design of Distribution Network (CADDiN) application based on geographic information system (GIS) and genetic algorithms designed to improve the planning of major investment in open-loop distribution network over the coming years. The system allows the planner to identify, from load forecast, data on the existing distribution system and all future projects, the projects to be undertaken together with the commissioning year, in such a way that the investment and maintenance costs, as well as cost of losses are minimized over a planning horizon. The application has been tested with real size distribution systems achieving optimal designs in reasonable CPU times compared with respect to the dimensions of such distribution systems View full abstract»

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

    Stabilization of inter-area modes by controllable phase shifter

    So, P.L. ; MacDonald, D.C.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 1
    DOI: 10.1109/AFRCON.1996.563149
    Publication Year: 1996 , Page(s): 419 - 424 vol.1

    IEEE Conference Publications

    This paper presents an application of a fast, fully controllable phase shifter (CPS) for stabilizing unstable or poorly damped inter-area oscillatory modes in an interconnected system. The study is based on eigenvalue analysis of a linearized interconnected system model. Inter-area modes are first identified for an oscillation incident and then stabilization of these modes using a CPS is obtained. The best location for installing a CPS is determined by analyzing the mode controllability. A decentralized control scheme using tie line power deviation as the feedback signal for the CPS control system is shown to be effective in damping inter-area modes of oscillation. Computer simulation of an interconnected study system is used to validate the proposed CPS controller View full abstract»

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

    Automatic forward motion compensation for micro satellites

    Mouton, C.J. ; du Plessis, J.J. ; Schoonwinkel, A.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146797
    Publication Year: 2002 , Page(s): 7 - 12 vol.1

    IEEE Conference Publications

    South Africa's first micro satellite, SUNSAT, was operational in orbit for 23 months since its NASA-sponsored launch on February 23, 1999. SUNSAT is a graduate student-developed satellite from the University of Stellenbosch in South Africa. Research work is in progress on improving SUNSAT's imager from 15 m to 2.5 m resolution. This will require the use of forward motion compensation for exposure control. This paper presents automatic forward motion compensation (FMC) for micro satellites using a exciting new Earth sensor that measures the boresight's projection speed on the earth directly with no drift by making use of a series of images. High-resolution imagers will be controlled by this technique to ensure high quality stereo images. View full abstract»

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

    Development of performance functions for economic performance assessment of process control systems

    Donghui Wei ; Craig, I.
    AFRICON, 2009. AFRICON '09.

    DOI: 10.1109/AFRCON.2009.5308379
    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    Economic performance assessment (EPA) remains important to predict and verify the benefits from process control systems. In the latest techniques of EPA, performance functions (PFs) have an essential function. However, to the extent of the authors' knowledge, there has been no systematic approach to developing PFs. In this paper, a methodology for developing PFs is given and two case studies are given to show how it works. The methodology includes six crucial stages. View full abstract»

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

    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»

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

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

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

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

    IEEE Conference Publications

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

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

    Technology roadmap process to compare commercial broadband technologies available to SME and SOHO owners in South Arica

    Slabbert, J.A. ; Buys, A.J.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401636
    Publication Year: 2007 , Page(s): 1 - 9

    IEEE Conference Publications

    A technology roadmap process is proposed to determine the stakeholders in the broadband Internet arena as well as their possible impact on future broadband adoption in Southern Africa. The current status for available broadband technologies is accessed and then compared to the technology specification as provided by standards authorities or technology providers. New broadband technologies, currently in advanced pilot projects, are identified and their possible impact on current broadband technologies is discussed. The importance of standards in the roll out of new technologies is assessed and recommendations regarding commercial broadband technologies available to SME and SOHO in South Africa are made. View full abstract»

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

    Smart demand response scenarios

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

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

    IEEE Conference Publications

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

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

    Repeat-puncture superorthogonal convolutional turbo codes in AWGN channel

    Pillay, N. ; Hongjun Xu ; Takawira, F.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401628
    Publication Year: 2007 , Page(s): 1 - 5

    IEEE Conference Publications

    In this paper we study the use of repeat- puncture superorthogonal convolutional turbo codes in an additive white Gaussian noise (AWGN) channel. The performance of turbo codes (TC) have been shown to be near the theoretical limit in the AWGN channel. By using orthogonal signaling, which allows for bandwidth expansion, the performance of the turbo coding scheme can be improved even further. Since this is a low-rate code, the code is mainly suitable for spread-spectrum modulation applications. In classical turbo codes the frame length is set equal to the interleaver size, however, the codeword distance spectrum of turbo codes improves with an increasing interleaver size. It has been reported that the performance of turbo codes can be improved by using repetition and puncturing. Repeat-puncture turbo codes (RPTC) have shown a significant increase in performance at moderate to high signal-to-noise ratios. In this paper, we study the use of orthogonal signaling and parallel concatenation together with repetition and puncturing to improve the performance of superorthogonal convolutional turbo codes for reliable and effective communications. Simulation results in AWGN channel are presented together with analytical upper bounds, which have been derived using transfer function bounding techniques. View full abstract»

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

    Virtual wired control networks: a wireless approach with Bluetooth

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

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

    IEEE Conference Publications

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

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

    Statistical clustering in the design of logical topologies for wide-area optical networks

    Gazendam, A.D. ; Leuschner, F.W.
    Africon Conference in Africa, 2002. IEEE AFRICON. 6th

    Volume: 1
    DOI: 10.1109/AFRCON.2002.1146835
    Publication Year: 2002 , Page(s): 209 - 210 vol.1
    Cited by:  Patents (3)

    IEEE Conference Publications

    A novel approach based on statistical clustering, using the Ward linkage as similarity metric, is proposed for designing optical network logical topologies. The influence of the geographic distribution of network traffic, and the intra/inter cluster traffic ratios on the number and positions of wide-area network hub nodes are investigated. View full abstract»

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

    AM/FM/GIS/CAD and enterprise support systems (ESS) for telecommunications

    Gregory, M.
    AFRICON, 1996., IEEE AFRICON 4th

    Volume: 2
    DOI: 10.1109/AFRCON.1996.562990
    Publication Year: 1996 , Page(s): 782 - 787 vol.2

    IEEE Conference Publications

    A number of fundamental changes are taking place in the telecommunication and cable industries. The increased bandwidth of the new networks is transforming the meaning of telecommunication and communication in general. Telecommunication is no longer a voice service between two individuals, and CATV (cable) is no longer just TV. As developing countries grow and open-up their largely ignored rural markets, wireless technologies become a part of the overall telecommunications environment of the future. The formulation of an information management infrastructure to assist engineers (users) and to support the operational and decision support systems within the corporation is needed for success. The author discusses computer aided drafting (CAD), automated mapping and facilities mapping (AM/FM) and geographic information systems (GIS) solutions View full abstract»

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

    Performance investigation of a sparse data compression technique with AWGN channel effects

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

    Volume: 1
    DOI: 10.1109/AFRICON.2004.1406673
    Publication Year: 2004 , Page(s): 275 - 278 Vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    The paper introduces a performance measure for data sources that may be used to evaluate the potential for good compression using a sparse source coding technique, as well as BER bounds in AWGN. The authors present comparative results of sparse source coding and, in terms of the introduced performance measure, complexity and error propagation in AWGN conditions. Simulation results show that the performance measure can be used effectively to predict the potential of a source for compression. Comparative PDF and BER results are shown for various sparseness levels in coded and uncoded systems View full abstract»

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

    A comparison study between double and single gate p-IMOS

    Hassani, F.A. ; Fathipour, M. ; Mehran, M.
    AFRICON 2007

    DOI: 10.1109/AFRCON.2007.4401526
    Publication Year: 2007 , Page(s): 1 - 7
    Cited by:  Papers (1)

    IEEE Conference Publications

    A double gate p-IMOS (DG p-IMOS) as well as a process definition for this device is proposed. Simulation studies show that at 400 (K) this device provides smaller subthreshold slope and threshold voltage than a single gate p-IMOS (SG p- IMOS). The ON/OFF current ratio for the DG p-IMOS is larger than that of an equivalent SG p-IMOS. Moreover, the double gate device has higher transconductance than the single gate device. The DG p-IMOS structural parameters affect its electrical characteristics. Reduction of the body thickness tends to lower threshold voltage and increase ON/OFF current ratio. Furthermore, for a given spacing between source and drain threshold voltage reduces as the gate length is increased. View full abstract»

Skip to Results

SEARCH HISTORY

Search History is available using your personal IEEE account.

Need Help?


IEEE Advancing Technology for Humanity About IEEE Xplore | Contact | Help | Terms of Use | Nondiscrimination Policy | Site Map | Privacy & Opting Out of Cookies

A not-for-profit organization, IEEE is the world's largest professional association for the advancement of technology.
© Copyright 2014 IEEE - All rights reserved. Use of this web site signifies your agreement to the terms and conditions.