AFRICON 2007Pub Date : 2007-12-12DOI: 10.1109/AFRCON.2007.4401440
R. Chidzonga, E. Chikuni
{"title":"Stabilizing a bicycle below critical speed","authors":"R. Chidzonga, E. Chikuni","doi":"10.1109/AFRCON.2007.4401440","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401440","url":null,"abstract":"This paper discusses the control of a naturally unstable bicycle at stand still based on local linearization of a nonlinear model which results in a 2times2 multiple input multiple output system. It is shown through simulation plus new insights on stabilizing non-minimum phase systems and f-domain design techniques that it is possible to keep the bicycle vertical outside the self stability speed domain where theory in the literature has predicted that it's not possible. In reality the stabilization goal is a skill which can be acquired through practice.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123296909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
AFRICON 2007Pub Date : 2007-12-12DOI: 10.1109/AFRCON.2007.4401508
Xiyin Liang, Jiangfeng Zhang, X. Xia
{"title":"Adaptive synchronization for a class of chaotic system","authors":"Xiyin Liang, Jiangfeng Zhang, X. Xia","doi":"10.1109/AFRCON.2007.4401508","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401508","url":null,"abstract":"In this article, we achieve chaotic synchronization in a new chaotic system suggested in [1], which cannot be estimated by some kind of adaptive observers without knowing the exact system parameters. Unlike the reference [1], we use the adaptive observer introduced in [2]. We also give conclusive proof that the output of the chaotic system satisfies the persistently exciting (PE) condition.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124050394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
AFRICON 2007Pub Date : 2007-12-12DOI: 10.1109/AFRCON.2007.4401527
O. Falowo, H. Chan
{"title":"Join call admission control algorithm to enhance connection-level QoS in heterogeneous cellular networks","authors":"O. Falowo, H. Chan","doi":"10.1109/AFRCON.2007.4401527","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401527","url":null,"abstract":"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.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"201 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115699616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
AFRICON 2007Pub Date : 2007-12-12DOI: 10.1109/AFRCON.2007.4401502
E. Lezar, D. Davidson
{"title":"Implementation of arbitrarily high order hierarchical vector basis functions for the finite element analysis of a rectangular waveguide","authors":"E. Lezar, D. Davidson","doi":"10.1109/AFRCON.2007.4401502","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401502","url":null,"abstract":"In any computational field there is an ever-present drive for better computational efficiency. This also holds true in the field of computational electro-magnetics where the finite element method (FEM) is regularly used. To improve the efficiency of a solution, various higher order basis functions are often employed. Two closely related sets of basis functions are considered, namely those implemented by Webb [1] and those of Slone [2] which are given as a correction to Webb's original basis functions. To facilitate the comparison between these two sets of basis functions, an efficient representation scheme is devised which allows for generation of these basis functions to any order. This representation is then used to perform a direct comparison between the results for the eigen-analysis of a rectangular PEC waveguide in two dimensions.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115741929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
AFRICON 2007Pub Date : 2007-12-12DOI: 10.1109/AFRCON.2007.4401497
James Swart, Trudy Sutherland
{"title":"Fusing theory and practical in a curriculum for engineering students - A case study","authors":"James Swart, Trudy Sutherland","doi":"10.1109/AFRCON.2007.4401497","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401497","url":null,"abstract":"Engineering students at the Vaal University of Technology are exposed to both theoretical and practical instruction within their specified disciplines. This provides the students with greater learning opportunities, which is a core academic function of a university of technology. The department of Electronic Engineering comprises one of eight departments within the Faculty of Engineering and Technology that emphasizes the importance of practical instruction for engineering students. This department focuses primarily on finding solutions to industrial problems in the power electronics and telecommunications world. This paper will attempt to highlight the importance of fusing theory and practical in a curriculum for engineering students. Two different approaches exist in this regard, namely presenting the theory before the practical and the practical before the theory. Both approaches were included in a module, Radio Engineering III, which serves as the case study for this paper. It comprises five different theory sections and 10 practical assignments. Most of the engineering students enrolled for this module successfully completed the practical work, which was designed with both approaches in mind. A post-practical survey revealed that the students felt that the practical work done in the laboratory was relevant to the theory work done in the classroom. It also revealed that students enjoyed the practical work, acquiring needed skills relevant to their engineering discipline.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"82 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115752042","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
AFRICON 2007Pub Date : 2007-12-12DOI: 10.1109/AFRCON.2007.4401587
M. Božanić, S. Sinha
{"title":"Design methodology for a CMOS based power amplifier deploying a passive inductor","authors":"M. Božanić, S. Sinha","doi":"10.1109/AFRCON.2007.4401587","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401587","url":null,"abstract":"This paper presents the design methodology of an integrated power amplifier (PA), and coins the methodology as a software routine: for a given set of PA specifications, CMOS process parameters, the routine computes the passive component values for a Class-E based PA. The routine includes the matching network for standard impedance loads. The program also provides its user with a spiral inductor calculator, which can be used to determine inductance and parasitic values for an integrated square planar spiral inductor. The same tool has the ability to extract SPICE (tSPICE) netlist of inductor geometry, which can be used in the post-layout simulations of the PA. Operation of the program was demonstrated by simulations in AMS 0.35 mum single-supply process for a 10 dBm, 2.4 GHz PA design.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"237 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132602769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
AFRICON 2007Pub Date : 2007-12-12DOI: 10.1109/AFRCON.2007.4401646
C. Kriger, R. Tzoneva
{"title":"Neural networks for prediction of wastewater treatment plant influent disturbances","authors":"C. Kriger, R. Tzoneva","doi":"10.1109/AFRCON.2007.4401646","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401646","url":null,"abstract":"In order to develop an effective control strategy for the activated sludge process (ASP) of a wastewater treatment plant, an understanding of the nature of the influent load disturbances to the wastewater treatment plant is necessary. The wastewater treatment processes are dynamic and the interrelationships between variables are very complex. The values of the influent disturbances are usually measured off-line in a laboratory, as there are still no reliable on-line sensors available. This work proposes development of a neural network model for prediction of the values of the influent disturbances, which ultimately affect the activated sludge process. Three different dynamic multilayer perceptron feed-forward neural network models and three recurrent neural networks are developed for the prediction of the influent disturbances of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and flowrate respectively. The predictive performance of the multi-layer perceptron is compared to that of the recurrent neural network.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132659835","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
AFRICON 2007Pub Date : 2007-12-12DOI: 10.1109/AFRCON.2007.4401533
D. Kovacevic, M. Jovic, A. Kovacevic, V. Paic
{"title":"Circuit simulation program as a support tool in mathematical environment","authors":"D. Kovacevic, M. Jovic, A. Kovacevic, V. Paic","doi":"10.1109/AFRCON.2007.4401533","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401533","url":null,"abstract":"General circuit simulation program can be used as a problem solving support in the domain of analytic geometry. Simulated analytic curve generators create a new interdisciplinary tutorial field correlating mathematics and electronics.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132323916","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
AFRICON 2007Pub Date : 2007-12-12DOI: 10.1109/AFRCON.2007.4401576
O. J. Oyedapo, D. Ngwenya
{"title":"Evaluation of TCP-variants performances in an ad-hoc mobile network","authors":"O. J. Oyedapo, D. Ngwenya","doi":"10.1109/AFRCON.2007.4401576","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401576","url":null,"abstract":"The prevalence of wireless networks has become imminent over the past few years, because of the unpredictable nature of their channels; they introduce different types of errors. The congestion control algorithm of the standard transmission control protocol (TCP) assumes packet losses are due to congestion and hence not suitable to handle such channel and transmission errors. This leads to ineffective utilization of the channel bandwidth. A number of TCP variants have been developed to cater for different types of networks. In this paper we evaluate the performances of some of these variants in ad hoc mobile network by simulations using NS-2. These variants are then evaluated in terms of the congestion window evolution and throughput. We showed by the results of our simulations that the BITCP is the most stable with the packet error rates introduced, followed by the TCP-Jersey.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"79 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128382994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
AFRICON 2007Pub Date : 2007-12-12DOI: 10.1109/AFRCON.2007.4401534
Yi-Sheng Liu, F. Takawira, Hongjun Xu
{"title":"Approximate discrete time analysis of the hybrid token-CDMA MAC system","authors":"Yi-Sheng Liu, F. Takawira, Hongjun Xu","doi":"10.1109/AFRCON.2007.4401534","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401534","url":null,"abstract":"In this paper a hybrid Token-CDMA based medium access control (MAC) protocol is considered. The MAC scheme is analytically modeled as a multiserver multiqueue (MSMQ) system in the case of a gated service discipline. We present an approximated discrete time analysis for the queue inside the system where the analysis is concerned with the general case in which the system accommodates several traffic classes. Each queue in the system is assumed to incorporate the input model, the vacation model and the buffer model. The packet arrival process is assumed to be a Poisson distribution, with the same rate for the queues in each traffic class, and data rate quality of service (c) is incorporated to regulate the input. Packet service time is modeled with independent, identically distributed random variables with geometric distributions. Moments of the packet delay are derived using the probability generating function approach.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127480773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}