{"title":"Earth current memory sensor for use in power distribution lines","authors":"J. Nderu, M. Soeda, J. Yamasaki","doi":"10.1109/AFRCON.2002.1159984","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1159984","url":null,"abstract":"This paper discusses an earth current memory sensor (for use in power distribution lines) that we have suggested, constructed and evaluated. The sensor employs a semi-hard magnetic material to record whether there has been an earth current in a given earthing conductor or not, and an amorphous magnetostrictive metal wire to retrieve the information stored in the memory (semi-hard material). So far we have achieved a sensitivity of 6 A. The sensor permanently stores the information of an earth current, making it possible to retrieve the information even long after the earth current has ceased. Furthermore, the sensor is fairly cheap to be viable for installation on each and every distribution line pole without significantly increasing the cost.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134157765","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}
{"title":"Ferro-resonance in a series capacitor system supplying a submerged-arc furnace","authors":"J. Pienaar, P. Swart","doi":"10.1109/AFRCON.2002.1160014","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1160014","url":null,"abstract":"This paper addresses a ferro-resonance problem encountered at two 30 MVA submerged-arc furnaces resulting in unnecessary furnace downtime. The electrical supply system under consideration includes a series capacitor battery system in conjunction with a step down furnace transformer. A mathematical model is used to explain how the electrical supply system brings about saturation in the core of the furnace transformer and then describes how the electrical system reacts to this phenomenon. The typical submerged-arc furnace characteristics that triggers the ferro-resonance response is identified and explained in order to furnish an understanding of the severity of the problem.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124417826","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}
{"title":"New family of constant-envelope root-of-unity filtered complex spreading sequences with zero cross-correlation properties","authors":"I. Pryra, L. Linde, S. A. Swanepoel","doi":"10.1109/AFRCON.2002.1146852","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1146852","url":null,"abstract":"A novel family of root-of-unity filtered complex spreading sequences is introduced. The new sequences, called constant-envelope root-of-unity filtered zero-cross-correlation (CE-RU-ZCC) sequences, are a nonlinear derivative of a family of polyphase sequences originally proposed by Suehiro et al. (1994). CE-RU-ZCC sequences can be shown to exhibit superior properties compared to the former, with little correspondence with the original Suehiro source sequences, apart from their desirable autocorrelation properties, which are perfectly retained despite the RU-filtering employed. The sequences are shown to be unique in several ways. Firstly, the unique filtering method results in sequences with perfectly constant envelope when modulated onto quadrature carriers, resulting in superior power efficiency compared to Nyquist-filtered sequences. The sequences secondly exhibit zero cross-correlation amongst the members of a family, and are therefore of particular interest in multi-user cellular environments, such as wireless CDMA, where, thirdly, their use results in a significant reduction in multi-user interference (MUI). The new sequences finally have excellent spectral efficiency, their power spectral distributions (densities) being practically equivalent to Nyquist-filtered sequences with sharp spectral roll-off. The paper includes results to verify the various claims made, and compares the CE-RU-ZCC sequences to several of the more commonly known spreading sequence families, such as the binary Gold (1967) family and the family of so-called generalised chirp-like (GCL) sequences originally proposed by Popovic (1992).","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"98 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124247489","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}
{"title":"Performance evaluation of Viterbi decoded binary and non-binary linear block codes in flat fading channels","authors":"L. Staphorst, L. Linde","doi":"10.1109/AFRCON.2002.1146830","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1146830","url":null,"abstract":"In recent years, much attention has been given to the decoding of linear block codes by means of trellis decoding algorithms, such as the Bahl-Cocke-Jelinek-Raviv (BCJR) and Viterbi algorithms. Not only do these algorithms support soft in. put decoding, but also the application of channel state information for improved decoding performances in fading channel environments. This paper presents a performance evaluation, based on an extensive simulation study, of Viterbi decoded binary Hamming and non-binary Reed-Solomon block codes under flat fading channel conditions with varying Doppler frequencies and line-of-sight signal strengths. Special attention is given to the influence of channel state information on the bit error rate performance.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124459016","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}
{"title":"The electric field of polluted insulators","authors":"W. Vosloo, J. Holtzhausen, Eskom","doi":"10.1109/AFRCON.2002.1159977","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1159977","url":null,"abstract":"In this paper a boundary element field simulation package was used to investigate the electric fields surrounding energised polymeric insulators. Clean and polluted insulators and the effect of dry bands were considered. The high stress regions were Identified and related to field observations, including water drop corona and dry band arcing.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"173 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116387787","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}
{"title":"Generalized irregular low-density (Tanner) codes based on Hamming component codes","authors":"T. Ngatched, F. Takawira","doi":"10.1109/AFRCON.2002.1146832","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1146832","url":null,"abstract":"In this paper we introduce the construction of new families of error-correcting codes based on Irregular low-density parity-check codes, which we called generalized irregular low density (GILD) codes, where as component codes, single-error correcting Hamming codes are used instead of single-error detecting parity-check codes. The decoding of GILD Is based on simple and fast SISO (soft input-soft output) decoding of Hamming component codes. Simulation results over an AWGN channel indicate that excellent performances can be achieved.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116988798","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}
{"title":"On using genetic algorithms to optimize high frequency superconducting digital circuits for optimal yield","authors":"C. Fourie, W. Perold","doi":"10.1109/AFRCON.2002.1159959","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1159959","url":null,"abstract":"Even simple superconducting logic gates can contain tens of inductors, resistors and Josephson junctions. In order to increase the yield and reliability of such circuits to acceptable levels, it is often needed to adjust all the element values. The search space is therefore very large, and genetic algorithms have been used with remarkable success to optimize such gates.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115064494","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}
{"title":"Analytical model for evaluating blocking probability in wireless ad hoc networks","authors":"Y. Gugrajah, F. Takawira","doi":"10.1109/AFRCON.2002.1146848","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1146848","url":null,"abstract":"Routing protocols for ad hoc networks need to overcome the problems associated with dynamic and unpredictable topologies due to mobile nodes and the absence of base stations and central controllers. Currently, routing protocols are evaluated using discrete event simulators. Analytical methods to evaluate the end to end blocking probability are required in order to generate faster results for routing protocol comparison and network optimization. This paper proposes a semi-analytical method that incorporates fixed point approximation to account for mobility in ad hoc networks. Results are compared to those obtained by discrete event simulation.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124171573","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}
{"title":"Practical considerations for interference suppression cylindrical arrays","authors":"P. Niemand, J. Joubert, J. Odendaal","doi":"10.1109/AFRCON.2002.1159967","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1159967","url":null,"abstract":"The practical considerations in the design of a cylindrical array for interference suppression, is presented. The influence of the mutual coupling between the antenna elements on the degree of suppression is investigated. The possibility of correcting the element input impedances for certain array configurations is also studied.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130777291","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}
{"title":"Fieldbus device description using tag-based trees","authors":"Steffen Deter","doi":"10.1109/AFRCON.2002.1146845","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1146845","url":null,"abstract":"Fieldbus systems are generally static configured systems. However, the configuration processes are often complex and would take advantages of technologies providing flexibility, adaptability, etc. Specifically, fieldbus technologies are often incompatible to each other. A technology bringing on the one hand a homogeneous interface between different fieldbusses and, on the other hand providing a simple addressing mechanism and plug-and-play capability could bring advantages to fieldbus systems. Therefore, an alternative data format offering the aforementioned features is presented in this paper. This data format, called tag-based trees, is strongly related to XML and XML DOM trees, and basically provides a generic data format, which is suitable for almost all types of data. Moreover, it also gives the opportunity for fieldbus networks to provide semantics to the system by enriching the data with an appropriate structure describing the meaning of the data. Hence, it is also possible to provide a kind of interpretation instructions to the data consumer.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130569592","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}