Pub Date : 2013-11-18DOI: 10.1109/AFRCON.2013.6757829
D. Barbosa, M. Bergano, Valério Ribeiro, A. Loots, V. Thondikulam, M. Gaylard, A. Ardenne, C. Paulo, S. Colafrancesco, Jose Carlos Amador, Rodrigo Maia, Rui Melo
The Mozambique Radio Astronomy Observatory (MRAO) will be a first milestone towards development of radioastronomy in Mozambique. Development of MRAO will constitute a preparation step towards participation in the upcoming Africa VLBI Network and the Square Kilometer Array project. The MRAO first antenna is planned to serve as a capacitation and training facility and will be installed after the conversion of a 7-meter telecom dish in South Africa. Therefore, this first radiotelescope design has to comply with local spectral and environmental constraints. Furthermore, power availability and long term sustainability with potential inclusion of solar power and control of Radio Frequency Interference are analyzed. Here we outline some of the design, environmental and power sustainability constraints.
{"title":"Design, environmental and sustainability constraints of new African observatories: The example of the Mozambique Radio Astronomy Observatory","authors":"D. Barbosa, M. Bergano, Valério Ribeiro, A. Loots, V. Thondikulam, M. Gaylard, A. Ardenne, C. Paulo, S. Colafrancesco, Jose Carlos Amador, Rodrigo Maia, Rui Melo","doi":"10.1109/AFRCON.2013.6757829","DOIUrl":"https://doi.org/10.1109/AFRCON.2013.6757829","url":null,"abstract":"The Mozambique Radio Astronomy Observatory (MRAO) will be a first milestone towards development of radioastronomy in Mozambique. Development of MRAO will constitute a preparation step towards participation in the upcoming Africa VLBI Network and the Square Kilometer Array project. The MRAO first antenna is planned to serve as a capacitation and training facility and will be installed after the conversion of a 7-meter telecom dish in South Africa. Therefore, this first radiotelescope design has to comply with local spectral and environmental constraints. Furthermore, power availability and long term sustainability with potential inclusion of solar power and control of Radio Frequency Interference are analyzed. Here we outline some of the design, environmental and power sustainability constraints.","PeriodicalId":159306,"journal":{"name":"2013 Africon","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130046291","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}
Pub Date : 2013-11-01DOI: 10.1109/ICASTECH.2013.6707511
Nevesh Rajaram, S. Viriri
The use of medical images by medical practitioners has increased to an extent that computers have become a necessity in the image processing and analysis. These images along with their detail are crucial when practitioners are diagnosing medical problems in patients. This research investigates if the edge density of a medical image can be used to characterize it. The performance of the edge density feature is assessed by finding its accuracy to retrieve images of the same group from a database. The medical images used in this research are x-rays of the humane body from five different regions, namely; hands, breast, pelvis, skull and chest regions. The edge density feature has shown to produce considerably good results in both, classification of medical images and image retrieval. For the classification using the nearest neighbor and 5-nearest neighbor techniques yielded 82.5% and 85% classification success rates respectively and 75.75% for image retrieval. The edge density approach used in this research is comparable to approaches used in literature considering that other approaches used more than one feature to achieve a higher accuracy and the results obtained in this paper only uses the edge density feature.
{"title":"Characterization of medical images using edge density","authors":"Nevesh Rajaram, S. Viriri","doi":"10.1109/ICASTECH.2013.6707511","DOIUrl":"https://doi.org/10.1109/ICASTECH.2013.6707511","url":null,"abstract":"The use of medical images by medical practitioners has increased to an extent that computers have become a necessity in the image processing and analysis. These images along with their detail are crucial when practitioners are diagnosing medical problems in patients. This research investigates if the edge density of a medical image can be used to characterize it. The performance of the edge density feature is assessed by finding its accuracy to retrieve images of the same group from a database. The medical images used in this research are x-rays of the humane body from five different regions, namely; hands, breast, pelvis, skull and chest regions. The edge density feature has shown to produce considerably good results in both, classification of medical images and image retrieval. For the classification using the nearest neighbor and 5-nearest neighbor techniques yielded 82.5% and 85% classification success rates respectively and 75.75% for image retrieval. The edge density approach used in this research is comparable to approaches used in literature considering that other approaches used more than one feature to achieve a higher accuracy and the results obtained in this paper only uses the edge density feature.","PeriodicalId":159306,"journal":{"name":"2013 Africon","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130940992","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}
This paper describes and discusses the algorithms required to perform face detection and face recognition in real-time. Simple features, similar to Haar basis functions, are used for detection and the eigenfaces technique is used for recognition. Further to the above, a novel method of increasing face recognition rates is presented for situations where a database containing multiple images of the same subject is being used. It is shown that these well-known, existing techniques for both detection and recognition can be combined in a manner that runs in real-time, but still preserves the original success rates mentioned in literature.
{"title":"Robust real-time face recognition","authors":"B. Lagerwall, Serestina Viriri","doi":"10.1145/2513456.2513494","DOIUrl":"https://doi.org/10.1145/2513456.2513494","url":null,"abstract":"This paper describes and discusses the algorithms required to perform face detection and face recognition in real-time. Simple features, similar to Haar basis functions, are used for detection and the eigenfaces technique is used for recognition. Further to the above, a novel method of increasing face recognition rates is presented for situations where a database containing multiple images of the same subject is being used. It is shown that these well-known, existing techniques for both detection and recognition can be combined in a manner that runs in real-time, but still preserves the original success rates mentioned in literature.","PeriodicalId":159306,"journal":{"name":"2013 Africon","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122503900","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}
Pub Date : 2013-09-09DOI: 10.1109/AFRCON.2013.6757744
Samuel Ajiboye, Yi Wang
It is widely accepted that the unwanted radiation from some feeding networks could degrade the performance of the antenna array. However, this interfering effect was not seen to be characterized in the open literature. This paper investigated this effect by a comparative study on a microstrip 4 × 4 Butler matrix fed linear patch antenna array at 2 GHz. The designs and measurement of the Butler matrix and the array are presented.
{"title":"Investigation on the interfering effect of feeding network on the performance of a beamforming antenna array","authors":"Samuel Ajiboye, Yi Wang","doi":"10.1109/AFRCON.2013.6757744","DOIUrl":"https://doi.org/10.1109/AFRCON.2013.6757744","url":null,"abstract":"It is widely accepted that the unwanted radiation from some feeding networks could degrade the performance of the antenna array. However, this interfering effect was not seen to be characterized in the open literature. This paper investigated this effect by a comparative study on a microstrip 4 × 4 Butler matrix fed linear patch antenna array at 2 GHz. The designs and measurement of the Butler matrix and the array are presented.","PeriodicalId":159306,"journal":{"name":"2013 Africon","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116003539","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}
Pub Date : 2013-09-09DOI: 10.1109/AFRCON.2013.6757659
Y. Khaled, J. Barbot, K. Busawon, D. Benmerzouk
In this paper, we consider the issue of stabilizing a class of linear systems using irregular sampled output measurements. For this purpose, we design a standard linear state feedback controller and an impulsive observer to provide an estimate the non-measured states, which are subsequently fed back in the control algorithm. We consider linear systems that can be decomposed, via a change of coordinates, into their respective measured and unmeasured dynamics. We consider the cases where the unmeasured subspace is stable and unstable respectively. In the case where the unmeasured subspace is stable, we employ a standard impulsive observer coupled with a continuous linear feedback control to stabilise the system. In the case where the unmeasured subspace is unstable, we employ two cascaded observers - an impulsive and a Luenberger observer - in conjunction with a linear feedback control to stabilise the latter. In order to prove the stability of the overall closed-loop system we proposed a practical stability result for a class of linear impulsive systems. Some simulation results are presented to show the performance of the observer-based control. Finally, some conclusions are drawn.
{"title":"Impulsive observer-based control for linear systems using irregularly sampled measurements","authors":"Y. Khaled, J. Barbot, K. Busawon, D. Benmerzouk","doi":"10.1109/AFRCON.2013.6757659","DOIUrl":"https://doi.org/10.1109/AFRCON.2013.6757659","url":null,"abstract":"In this paper, we consider the issue of stabilizing a class of linear systems using irregular sampled output measurements. For this purpose, we design a standard linear state feedback controller and an impulsive observer to provide an estimate the non-measured states, which are subsequently fed back in the control algorithm. We consider linear systems that can be decomposed, via a change of coordinates, into their respective measured and unmeasured dynamics. We consider the cases where the unmeasured subspace is stable and unstable respectively. In the case where the unmeasured subspace is stable, we employ a standard impulsive observer coupled with a continuous linear feedback control to stabilise the system. In the case where the unmeasured subspace is unstable, we employ two cascaded observers - an impulsive and a Luenberger observer - in conjunction with a linear feedback control to stabilise the latter. In order to prove the stability of the overall closed-loop system we proposed a practical stability result for a class of linear impulsive systems. Some simulation results are presented to show the performance of the observer-based control. Finally, some conclusions are drawn.","PeriodicalId":159306,"journal":{"name":"2013 Africon","volume":"13 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132606051","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}
Pub Date : 2013-09-09DOI: 10.1109/AFRCON.2013.6757627
R. Randriatsiferana, F. Alicalapa, R. Lorion, A. Mohammed
In Wireless Sensor Network (WSN), the clustering algorithm was developed to reduce the total energy consumption which determines the lifetime of the whole network. As a result, a number of recently-designed energy-efficient routing algorithms stated that clustering approach has an important issue for organizing a network into a connected hierarchy and increasing the network lifetime. This paper proposes a new algorithm to improve the performance of Low Energy Adaptive Clustering Centralized (LEACH-C) by improving the criterion for electing a cluster-head and the determination of optimal number of cluster-heads. Firstly, the optimal number of cluster-heads is based on the density of the covering. The sensor nodes are deployed randomly on the plane area of the sensing field covered by the communication range of the node. Secondly, nodes having the highest remaining energy and the lowest energy variance consumption becomes cluster-heads. The variance parameter keeps energy consumption dispersion, if the considered node is elected as cluster-head. This dispersion highly depends on the relative positioning of the node to the base station. This is useful for predicting node status when elected as cluster-head in the current round in order to balance the network energy. The simulation and analytical results of the proposed algorithm outperform the existing protocols in terms of lifetime of the network.
{"title":"A clustering algorithm based on energy variance and coverage density in centralized hierarchical Wireless Sensor Networks","authors":"R. Randriatsiferana, F. Alicalapa, R. Lorion, A. Mohammed","doi":"10.1109/AFRCON.2013.6757627","DOIUrl":"https://doi.org/10.1109/AFRCON.2013.6757627","url":null,"abstract":"In Wireless Sensor Network (WSN), the clustering algorithm was developed to reduce the total energy consumption which determines the lifetime of the whole network. As a result, a number of recently-designed energy-efficient routing algorithms stated that clustering approach has an important issue for organizing a network into a connected hierarchy and increasing the network lifetime. This paper proposes a new algorithm to improve the performance of Low Energy Adaptive Clustering Centralized (LEACH-C) by improving the criterion for electing a cluster-head and the determination of optimal number of cluster-heads. Firstly, the optimal number of cluster-heads is based on the density of the covering. The sensor nodes are deployed randomly on the plane area of the sensing field covered by the communication range of the node. Secondly, nodes having the highest remaining energy and the lowest energy variance consumption becomes cluster-heads. The variance parameter keeps energy consumption dispersion, if the considered node is elected as cluster-head. This dispersion highly depends on the relative positioning of the node to the base station. This is useful for predicting node status when elected as cluster-head in the current round in order to balance the network energy. The simulation and analytical results of the proposed algorithm outperform the existing protocols in terms of lifetime of the network.","PeriodicalId":159306,"journal":{"name":"2013 Africon","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130569082","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}
Pub Date : 2013-09-01DOI: 10.1109/AFRCON.2013.6757825
R. Millenaar
A range of factors determine whether a potential site to locate a radio astronomy observatory is optimal for the intended research, and for the duration of the projected lifetime of the observatory. On the science side the most prominent factors are the interference environment, the behaviour of the ionosphere, that of the troposphere and suitability of the topology. Factors related to the economy of the chosen site are just as important, relating to the cost of infrastructure and supply of power. For new large-scale observatories power-demand is substantial and renewable sources in remote areas important. In addition, there are secondary factors that influence the viability of the sites. An overview is presented taking the SKA as an example for siting an internationally scoped radio observatory.
{"title":"Considerations for the optimal radio astronomy site featuring the square kilometre array as an example","authors":"R. Millenaar","doi":"10.1109/AFRCON.2013.6757825","DOIUrl":"https://doi.org/10.1109/AFRCON.2013.6757825","url":null,"abstract":"A range of factors determine whether a potential site to locate a radio astronomy observatory is optimal for the intended research, and for the duration of the projected lifetime of the observatory. On the science side the most prominent factors are the interference environment, the behaviour of the ionosphere, that of the troposphere and suitability of the topology. Factors related to the economy of the chosen site are just as important, relating to the cost of infrastructure and supply of power. For new large-scale observatories power-demand is substantial and renewable sources in remote areas important. In addition, there are secondary factors that influence the viability of the sites. An overview is presented taking the SKA as an example for siting an internationally scoped radio observatory.","PeriodicalId":159306,"journal":{"name":"2013 Africon","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127351314","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}
Pub Date : 2013-09-01DOI: 10.1109/AFRCON.2013.6757706
G. Coviello, F. Cannone, G. Avitabile
The paper introduces a linearization technique based on a modified complex gain predistorter. The look-up table (LUT) digital adaptive predistortion (PD) approaches are effective for power amplifier (PA) linearization for reducing the PA power back-off and increasing the efficiency. Unlike other LUT predistorter based on uniform spacing of the LUT entries, the paper proposes a robust and behavioral method. The density of the table entries is directly proportional to the amplifier nonlinearity so the optimum table spacing could be realized. Besides, the proposed algorithm is able to optimize the LUT spacing without prior knowledge of the PA characteristics or input signal statistics and the LUT index calculation is made by a simple and fast algorithm.
{"title":"Robust behavioral non uniform look-up table spacing in adaptive digital baseband predistortion technique for RF power amplifier","authors":"G. Coviello, F. Cannone, G. Avitabile","doi":"10.1109/AFRCON.2013.6757706","DOIUrl":"https://doi.org/10.1109/AFRCON.2013.6757706","url":null,"abstract":"The paper introduces a linearization technique based on a modified complex gain predistorter. The look-up table (LUT) digital adaptive predistortion (PD) approaches are effective for power amplifier (PA) linearization for reducing the PA power back-off and increasing the efficiency. Unlike other LUT predistorter based on uniform spacing of the LUT entries, the paper proposes a robust and behavioral method. The density of the table entries is directly proportional to the amplifier nonlinearity so the optimum table spacing could be realized. Besides, the proposed algorithm is able to optimize the LUT spacing without prior knowledge of the PA characteristics or input signal statistics and the LUT index calculation is made by a simple and fast algorithm.","PeriodicalId":159306,"journal":{"name":"2013 Africon","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123334121","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}
Pub Date : 2013-09-01DOI: 10.1109/AFRCON.2013.6757605
T. O. Sanya, T. Swart, H. Ferreira
Optimized frequency tones for the power line channel is presented from an experimental scenario. Four sets of frequency tones, grouped according to CENELEC's regulation on frequency use for narrow band power line applications are selected according to their signal-to-noise ratio (SNR) performance. COMBLOCKS, a prototyping hardware was used for the implementation. Often times, M-FSK/OFDM have been presented and used as the modulation scheme of choice for power line communications (PLC), the choice of best frequencies to use is however, an area that has hardly been explored. This paper is concentrated on the choice of such optimal frequencies.
{"title":"Frequency optimization for narrowband power-line communications","authors":"T. O. Sanya, T. Swart, H. Ferreira","doi":"10.1109/AFRCON.2013.6757605","DOIUrl":"https://doi.org/10.1109/AFRCON.2013.6757605","url":null,"abstract":"Optimized frequency tones for the power line channel is presented from an experimental scenario. Four sets of frequency tones, grouped according to CENELEC's regulation on frequency use for narrow band power line applications are selected according to their signal-to-noise ratio (SNR) performance. COMBLOCKS, a prototyping hardware was used for the implementation. Often times, M-FSK/OFDM have been presented and used as the modulation scheme of choice for power line communications (PLC), the choice of best frequencies to use is however, an area that has hardly been explored. This paper is concentrated on the choice of such optimal frequencies.","PeriodicalId":159306,"journal":{"name":"2013 Africon","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126640640","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}
Pub Date : 2013-09-01DOI: 10.1109/AFRCON.2013.6757816
A. Malik, C. Kuba
Many options can be effectively used to meet the future power needs of a country in ways which would be more economically viable, environmentally sound, and socially just. A least-cost generation expansion planning study is conducted to find the economic feasibility of large scale integration of wind farms in Main interconnected transmission system of Oman. The generation expansion planning software used is WASP which is restricted in its capability to model intermittent nature of wind. Therefore, a wind turbine is modeled as a thermal plant with high forced outage rate related to its capacity factor. The result of the study has shown that wind turbines forms as part of the overall least-cost generation expansion plan for Main Interconnected System of Oman.
{"title":"Strategic planning of power supply in Oman including wind energy considerations","authors":"A. Malik, C. Kuba","doi":"10.1109/AFRCON.2013.6757816","DOIUrl":"https://doi.org/10.1109/AFRCON.2013.6757816","url":null,"abstract":"Many options can be effectively used to meet the future power needs of a country in ways which would be more economically viable, environmentally sound, and socially just. A least-cost generation expansion planning study is conducted to find the economic feasibility of large scale integration of wind farms in Main interconnected transmission system of Oman. The generation expansion planning software used is WASP which is restricted in its capability to model intermittent nature of wind. Therefore, a wind turbine is modeled as a thermal plant with high forced outage rate related to its capacity factor. The result of the study has shown that wind turbines forms as part of the overall least-cost generation expansion plan for Main Interconnected System of Oman.","PeriodicalId":159306,"journal":{"name":"2013 Africon","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115526567","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}
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