Living organisms throughout evolution have developed desired properties, such as the ability of maintaining functionality despite changes in the environment or their inner structure, the formation of functional modules, from metabolic pathways to organs, and most essentially the capacity to adapt and evolve in a process called natural selection. It can be observed in the metabolic networks of modern organisms that many key pathways such as the citric acid cycle, glycolysis, or the biosynthesis of most amino acids are common to all of them. Understanding the evolutionary mechanisms behind this development of complex biological systems is an intriguing and important task of current research in biology as well as artificial life. Several competing hypotheses for the formation of metabolic pathways and the mecha- nisms that shape metabolic networks have been discussed in the literature, each of which finds support from comparative analysis of extant genomes. However, while being powerful tools for the investigation of metabolic evolution, these traditional methods do not allow to look back in evolution far enough to the time when metabolism had to emerge and evolve to the form we can observe today. To this end, simulation studies have been introduced to discover the principles of metabolic evolution and the sources for the emergence of metabolism prop- erties. These approaches differ considerably in the realism and explicitness of the underlying models. A difficult trade-off between realism and computational feasibility has to be made and further modeling decisions on many scales have to be taken into account, requiring the combination of knowledge from different fields such as chemistry, physics, biology and last but not least also computer science. In this thesis, a novel computational model for the in silico evolution of early metabolism is introduced. It comprises all the components on different scales to resemble a situation of evolving metabolic protocells in an RNA-world. Therefore, the model contains a minimal RNA-based genetics and an evolving metabolism of catalytic ribozymes that manipulate a rich underlying chemistry. To allow the metabolic organization to escape from the confines of the chemical space set by the initial conditions of the simulation and in general an open- ended evolution, an evolvable sequence-to-function map is used. At the heart of the metabolic subsystem is a graph-based artificial chemistry equipped with a built-in thermodynamics. The generation of the metabolic reaction network is realized as a rule-based stochastic simulation. The necessary reaction rates are calculated from the chemical graphs of the reactants on the fly. The selection procedure among the population of protocells is based on the optimal metabolic yield of the protocells, which is computed using flux balance analysis. The introduced computational model allows for profound investigations of the evolution of early metabolism and the underlying evolutionary mechanisms. One application in this thesis is the study of the formation of metabolic pathways. Therefore, four established hypothe- ses, namely the backwards evolution, forward evolution, patchwork evolution and the shell hypothesis, are discussed within the realms of this in silico evolution study. The metabolic pathways of the networks, evolved in various simulation runs, are determined and analyzed in terms of their evolutionary direction. The simulation results suggest that the seemingly mutually exclusive hypotheses may well be compatible when considering that different pro- cesses dominate different phases in the evolution of a metabolic system. Further, it is found that forward evolution shapes the metabolic network in the very early steps of evolution. In later and more complex stages, enzyme recruitment supersedes forward evolution, keeping a core set of pathways from the early phase. Backward evolution can only be observed under conditions of steady environmental change. Additionally, evolutionary history of enzymes and metabolites were studied on the network level as well as for single instances, showing a great variety of evolutionary mechanisms at work. The second major focus of the in silico evolutionary study is the emergence of complex system properties, such as robustness and modularity. To this end several techniques to analyze the metabolic systems were used. The measures for complex properties stem from the fields of graph theory, steady state analysis and neutral network theory. Some are used in general network analysis and others were developed specifically for the purpose introduced in this work. To discover potential sources for the emergence of system properties, three different evolutionary scenarios were tested and compared. The first two scenarios are the same as for the first part of the investigation, one scenario of evolution under static conditions and one incorporating a steady change in the set of ”food” molecules. A third scenario was added that also simulates a static evolution but with an increased mutation rate and regular events of horizontal gene transfer between protocells of the population. The comparison of all three scenarios with real world metabolic networks shows a significant similarity in structure and properties. Among the three scenarios, the two static evolutions yield the most robust metabolic networks, however, the networks evolved under environmental change exhibit their own strategy to a robustness more suited to their conditions. As expected from theory, horizontal gene transfer and changes in the environment seem to produce higher degrees of modularity in metabolism. Both scenarios develop rather different kinds of modularity, while horizontal gene transfer provides for more isolated modules, the modules of the second scenario are far more interconnected.

The theological theme missio Dei functions increasingly as the paradigm for local faith communities to renew the self-understanding of their identity and purpose in a changing world. There is, therefore, great interest in theological publications and religious practices regarding the so-called missional church. The missio Dei does not only have implications for the local faith community to be missional, but also for the way in which these faith communities should act in relation to each other in light of their new self-understanding. The missio Dei should, therefore, also shape the relationship between faith communities. This is already happening, especially in missional church-planting networks, but these networks have not thoroughly been grounded theologically or researched empirically in the light of the missio Dei. The purpose of this study is to develop a Scriptural matrix for the establishment of the relationship between faith communities in light of the missio Dei. The research is done by way of the practical theological methodology of Gerben Heitink (1999). * The first section of this study is a hermeneutic process, seeking to put the current state of affairs into perspective and develop Scriptural principles. Chapter 2 of the hermeneutic inquiry seeks to understand the way in which the missio Dei functions in existing literature on the role of the missio Dei in the relationship between faith communities. Literature on existing missional networks are also included. In Chapter 3, an understanding is developed of the role of the Trinity in the missio Dei and of the fact that its elements should also be present in the relationship between faith communities that are participating in the missio Dei. This is done by way of grammatical-historical exegesis of John 17. Chapter 2, therefore, helps to understand what needs to be changed, and Chapter 3 helps to understand the preferred practice. * The second section involves an empirical research in Chapter 4 of four missional networks in the United States of America and in Canada to determine the role of the missio Dei in the practice of those networks. These networks are Redeemer City to City, Church Innovations, Acts 29 and Forge Canada. * The third section is the strategic moment and involves the integration of the research results from Chapters 2, 3 and 4 in a practice theory. In Chapter 5, a practise-theory matrix is eventually developed for the establishment of the relationship between faith communities in light of the missio Dei. This matrix may also have many useful applications, ranging from being used as an instrument for measuring and developing the missionality of local faith communities to the evaluation or even development of missional networks. The conclusion of the study is that the degree of insight into the role of the Trinity in the missio Dei determines the extent to which faith communities and missional networks function missionally. The nature, boundaries, function and purpose of the unity of the Persons of the Trinity determine the nature, boundaries, function and purpose of the unity of missional communities of faith in their relationship with each other. The better a faith community's understanding is of the role of the Trinity in the missio Dei, the better that faith community will be able to function missionally with other faith communities. The matrix that has been developed helps the assessment, adjustment, establishment and prediction of the effectiveness of missional relationships between faith communities. / PhD (Pastoral Studies), North-West University, Potchefstroom Campus, 2014

The theological theme missio Dei functions increasingly as the paradigm for local faith communities to renew the self-understanding of their identity and purpose in a changing world. There is, therefore, great interest in theological publications and religious practices regarding the so-called missional church. The missio Dei does not only have implications for the local faith community to be missional, but also for the way in which these faith communities should act in relation to each other in light of their new self-understanding. The missio Dei should, therefore, also shape the relationship between faith communities. This is already happening, especially in missional church-planting networks, but these networks have not thoroughly been grounded theologically or researched empirically in the light of the missio Dei. The purpose of this study is to develop a Scriptural matrix for the establishment of the relationship between faith communities in light of the missio Dei. The research is done by way of the practical theological methodology of Gerben Heitink (1999). * The first section of this study is a hermeneutic process, seeking to put the current state of affairs into perspective and develop Scriptural principles. Chapter 2 of the hermeneutic inquiry seeks to understand the way in which the missio Dei functions in existing literature on the role of the missio Dei in the relationship between faith communities. Literature on existing missional networks are also included. In Chapter 3, an understanding is developed of the role of the Trinity in the missio Dei and of the fact that its elements should also be present in the relationship between faith communities that are participating in the missio Dei. This is done by way of grammatical-historical exegesis of John 17. Chapter 2, therefore, helps to understand what needs to be changed, and Chapter 3 helps to understand the preferred practice. * The second section involves an empirical research in Chapter 4 of four missional networks in the United States of America and in Canada to determine the role of the missio Dei in the practice of those networks. These networks are Redeemer City to City, Church Innovations, Acts 29 and Forge Canada. * The third section is the strategic moment and involves the integration of the research results from Chapters 2, 3 and 4 in a practice theory. In Chapter 5, a practise-theory matrix is eventually developed for the establishment of the relationship between faith communities in light of the missio Dei. This matrix may also have many useful applications, ranging from being used as an instrument for measuring and developing the missionality of local faith communities to the evaluation or even development of missional networks. The conclusion of the study is that the degree of insight into the role of the Trinity in the missio Dei determines the extent to which faith communities and missional networks function missionally. The nature, boundaries, function and purpose of the unity of the Persons of the Trinity determine the nature, boundaries, function and purpose of the unity of missional communities of faith in their relationship with each other. The better a faith community's understanding is of the role of the Trinity in the missio Dei, the better that faith community will be able to function missionally with other faith communities. The matrix that has been developed helps the assessment, adjustment, establishment and prediction of the effectiveness of missional relationships between faith communities. / PhD (Pastoral Studies), North-West University, Potchefstroom Campus, 2014

Living organisms throughout evolution have developed desired properties, such as the ability of maintaining functionality despite changes in the environment or their inner structure, the formation of functional modules, from metabolic pathways to organs, and most essentially the capacity to adapt and evolve in a process called natural selection. It can be observed in the metabolic networks of modern organisms that many key pathways such as the citric acid cycle, glycolysis, or the biosynthesis of most amino acids are common to all of them. Understanding the evolutionary mechanisms behind this development of complex biological systems is an intriguing and important task of current research in biology as well as artificial life. Several competing hypotheses for the formation of metabolic pathways and the mecha- nisms that shape metabolic networks have been discussed in the literature, each of which finds support from comparative analysis of extant genomes. However, while being powerful tools for the investigation of metabolic evolution, these traditional methods do not allow to look back in evolution far enough to the time when metabolism had to emerge and evolve to the form we can observe today. To this end, simulation studies have been introduced to discover the principles of metabolic evolution and the sources for the emergence of metabolism prop- erties. These approaches differ considerably in the realism and explicitness of the underlying models. A difficult trade-off between realism and computational feasibility has to be made and further modeling decisions on many scales have to be taken into account, requiring the combination of knowledge from different fields such as chemistry, physics, biology and last but not least also computer science. In this thesis, a novel computational model for the in silico evolution of early metabolism is introduced. It comprises all the components on different scales to resemble a situation of evolving metabolic protocells in an RNA-world. Therefore, the model contains a minimal RNA-based genetics and an evolving metabolism of catalytic ribozymes that manipulate a rich underlying chemistry. To allow the metabolic organization to escape from the confines of the chemical space set by the initial conditions of the simulation and in general an open- ended evolution, an evolvable sequence-to-function map is used. At the heart of the metabolic subsystem is a graph-based artificial chemistry equipped with a built-in thermodynamics. The generation of the metabolic reaction network is realized as a rule-based stochastic simulation. The necessary reaction rates are calculated from the chemical graphs of the reactants on the fly. The selection procedure among the population of protocells is based on the optimal metabolic yield of the protocells, which is computed using flux balance analysis. The introduced computational model allows for profound investigations of the evolution of early metabolism and the underlying evolutionary mechanisms. One application in this thesis is the study of the formation of metabolic pathways. Therefore, four established hypothe- ses, namely the backwards evolution, forward evolution, patchwork evolution and the shell hypothesis, are discussed within the realms of this in silico evolution study. The metabolic pathways of the networks, evolved in various simulation runs, are determined and analyzed in terms of their evolutionary direction. The simulation results suggest that the seemingly mutually exclusive hypotheses may well be compatible when considering that different pro- cesses dominate different phases in the evolution of a metabolic system. Further, it is found that forward evolution shapes the metabolic network in the very early steps of evolution. In later and more complex stages, enzyme recruitment supersedes forward evolution, keeping a core set of pathways from the early phase. Backward evolution can only be observed under conditions of steady environmental change. Additionally, evolutionary history of enzymes and metabolites were studied on the network level as well as for single instances, showing a great variety of evolutionary mechanisms at work. The second major focus of the in silico evolutionary study is the emergence of complex system properties, such as robustness and modularity. To this end several techniques to analyze the metabolic systems were used. The measures for complex properties stem from the fields of graph theory, steady state analysis and neutral network theory. Some are used in general network analysis and others were developed specifically for the purpose introduced in this work. To discover potential sources for the emergence of system properties, three different evolutionary scenarios were tested and compared. The first two scenarios are the same as for the first part of the investigation, one scenario of evolution under static conditions and one incorporating a steady change in the set of ”food” molecules. A third scenario was added that also simulates a static evolution but with an increased mutation rate and regular events of horizontal gene transfer between protocells of the population. The comparison of all three scenarios with real world metabolic networks shows a significant similarity in structure and properties. Among the three scenarios, the two static evolutions yield the most robust metabolic networks, however, the networks evolved under environmental change exhibit their own strategy to a robustness more suited to their conditions. As expected from theory, horizontal gene transfer and changes in the environment seem to produce higher degrees of modularity in metabolism. Both scenarios develop rather different kinds of modularity, while horizontal gene transfer provides for more isolated modules, the modules of the second scenario are far more interconnected.

Taking into consideration the dramatic changes ushered in by the exponential growth of social networking, marketers are left without a dependable framework on how to implement social networking strategically and in alignment with other modern as well as traditional marketing disciplines. In light of this, the study aims to explore the strategic implementation of social networking within the context of a dependable marketing theoretical model, known as the marketing communications mix. During the study’s literary exploration, social networking’s capacity as a viable professional marketing tool was discussed. Thereafter, the study’s main theoretical underpinning, marketing communications was discussed and analysed. During the empirical phase of the research, a process of grounded theory was firstly followed in order to compile a list of typical social networking communications actions that are performed on social networking platforms. The list of typical social networking communication actions were then compared with the five disciplines of the marketing communications mix and consequently paired, based on their inherent similarities in regards to characteristics. In an attempt to illustrate the practical use of the paring of social networking actions and the disciplines of the marketing communications mix, the empirical study conclusively followed a process of action research in order to analyse an organisation’s social networking strategy. It was established that the model could possibly increase the strategic alignment of an organisation’s social networking initiatives but that it should only be used as a guiding and adaptable framework as to not hamper the creative capacity of social networking marketing. It was suggested that a follow-up study explore the ways in which social networking can complement and support other modern as well as traditional marketing initiatives as way to strengthen the case for an integrated approach to professional, strategic marketing. / Thesis (MA (History of Art))--North-West University, Potchefstroom Campus, 2013.

Taking into consideration the dramatic changes ushered in by the exponential growth of social networking, marketers are left without a dependable framework on how to implement social networking strategically and in alignment with other modern as well as traditional marketing disciplines. In light of this, the study aims to explore the strategic implementation of social networking within the context of a dependable marketing theoretical model, known as the marketing communications mix. During the study’s literary exploration, social networking’s capacity as a viable professional marketing tool was discussed. Thereafter, the study’s main theoretical underpinning, marketing communications was discussed and analysed. During the empirical phase of the research, a process of grounded theory was firstly followed in order to compile a list of typical social networking communications actions that are performed on social networking platforms. The list of typical social networking communication actions were then compared with the five disciplines of the marketing communications mix and consequently paired, based on their inherent similarities in regards to characteristics. In an attempt to illustrate the practical use of the paring of social networking actions and the disciplines of the marketing communications mix, the empirical study conclusively followed a process of action research in order to analyse an organisation’s social networking strategy. It was established that the model could possibly increase the strategic alignment of an organisation’s social networking initiatives but that it should only be used as a guiding and adaptable framework as to not hamper the creative capacity of social networking marketing. It was suggested that a follow-up study explore the ways in which social networking can complement and support other modern as well as traditional marketing initiatives as way to strengthen the case for an integrated approach to professional, strategic marketing. / Thesis (MA (History of Art))--North-West University, Potchefstroom Campus, 2013.

Wireless sensor networks are used in several multi-disciplinary areas covering a wide variety of applications. They provide distributed computing, sensing and communication in a powerful integration of capabilities. They have great long-term economic potential and have the ability to transform our lives. At the same time however, they pose several challenges – mostly as a result of their random deployment and non-renewable energy sources.Among the most important issues in wireless sensor networks are energy efficiency and radio interference. Topology control plays an important role in the design of wireless ad hoc and sensor networks; it is capable of constructing networks that have desirable characteristics such as sparser connectivity, lower transmission power and a smaller node degree.In this research a distributed topology control technique is presented that enhances energy efficiency and reduces radio interference in wireless sensor networks. Each node in the network makes local decisions about its transmission power and the culmination of these local decisions produces a network topology that preserves global connectivity. The topology that is produced consists of a planar graph that is a power spanner, it has lower node degrees and can be constructed using local information. The network lifetime is increased by reducing transmission power and the use of low node degrees reduces traffic interference. The approach to topology control that is presented in this document has an advantage over previously developed approaches in that it focuses not only on reducing either energy consumption or radio interference, but on reducing both of these obstacles. Results are presented of simulations that demonstrate improvements in performance. AFRIKAANS : Draadlose sensor netwerke word gebruik in verskeie multi-dissiplinêre areas wat 'n wye verskeidenheid toepassings dek. Hulle voorsien verspreide berekening, bespeuring en kommunikasie in 'n kragtige integrate van vermoëns. Hulle het goeie langtermyn ekonomiese potentiaal en die vermoë om ons lewens te herskep. Terselfdertyd lewer dit egter verskeie uitdagings op as gevolg van hul lukrake ontplooiing en nie-hernubare energie bronne. Van die belangrikste kwessies in draadlose sensor netwerke is energie-doeltreffendheid en radiosteuring. Topologie-beheer speel 'n belangrike rol in die ontwerp van draadlose informele netwerke en sensor netwerke en dit is geskik om netwerke aan te bring wat gewenste eienskappe het soos verspreide koppeling, laer transmissiekrag en kleiner nodus graad.In hierdie ondersoek word 'n verspreide topologie beheertegniek voorgelê wat energie-doeltreffendheid verhoog en radiosteuring verminder in draadlose sensor netwerke. Elke nodus in die netwerk maak lokale besluite oor sy transmissiekrag en die hoogtepunt van hierdie lokale besluite lewer 'n netwerk-topologie op wat globale verbintenis behou.Die topologie wat gelewer word is 'n tweedimensionele grafiek en 'n kragsleutel; dit het laer nodus grade en kan gebou word met lokale inligting. Die netwerk-leeftyd word vermeerder deur transmissiekrag te verminder en verkeer-steuring word verminder deur lae nodus grade. Die benadering tot topologie-beheer wat voorgelê word in hierdie skrif het 'n voordeel oor benaderings wat vroeër ontwikkel is omdat dit nie net op die vermindering van net energie verbruik of net radiosteuring fokus nie, maar op albei. Resultate van simulasies word voorgelê wat die verbetering in werkverrigting demonstreer. / Dissertation (MEng)--University of Pretoria, 2010. / Electrical, Electronic and Computer Engineering / unrestricted

Social Tagging und soziale Netzwerke sind zentrale Bausteine des Web 2.0 und Enterprise 2.0. In diesem Beitrag werden die sozialen Aspekte von Social Tagging beleuchtet und ein Ansatz aufgeführt, um in Folksonomies Personen mit ähnlichen Interessen zu finden. Ferner wird ein Tagging-Framework beschrieben, das im Use Case Alexandria im Rahmen des BMWi-Projekts Theseus entstanden ist.

Wireless Sensor Networks (WSN) may consist of hundreds or even thousands of nodes and could be used for a multitude of applications such as warfare intelligence or to monitor the environment. A typical WSN node has a limited and usually irreplaceable power source and the efficient use of the available power is of utmost importance to ensure maximum lifetime of each WSN application. Each of the nodes needs to transmit and communicate sensed data to an aggregation point for use by higher layer systems. Data and message transmission among nodes collectively consume the largest amount of the energy available in a WSN. The network routing protocols ensure that every message reaches the destination and has a direct impact on the amount of transmissions to deliver a messages successfully. To this end the transmission protocol within the WSN should be scalable, adaptable and optimized to consume the least possible amount of energy to suite different network architectures and application domains. This dissertation proposes a Mobile Tolerant Hybrid Energy Efficient Routing Protocol (MT-HEER), where hybrid refers to the inclusion of both flat and hierarchical routing architectures as proposed by Page in the Hybrid Energy Efficient Routing Protocol (HEER). HEER was previously developed at the University of Pretoria and forms the starting point of this research. The inclusion of mobile nodes in the WSN deployment proves to be detrimental to protocol performance in terms of energy efficiency and message delivery. This negative impact is attributable to assuming that all nodes in the network are statically located. In an attempt to adapt to topological changes caused by mobile nodes, too much energy could be consumed by following traditional network failure algorithms. MT-HEER introduces a mechanism to pro-actively track and utilise mobile nodes as part of the routing strategy. The protocol is designed with the following in mind: computational simplicity, reliability of message delivery, energy efficiency and most importantly mobility awareness. Messages are propagated through the network along a single path while performing data aggregation along the same route. MT-HEER relies on at least 40% of the nodes in the network being static to perform dynamic route maintenance in an effort to mitigate the risks of topological changes due to mobile nodes. Simulation results have shown that MT-HEER performs as expected by preserving energy within acceptable limits, while considering the additional energy overhead introduced by dynamic route maintenance. Mobile node tolerance is evident in the protocol's ability to provide a constant successful message delivery ratio at the sink node with the introduction and increase in the number of mobile nodes. MT-HEER succeeds in providing tolerance to mobile nodes within a WSN while operating within acceptable energy conservation limits. AFRIKAANS : Koordlose Sensor Netwerke mag bestaan uit honderde of selfs duisende nodes en kan gebruik word vir 'n legio van toepassings soos oorlogs intellegensie of om die omgewing te monitor. 'n Tipiese node in so 'n netwerk het 'n beperkte en soms onvervangbare energie bron. Die effektiewe gebruik van die beskikbare energie is dus van uiterste belang om te verseker dat die maksimum leeftyd vir 'n koordlose sensor network behaal kan word. Elkeen van die nodes in the network moet die waargeneemde data aanstuur oor die netwerk na 'n versamelings punt vir latere gebruik deur applikasie vlak stelsels. Informasie en boodskap transmissie tussen die nodes is wel een van die aktiwiteite wat die meeste energie verbruik in the netwerk. Die roeterings protokol verseker dat die boodskappe die eindbestemming behaal en het 'n direkte impak op die hoeveelheid transmissies wat kan plaas vind om dit te bewerkstellig. Die roeterings protokol moet dus skaleerbaar, aanpasbaar en verfyn word om die minste moontlike energie te verbruik in verskillende toepassings velde. Hierdie verhandeling stel 'n Bewegings Tolerante Hybriede Netwerk Roeterings Protokol vir Koordlose Sensor Netwerke (“MT-HEER”) voor. In hierdie konteks verwys hybried na die samesmelting van beide plat en hierargiese roeterings beginsels soos voor gestel deur Page in Hybriede Netwerk Roeterings Protokol (“HEER”). HEER was ontwikkel by die Universiteit van Pretoria en vorm die begin punt van hierdie navorsing. Die insluiting van bewegende nodes in 'n Koordlose Sensor Netwerk toon 'n negatiewe tendens in terme van energie effektiwiteit en suksesvolle boodskap aflewerings by die eindbestemming. Die grootste rede vir hierdie negatiewe tendens is die aanname deur gepubliseerde werke dat alle nodes in die netwerk staties is. Te veel energie sal vermors word indien tradisionele fout korregerende meganismes gevolg word om aan te pas by die bewegende nodes. MT-HEER stel 'n meganisme voor om die bewegende nodes te gebruik as deel van die roetering strategie en gevolglik ook hierdie nodes te volg soos hulle beweeg deur die netwerk. Die protokol is ontwikkel met die volgende doelstellings: rekenkundig eenvoudigheid, betroubare boodskap aflewering, energie effektiwiteit en bewustheid van bewegende nodes. Boodskappe word langs 'n enkele pad gestuur deur die netwerk terwyl boodskap samevoeging bewerkstellig word om die eind bestemming te bereik. MT-HEER vereis wel dat ten minste 40% van die netwerk nodes staties bly om die dienamiese roeterings instandhouding te bewerkstellig. Simulasie toetse en resultate het bewys dat MT-HEER optree soos verwag in gevalle waar daar bewegende nodes deel uit maak van die netwerk. Energie bewaring is binne verwagte parameters terwyl die addisionele energie verbruik binne rekening gebring word om te sorg vir bewegende nodes. Die protokol se toleransie teen bewegende nodes word ten toon gestel deur die vermoë van die protokol om konstant 'n hoë suksesvolle bookskap aflewerings verhouding te handhaaf. MT-HEER behaal die uitgesette doel om 'n toleransie teen bewegende nodes beskikbaar te stel, terwyl die protokol steeds funksioneer binne verwagte energie besparings limiete. Copyright / Dissertation (MEng)--University of Pretoria, 2010. / Electrical, Electronic and Computer Engineering / unrestricted

As information is becoming more available online and will forevermore be part of any business, the true value of the large amounts of stored data is in the discovery of hidden and unknown relations and connections or traits in the data. The acquisition of these hidden relations can influence strategic decisions which have an impact on the success of a business. Data clustering is one of many methods to partition data into different groups in such a way that data patterns within the same group share some common trait compared to patterns across different groups. This thesis proposes a new artificial immune model for the problem of data clustering. The new model is inspired by the network theory of immunology and differs from its network based predecessor models in its formation of artificial lymphocyte networks. The proposed model is first applied to data clustering problems in stationary environments. Two different techniques are then proposed which enhances the proposed artificial immune model to dynamically determine the number of clusters in a data set with minimal to no user interference. A technique to generate synthetic data sets for data clustering of non-stationary environments is then proposed. Lastly, the original proposed artificial immune model and the enhanced version to dynamically determine the number of clusters are then applied to generated synthetic non-stationary data clustering problems. The influence of the parameters on the clustering performance is investigated for all versions of the proposed artificial immune model and supported by empirical results and statistical hypothesis tests. AFRIKAANS: Soos wat inligting meer aanlyn toeganglik raak en vir altyd meer deel vorm van enige besigheid, is die eintlike waarde van groot hoeveelhede data in die ontdekking van verskuilde en onbekende verwantskappe en konneksies of eienskappe in die data. Die verkryging van sulke verskuilde verwantskappe kan die strategiese besluitneming van ’n besigheid beinvloed, wat weer ’n impak het op die sukses van ’n besigheid. Data groepering is een van baie metodes om data op so ’n manier te groepeer dat data patrone wat deel vorm van dieselfde groep ’n gemeenskaplike eienskap deel in vergelyking met patrone wat verspreid is in ander groepe. Hierdie tesis stel ’n nuwe kunsmatige immuun model voor vir die probleem van data groepering. Die nuwe model is geinspireer deur die netwerk teorie in immunologie en verskil van vorige netwerk gebaseerde modelle deur die model se formasie van kunsmatige limfosiet netwerke. Die voorgestelde model word eers toegepas op data groeperingsprobleme in statiese omgewings. Twee verskillende tegnieke word dan voorgestel wat die voorgestelde kunsmatige immuun model op so ’n manier verbeter dat die model die aantal groepe in ’n data stel dinamies kan bepaal met minimum tot geen gebruiker invloed. ’n Tegniek om kunsmatige data stelle te genereer vir data groepering in dinamiese omgewings word dan voorgestel. Laastens word die oorspronklik voorgestelde model sowel as die verbeterde model wat dinamies die aantal groepe in ’n data stel kan bepaal toegepas op kunsmatig genereerde dinamiese data groeperingsprobleme. Die invloed van die parameters op die groepering prestasie is ondersoek vir alle weergawes van die voorgestelde kunsmatige immuun model en word toegelig deur empiriese resultate en statistiese hipotese toetse. / Thesis (PhD)--University of Pretoria, 2011. / Computer Science / unrestricted