In dieser Dissertation wird eine Suche nach der Produktion von ''down''-artigen b'' Anti-b'' Quark-Antiquark-Paaren einer sequentiellen vierten Generation von Fermionen präsentiert. Für die Suche wurden Endzustände mit zwei gleich geladenen Leptonen (e oder mu), mindestens zwei Jets (davon ein b-Jet), fehlender transversaler Energie und einer großen Summe der Transversalimpulse aller Elektronen, Muonen und Jets betrachtet. Für den Zerfall dieser b'' Anti-b'' Quark-Antiquark-Paare wurden zwei verschiedene Szenarien untersucht. Im ersten Szenario wird angenommen, dass beide b'' Quarks ausschliesslich in ein t Quark und ein W Boson zerfallen. Für das zweite Szenario werden variable Verzweigungsverhältnisse für die Zerfälle der b'' Quarks nach tW, cW und uW erlaubt. Die Suche wurde mit Daten durchgeführt, die von pp Kollisionen mit einer Schwerpunktsenergie von sqrt(s) = 8 TeV vom ATLAS Detektor am Large Hadron Collider aufgezeichnet wurden. Der benutzte Datensatz entspricht einer integrierten Luminosität von 14.3 fb^-1. Es wurde kein signifikanter Überschuss an Ereignissen über den erwarteten Ereignissen vom Untergrund beobachtet. Daher wurde im ersten Szenario eine untere Grenze auf die b''-Masse (m_b'') von 0.724 TeV mit einem Konfidenzniveau von 95% bestimmt. Im Falle des zweiten Szenarios mit variablen Verzweigungsverhältnissen wurden Ausschlussregionen mit einem Konfidenzniveau von 95% als Funktion der Masse des b''-Quarks und seiner Verzweigungsverhältnisse bestimmt. Die erhaltenen Grenzen auf m_b'' sind schwächer verglichen mit dem Ergebnis für ein Verzweigungsverhältniss von 100% für b''->tW. / This thesis presents a search for the production of down-type b'' anti-b'' quark-antiquark pairs of a sequential fourth generation of fermions. In this search, final states with two same-sign charged leptons (e or mu), at least two jets (including at least one b-jet), missing transverse energy and a large total sum of the transverse momenta of all electrons, muons and jets were considered. Two different scenarios were assumed for the decays of these $b'' anti-b'' quark pairs. In the first scenario the two b'' quarks were considered to decay exclusively into a t quark and a W boson. For the second scenario, variable branching fractions for the decays of the b'' quarks into tW, cW and uW were allowed. The search was performed using data from pp collisions at a center-of-mass energy of sqrt(s) = 8 TeV recorded by the ATLAS detector at the Large Hadron Collider. The used dataset corresponds to an integrated luminosity of 14.3 fb^-1. No significant excess of events over the background expectation was observed. Hence a lower limit on the b'' mass of 0.724 TeV was set with 95% confidence level in the first scenario. In case of the second scenario with variable branching fractions, exclusion areas with 95% confidence level were derived as a function of the b'' mass and its decay branching fractions. These limits are less stringent compared to the result assuming a branching fraction of 100% for b''->tW.

Sistemas modernos de comunicação móvel sem fio, como os de quarta geração (4G), têm como principais metas prover elevada capacidade e alta qualidade de serviço (QoS) para os usuários. Para prover tal aumento de capacidade e QoS, sistemas 4G empregam diversas técnicas avançadas de transmissão e maior largura de banda, combinados com algoritmos de alocação de recursos que possam explorar de maneira eficiente tais técnicas, como por exemplo aproveitando as dimensões de diversidade do sistema. Em geral, porém, é necessário também aumentar a potência de transmissão para se atingir o ganho de capacidade desejado, o que implica maior custo para os provedores de serviço, menor tempo de vida para os dispositivos móveis e impacto ambiental cada vez mais pronunciado. Dado que a expectativa é que o número de usuários e a necessidade de dados continuem crescendo rapidamente, torna-se evidente a importância de analisar a relação entre capacidade e potência dispendida pelo sistema. Essa relação pode ser vista através da métrica de eficiência energética (EE), que é dada pela razão entre o número de bits efetivamente recebidos e a energia consumida no processo, revelando quão eficientemente o sistema transforma a energia consumida em informação efetivamente recuperada no receptor. Um sistema otimizado em relação à EE é capaz de transmitir mais informação por unidade de energia consumida, resultando em utilização mais racional e eficiente dos escassos recursos energéticos. Uma segunda questão acerca das metas é em relação à distribuição dos ganhos de capacidade/ QoS pela célula, i.e., quais usuários serão capazes de usufruir da maior capacidade e QoS. Em ambientes macrocelulares urbanos, a perda de percurso pode chegar a várias dezenas de decibéis em distâncias relativamente pequenas, além dos obstáculos naturais, como relevo, e artificiais, como prédios, o que limita ainda mais o desenvolvimento de sistemas energeticamente eficientes. Em abordagens tradicionais, tais problemas exigem a utilização de potências elevadas, em geral superiores à potência que os dispositivos podem utilizar, ou então requerem o aumento da densidade de estações rádio-base (BSs), o que geralmente resulta em custos inviáveis do ponto de vista dos operadores. Assim, busca-se em sistemas 4G emular o aumento da densidade de BSs através do conceito de redes heterogêneas, que são células com menor área de cobertura instaladas em pontos críticos de cobertura da célula original, como por exemplo a região de borda de célula, atendendo de maneira eficiente os usuários. No cenário de redes heterogêneas, um dos principais paradigmas é o conceito de redes cooperativas, no qual estações retransmissoras (RSs) reenviam o sinal recebido da estação fonte para estação destino, reduzindo a potência consumida com o canal móvel sem fio. Como utilizam conexão sem fio com a BS, as RSs podem ser instaladas em regiões com pouca infraestrutura sem a necessidade de grandes modificações, resultando em implantações bastante flexíveis. Assim, este trabalho de doutorado visa investigar estratégias de alocação de recursos baseadas no incremento da eficiência energética para sistemas celulares de quarta e quinta gerações utilizando o paradigma de redes cooperativas, determinando potencialidades e também itens que necessitam ser modificados, otimizados ou mesmo redefinidos, tendo em vista um aumento substancial da eficiência energética global da rede de comunicação sem fio. Busca-se durante o desenvolvimento do modelo de sistema capturar e quantificar as principais características de importantes sistemas celulares em uso atualmente, i.e., LTE-A e WiMAX, de modo que as decisões de design considerem os esforços de padronização, porém não se limitem a eles. Como a abordagem de alocação de recursos baseada em EE pode impactar nas métricas de desempenho do sistema, investiga-se também o compromisso entre as eficiências energética e espectral (SE), de modo que o aumento da EE não seja causado apenas pela degradação da SE e que seja possível obter maior EE para uma mesma SE e QoS. / Modern wireless communication systems, such as the fourth generation (4G) ones, have as main objectives to provide high capacity and quality of service (QoS) for the users. In order to provide such capacity and QoS gain, 4G systems use several advanced transmission techniques and higher bandwidth, combined with resource allocation algorithms that are able to efficiently exploit such techniques, as for example taking advantage of the diversity dimensions of the system. Generally, however, it is also necessary to increase the transmission power to achieve the desired capacity gain, which implies increased costs for service providers, shorter lifetime for the mobile devices and increasingly pronounced environmental impact. Since the expectation is that the number of users and data necessity will continue growing rapidly, it is evident the importance of analyzing the relation between capacity and power expended by the system. This relation can be seen through the energy efficiency (EE) metric, which is given by the ratio between the number of effectively received information bits and the energy consumed in the transmission process, revealing how efficiently the system transform consumed energy into effectively recovered information at the receiver. A system optimized regarding EE is able to transmit more information per unit of energy consumed, resulting in a more rational and efficient utilization of the scarce energetic resources. A second issue is relative to the distribution of the capacity/QoS gains over the whole cell, i.e, which users will be able to take advantage of the higher capacity and QoS. In urban macrocellular environments, the path-loss can reach several tens of decibels in relatively short distances, in addition to natural obstacles, such as land relief, or artificial, such as buildings, which further limits the development of energetically efficient systems. In traditional approaches, such problems require the use of high transmission power, generally greater than the power that the devices can use, or else require increased density of base-stations (BSs), which generally results in unviable costs from the operators point of view. Thus, in 4G systems it is sought to emulate the increase in the density of BSs through the concept of heterogeneous networks, which are cells with smaller coverage area installed in critical points of the original macrocell coverage, as for example the cell-edge area, serving efficiently the users. In the heterogeneous networks scenario, one of the main paradigms is the concept of cooperative networks, in which relay stations (RSs) retransmit the signal received from the source station to the destination station, reducing the power consumed with the mobile wireless channel. As the RSs use a wireless connection to the BS, they can be installed in places with poor infrastructure without requiring major modifications, resulting in very flexible deployments. Thus, this PhD work aims to investigate resource allocation strategies based on the improvement of the energy efficiency for fourth and fifty generation cellular systems using the cooperative networks paradigm, determining potentialities and also items that need to be modified, optimized or even redefined, aiming to a substantial increase in the overall energy efficiency of the wireless communication network. It is sought during the development of the system model to capture and quantify the main features of important cellular systems currently in use, i.e., LTE-A and WiMAX, so that the design decisions consider the standardization efforts, but do not be limited by them. Since the EE-based resource allocation approach can impact the performance metrics of the system, it will be investigated also the tradeoff between energy and spectral (SE) efficiencies, so that the increase in energy efficiency is not caused by degradation of the SE and also to be possible to obtain a higher EE for a same SE and QoS.

Sistemas modernos de comunicação móvel sem fio, como os de quarta geração (4G), têm como principais metas prover elevada capacidade e alta qualidade de serviço (QoS) para os usuários. Para prover tal aumento de capacidade e QoS, sistemas 4G empregam diversas técnicas avançadas de transmissão e maior largura de banda, combinados com algoritmos de alocação de recursos que possam explorar de maneira eficiente tais técnicas, como por exemplo aproveitando as dimensões de diversidade do sistema. Em geral, porém, é necessário também aumentar a potência de transmissão para se atingir o ganho de capacidade desejado, o que implica maior custo para os provedores de serviço, menor tempo de vida para os dispositivos móveis e impacto ambiental cada vez mais pronunciado. Dado que a expectativa é que o número de usuários e a necessidade de dados continuem crescendo rapidamente, torna-se evidente a importância de analisar a relação entre capacidade e potência dispendida pelo sistema. Essa relação pode ser vista através da métrica de eficiência energética (EE), que é dada pela razão entre o número de bits efetivamente recebidos e a energia consumida no processo, revelando quão eficientemente o sistema transforma a energia consumida em informação efetivamente recuperada no receptor. Um sistema otimizado em relação à EE é capaz de transmitir mais informação por unidade de energia consumida, resultando em utilização mais racional e eficiente dos escassos recursos energéticos. Uma segunda questão acerca das metas é em relação à distribuição dos ganhos de capacidade/ QoS pela célula, i.e., quais usuários serão capazes de usufruir da maior capacidade e QoS. Em ambientes macrocelulares urbanos, a perda de percurso pode chegar a várias dezenas de decibéis em distâncias relativamente pequenas, além dos obstáculos naturais, como relevo, e artificiais, como prédios, o que limita ainda mais o desenvolvimento de sistemas energeticamente eficientes. Em abordagens tradicionais, tais problemas exigem a utilização de potências elevadas, em geral superiores à potência que os dispositivos podem utilizar, ou então requerem o aumento da densidade de estações rádio-base (BSs), o que geralmente resulta em custos inviáveis do ponto de vista dos operadores. Assim, busca-se em sistemas 4G emular o aumento da densidade de BSs através do conceito de redes heterogêneas, que são células com menor área de cobertura instaladas em pontos críticos de cobertura da célula original, como por exemplo a região de borda de célula, atendendo de maneira eficiente os usuários. No cenário de redes heterogêneas, um dos principais paradigmas é o conceito de redes cooperativas, no qual estações retransmissoras (RSs) reenviam o sinal recebido da estação fonte para estação destino, reduzindo a potência consumida com o canal móvel sem fio. Como utilizam conexão sem fio com a BS, as RSs podem ser instaladas em regiões com pouca infraestrutura sem a necessidade de grandes modificações, resultando em implantações bastante flexíveis. Assim, este trabalho de doutorado visa investigar estratégias de alocação de recursos baseadas no incremento da eficiência energética para sistemas celulares de quarta e quinta gerações utilizando o paradigma de redes cooperativas, determinando potencialidades e também itens que necessitam ser modificados, otimizados ou mesmo redefinidos, tendo em vista um aumento substancial da eficiência energética global da rede de comunicação sem fio. Busca-se durante o desenvolvimento do modelo de sistema capturar e quantificar as principais características de importantes sistemas celulares em uso atualmente, i.e., LTE-A e WiMAX, de modo que as decisões de design considerem os esforços de padronização, porém não se limitem a eles. Como a abordagem de alocação de recursos baseada em EE pode impactar nas métricas de desempenho do sistema, investiga-se também o compromisso entre as eficiências energética e espectral (SE), de modo que o aumento da EE não seja causado apenas pela degradação da SE e que seja possível obter maior EE para uma mesma SE e QoS. / Modern wireless communication systems, such as the fourth generation (4G) ones, have as main objectives to provide high capacity and quality of service (QoS) for the users. In order to provide such capacity and QoS gain, 4G systems use several advanced transmission techniques and higher bandwidth, combined with resource allocation algorithms that are able to efficiently exploit such techniques, as for example taking advantage of the diversity dimensions of the system. Generally, however, it is also necessary to increase the transmission power to achieve the desired capacity gain, which implies increased costs for service providers, shorter lifetime for the mobile devices and increasingly pronounced environmental impact. Since the expectation is that the number of users and data necessity will continue growing rapidly, it is evident the importance of analyzing the relation between capacity and power expended by the system. This relation can be seen through the energy efficiency (EE) metric, which is given by the ratio between the number of effectively received information bits and the energy consumed in the transmission process, revealing how efficiently the system transform consumed energy into effectively recovered information at the receiver. A system optimized regarding EE is able to transmit more information per unit of energy consumed, resulting in a more rational and efficient utilization of the scarce energetic resources. A second issue is relative to the distribution of the capacity/QoS gains over the whole cell, i.e, which users will be able to take advantage of the higher capacity and QoS. In urban macrocellular environments, the path-loss can reach several tens of decibels in relatively short distances, in addition to natural obstacles, such as land relief, or artificial, such as buildings, which further limits the development of energetically efficient systems. In traditional approaches, such problems require the use of high transmission power, generally greater than the power that the devices can use, or else require increased density of base-stations (BSs), which generally results in unviable costs from the operators point of view. Thus, in 4G systems it is sought to emulate the increase in the density of BSs through the concept of heterogeneous networks, which are cells with smaller coverage area installed in critical points of the original macrocell coverage, as for example the cell-edge area, serving efficiently the users. In the heterogeneous networks scenario, one of the main paradigms is the concept of cooperative networks, in which relay stations (RSs) retransmit the signal received from the source station to the destination station, reducing the power consumed with the mobile wireless channel. As the RSs use a wireless connection to the BS, they can be installed in places with poor infrastructure without requiring major modifications, resulting in very flexible deployments. Thus, this PhD work aims to investigate resource allocation strategies based on the improvement of the energy efficiency for fourth and fifty generation cellular systems using the cooperative networks paradigm, determining potentialities and also items that need to be modified, optimized or even redefined, aiming to a substantial increase in the overall energy efficiency of the wireless communication network. It is sought during the development of the system model to capture and quantify the main features of important cellular systems currently in use, i.e., LTE-A and WiMAX, so that the design decisions consider the standardization efforts, but do not be limited by them. Since the EE-based resource allocation approach can impact the performance metrics of the system, it will be investigated also the tradeoff between energy and spectral (SE) efficiencies, so that the increase in energy efficiency is not caused by degradation of the SE and also to be possible to obtain a higher EE for a same SE and QoS.

Stridsfordon 90 togs fram för att möta en reguljär motståndare på vårt eget territorium. Dagens krav och förutsättningar är annorlunda då striden främst genomförs i konfliktzoner utomlands, men även på vårt eget territorium. Motståndaren vi möter nyttjar andra metoder för att genomföra sin strid och agerar på ett annorlunda sätt än vad vi är övade vid. Syftet med arbetet är att undersöka hur ett förband med stridsfordon 90 lämpar sig i strid på dagens stridsfält mot en irreguljär motståndare. För att ta reda på detta så beskriver jag fjärde generationens krigföring och stridsfordon9040Cför att sedan kunna analysera och jämföra den taktiska nivån utifrån de grundläggande förmågorna. Användningen av strf 90 och mekskytteplutonens taktik mot en 4GW motståndare är lämpliga att användaapligt på den taktiska nivån. Mekskytteplutonens taktik är flexibel och sätter få begränsningar mot taktiken hos en anfallande 4GW motståndare. / Combat vehicle 90 was developed to meet a conventional opponent on our own territory. Today's demands and conditions are different, today’s battles is mainly carried out in foreign conflict zones but also on our own territory. The opponent we face uses other means to carry out their combat, and acts in a different way than we are trained for.    The purpose of this work is to investigate how a unit equipped with combat vehicle 90 is suitable in today's battlefield against an irregular opponent. In order to answer this question, I have described the fourth generation warfare and combat vehicle 9040C, then analyzed and compared the tactical levels from the theory of the basic abilities.               The use of CV90 and the mechanized infantry platoons tactics against a 4GW opponent is appropriate to use at the tactical level. The flexible tactics of the mechanized infantry platoon gives an advantage over a 4GW opponent and the tactics used by such an opponent.

District heating plays a major part of the energy system used for heat supply in Sweden. The starting point of this parameter study have been to investigate the possibilities to provide the area Tullkammarkajen with efficient district heating supply in help of low temperature residual heat and waste heat from a nearby industry. The area is located in the city center of Halmstad and is currently in its planning phase. Facilities and apartments are planned to be built.The study is based on three different parameters: type of system, system temperatures and energy demand. The different type of systems that is analyzed is conventional districtheating, low-temperature district heating with a heat pump as a complement as well as low-temperature district heating with the primary network’s feed line as a complement. Further comparison was made between these parameters, both from an energy wise perspective as well as from an economic perspective.The underlying idea to this study has been to obtain an energy efficient solution that at the same time suits the principle of sustainable development. However, it can clearly be seen in the presented results that it is more profitable to use more conventional methods that are not adapted to sustainable development, based on today’s market. Thus, the question becomes whether the future of innovative solutions or economical funds should be prioritized.

Sedan 2007 har ett forskningsprojekt på s.k. ”framtidens kärnkraft”, även kallat för fjärde generationens kärnkraft pågått i Sverige. För den här studien har jag dels antagit ett historiskt perspektiv för att undersöka hur detta projekt har utvecklats och förändrats över tiden. Jag har även använt mig av Faircloughs kritiska diskursanalys som metod och teori för att undersöka vilka argument som har använts (och på vilket sätt som dessa argument har förmedlats) när olika representanter bakom projektet försökte övertyga både Regeringskansliet 2012 och Energikommissionen 2015 om värdet av denna teknik. I den teknikhistoriska undersökningen uppdagades det att mellan åren 2007 - 2017 hade syftet och designen hos den föreslagna reaktorkonstruktionen förändrats avsevärt. Från början hade projektet handlat om att upprätta en forskningsanläggning i Sverige med både tillhörande reaktor, bränsletillverkningsanläggning och upparbetningsanläggning för produktion av plutonium som reaktorbränsle. Projektet fick däremot avslag från regeringen efter att både KVA och Vetenskapsrådet hade ställt sig kritiska till projektets utformning, ur både tekniska och samhällsekonomiska perspektiv. Därefter förändrades projektets utformning till att istället handla om kommersiell elproduktion för den kanadensiska gruvindustrin i Arktis. I den diskursanalytiska undersökningen visade det sig att framställningen av fjärde generationens kärnkraft i det analyserade materialet har vilat bakom en okritisk och positiv inställning till tekniken. Argumenten som har använts har för det mesta handlat om teknikens teoretiska möjligheter, men väldigt lite om realismen i dessa visioner. När åsikter eller värderingar har förekommit, har dessa nästan uteslutande formulerats som vedertagna sanningar, vilket både förstärker och upprätthåller aktörerna som auktoriteter på området. I analysen diskuterar jag även fem olika diskurser som jag identifierade i det analyserade materialet. Dessa diskurser menar jag verkar både reproducerande och omstrukturerande på den rådande diskursordningen, vars syfte har varit att försöka skapa ett förnyat intresse för fjärde generationens kärnkraft som tidigare gick under namnet ”bridreaktor”. / Since 2007 a Swedish research project have been attempting to develop “the next generation” of nuclear power plants, also called the fourth generation of nuclear power. In this study, I have partly adopted a historical perspective in order to investigate how this research project have developed and changed over time. I have also applied the methodology of Faricloughs critical discourse analysis in order to identify what kind of arguments and rhetoric’s that were used by some of the representatives of this project when they tried to convince the Swedish cabinet office in 2012 and the Swedish Energy commission in 2015 of the value of this technology. In the historical investigation, it was discovered that between the years of 2007 and 2017, the purpose and design of the proposed reactor had undergone several transformations and changes. At first, the leaders of the research project had been considering building a research facility in Sweden that would not only include a reactor, but also a fuel fabrication and reprocessing facility for production of plutonium fuel. However, the project was never approved by the Swedish government, after both KVA and Vetenskapsrådet had expressed criticism towards the project, due to both technical and socio-economic considerations. As a result, the direction of the project was transformed into commercial power production for the mining industry in the Canadian Arctic. In the discourse analysis, it became evident that the information and arguments that had been presented in the analysed material had been framed in a strictly positive and uncritical manner. The arguments that were portrayed had mostly addressed the theoretical possibilities of the technology, but very little about the realism of these visions. When opinions or values had been expressed, they had almost exclusively been phrased as inherent truths, which can contribute to both strengthening and upholding their status in society as authority figures. In the discourse analysis, I also discuss five different discourses which I have identified in the material that was analysed. These discourses were then concluded to be both reproducing and restructuring on the current order of Swedish nuclear and energy discourse.

The National Professional Diploma in Education is an in-service programme for classroom-based educators who have less than three years of professional training. The programme seeks to create a pathway to qualified teacher status in ways that will impact positively on classroom practice, prepare teacher-learners for the implementation of the new curriculum and provide a sufficiently rigorous foundation for further study. This evaluation adopted a fourth generation evaluation approach characterised by extensive engagement with programme stakeholders. Chapter 2 outlines an epistemological and philosophical framework of reference whilst Chapters 3 and 4 explore learning and teaching strategies and management and costing issues. The findings of these investigations lead to the recommendations made in Chapter 5. It is felt that the Unisa NPDE meets many of the goals of the programme, but further research is needed into the impact on classroom practice and into the management of the decentralised learner support. / Educational Studies / M.Ed. (Didactics)

The article provides introductory notions about the new regulatory framework of the European Union on public procurement. The author argues that this new legislation forces us to rethink how articulate it to satisfies the public interest with respect to the principles of equality, efficiency, transparency, efficiency and accountability. It also forces us to rethink the administrative organization in the light of the own principles of public law. All that with the objective to approach us to the paradigm of the right to good administration as an element of control and accountability. / El artículo brinda nociones introductorias sobre el nuevo marco regulatorio de la Unión Europea sobre contratación pública. El autor sostiene que esta nueva normativa obliga a repensar en cómo articularla a fin de que satisfaga los intereses públicos con respeto a los principios de igualdad, eficacia, transparencia, eficiencia y rendición de cuentas. Además, obliga a repensar la organización administrativa a la luz de los propios fundamentos del derecho público. Todo ello con miras a acercarse al paradigma del derecho a una buena administración como elemento del control y de rendición de cuentas.

The National Professional Diploma in Education is an in-service programme for classroom-based educators who have less than three years of professional training. The programme seeks to create a pathway to qualified teacher status in ways that will impact positively on classroom practice, prepare teacher-learners for the implementation of the new curriculum and provide a sufficiently rigorous foundation for further study. This evaluation adopted a fourth generation evaluation approach characterised by extensive engagement with programme stakeholders. Chapter 2 outlines an epistemological and philosophical framework of reference whilst Chapters 3 and 4 explore learning and teaching strategies and management and costing issues. The findings of these investigations lead to the recommendations made in Chapter 5. It is felt that the Unisa NPDE meets many of the goals of the programme, but further research is needed into the impact on classroom practice and into the management of the decentralised learner support. / Educational Studies / M.Ed. (Didactics)

In most breeding programmes breeders use phenotypic data obtained in breeding trials to rank the performance of the parents or progeny on pre-selected performance criteria. Through this ranking the best candidates are identified and selected for breeding or production purposes. Best Linear Unbiased Prediction (BLUP), is an efficient selection method to use, combining information into a single index. Unbalanced or messy data is frequently found in tree breeding trial data. Trial individuals are related and a degree of correlation is expected between individuals over sites, which can lead to collinearity in the data which may lead to instability in certain selection models. A high degree of collinearity may cause problems and adversely affect the prediction of the breeding values in a BLUP selection index. Simulation studies have highlighted that instability is a concern and needs to be investigated in experimental data. The occurrence of instability, relating to collinearity, in BLUP of tree breeding data and possible methods to deal with it were investigated in this study. Case study data from 39 forestry breeding trials (three generations) of Eucalyptus grandis and 20 trials of Pinus patula (two generations) were used. A series of BLUP predictions (rankings) using three selection traits and 10 economic weighting sets were made. Backward and forward prediction models with three different matrix inversion techniques (singular value decomposition, Gaussian elimination - partial and full pivoting) and an adapted ridge regression technique were used in calculating BLUP indices. A Delphi and Clipper version of the same BLUP programme which run with different computational numerical precision were used and compared. Predicted breeding values (forward prediction) were determined in the F1 and F2 E. grandis trials and F1 P. patula trials and realised breeding performance (backward prediction) was determined in the F2 and F3 E. grandis trials and F2 P. patula trials. The accuracy (correlation between the predicted breeding values and realised breeding performance) was estimated in order to assess the efficiency of the predictions and evaluate the different matrix inversion methods. The magnitude of the accuracy (correlations) was found to mostly be of acceptable magnitude when compared to the heritability of the compound weighted trait in the F1F2 E. grandis scenarios. Realised genetic gains were also calculated for each method used. Instability was observed in both E. grandis and P. patula breeding data in the study, and this may cause a significant loss in realised genetic gains. Instability can be identified by examining the matrix calculated from the product of the phenotypic covariance matrix with its inverse, for deviations from the expected identity pattern. Results of this study indicate that it may not always be optimal to use a higher numerical precision programme when there is collinearity in the data and instability in the matrix calculations. In some cases, where there is a large amount of collinearity, the use of a higher precision programme for BLUP calculations can significantly increase or decrease the accuracy of the rankings. The different matrix inversion techniques particularly SVD and adapted ridge regression did not perform much better than the full pivoting technique. The study found that it is beneficial to use the full pivoting Gaussian elimination matrix inversion technique in preference to the partial pivoting Gaussian elimination matrix inversion technique for both high and lower numerical precision programmes. / Thesis (PhD)--University of Pretoria, 2013. / gm2014 / Genetics / unrestricted