Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The slip synchronous permanent magnet generator (SSG) is a direct-driven direct-grid connected generator developed to alleviate the need for expensive gearboxes and solid-state power converters on wind turbine generators. This study identifies certain key areas where the current wind turbine generator (WTG) system does not comply with the grid code for wind energy facilities (WEF) as specified by the National Energy Regulator of South Africa. The current WTG system does not have a reactive power compensation device. The main focus in this study is the development of an on-load tap changer (OLTC) transformer to control the terminal voltage of the generator. By controlling the terminal voltage of the generator the excitation-mode of the SSG can be changed allowing for control over the reactive power output of the SSG. An OLTC transformer utilising a solid-state assisted mechanical diverter circuit is built and tested to determine the viability of using an OLTC as a reactive power control device. Practical test results show that the OLTC can successfully control the terminal voltage of the SSG without interrupting the load current. The required accuracy regarding power factor control capability was not met due to the large change in reactive power output per tap change operation. A method of using small shunt capacitor banks to provide additional reactive power in between consecutive tap changes is evaluated in simulation. Simulation results show that the addition of these small shunt capacitor banks dramatically improves the reactive power control accuracy. Additionally the grid code specifies that a WEF must have the ability to curtail the active power output during frequency disturbances. The effects of frequency disturbances on the SSG output is simulated and it was found that the SSG will comply with the minimum connection requirements as specified in the grid code. A method of using an IGBT switched DC load to limit the active power output of the WEF is developed and simulated. From the simulation results it was found that the proposed active power curtailment device will meet the minimum power curtailment response time requirements as specified in the grid code. / AFRIKAANSE OPSOMMING: Die glip sinchroon permanente magneet generator (SSG) is ʼn direkte dryf, direkte netwerk gekoppelde wind generator wat ontwikkel is om behoefte aan duur ratkaste en drywing elektroniese omsetters te verlig. Hierdie studie identifiseer sekere sleutel areas waar die huidige wind generator opstelling nie aan die netwerk kode spesifikasie soos uiteengesit deur die Nasionale Energie Reguleerder van Suid-Afrika voldoen nie. Die wind turbine generator stelsel beskik nie oor ʼn reaktiewe drywing beheer meganisme nie. Die belangrikste fokus in hierdie studie is die ontwikkeling van ʼn transformator tap wisselaar wat gebruik sal word om die generator se terminale spanning te beheer. Deur die terminaal spanning te beheer kan die opwekking modus van die generator verander word om dan die uittree reaktiewe drywing te beheer. ʼn Tap wisselaar wat gebruik maak van ʼn drywingelektronies gesteunde meganiese skakelaar is ontwikkel en getoets om die lewensvatbaarheid van die tegniek te ondersoek. Praktiese toets resultate toon dat die tap wisselaar suksesvol beheer oor die generator se terminaal spanning kon uitvoer, sonder om die las-stroom te onderbreuk. Ongelukkig is die vereiste akkuraatheid ten opsigte van die reaktiewe drywing beheer nie gehaal nie. Die rede hiervoor is dat die verandering in uittree reaktiewe drywing baie groot is vir opeenvolgende tap verstellings. ʼn Metode waar twee klein kapasitor banke geskakel word om reaktiewe drywing te lewer, tussen opeenvolgende tap veranderinge, is deur middel van simulasie ondersoek. Die simulasie resultate toon aan dat die toevoeging van die kapasitors ʼn drastiese verbetering in die beheerbaarheid van die uittree reaktiewe drywing het. Verder spesifiseer die netwerk kode ook dat ʼn wind plaas oor die vermoë moet beskik om die aktiewe drywing te verminder tydens ʼn netwerk frekwensie versteuring. Die effek wat ʼn frekwensie versteuring op die SSG het, is deur middel van simulasie ondersoek en daar is gevind dat die SSG aan die netwerk verbinding spesifikasie sal voldoen. ʼn Metode waarby ʼn IGBT geskakelde GS las gebruik word om die aktiewe drywing van die wind generator te beperk is ondersoek en gesimuleer. Vanaf die simulasie resultate is daar gevind dat die drywing beperkings toestel aan die minimum drywing en reaksie tyd spesifikasies soos vereis sal voldoen.

Les travaux de cette thèse portent sur un insert dipolaire de supraconducteur à haute TC (SHT) en utilisant un câble multi-rubans torsadé pour un accélérateur des particules dans le cadre du projet EuCARD2 au CERN. L’insert dipolaire SHT est la seule possibilité aujourd'hui pour aller au-dessus de 16 T pour le futur accélérateur des particules à haute énergie. Deux spécifications de cet insert SHT sont les grands courants de fonctionnement (> 10 kA) et les champs de fond élevés (> 13 T) conduisant à des conditions de fonctionnement sévères. Pour répondre à ces attentes, un premier insert SHT de multi-rubans torsadé/ type de bloc est proposé sur la base des approches analytiques, numériques et expérimentales. Les travaux sont principalement classés dans le design d’insert dipolaire et le design de câble multi-rubans torsadé. Cette thèse se terminée avec la meilleure solution pour l’insert SHT de multi-rubans torsadé/ type de bloc en utilisant le câble partiellement isolé. / This Ph.D. deals with a high Tc superconducting (HTS) dipole insert using a twisted stacked cable for a particle accelerator in the framework of EuCARD2 project in CERN. The HTS dipole insert is the only possibility today to go above 16 T for the future high-energy particle accelerator. Two specifications of these HTS insert are large operating currents (> 10 kA) and high background fields (> 13 T) leading to severe operating conditions. To meet these expectations, a first Twisted Stacked/ Block-type HTS insert is proposed based on analytical, numerical and experimental approaches. The works are mainly classified into dipole insert design and twisted stacked cable design. This Ph.D. ends with the best solution for Twisted Stacked/ Block-type HTS insert using partially-insulated cable.

A determinação das principais propriedades magnéticas de um ímã permanente geralmente requer sistemas de medição sofisticados e custosos. Este trabalho analisa e propõe um sistema de caracterização de ímãs permanentes de Terras Raras à temperatura ambiente de baixo custo e de implementação mais simples e rápida. Ele consiste de um circuito magnético formado pelo ímã permanente sob caracterização, uma culatra de aço, um entreferro variável e uma sonda de efeito Hall com seu respectivo gaussímetro para a medição da intensidade do campo magnético no entreferro. Como introdução se apresenta o estado da arte da caracterização dos ímãs permanentes, conceitos básicos de magnetismo e em relação aos ímãs permanentes, sua história, os principais tipos, sua importância e suas aplicações principais. Os resultados teóricos e experimentais são comparados a resultados certificados, validando o método como proposto. / Determining the main magnetic properties of a permanent magnet usually requires sophisticated and expensive measurement setups. This work analyses and proposes a low-cost system to characterize Rare Earth permanent magnets at ambient temperature with easy and fast implementation. It consists of a magnetic circuit with the permanent magnet under test, appropriate pole pieces, a variable air gap and a Hall Effect probe with its respective Gaussmeter. As an introduction, it is presented the state of the art of permanent magnets characterization, basic concepts of magnetism and its history, the main types of permanent magnets, their importance and applications. The theoretical and experimental results are compared to certified ones, validating so the method as proposed.

A determinação das principais propriedades magnéticas de um ímã permanente geralmente requer sistemas de medição sofisticados e custosos. Este trabalho analisa e propõe um sistema de caracterização de ímãs permanentes de Terras Raras à temperatura ambiente de baixo custo e de implementação mais simples e rápida. Ele consiste de um circuito magnético formado pelo ímã permanente sob caracterização, uma culatra de aço, um entreferro variável e uma sonda de efeito Hall com seu respectivo gaussímetro para a medição da intensidade do campo magnético no entreferro. Como introdução se apresenta o estado da arte da caracterização dos ímãs permanentes, conceitos básicos de magnetismo e em relação aos ímãs permanentes, sua história, os principais tipos, sua importância e suas aplicações principais. Os resultados teóricos e experimentais são comparados a resultados certificados, validando o método como proposto. / Determining the main magnetic properties of a permanent magnet usually requires sophisticated and expensive measurement setups. This work analyses and proposes a low-cost system to characterize Rare Earth permanent magnets at ambient temperature with easy and fast implementation. It consists of a magnetic circuit with the permanent magnet under test, appropriate pole pieces, a variable air gap and a Hall Effect probe with its respective Gaussmeter. As an introduction, it is presented the state of the art of permanent magnets characterization, basic concepts of magnetism and its history, the main types of permanent magnets, their importance and applications. The theoretical and experimental results are compared to certified ones, validating so the method as proposed.

Diplomová práce se zabývá návrhem a sestavením nového spektrometru opticky detekované magnetické rezonance (ODMR) modifikací stávajícího spektrometru magnetického kruhového dichroismu (MCD) přivedením mikrovlnného ozařování. Je navrhnut nový držák vzorku umožnující osvětlení jak viditelným světlem, tak mikrovlnným zářením. Pro přivedení vlnění o nižších frekvencích je navržena anténa, určená k umístění pod vzorkem. Schopnosti celého systému jsou demonstrovány na sloučenínách kovových komplexů.

IT-relaterad brottslighet ökar lavinartat och Polismyndigheten står inför nya utmaningar i att identifiera gärningsmän. Allt mer mjukvaror och tjänster blir automatiserade och det gäller även mjukvarorna som Polismyndigheten använder sig av. En av utmaningarna är den oerhörda mängd data som måste processas och analyseras i undersökningar och då förutsätts det att verktygen presenterar data med bibehållen integritet. Verktygen som används är nästan alltid tredjepartsmjukvara och då är det viktigt att rätt data plockas ut och att datan är korrekt. Denna studie har som mål att jämföra två mjukvaror i hur de identifierar och presenterar data. Studien görs i samverkan med Polismyndigheten vid Regionalt IT-brottscentrum Väst – Skövde och hoppas inbringa nya insikter och kunskaper i de verktyg som jämförelsen grundas på och med hjälp av kunskaperna kunna värdesätta integriteten hos verktygen. Resultatet som framträder i studien är att verktygen presenterar data med bibehållen integritet. / Cybercrime is on the rise in society and the Swedish Police is facing new challenges in identifying criminals. More tools and services are becoming automated, and this also applies to the tools that the Swedish Police uses. One of the challenges is the enormous amount of data that must be processed and analyzed during investigations. The tools used are always third-party programs and IT-forensics needs to rely on the organization that makes the software. This study aims to evaluate two different tools in how they identify and present artifacts. The study is conducted in collaboration with the Police Authority at the Regional IT Crime Center West - Skövde and hopes to bring new insights and knowledge into the tools on which the comparison is based on and with the help of the knowledge be able to value the integrity of the tools. The result that the study presents is that the tools are presenting data with preserved integrity.

Bakgrund: Både nationellt och internationellt syns en ökad sjuksköterskebrist, vilket ökar risken för utebliven omvårdnad och försämrad vårdkvalitet. Magnetmodellen är en erkänd model lför att både behålla och attrahera sjuksköterskor till en arbetsplats och därmed intressant att sätta i relation till de anledningar sjuksköterskor uppger för att lämna yrket.Syfte: Att beskriva sjuksköterskors uppfattningar om bakomliggande faktorer att lämna yrket i relation till Magnetmodellen.Metod: En strukturerad litteraturöversikt. Systematiska sökningar har genomförts i CINAHL och PubMed som resulterade i 14 vetenskapliga artiklar. Samtliga artiklar har kvalitetsgranskats och bearbetats genom ett deduktivt förhållningssätt.Resultat: Resultatet visar 26 unika anledningar att lämna yrket som delades upp i fem kategorier: Dålig arbetsmiljö, bristande stöd till nyutexaminerade sjuksköterskor, dåliga relationer till övriga teamet samt bristande ledarskap. De unika anledningarna kunde relateras till nio av 14 magneter, övriga anledningar placerades in i en kategori Anledningar som inte kan relateras till Magnetmodellen.Slutsats: Organisationer måste se över brister i arbetsmiljön. Genom att skapa attraktiva arbetsplatser med omvårdnadskompetenta ledare som sätter omvårdnad i fokus stärks sjuksköterskor i deras profession, engagemang och arbetstillfredsställelse. / Background: Both nationally and internationally, there is an increased shortage of nurses, which increases the risk of non-care and deteriorating quality of care. The magnet model is a recognized model for both retaining and attracting nurses to a workplace and thus interesting to put in relation to the reasons nurses state for leaving the profession.Aim: To describe registered nurses´ perceptions of intentions to leave the profession in relation to the Magnet model.Method: A structured literature review. Systematic searches have been performed in CINAHL andPubMed which resulted in 14 scientific articles. All articles have been quality reviewed and then processed through a deductive approach.Results: The result show 26 unique reasons for leaving the profession, which were divided into five categories, Poor work environment, Lack of support for newly graduated nurses, Poor relations with the rest of the team, and lack of leadership. The unique reasons could be related to nine of 14 magnets, other reasons were placed in a category, Reasons that can not be related to the Magnet model.Conclusions: Organizations need to review shortcomings in the work environment. By creating attractive workplaces with nursing-competent leaders who put nursing in focus, nurses are strengthened in their profession, commitment and job satisfaction.

This thesis studies the brushless permanent magnet synchronous (BLPM) machine design for electric vehicle (EV) and hybrid electric vehicle (HEV) application. Different rotor topologies design, winding design, and multiphase designs are investigated and discussed. The Nissan Leaf interior permanent magnet (IPM) traction machine has been widely analyzed and there is much public domain data available for the machine. Hence, this machine is chosen as a representative benchmark design. First, the Nissan Leaf machine is analyzed via finite element analysis (FEA) and the results confirmed via published experimental test data. The procedure is then applied to all the following machine designs and results compared. Then the Nissan Leaf machine rotor is redesigned to satisfy the performance specification with sinusoidal phase current in the full range for the same performance specification and permanent magnet material. Afterword, a comparative study assessing the design and performance attributes of the Nissan Leaf IPM machine, when compared to a surface permanent magnet (SPM) machine designed within the main Nissan Leaf machine dimensional constraints. The study illustrates and concludes that both the IPM and SPM topologies have very similar capabilities with only subtle differences between the design options. The results highlight interesting manufacturing options and materials usage. The grain boundary diffusion processed (GBDP) magnets are proposed to reduce the rare earth material content in the permanent magnet machines, especially subject to high load and high temperature operating scenarios by preventing or reducing the onset of demagnetization. The design and analysis procedure of BLPM machine with GBDP magnets are put forward. In the end, the Nissan Leaf IPM machine is taken as an example to verify the analysis procedure. and the results illustrates that IPM machines with GBDP magnets can realize torque and maintain efficiency at high loads while being less prone to demagnetization. A new multi-phase synchronous reluctance machine (SRM) with good torque performance and conventional voltage source inverter is introduced for traction machine applications. Although the torque density is low compared with BLPM machine, the SRM machine gets rid of permanent magnets and achieve low torque ripple compared with switched reluctance machine when the asymmetric inverter is replaced with conventional voltage source inverter. The concentrated windings are designed and studied with both IPM and SPM rotor according to the Nissan Leaf machine requirements of performance and dimension to investigate how the concentrated windings affect the machine performance and manufacturability and cost. 9-, 12-, 15- slot concentrated windings’ stator share the same slot area with the Nissan Leaf machine distributed winding and the performance are evaluated and compared. Multi-phase concentrated windings machines with IPM and SPM rotor are designed and analyzed based on the Nissan Leaf machine specification and dimension constraints. The performance of 23-phase, 5-phase, 9-phase machine at low speed and top speed are studied and the advantages and disadvantages are compared in terms of torque quality, efficiency, and power electronic requirements. / Thesis / Doctor of Philosophy (PhD)

This case study examined the perceptions of administrators, teachers and parents of the implementation of an elementary school science, technology, engineering and math (STEM) academy program that featured characteristics of both magnet school programs and schoolwithin-a-school programs. I conducted interviews of key personnel, informed by classroom observations and a survey of parents to determine how stakeholders perceived equity in the access and allocation of opportunities and resources. The STEM Academy selected students from neighboring elementary schools and was housed within a larger K-5 elementary school. I found the STEM Academy teachers were widely praised for their innovations and teaching excellence, and alignment with emerging best practices. However, there were perceptions that their curriculum was neither sufficiently documented nor aligned with school division priorities, and was insufficiently communicated with school division central office leaders Academy parents, teachers, and community partners praised the Academy’s approach to curriculum, instruction, and uncommon learning experiences; but resentment and perceptions of inequity and exclusivity among most other stakeholders compromised the program implementation, leading to administrative and political pressure that challenged the Academy’s sustainability. I provide discussion and recommendations concerning elementary STEM programs, highlighting the importance of stakeholder perceptions and program evaluation. I also provide several suggestions for further research. / Ed. D.

Ce travail de thèse décrit (i) la synthèse de complexes hétérométalliques d’ions 3d et 4f à partir de précuseurs de Mn, Fe et Co, de sels de lanthanides et de ligands organiques et (ii) l'étude de leurs structures et propriétés. 41 complexes polynucléaires ont été synthétisés dans le cadre de ce travail. Les structures moléculaires de tous les composés ont été déterminées par diffraction des rayons X. Les propriétés magnétiques de 22 complexes ont été étudiées, dont quatre montrent une relaxation lente de leur aimantation considérée comme la signature d’un comportement de molécule-aimant. L'activité catalytique du complexe {Mn4Dy6Li2} calciné a aussi été étudiée et s'est avérée efficace pour l'oxydation du monoxyde de carbone. L'étude systématique de complexes isostructuraux de lanthanides a montré que l'incorporation d’ions 4f peut introduire de l’anisotropie magnétique et que l’ion DyIII est généralement le meilleur candidat pour le ciblage de molécules-aimants hétérométalliques 3d- 4f. / This dissertation describes the syntheses of 3d-4f-metal complexes starting from preformed compounds of Mn, Fe and Co, lanthanide salts and organic ligands and also the investigation of their structures and properties. 41 new polynuclear heterometallic metal complexes were synthesised in the course of this work with different interesting properties. The structures of all obtained compounds have been confirmed using X-ray diffraction. The magnetic properties of 22 complexes were studied, of which four show frequency dependent out-of-phase signals as expected for SMMs. The catalytic activity of calcinated {Mn4Dy6Li2} was investigated and proved effective for the oxidation of CO. It was established, that the use of precursors leads to new families of compounds. Moreover the study of isostructural compounds across the lanthanide series showed 1) that the incorporation of 4f ions introduces magnetic anisotropy and 2) DyIII is usually the best candidate for targeting 3d-4f-SMMs.