Short fibres of different materials are used for crack bridging in strain-hardening cement-based composites (SHCC). Their mechanical properties and the fibre-matrix interphase on the micro level have a significant influence on the macroscopic component properties. Investigations on the specific modification and adaptation of fibre properties in relation with the failure mechanisms at different strain rates hardly exist so far, since mainly commercially available fibres are used. In the frame of this work, two different fibre types – polypropylene (PP) fibres and alkali-resistant (AR) glass fibres – were produced on lab spinning devices and the properties were adapted in such a way that fundamental correlations between the influence of fibre geometry, mechanical properties, chemical functionalities and surface structure on the behaviour during fibre pull-out from the concrete matrix can be derived. The PP fibres were produced with different degrees of stretching, cross-sectional geometries (circular, trilobal) and fibre diameters, as well as without and with sizing. The resulting changes in the crystallinity of the PP structure, surface roughness and wetting behaviour could be demonstrated by differential scanning calorimetry (DSC), roughness measurements by atomic force microscopy (AFM), and contact angle measurements. AR glass fibres were used in the unsized state and various chemical surface treatments were applied. Aqueous polymer dispersions of different materials were characterized in detail regarding particle size, pH value, solid content, and surface tension. In addition, their film-forming properties were evaluated using prepared polymer films. Furthermore, the influence of cross-linking agents on the thermal and mechanical stability of polyurethane sizings was investigated using thermal analysis methods. After application of the sizings to the AR glass surface, changes in surface structure and roughness could be observed by scanning electron microscopy (SEM) and AFM. The amount of sizing, or rather the polymer content on the fibres, was systematically increased and investigated in the non-cross-linked and cross-linked state with respect to energy absorption during fibre pull-out. Using a high-strength concrete matrix, all modified PP and AR glass fibres were used to produce and test single-fibre model composites by single-fibre pull-out tests, whereby the fibre pull-out was either quasi-static or dynamic. Based on the test results, design strategies for PP and AR glass fibres were derived at the end of the thesis. / Für die Rissüberbrückung in hochduktilen Betonen (Strain-Hardening Cement-based Composites – SHCC) werden Kurzfasern verschiedener Materialien eingesetzt. Ihre mechanischen Eigenschaften und die Faser-Matrix-Grenzschicht auf der Mikroebene beeinflussen die makroskopischen Bauteileigenschaften deutlich. Untersuchungen zur gezielten Veränderung und Anpassung von Fasereigenschaften im Zusammenhang mit den Versagensmechanismen bei unterschiedlichen Dehnraten existieren bisher kaum, da überwiegend kommerziell verfügbare Fasern eingesetzt werden. Im Rahmen dieser Arbeit wurden daher zwei verschiedene Fasertypen – Polypropylen (PP)-Fasern und alkaliresistente (AR)-Glasfasern – an Laborspinnanlagen selbst hergestellt und die Eigenschaften so angepasst, dass sich grundlegende Zusammenhänge zwischen dem Einfluss von Fasergeometrie, mechanischen Eigenschaften, chemischen Funktionalitäten und Oberflächenstruktur auf das Verhalten bei Faserauszug aus der Betonmatrix ableiten lassen. Die PP-Fasern wurden mit verschiedenen Verstreckungsgraden, Querschnittsgeometrien (rund, trilobal), Faserdurchmessern sowie ohne und mit Schlichte hergestellt. Die dadurch hervorgerufenen Eigenschaftsveränderungen hinsichtlich Kristallinität der PP-Struktur, der Oberflächenrauheit und des Benetzungsverhaltens konnten durch dynamische Differenzkalorimetrie (DSC), Rauheitsmessungen mittels Rasterkraftmikroskopie (AFM) und Kontaktwinkelmessungen nachgewiesen werden. AR-Glasfasern wurden im ungeschlichteten Zustand verwendet und verschiedene chemische Oberflächenbehandlungen durchgeführt. Es wurden wässrige Polymerdispersionen verschiedener Materialien detailliert hinsichtlich ihrer Partikelgröße, pH-Wert, Feststoffgehalt und Oberflächenspannung charakterisiert sowie ihre Filmbildungseigenschaften anhand hergestellter Polymerfilme bewertet. Weiterhin wurde der Einfluss von Vernetzern auf die thermische und mechanische Stabilität von Polyurethanschlichten mit Methoden der thermischen Analyse untersucht. Nach dem Applizieren der Schlichten auf die AR-Glasoberfläche konnten Veränderungen der Oberflächenstruktur und Rauheit mit Rasterelektronenmikroskopie (REM) sowie AFM beobachtet werden. Die Schlichtemenge bzw. der Polymeranteil auf den Fasern wurde systematisch erhöht und im unvernetzten sowie vernetzten Zustand hinsichtlich der Energieabsorption bei Faserauszug untersucht. Mit allen modifizierten PP-Fasern und AR-Glasfasern wurden unter Einsatz einer hochfesten Betonmatrix Einzelfaser-Modellverbunde zur Durchführung von Einzelfaserauszugversuchen (Single-Fibre Pull-Out) hergestellt und geprüft, wobei der Faserauszug entweder quasistatisch oder dynamisch erfolgte. Basierend auf den Versuchsergebnissen wurden am Ende der Arbeit für PP-Fasern und AR-Glasfasern Designstrategien abgeleitet.

Zur Untersuchung der Faser-Matrix-Haftung in Faser-Kunststoff-Verbunden werden neben makromechanischen Methoden wie dem Querzug und der Drei-Punkt-Biegung mikromechanische Methoden an Einzelfaser-Modellverbunden eingesetzt. Zu letzteren Methoden zählen bspw. der Tropfenabscherversuch, der Einzelfaserauszugversuch (engl. single-fibre pull-out test, SFPO) und der Einzelfaserfragmentierungsversuch (engl. single fibre fragmentation test, SFFT). Bei ihrem Einsatz ist zu beachten, dass sich unterschiedliche Einflussgrößen auf ihre Ergebnisse auswirken können. In der vorliegenden Arbeit wird eine ausführliche Literaturübersicht mit einem detaillierten Überblick zu einer größeren Anzahl verschiedener Einflussgrößen durchgeführt. Daraus werden die Einflussgrößen Härtungsdauer, Feuchtigkeit, freie Faserlänge und Abzugsgeschwindigkeit als Untersuchungsgegenstände dieser Arbeit erarbeitet. Wesentliche aus dieser Arbeit resultierende Ergebnisse und Schlussfolgerungen sind nachstehend zusammengefasst. Härtungsdauer: Bei SFFT-Untersuchungen an Keramikfaser/Epoxidharz-Prüfkörpern wird ein degressiver Anstieg der Faser-Matrix-Haftung über der Härtungsdauer beobachtet. Die Ergebnisse geben Hinweise darauf, dass sich die Härtungsdauer beim SFFT und SFPO prinzipbedingt unterschiedlich auswirkt (aufgrund destruktiver bzw. konstruktiver Überlagerungen von Eigenspannungen und Prüfkraft-induzierten Spannungen). Feuchtigkeit: SFPO-Untersuchungen an Kohlenstoffaser/Epoxidharz-Prüfkörpern nach einmonatiger Konditionierung in feuchtem (50 %rF, 23 °C) bzw. trockenem Klima (0 %rF, 23 °C) belegen eine feuchtebedingt verringerte Haftung. Daraus wird geschlussfolgert, dass eine schwankende Luftfeuchtigkeit auch in diesem eingegrenzten klimatischen Spektrum (bspw. in teilklimatisierten Laboren) als wichtiger potentieller Störfaktor zu beachten ist. Prüfparameter: Auf Basis des Hooke’schen Gesetzes kann für den SFPO gezeigt werden, dass die freie Faserlänge die Maximalkraft beeinflusst und die Einflüsse der freien Faserlänge und der Abzugsgeschwindigkeit auf die Maximalkraft in Zusammenhang stehen. Beides wird anhand von SFPO-Untersuchungen an Glasfaser/Epoxidharz-Prüfkörpern bestätigt. Ferner wird aus den Untersuchungen geschlussfolgert, dass eine Geschwindigkeitserhöhung von 0,01 µm/s auf 0,1 µm/s zur Reduzierung der Versuchsdauer – im vorliegenden Fall von 30 45 min auf 6 8 min – vertretbar ist. Darüber hinaus werden anhand von Fehlerverstärkungsfaktoren differenzierte Aussagen zum Einfluss fehlerhaft bestimmter Eingangsdaten auf die Berechnung der lokalen Grenzflächenscherfestigkeit generiert. / For investigating fibre-matrix adhesion in fibre-polymer composites, macromechanical methods such as transverse tensile and three-point bending tests can be applied as well as micromechanical methods for which single-fibre model composites are used. The latter category of methods includes microbond, single-fibre pull-out (SFPO) and single-fibre fragmentation tests (SFFT). When applying these methods, it needs to be considered that their results can be affected by different influencing factors. In the present thesis, an extensive literature survey with a detailed overview of a larger number of influencing factors is conducted. Based on this overview, the factors curing time, moisture, free fibre length and test speed are acquired as objects of investigation of this thesis. Main results and conclusions of this work are summarised below. Curing time: Results from SFFT investigations on ceramic fibre/epoxy-specimens exhibit a degressive increase of fibre-matrix adhesion with curing time. This indicates that curing time affects SFFT and SFPO results differently due to different underlying principles (based on destructive and, respectively, constructive superposition of internal stresses and load-induced stresses). Moisture: SFPO specimens (carbon fibre/epoxy) are conditioned in humid (50 %rH, 23 °C) and dry climate (0 %rH, 23 °C) for one month prior to testing. The results show lower adhesion due to moisture. It is concluded that uncontrolled humidity, even in this limited climatic spectrum, needs to be considered as an important potential factor of influence (e.g. in partially climatised laboratories). Test parameters: Based on Hooke’s law, it is demonstrated for the SFPO that a) the free fibre length affects the maximum force and b) the effects of the free fibre length and the test speed on the maximum force are interrelated. Both is confirmed with results from SFPO investigations on glass fibre/epoxy-specimens. Furthermore, it is deduced from the above investigations that an increase in test speed from 0.01 µm/s to 0.1 µm/s is legitimate for reducing test duration – in the present case from 30 45 min to 6 8 min. In addition, the effect of erroneously determined input data on the calculation of the local interfacial shear strength is studied using conditions numbers (a measure for the propagation of error). With this, differentiated statements are generated.

Idag står världen inför nya typer av utmaningar för att möta hållbarhetsmål och nya behov somuppkommer. Många städer genomgår därför stora förändringar i utvecklingen där både förväntadeoch oväntade konsekvenser kommer att uppstå. Sedan Northvolt beslutade att etablera sig iSkellefteå år 2017, står staden inför den stora möjligheten att bli en pionjär stad för grön utveckling.Den nya utvecklingen har inte bara satt industrin på prov, utan även staden som helhet. Kommunensutmaning är att sprida budskapet om vad den kommande utvecklingen har att erbjuda, i hopp om attsätta fart på inflyttningen då kompetensbehovet är Skellefteås främsta utmaning idag. För att mötavisionerna kring utvecklingen behöver alla aktörer samverka för att bli en stad för grön elektrifiering.Välfungerande socialt kapital mellan offentlig sektor, industri, akademi och medborgare är enförutsättning för att skapa en framgångsrik utveckling.Arbetet utforskar hur en stad som genomgår en omfattande och snabb industriell expansionpåverkas. Genom att studera migrationsmönster ur “push and pull”-teorin undersöker arbetet hur detär möjligt att generera en ökad in-migration i olika målgrupper, som studenter eller hemvändare.Samtidigt som Skellefteå är beroende av att ha ett positiv inflyttningsnetto behöver även denuvarande invånarna bibehållas. Därför har intervjuer och en enkät genomförts för att få en tydligbild av styrkor och svagheter i utvecklingen av Skellefteå. Resultaten av enkäten och intervjuernaanalyserades och diskuterades genom en exemplifiering av de två teorierna push and pull och teorinom socialt kapital.Stora industriella expansioner av denna storlek skakar städerna till sin kärna, eftersom stadensidentitet och attribut ifrågasätts under denna typ av förändring. Vid en utveckling av denna storleksätts det sociala kapitalet på prov och beroende på dess effektivitet kan utfallen skilja sig åt. Stadentvingas väga olika faktorer mot varandra; ekonomiska, sociala och miljömässiga, då alla inte är möjligaatt upprätthålla till samma grad. Eftersom det största målet är att skapa en ökad in-migration till denexpanderande staden måste de pull-faktorer som finns och främjas ifrågasättas; Vad erbjuderegentligen Skellefteå? Arbetet identifierade sex möjliga grupper av in-migration; kontraurbanister,livsstilsmigranter, människor som flyttar för relationer/hemvändare, människor som flyttar förjobbmöjligheter, studenter och människor som flyttar för hållbarhetsskäl. Genom att lyfta fram enuppsättning av pull-faktorer specifikt för Skellefteå har staden den unika möjligheten att påverkamigrationsmönstren till deras behov och skapa en hållbar och attraktiv stad för den nuvarande ochframtida invånaren. / Today the world stands in front of the challenge of adapting to new demands, where solutions thatincrease sustainability are required. Many cities are therefore undergoing big changes indevelopments where both expected and unexpected consequences will arise. Since 2017, whenNorthvolt decided to establish in Skellefteå, the city stands in front of the opportunity to become apioneer city of green evolution. The new development has not only put the demands of the industryat test, but also the city as whole. The challenge of the municipality is how to spread the message ofwhat the upcoming development has to offer to boost the in-migration, as the need for competence isthe main challenge of Skellefteå today. To be able to fulfil and meet the visions of the transformation,all actors need to work together in becoming the green city of electrification. To create a successfuldevelopment, the overlapping collaboration between the government, industry, academia andcommunity needs to be of high quality and thus the social capital will increase.The thesis explores the effects of a city that undergoes a fast expansion. By studying migrationpatterns through push and pull theory, the thesis investigates how to generate an increasedin-migration in different target groups, such as students and returners. While Skellefteå is dependenton having a positive netto in-migration, the current residents also need to be maintained, thusinterviews and a questionnaire has allowed the thesis to obtain a clear picture of strengths andweaknesses of the development in Skellefteå. The results of the questionnaire and the interviews areanalysed and discussed through an exemplification of the two theories of push and pull and thetheory of social capital.Large industrial expansions of this size shake cities to their core, as the identity and attributes of thecity are questioned as they change. When dealing with a development of this size, the social capital isput to the test and depending on its effectiveness, the outcomes can differ. The city is forced to weighdifferent factors against each other, the benefits of accommodating economic, social andenvironmental factors are measured and prioritised as all are not possible to sustain. As the main goalis to create an increased in-migration to the expanding city, the pull factors available and promotedneed to be questioned; What is Skellefteå in fact offering? The thesis identified six possible groups ofin-migration; counterurbanists, lifestyle migrants, people moving for social ties/the returners, peoplemoving for job opportunities, students and people moving for sustainability reasons. By highlightingone set of pull factors, Skellefteå has the unique opportunity to influence the migration patterns totheir needs and create a sustainable and attractive city for the current and future residents.

Zimbabwe is suffering from an acute shortage of teachers mainly as a result of teacher emigration to South Africa and abroad. The southern migration of Zimbabwean teachers has received little research attention which has mainly focused on the migration of medical personnel. The purpose of this study is to uncover the factors that drive the migration of teachers from Zimbabwe to South Africa and to explain how these factors function within a grounded theory approach to teacher migration. To achieve this, a review of literature and an empirical study of a small sample of migrant Zimbabwean teachers resident in South Africa were undertaken. A constructivist grounded theory design was used. A theoretical sampling method generated a sample group of thirteen participants who were all qualified Zimbabwean teachers who had migrated to South Africa and been in the country for between one and five years. Data generation and collection consisted of two phases: in the first phase the participants were asked to write a life history narrative or provide a verbal narrative of their life history focussing on their migration. In the second phase they participated in individual interviews to clarify or expand on issues raised in the first phase. Three stages of coding were used in the analysis of the data, namely initial, intermediate and advanced coding. This led to the generation of a grounded theory on teacher migration. The grounded theory indicated that Zimbabwean teachers see migration as the best way to attain an ideal status. An ideal status is conceived to be the ideal interplay between the work conditions, standard of living and social esteem which teachers believe befits members of their profession. Depending on various criteria, teachers fall into one of the following status categories: further diminished status, diminished status, ideal status or ideal status surpassed. Migration is a drastic and demanding way to improve one’s status and it is adopted by teachers only after other strategies to this end have been exhausted. Weighed against existing theories of migration, the grounded theory contributes to understanding teacher migration and retention through the innovative use of the core category status. / Educational Studies / D. Ed. (Socio-Education)

Vor dem Hintergrund zukünftiger Sensoren, basierend auf dem piezoresistiven Effekt von einwandigen Kohlenstoffnanoröhren (SWCNT), werden in dieser Arbeit umfangreiche Ergebnisse zum mechanischen Verhalten von Grenzflächen zwischen SWCNTs und edlen Metallen am Beispiel von Pd und Au präsentiert. Im Fokus steht dabei die Synergie von rechnerischen und experimentellen Methoden Molekulardynamik (MD), nanoskalige Tests und Analytik , um (1) mit guter Genauigkeit maximale Kräfte von gezogenen SWCNTs, welche in Metall eingebettet sind, vorauszuberechnen und (2) einen wertvollen Beitrag zum Verständnis der zu Grunde liegenden Fehlermechanismen zu liefern. Es wurde ein MDModell eines in eine einkristalline Matrix eingebetteten SWCNTs mit Randbedingen eines Auszugsversuchs entwickelt. Mit diesem Modell können Kraft-Weg-Beziehungen und Energieverläufe für einen quasistatischen verschiebungsgesteuerten Auszugsversuch errechnet werden. Das Modell liefert kritische Kräfte bei Versagen des Systems. Des Weiteren können mit diesem Modell der Einfluss des SWCNT-Typus, der Einbettungslänge, der Temperatur, von intrinsischen Defekten und Oberflächengruppen (SFGs) auf das Grenzflächenverhalten untersucht werden. Zum Vergleich wurden kritische Kräfte experimentell durch in situ Auszugsversuche in einem Rasterelektronenmikroskop bestimmt. Es wurde eine sehr gute Übereinstimmung von rechnerischen und experimentellen Daten festgestellt. Der vorherrschende Fehler im Experiment ist der SWCNT-Bruch, jedoch wurden auch einige SWCNT-Auszüge beobachtet. Mit Hilfe der MD-Simulationen wurde gefunden, dass die SFGs als kleine Anker in der umgebenden metallischen Matrix wirken und somit die maximalen Kräfte signifikant erhöhen. Diese Grenzflächenverstärkung kann Zugspannungen verursachen, die genügend hoch sind, so dass SWCNT-Bruch initiert wird. Im Gegensatz dazu zeigten Simulationen von Auszugstests mit idealen SWCNTs nur kleine Auszugskräfte, welche meistens unabhängig von der Einbettungslänge des SWCNTs sind. Dieses Verhalten wird mit einer inkommensurablen Konfiguration der Kristallstrukturen an der Grenzfläche von SWCNTs und der einbettenden Edelmetalle interpretiert. Zur Qualifizierung der Existenz von carboxylatischen Oberflächengruppen auf dem genutzten SWCNT-Material wurden analytische Untersuchungen mittels Fluoreszenzmarkierung von Oberflächengruppen durchgeführt. In Übereinstimmung mit Literaturstellen zum gesicherten Nachweis von SFGs, bedingt durch technologische Behandlungen, weisen diese Experimente stark auf das Vorhandensein von carboxylatischen Oberflächengruppen auf dem genutzten SWCNT-Material hin. Demnach kann der dominante SWCNT-Bruch Fehler durch die Grenzflächenverstärkung auf Grund von SFGs erklärt werden. / In the light of future sensors, that are based upon the piezoresistive effect of singlewalled carbon nanotubes (SWCNTs), this work presents comprehensive results of studies on the mechanical behavior of interfaces between SWCNTs and noble metals using the examples of Pd and Au. With this contribution, the focus is on a synergy between computational and experimental approaches involving molecular dynamics (MD) simulations, nanoscale testing, and analytics (1) to predict to a good degree of accuracy maximum forces of pulled SWCNTs embedded in a noble metal matrix and (2) to provide valuable input to understand the underlying mechanisms of failure. A MD model of a SWCNT embedded in a single crystalline matrix with pull-out test boundary conditions was developed. With this model, force-displacement relations and energy evolutions for a quasi-static displacement controlled test can be computed. The model provides critical forces for failure of the system. Furthermore, the influence of SWCNT type, embedding length, temperature, intrinsic defects and surface functional groups (SFGs) on the interface behavior can be studied using this model. For comparison, critical forces were experimentally determined by conducting pull-out tests in situ, inside a scanning electron microscope. A very good agreement of computational and experimental values was discovered. The dominant failure mode in the experiment was a SWCNT rupture, although several pull-out failures were also observed. From MD simulations, it was found that SFGs act as small anchors in the metal matrix and significantly enhance the maximum forces. This interface reinforcement can lead to tensile stresses sufficiently high to initiate SWCNT rupture. In contrast, pull-out test simulations of ideal SWCNTs show only small pull-out forces, which are mostly independent on SWCNT embedding length. This behavior is interpreted with an incommensurate configuration of crystal structures at the interface between SWCNTs and embedding noble metals. To qualify the existence of carboxylic SFGs on the used SWCNT material, an analytical investigation by means of fluorescence labeling of surface species was performed. In agreement with literature reports on the secured verification of SFGs due to necessary technological treatments, these experiments strongly indicate the presence of carboxylic SFGs on the used SWCNT material. Thus, the dominant SWCNT rupture failure is explained with an interface reinforcement by SFGs.

九0年代初，捷克以及其他東、中歐國家成爲世界移民系統的一部份。當時，捷克的開放移民政策及國家的經濟發展吸引全世界移民的目光，其中也包含了中國大陸移民在内。然而，自1995年開始，爲了準備加入歐盟及申根地區，捷克逐漸將移民政策調整成與歐盟目標一致。因而，捷克的政府推行所謂的限制移民政策。因此，隨著開放移民政策的變遷，捷克對移民的拉力減弱。在限制移民政策的狀況之下，在移民過程中，移民國的社會網絡成爲關鍵的移民因素。本文旨在研究探討捷克移民政策的變遷以及中國移民社會網絡的加強對捷克中國移民人數的影響。 / At the beginning of the 1990’s, the Czech Republic, together with other European post-communist countries became a part of the world migration system. Its liberal migration policy and new business opportunities attracted a lot of migrants from different countries, including mainland China, as well. However, in the mid 1990’s, the Czech Republic initiated an effort leading to the membership in the European Union and Shengen Space. Thus, this central European country adopted a far more strict migration policy which corresponded to the EU’s migration rules. As a result, one of the main pull factor of the Czech Republic, i.e., openess to migrants, disappeared with the enlargement of the EU, and moreover migration process involved many restrictions. In this situation social migration networks undertook the role of the main factor which could enable new migrants access the Czech Republic. This thesis describes and analyzes the influence of changing Czech migration policy and subsequent strengthening of social migration ties on the development of Chinese community in the Czech Republic.

Le boulonnage et le câblage à ancrage réparti sont deux techniques de renforcement du terrain couramment utilisées dans l'industrie minière et dans le génie civil. Au fil de cette recherche, on s'intéresse à la réponse de ces éléments sous des sollicitations axiales de traction, en régime statique. Dans ces conditions, l'expérience montre que la rupture se produit le plus fréquemment à l'interface barre-scellement via un processus de décohésion qui commence dès que la force sur la barre atteint une valeur limite. L'objectif est de mieux comprendre le comportement de cette interface, avant et après rupture. Premièrement, on revoit l'état de l'art afin de comprendre le travail effectué et les aspects non maîtrisés à ce jour. Deuxièmement, on décrit des outils analytiques qui permettent de comprendre la réponse d'un boulon ou d'un câble à ancrage réparti soumis à une force de traction. Ensuite, on présente les études expérimentales menées en laboratoire et in situ. Des essais d'arrachement ont été effectués pour déterminer les principaux facteurs qui régissent la réponse de l'interface. Finalement, on analyse les résultats des essais effectués en laboratoire sur les boulons. Après l'obtention des variables nécessaires, on propose un modèle semi-empirique d'interface, qui devra être validé par des essais complémentaires. Cette perspective et d'autres améliorations sont également présentées. / Rockbolting and cablebolting are two ground reinforcement techniques broadly used in civil and mining engineering. This research focuses on the behaviour of fully grouted bolts subjected to tensile axial loads, in static conditions. Under these circumstances, experience throughout the world proves that failure usually takes place at the bolt-grout interface via a decoupling process that starts if the load on the bolt exceeds a critical value. The objective is to gain more insight into the behaviour of this interface, before and after failure. First, the state-of-the-art is presented to understand the existing advances and to identify the lacking aspects. Secondly, analytical tools that help understand the response of a fully grouted bolt subjected to a tensile load are described. Then, the field and laboratory experimental campaigns are exposed. Pull-out tests have been conducted to determine the most influencing parameters on the interface behaviour. Finally, the laboratory results on rockbolts are analyzed. Once the necessary variables are obtained, a semi-empirical interface behaviour model is proposed. The further evaluation of this model and other improvements are suggested as perspectives of evolution.

Ship Manoeuvring Simulators have proved to be powerful tools on analyzing the feasibility of new maritime maneuvers and new port constructions. In order to provide a complete immersive and real environment, such simulators must correctly represent the dynamics of the controlled vessel as well as the actuation of the tugboats, which have been extremely used over the last years due to the increasing complexity on the maritime maneuvers. Although few simulators can correctly model the dynamics of the tugboats, they still represent their actuation through the so-called \"vector tug model\". This is usually the case because it is expensive to run several integrated-simulators in real-time and the simulator centers do not have trained tugboat captains available. The vector tugs are usually represented as simplified external forces actuating on a vessel. The simplicity of such models causes a loss of realism during a maritime simulation due to the fact that neither the forces exerted on a towed vessel nor the tugboat\'s actuation position are accurate. In addition, tugboats\' actuation response time is usually not taken into account under the current vector tug models used on Ship Manoeuvring Simulators. The main objective of this work is to provide an innovative approach for vector tug actuation modeling in such a way that the towing force magnitude and actuation positions are accurate either in push or pull operation modes. The author will expand the static equilibrium model for tugboat force prediction presented in Brandner (1995) and Artyszuk (2014) and combine it along with optimization techniques in order to accurately obtain the tugboats\' actuation either working under the direct maneuver (i.e., tugboat uses solely its propeller power in order to exert force on a towed vessel) or working under the indirect maneuver (i.e., tugboats use the environmental disturbances and the hull drag in order to maximize their actuation force on a towed vessel). The implementation of the new mathematical model provides a new level of reality when vector tugs are used in Ship Manoeuvring Simulators. / Simuladores Navais têm provado ser poderosas ferramentas, tanto na análise de viabilidade de novas manobras portuárias, quanto na construção de novos portos. De modo a conseguir criar um ambiente imersivo e realista, tais simuladores devem conseguir representar corretamente a dinâmica de um navio a ser controlado e a atuação dos rebocadores portuários no mesmo. Embora alguns simuladores consigam modelar corretamente a dinâmica de rebocadores portuários, eles ainda representam tal atuação utilizando o modelo comumente chamado de \"rebocadores vetoriais\". Tal fato normalmente acontece pois é muito caro utilizar diversos simuladores conectados em tempo real. Além disso, em muitas ocasiões, os centros de simulação não têm disponível um comandante de rebocador treinado e capaz de manusear o mesmo de forma correta. Os rebocadores vetoriais normalmente são representados com modelos simplificados de forças externas atuantes em um navio a ser rebocado. A simplicidade de tais modelos gera uma grande perda de realismo durante uma simulação marítima dado que tanto as forças exercidas em um navio a ser rebocado quanto as posições de atuação dos rebocadores são imprecisas. Ainda, os tempos de resposta para a atuação dos rebocadores normalmente não é levado em conta nos modelos de rebocadores vetoriais presentes atualmente. O principal objetivo deste trabalho é prover uma abordagem inovadora para a modelagem da atuação de rebocadores vetoriais, de tal modo que a magnitude da sua força de reboque e seu posicionamento, tanto atuando no modo empurrar quanto no modo puxar, sejam fidedignos a realidade. O autor irá expandir o modelo de equilíbrio estático para predição de forças de atuação de rebocadores apresentado tanto em Brandner (1995) quanto em Artyszuk (2014), e irá introduzir técnicas de otimização de modo a obter a configuração precisa de atuação dos rebocadores tanto na manobra de modo direto quanto na manobra de modo indireto. As implementações propostas elevarão o nível de realidade de Simuladores Navais quando rebocadores vetoriais forem empregados.

[pt] Este trabalho descreve o desenvolvimento completo de um Amplificador de Potência de RF para Transceptores Multibanda. Em sua etapa inicial mostra um apanhado geral da teoria de todos os parâmetros relevantes para a medida de desempenho desses dispositivos, como potência, ganho e parâmetros de não linearidades. Em seguida são expostas as teorias básicas para o entendimento dos mecanismos para extração da máxima potência de um transistor, focando nos transistores de efeito de campo FET, incluindo a caracterização para regimes de alta potência. São apresentados os modos de operação de um amplificador de potência, focando nos chamados modos clássicos, dado que esses modos são convenientes para operação em banda larga. Para a correta operação de qualquer dispositivo que apresente ganho, a análise de estabilidade é apresentada com o procedimento de estabilização de transistores. A partir de todo o apanhado teórico, é desenvolvida uma metodologia de projeto de amplificadores de potência utilizando a ferramenta de simulação computacional Advanced Design System. Então, após toda a modelagem do amplificador, a construção e medidas são realizadas e boa concordância com a simulação foi obtida. / [en] This work describes the full development of a RF Power Amplifier for Multiband Transceivers. In its initial stage shows an overview of the theory of all relevant parameters to measure the performance of these devices, like power, gain and nonlinearity parameters. Then it exposes the basic theories for the understanding of the mechanisms for extracting the maximum power of a transistor, focusing on field effect transistors FET, including characterization for regimes of high power. It presents the modes of operation of a power amplifier, focusing on so-called classical modes, since these modes are suitable for broadband operation. For proper operation of any device that presents gain, the stability analysis is presented with the stabilization procedure of transistors. From all theoretical basis, is developed a design methodology of power amplifiers using the computational simulation tool Advanced Design System. So after all the amp modeling, construction and measurements are performed and good agreement was obtained with the simulation.

Ancoragens são muito utilizadas na estabilização do maciço rochoso pela rapidez e baixo custo, embora sua análise não seja completamente entendida devido à interação de diferentes materiais como rocha, graute e aço. Este documento apresenta os resultados de um estudo realizado em juntas lisas reforçadas com ancoragens. Foram ensaiadas ancoragens com barras de diferentes diâmetros e diferentes orientações em relação ao plano da descontinuidade. Os ensaios realizados para avaliar o comportamento deste tipo de reforço foram o ensaio de arrancamento em tubo duplo e o ensaio de cisalhamento em juntas lisas reforçadas. Os ensaios de arrancamento em tubo duplo demonstraram que a resistência ao arrancamento é dependente da resistência à tração da barra. As deformações internas no sistema foram idealizadas através da obtenção de um comprimento livre hipotético de uma barra livre submetida a tração. Nos ensaios de cisalhamento, avaliou-se a melhora da resistência ao cisalhamento de descontinuidades lisas reforçadas com barras ancoradas. Observaram-se dois picos de carga mobilizada antes da ruptura do sistema no caso de barras perpendiculares ao plano da descontinuidade. Este fato introduz significativa ductilidade ao sistema e é importante do ponto de vista de confiabilidade do sistema. A ruptura das ancoragens se produz devido a uma combinação de efeitos de tração, flexão, e cortantes. Os sistemas reforçados com áreas maiores de aço apresentaram maior ductilidade, e, portanto oferecem maior segurança. Os resultados sugerem que uma vez superado o comprimento mínimo ancorado a ruptura das ancoragens acontecerá por ruptura das barras de aço e não por aderência na interface barra-graute, concluindo-se que a resistência das ancoragens é dependente da resistência de ruptura e da área de aço utilizada. Finalmente, esta pesquisa contribui ao entendimento dos mecanismos de ruína que acontecem num maciço reforçado com ancoragens. / Rock anchors are widely used to stabilize rock masses due to their rapid installation and low cost. Their behavior is not fully understood because of the interaction of different elements such as rock, grout and steel. This document presents the results of both pull-out and shear tests on steel bar reinforced discontinuities. Tests were carried out with different diameters and orientations of bars with respect to the discontinuity plane. Double-pipe pullout tests and smooth-joint anchor-reinforced shear tests were performed. The results of double-pipe pull-out tests were analyzed in terms of both strength and deformations. Internal strains were idealized through a model based on hypothetical length of a free bar. In the smooth-joint anchor-reinforced shear tests, both increase in shear strength and ductility were evaluated. Two load peaks were observed in test with bars perpendicular to the joint plane. Ductility is significantly increased with respect to joints reinforced with inclined bars. This is important for reliability evaluation. The failure of anchors is produced by a combination of tensile, bending, and shear internal forces. The systems reinforced with a greater amount of steel presented more ductile behavior than those less reinforced. The results suggest that since the minimum anchor length is exceeded, the system failure is governed by the rebar failure and not by the adhesion in the rebar-grout interface. From this, it is concluded that the anchor strength is dependent on the strength and cross section area of the rebar. Finally, this research contributes to better understanding of the failure mechanisms of anchor-reinforced rock masses.