An important component in understanding the laser sintering process is knowledge of the thermal properties of the processed material. Thermal conductivity measurements of pure polyamide 12 and polyamide11 with multi-wall carbon nanotubes were conducted based on transient plane source technology using a Hot Disk® TPS500 conductivity measurement device. Polyamide powder was packed to three different densities in nitrogen at room temperature. Thermal diffusivity and conductivity were measured from 40°C to 170°C for both fresh powder and previously heated (“recycled”) powder. The fresh powder tests revealed that thermal conductivity increased linearly with temperature whereas for previously heated powder, more constant and higher thermal conductivity was observed as it formed a powder cake. Tests were also performed on fully dense polyamide 12 to establish a baseline. Polyamide 12 powder had a room-temperature thermal conductivity of approximately 0.1 W/mK which increased with temperature, whereas the bulk laser sintered polyamide 12 room-temperature value was 0.26 W/mK and generally decreased with increasing temperature. / text

One of the most common building materials is concrete and it has been for a long time. To overcome its low tensile capacity concrete structures are normally reinforced with steel rebars. The use of FRP (Fibers Reinforced Polymers) bars in concrete structures has emerged as an alternative to conventional steel reinforcement, due to the corrosion of steel in aggressive environments. FRP has been used as internal reinforcement for more than 30 years, bridges and parking garages are examples of structures in harsh environments where FRP is a good replacement for steel reinforcement. This due to the higher strength of FRP compared to steel and non-corrosive properties, however FRP as internal reinforcement is not commonly used in Scandinavia. This work has been divided into four parts, a Literature survey, a Literature study on durability, structural behaviour in the serviceability limit state and a FE analysis of previously carried out laboratory tests. In the literature survey the material FPR is described with its components, manufacturing process, history and various applications. A literature study was done to determent the long-term durability of GFRP by accelerated laboratory tests for durability, then compared to field tests on durability of GFRP rebars. The accuracy of FRP design international standards has been evaluated in terms of serviceability limit stat, such as ACI 440.1R-15, ISIS and a variant of Eurocode 2 (EC2). The design models for deflection available for these standards were compared to a database of experimental studies collected by the author. The stiffness of structures reinforced with FRP is such an important parameter so a non-linear calculation using ATENA software was conducted. Results were compared to laboratory tests performed at Denmark Technical University (DTU). In several accelerated laboratory experiments where bare FRP bars were exposed to different harsh environments the degradation of strength was significant, where an alkaline solution at elevated temperature was the harshest environment for the GFRP bars. When GFRP rebars are embedded in concrete the degradation was significantly lower (around 40 percentage points), the concrete protects the GFRP rebars considerably. The largest rate of degradation on GFRP rebars is in the initial state, in comparison to steel which starts to corrode when carbonation and/or chloride penetration critical levels reaches the reinforcement. In field studies there were small signs of degradation of the GFRP rebars, mainly in tropical climates. De-icing salts have a limited effect on the degradation. Laboratory experiments are very conservative with unrealistic harsh environments compared to the natural harsh environments. Therefore, after 20 years of service in harsh environment there were no or small signs of degradation on the GFRP rebars which indicates the validity of GFRP. All three standards evaluated had a large spread on the predicted deflection compared to the experiments, with ACI 440.1R-15 as the most conservative standard with a mean value of the deflection ratio at 0.81. The mean value of the deflection ratio when using ISIS was 0.87, slightly less conservative but with the same spread as ACI 440.1R-15. The calculation using a variant of EC2 had the most spread of results, but with a mean value of the deflection ratio at 0.93, this excluding 11 beams that had an unrealistic prediction due to the wrong prediction of the crack moment. The FEM model created had a similar stiffness as compared to the experiment from DTU, which indicates that the use of Atena was accurate for calculating the deflection of the beams. Although the ultimate load was not well predicted, probably due to the failure mode crushing of concrete in the compressive zone. Despite this, there are many structural parts where FRP could be beneficial, for example in splash zones, in edge beams and slabs etc. This could bring down the costs for maintenance and also prolong the life span of the structure.

This study has taken place in Mullsjö at Kongsberg Automotive (KA). The purpose of the study was to evaluate how to construct an easy mountable gearknob to the lowest cost based on design and functionality by using the techniques of concept generation and sifting. The knob is intended to be integrated in a Shift-ByWire shifter and generate prototypes through SLS. Researchers followed a concept study methodology following an abductive approach, to generate an appropriate mechanical design for the gearknob. Concepts were formed by a brainstorming process, followed by weighing criteria for the knob and were finalised by evaluating the formed concepts using a Pughs Matrix constructed by the researches. Relevant literature of mechanical designs processes was reviewed to develop the theoretical framework. In addition, data was collected from Kongsberg´s computer system and unstructured interviews with employees within certain specific areas to gain additional understanding. In cooperation with supervisors, pros and cons analysis of cost, functionality and mounting capability were used to enable the researchers to draw recommendations for mechanical designs meeting the requirements of specification. The study resulted in several findings in relation to each research question. In general, a gear knob has been constructed using SLS that can be both used for mounting and demounting purposes. In addition, this construction met the specification of requirements by KA. The Printed Circuit Board (PCB) were constructed using the geometrics in the inherent components of the knob. The study further resulted in a leather gaiter that were constructed as a link between the dashboard and the knob. Results from this study imply that more screws would be used for mounting different components in the prototype phase, which will impact the view on criteria for forthcoming knobs and their mounting methods. In addition, data collection have also shown that snaps in chromium details easily break, which can also further question the use of chromium snaps for dismantling purposes. Finalised recommendations for the gearknob met the requirements of specification since researchers constructed the most simple mounting on the current surface design. Researchers conclude that these concepts are applicable and could be presented in a following prototype phase. However, if the knob is to be produced, researchers do not have enough support regarding the liquid injection moulding, which requires to be further considered. Materials will require the design constructed in this study to be modified. / Arbetet har skett i Mullsjö på Kongsberg Automotive (KA). Syftet med studien var att konstruera en lättmonterad växelspaksknopp till lägsta kostnad utifrån design och funktionalitet. Detta baserat på konceptgenerering och sållningstekniker. Knoppen kommer att integreras i en Shift-by-Wire växelspak och tillverkas i SLS prototyper. Arbetet är en konceptstudie som har följt en abduktiv ansats. Tidigare konstruktionslösningar har studerats för att få kunskap om hur en knopp utformas. Koncepten har genererats via brainstorming och har följts upp av parvis viktning. Koncepten har sedan sållats med hjälp av Pughs matris. Relevant litteratur inom produktutvecklingsprocesser samt intervjuer med anställda har gett grunden till det teoretiska ramverket. Handledare har givit sin input under hela arbetsprocessen för att hjälpa studenterna att välja rätt koncept utifrån monterbarhet, funktionalitet och pris. Studien har svarat på de tre frågeställningarna som utformats. En knopp i SLS har konstruerats utifrån enkel montering och demontering som möter företagets kravspecifikation. Kretskorten inuti knoppen har formats utefter de ingående delarnas geometrier. Vidare har övergången mellan knopp och centerkonsol resulterat i en läderdamask. Studiens resultat kan få konsekvenser i att mer skruv kommer att användas i prototypfasen vid framtida projekt. Detta kan komma att ändra synen på hur viktigt monterbarheten kan vara i kommande knoppar. Informationsinsamling har också visat att snäppen i kromdetaljer lätt går av och detta kan ifrågasätta användningen av dessa. Vid materialval rekommenderas det att se över konstruktionslösningarna då de uppnådda egenskaperna kan avvika. Arbetet har utformat konstruktionen så att det fungerar bra för SLS prototyper men studenterna kan inte garantera att dessa fungerar om komponenterna ska formsprutas.

A year long learning strategy course was designed and embedded in a Year 8 science curriculum. The Science Learning Strategy (SLS) program aimed to improve student ability to apply learning strategies to science, increase student achievement in science and to augment students' feelings of control over their science learning, so that their perceived competence was maximised. Achievement of these aims was monitored by collecting perceptions from students, parents and the teacher/researcher via a range of devices including questionnaires, work samples and interviews. The program overall was regarded as successfully achieving all three aims by 22 of the 24 students. The other two students found that only some aspects of the course were helpful, and felt they had learned little from the program. Thirty three percent of parents attributed positive changes in their daughter's study and learning strategies to participation in the SLS program (the remainder were unsure, or did not know of any changes). In relation to perception of academic performance, 38% of the parents interviewed believed that the SLS had a positive effect on their daughter's achievement in science. Several of these parents reported very positive effects on performance. The remainder were not sure or did not know if there had been any positive effects. No parents mentioned that the SLS program had caused a drop in science performance. The proportion of parents believing their daughters blamed disappointing results on factors they couldn't control dropped from 45% at the start of the year, to 22% by the end of the SLS program. After the intervention, 33% of parents reported that their daughters had come to believe that their science performance was affected by many factors, most of which they could control. / The teacher/researcher observed strong improvement in student ability to apply learning strategies to science as a result of participation in the program. Students were also observed by the teacher/researcher, to have been assisted by the intervention to realise that their science performance was governed not only by their natural ability, but also by factors such as studying behaviour and affective influences. In particular, the program appeared to the teacher/researcher to have helped students realise that they had control over their use of learning strategies, and that this control could influence their science performance. However, the teacher/researcher found that no statistically significant changes in science achievement resulted from student participation in the SLS course. The other objective of the research was to investigate the extent to which learning strategy education was valued and implemented by Western Australian science teachers. The 218 returned surveys revealed that most respondents recognised the need to teach these skills during science lessons. Seventy six percent of respondents considered the delivery of learning strategy instruction in the lower school science classroom to be as important, or more important, than teaching subject processes and content. Sixty seven percent recognised that improving study strategies can improve confidence and/or motivation. / Many teachers, however, had not been able to convert these views into consistent classroom practice. A moderate proportion of teachers reported teaching a variety of learning strategies; 74% of the respondents agreed that learning strategy instruction could improve performance in science. Only one teacher specifically mentioned incorporating the teaching of learning strategies with instruction in science process and content. As a future outcome of this project, the teacher/researcher will encourage other teachers to embed learning strategy instruction within the science curriculum, so that their students come to feel more in control of their learning and can learn more effectively.

A phased array antenna differs from a conventional antenna, such as a dish antenna, in that it coherently adds radiation from multiple radiating elements instead of mechanical positioning to direct RF energy. When transmitting and receiving information from a source while in motion, a phased array antenna can continuously adjust its signal to focus on the source. New antenna designs focus on integrating phased array antennas into the structure of the antenna platform, as advanced antenna platforms require the antenna to take up less and less real estate. With further development of phased array antennas, new designs become increasingly complex. The manufacturing techniques to facilitate the integration of complex antenna designs into the structure of an antenna platform must be developed, as traditional manufacturing operations, such as injection molding, machining and bulk deformation processes, are not well suited to create the small details and complex three dimensional lattice designs of the antennas. Innovative solutions need to be developed that allow the manufacture of complex antennas, thereby enabling testing to be performed on actual devices. The results from testing physical models can buttress analytical models and lead to better antenna designs. This work developed and studied suitable methods for manufacturing three-dimensional, structurally-integrated antennas.

In an effort to gain a more comprehensive and complete understanding of the thermal behaviors occurring during the selective laser sintering process, external temperature measurements were taken during the build process. To accomplish this, an infrared camera was aimed directly through a viewport on the front of the sinterstation. The temperature was monitored during the heating process which showed slightly non-uniform heating of the part bed surface. Temperatures were also recorded while the laser was sintering each layer and the subsequent cooling of the entire machine following the build. By directly capturing infrared images of the part bed’s surface, it is clearer how the temperature gradients behave and the impact such variables have on part build efficiency. / text

Thirty million tons of coal fly ash are produced each year in South Africa of which approximately 5% is utilised beneficially. With the growing concern about pollution and increasing landfill costs, the study of the utilisation and application of coal fly ash has increased worldwide. The morphology and particle size of fly ash make it suitable for application as filler in polymers, but its application is hindered by the lack of compatibility between the inorganic surface of the ash and the organic matrix of the polymer. Another concern is the agglomeration between fly ash particles. For this reasons, surface treatment is usually performed on mineral fillers to enhance workability and compatibility between the polymer and filler. This study involved the surface modification of South African coal fly ash with an anionic surfactant, sodium lauryl sulphate (SLS), under different treatment conditions. Surface and physical properties of the untreated and treated fly ash were studied systematically by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) in order to determine the extent of interaction between the SLS and the fly ash surface. Other analytical techniques applied include Thermogravimetric analysis (TGA-FTIR), Particle size distribution, X-ray diffraction (XRD) and X-ray fluorescence spectroscopy (XRF), Raman spectroscopy and Fourier Transform Infrared spectroscopy FTIR). Although the overall chemical composition of the SLS modified coal fly ash investigated in this study was not altered extensively, significant changes could be observed in its physical properties. The hydrophilic surface of untreated fly ash was rendered hydrophobic after SLS treatment. SEM results indicated a decrease in agglomeration between fly ash spheres upon surfactant treatment, while results obtained from TEM have shown agglomerates on the surface of most of the fly ash spheres. There is a distinct difference between the morphology of agglomerates on the untreated and SLS modified fly ash, and also between samples treated under different conditions. Not all SLS modified fly ash particles were covered with agglomerates to the same degree. Results obtained from FTIR and TGA-FTIR studies were promising in the sense that hydrocarbon fractions could be observed in the TGA-FTIR decomposition products. The possibility of interactions between fly ash and SLS could be deduced from the FTIR results of the solid samples, due to a small shift in peak positions of the S-O stretch vibration, which may be indicative of electrostatic interactions rather than bonding interactions between SLS and fly ash. The presence of SLS could not be confirmed by Raman spectroscopy, but rendered information about the spatial distribution of the various phases in the fly ash. Feasibility tests were performed on the application of fly ash samples as filler in PVC. These results indicate that SLS treated fly ash can successfully replace CaCO3 as filler in PVC under conditions of low filler loadings / Dissertation (MSc)--University of Pretoria, 2013. / Chemistry / unrestricted

For a launch vehicle, the Navigation System is responsible for determining the vehicle state and providing state and state derived information for Guidance and Controls. The accuracy required of the Navigation System by the vehicle is dependent upon the vehicle, vehicle mission, and other consideration, such as impact foot print. NASAs Ares I launch vehicle and SLS are examples of launch vehicles with are/where to employ inertial navigation systems. For an inertial navigation system, the navigation system accuracy is defined by the inertial instrument errors to a degree determined by the method of estimating the initial navigation state. Utilization of GPS aiding greatly reduces the accuracy required in inertial hardware to meet the same accuracy at orbit insertion. For a launch vehicle with lunar bound payload, the navigation accuracy can have large implications on propellant required to correct for state errors during trans-lunar injection.

In this work approaches for new detection system development for an Analytical Ultracentrifuge (AUC) were explored. Unlike its counterpart in chromatography fractionation techniques, the use of a Multidetection system for AUC has not yet been implemented to full extent despite its potential benefit. In this study we tried to couple existing fundamental spectroscopic and scattering techniques that are used in day to day science as tool for extracting analyte information. Trials were performed for adapting Raman, Light scattering and UV/Vis (with possibility to work with the whole range of wavelengths) to AUC. Conclusions were drawn for Raman and Light scattering to be a possible detection system for AUC, while the development for a fast fiber optics based multiwavelength detector was completed. The multiwavelength detector demonstrated the capability of data generation matching the literature and reference measurement data and faster data collection than that of the commercial instrument.<br><br> It became obvious that with the generation of data in 3-D space in the UV/Vis detection system, the user can select the wavelength for the evaluation of experimental results as the data set contains the whole range of information from UV/Vis wavelength. The detector showed the data generation with much faster speed unlike the commercial instruments. The advantage of fast data generation was exemplified with the evaluation of data for a mixture of three colloids. These data were in conformity with measurement results from normal radial experiments and without significant diffusion broadening. Thus conclusions were drawn that with our designed Multiwavelength detector, meaningful data in 3-D space can be collected with much faster speed of data generation. / In der vorliegenden Arbeit wurde die Entwicklung neuer Detektoren für die Analytische Ultrazentrifugation (AUZ) untersucht und vorangetrieben. Im Gegensatz zu chromatgraphischen. Fraktionierungsmethoden werden Multidetektionssysteme bis heute nicht in der AUZ eingesetzt. Hier wird die Möglichkeit geprüft, bekannte spektroskopische sowie Streumethoden simultan zur Probenanalyse in der AUZ einzusetzen mit dem Ziel, simultan komplimentäre Informationen über die Probe zu erhalten. So wurde versucht, Raman- und UV/VIS-Spektroskopie (letztere mit der Möglichkeit, das gesamte Wellenlängenspektrum auszunutzen) und statische Lichtstreuung zu kombinieren, um das Analytverhalten während des Ultrazentrifugationsexperimentes zu untersuchen. Es wurden zum einen die Ramanspektroskopie als Detektionssystem für chemische Funktionalität in der AUZ geprüft und zum anderen gezeigt, daß die statische Kleinwinkel Lichtstreuung als direkter Molmassendetektor für den Einsatz in der AUZ geeignet erscheint. Zum anderen wurde die Entwicklung eines Multi-Wellenlängen-UV/VIS-Detektors abgeschlossen, um seine Eignung für den Einsatz in der AUZ und die damit verbundene Möglichkeiten der schnelleren und umfassenderen Datenerzeugung gegenüber kommerziellen Geräten zu zeigen. Dieser Multiwellendetektor liefert anstelle eines Absorptionswertes für jede radiale Position in der Messzelle direkt ein ganzes UV-Vis Spektrum und erzeugt eine zusaetzliche Dimension der Messdaten, was die Möglichkeiten der Analyse von komplexen Systemen mit multiplen Chromophoren, Teilchengrößenbestimmung über Wellenlängenabhängigkeit der Trübung oder auch der Datenmittelung enorm vergrößert. Desweiteren erlaubt der Detektor die Anwendung von Geschwindigkeitsprofilen zur Analyse extrem polydisperser Systeme. Die Entwicklung des Detektors beruht auf einem auf Linsen basierenden System mit modularem Aufbau. Dabei war die sorgfältige Ausrichtung des optischen Systems ein essentieller Punkt, um seine Eignung zu überprüfen zu können. An einer Mischung von drei Kolloiden, Halbleiternanopartikeln sowie Proteinen und deren Mischungen ist es hier gelungen, die erfolgreiche Entwicklung des UV/VIS-Detektors zu demonstrieren: Die Daten konnten schneller und mit wesentlich mehr Informationsgehalt, als auf allen kommerziellen Geräten generiert werden. Die Sedimentationskoeffizientenverteilungen stimmen dabei mit denen aus herkömmlichen Sedimentationsgeschwindigkeitsexperimenten überein, unterliegen jedoch nicht einer signifikanten diffusionsbedingten Verbreiterung. Es ist in dieser Arbeit somit gelungen, zum einen die Lichtstreuung als aussichtsreiche Methode für ein Detektorsystem in der AUZ aufzuzeigen, und zum anderen einen Multi-Wellenlängen-UV/VIS-Detektor zu entwickeln, der eine Datenerzeugung von bislang noch nicht erreichter Schnelligkeit im dreidimensionalen Raum ermöglicht.

This thesis is focused on synthesis and polymerization of caprolactone and its derivatives by living ring opening polymerization (LROP), Self-assembly in aqueous solutions produced nanoaggregates comprised of amphiphilic block copolymers or telechelic polymers with incorporated boron compounds (phenyl boronic acids and boron clusters). Incorporation of boron compounds was facilitated either by covalent or non-covalent bonding. Obtained complex nanoparticle structures manifested stimuli-responsive behaviour and were investigated under varying conditions by combination of light scattering, fluorescence spectroscopy and electron microscopy. The obtained results on solution behaviour of polymers in combination with added value of boron compounds, yield general aspects of nano aggregate morphology, responsive character tuning and practical aspects of synthesis and self-assembly overcame in the preparation process. The publications wrote during this thesis are therefore adding valuable information to researchers engaged in biomedical utilization of such nano assemblies.