Functional polymer foams are considered as a promising field which could potentially produce foams with added value. Specifically, functionally graded foams are materials which are expected to provide better mechanical properties while preserving low density in comparison with regular foams. In this thesis, a preparation process of such foams is designed, examination of prepared structure and comparison of mechanical properties with regular foams is performed. The obtained results are discussed and further research in this field is proposed.

The thesis is aimed at deepening knowledge about the design and use of open-graded asphalt concrete filled with a special cement grout. The first part is the issue discussed theoretically with reference to the real possibility of practical application, a description of the various manufacturers and their patented technologies. The second part of this work is devoted to assess the resistance of this technology to chemical de-icing agents.

Daar bestaan nie duidelike riglyne waarvolgens Afrikaanse leesreekse wat in die grondslagfase gebruik word, geëvalueer kan word nie. Hierdie studie was verkennend van aard met die doel om kriteria te identifiseer wat aangewend kan word om Afrikaanse leesreekse in die grondslagfase te evalueer. Ek het ʼn interpretivistiese metateoretiese paradigma gevolg aangesien ek diepgaande kennis wou verkry oor die onderwerp. Daarvoor het ek gebruik gemaak van ʼn gevallestudie gerig deur Chall (1990) se model van leesontwikkeling. Daarby het ek uit die literatuur ʼn rubriek ontwikkel wat ek aangewend het om die drie leesreekse wat in die studie ondersoek is, se teoretiese onderbou te bepaal. Die literatuur het my ondersteun om vrae te onwikkel wat ek tydens drie fokusgroeponderhoude gevra het. Die fokusgroeponderhoude het by drie Afrikaanse laerskole binne die Tshwane-metropool in verskillende sosio-ekonomiese gebiede plaasgevind. Twaalf onderwysers het deelgeneem (n=12; vroue=12). Die deelnemende onderwysers is doelgerig geselekteer. Om my data te versterk, het ek ook gebruik gemaak van observasienotas verkry van 57 studente in die Vroeë Kinderontwikkeling en Grondslagfaseprogram, aan die Universiteit van Pretoria. Ek het die data gedokumenteer as oudio-opnames, verbatimtranskripsies en veldnotas. Verder het ek tematiese analise gebruik om die verbatimtranskripsies te analiseer, waarvolgens temas en subtemas geïdentifiseer is. Die volgende vier temas is geïdentifiseer: (i) relevansie van leesreekse, (ii) belangrike aspekte by die gebruik van leesreekse, (iii) onderwysers se gebruik van leesreekse tydens leesonderrig, (iv) wetenskaplike ontwikkeling van leesreekse vir grondslagfaseleesonderrig. Ek het inhoudsanalise gebruik om die leesreekse en observasienotas te analiseer. Bevindinge uit die studie dui daarop dat van die deelnemende skole verouderde leesreekse gebruik waarvan die inhoud nie relevant is vir die hedendaagse leerder se leefwêreld nie. Dit blyk ook dat onderwysers moontlik ʼn gebrekkige kennis van leesteorieë het. Verder het ek bevind dat onderwysers hul eie stories skryf om persepsie en fonologiese bewustheid te integreer, aangesien leesreekse nie dié leesvaardighede aanspreek nie. Ek het ook bevind dat onderwysers sekere aspekte belangrik ag by leesreekse, naamlik (i) leesreekse moet binne die leerder se leefwêreld wees, (ii) illustrasies moet die leerder uitnooi om te lees, (iii) progressie moet voorkom, (iv) herhaling van sigwoorde is belangrik, (v) uitgewers moet die volgorde van die aanleer van klanke in gedagte hou tydens die skryf van leesreekse, (vi) uitgewers moet die skriftipe, woordkeuses en korrekte spelling in ag neem, (vii) die behavioristiese benadering word algemeen aangewend tydens leesonderrig en (viii) slegs een leesreeks (leesreeks C) het voldoen aan meeste van die kriteria. <ul> “To learn to read is to light a fire; every syllable that is spelled out is a spark” Victor Hugo</ul> ENGLISH : No definite guidelines exist which can be used to evaluate Afrikaans graded readers in the foundation phase. The main goal of this study was to identify criteria which can be implemented within the foundation phase to evaluate graded readers. I made use of an interpretative metatheoretical paradigm, since I anticipated gaining in-depth knowledge regarding the subject by means of this method. Chall’s Model of Reading Development (1990) was used as a basis for this case study. I developed a rubric, which was used to identify the theoretical aspects related to the three graded readers used in the study. The literature furthermore supported me in the formation of questions which were posed to the focus groups. The focus group meetings took place at three Afrikaans primary schools within the Tshwane Metropole in different socio-economic areas. Twelve teachers participated (n=12; women=12). The participating teachers were selected using stratified sampling. In order to enhance the validity of the data, I made use of observation notes, obtained from 57 students in the Early Childhood Development and Foundation Phase programme at the University of Pretoria. The data was documented as audio-recordings, transcriptions and field notes. Thematic analysis was employed to analyse the transcriptions, whereafter themes and sub-themes were identified. The following four themes were identified: (i) The relevance of graded readers; (ii) important aspects related to the use of graded readers; (iii) the use of graded readers by teachers during reading instruction; and (iv) scientific development of graded readers for use during foundation phase reading instruction. The graded readers and observation notes were analysed by means of content analysis. The findings indicated that participating schools used graded readers of which the content is not relevant for the learner of today. It would also seem that teachers possibly lack knowledge of reading theories. In addition, teachers are writing their own stories in order to integrate perception and phonological awareness, since graded readers do not incorporate it. The findings further illuminated the fact that teachers value certain aspects in graded readers as important, namely: (i) Graded readers must fall within the context of the child’s world; (ii) illustrations must invite the learner to read, (iii) there must be progression, (iv) repetition of sight words are vital, (v) when publishers write graded readers, the range pertaining to how sounds are learned must be borne in mind, (vi) publishers must pay attention to the font type, word selection and spelling in readers, (viii) the behaviouristic approach is frequently used during reading instruction, and (viii) only one graded reader (graded reader C) met most of the set criteria. <ul>“To learn to read is to light a fire; every syllable that is spelled out is a spark” Victor Hugo</ul> / Dissertation (MEd)--University of Pretoria, 2012. / Educational Psychology / unrestricted

No description available.

In this investigation, the fabrication of functionally graded structures of SS316L to Ni-based alloys were studied, using the novel technique 3D plasma metal deposition. Two Ni-based alloys were used, a heat resistance alloy Ni80-20 and the solid-solution strengthened Ni625. Different configurations were analyzed, for the Ni80-20 a hard transition and a smooth transition with a region of 50% SS316L/50% Ni80-20. Regarding the structures with Ni625, a smooth transition configuration and variations in the heat input were applied. The effect of the process parameters on the geometry of the structures and the microstructures was studied. Microstructure examinations were carried out using optical and scanning electron microscopy. In addition, microhardness analysis were made on the interfaces. In general, the smooth transition of both systems showed a gradual change in the properties. The microstructural results for the SS316L (both systems) showed an austenite matrix with δ-phase. For the mixed zone and the Ni80-20 an austenite (γ) matrix with some M7C3 precipitates and laves phase were recognized. The as-built Ni625 microstructure was composed of an austenite (γ) matrix with secondary phases laves and δ-Ni3Nb, and precipitates M7C3. The mixed zone exhibited the same phases but with changes in the morphology.

El propósito del presente trabajo es desarrollar un modelo matemático que permita el análisis de estabilidad de una viga compuesta de materiales funcionalmente graduados sometida a una carga de compresión axial. La finalidad es analizar el comportamiento de una viga heterogénea y calcular las cargas y los modos de pandeo. En el desarrollo de la investigación se describe vectorialmente el campo de desplazamiento de la viga para obtener las ecuaciones de gobierno de la estructura; de este modo, mediante principios energéticos, se pueda desarrollar el modelo de elementos finitos y buscar una solución vectorial propia. El modelo matemático se divide en dos partes: formulación simbólica y modelo numérico computacional. En el modelo matemático, los materiales funcionalmente graduados afectan el módulo de elasticidad debido a la particularidad del material; y la energía potencial total es afectada por dos estados: estado fundamental (deformación de membrana o de pre-pandeo) y estado incremental (estado de perturbación arbitraria de equilibrio). Los resultados obtenidos fueron verificados con ejercicios benchmarking encontrados en la literatura, para corroborar la eficacia del modelo planteado; validados con informes de pruebas de laboratorio, para revisar la precisión; y estudiados paramétricamente, para analizar la influencia de las variables. / The purpose of the present work is to develop a mathematical model that allows the stability analysis of a beam composed of functionally graded materials subjected to an axial compressive load. The objective is to analyze the behavior of a heterogeneous beam and calculate the buckling loads and modes. In the development of the investigation, the field of displacement of the beam is described in vectors to obtain the governing equations of the structure. In this way, by energetic principles, the finite element model can be developed, and the solution can be found by eigenvalue and eigenvector exercise. The mathematical model is divided in two parts: symbolic formulation and computational numerical model. In the model, the functionally graded materials affect the modulus of elasticity due to the particularity of the material; and the total potential energy is affected by two states: fundamental state (membrane deformation or pre-buckling) and incremental state (arbitrary perturbation of the equilibrium). The results obtained were verified with benchmarking exercises found in literature, to corroborate the effectiveness of the proposed model; validated with lab test-reports, to check its accuracy; and studied parametrically, to analyze the influence of the variables. / Tesis

No description available.

Granular materials are widely used as unbound layers within the infrastructure system playing a significant role on performance and maintenance. However, fields like pavement and railway engineering still heavily rely on empirically-based models owing to the complex behaviour of these materials, which partly stems from their discrete nature. In this sense, the discrete element method (DEM) presents a numerical alternative to study the behaviour of discrete systems with explicit consideration of the processes at particulate level governing the macroscopic response.  This thesis aims at providing micromechanical insight into the effect of different particle sizes on the load-bearing structure of granular materials and its influence on the resilient modulus and permanent deformation response, both of which are greatly influenced by the stress level. In order to accomplish this, binary mixtures of elastic spheres under axisymmetric stress are studied using DEM as the simplest expression for gap-graded materials, which in turn also can be seen as a simplification of more complex mixtures. First, the effect of the fines content on the force transmission at contact level was studied. Results were used to define a soil fabric classification system where the roles of the coarse and fine fractions were defined and quantified in terms of force transmission. A behavioural correspondence between numerical mixtures and granular materials was established, where the mixtures were able to reproduce some of the most significant features regarding the resilient modulus and permanent strain dependency on stress level for granular materials. A good correlation between soil fabric and performance was also found. Generally, higher resilient modulus and lower deformation values were observed for interactive fabrics, whereas the opposite held for instable fabrics. Mixtures of elastic spheres are far from granular materials, where numerous additional factors should be considered. Nevertheless, it is the author’s belief that this work provides insight into the soil fabric structure and its effect on the macroscopic response of granular materials. / Grus i form av krossat bergmaterial används i stor utsträckning som obundna bär- och förstärkningslager inom tranportinfrastrukturen och spelar där en viktig roll för verkningsätt, drift och underhåll. Det finns emellertid begränsad kunskap om de fundamentala mekanismerna på partikelnivå (d.v.s. enskilda gruskorn), mekanismer som styr det makromekaniska verkningssättet. Områden såsom väg- och järnvägsbyggnad bygger fortfarande väsentligen på empiriskta baserade modeller p.g.a. dessa materials komplexa uppträdande under belastning. Denna komplexitet beror delvis på den diskreta naturen hos problemet vilket innebär att traditionell matematisk modellering som vore materialen homogena och kontinuerliga, blir inadekvat. Mot denna bakgrund utgör den s.k. diskreta elementmetoden (DEM) ett numeriskt alternativ för att studera verkningssätt hos diskreta system där man explicit beaktar mekanismerna på partikelnivå. Denna avhandling, som baseras på tre vetenskapliga bidrag, syftar till att ge mikromekaniska insikter vad gäller effekten av olika partikelstorlekar på bärförmågan hos grusmateral och dess inverkan på styvhet och motstånd mot permanenta deformationer. Båda dessa parametrar påverkas kraftigt av spänningsnivån och kan studeras genom triaxialförsök. För att undersöka detta studerades med hjälp av DEM binära blandningar av elastiska kulor – den enklaste modellen av grusmaterial med språng i fördelningskurvan – som utsattes för axialsymmetrisk belastning. Denna modell kan i sin tur ses som en förenkling av mer komplexa blandningar. Inledningsvis studerades effekten av finpartikelinnehållet på partikelkontakternas kraftöverföring. Resultaten användes för att klassificera olika typer av skelettstrukturer i grusmaterialet där den finare och den grövre fraktionens roller kvantifierades med utgångspunkt från kraftöverföringen i stället för från det makromekaniska verkningssättet. Resultaten visade en korrelation vad gäller verkningssättet mellan numeriska blandningar och grusmaterial, där de numeriska blandningarna kunde reproducera några av grusmaterials viktigaste kännetecken vad gäller spänningsberoendet för styvheten vid avlastning och motståndet mot permanent deformation. Vidare visades att styvheten kunde bestämmas ur första belastningscykeln vilket underlättar att övervinna de begränsningar avseende beräkningstid som annars förknippas med DEM. God överensstämmelse mellan grusmaterialets skelettstruktur och verkningssätt kunde också observeras. Generellt observerades högre styvhet och mindre permanenta deformationer för interaktiva skelettstrukturer medan det motsatta gällde för instabila strukturer. Numeriska blandningar av elastiska kulor är långt från verkliga grusmaterial, för vilka ett stort antal ytterligare faktorer måste beaktas. Icke desto mindre är det författarens övertygelse att detta arbete ger insikter i grusmaterialets skelettstruktur och dess effekter på det makromekaniska verkningssättet hos grusmaterial. / <p>QC 20161116</p>

Syfte: Att ta reda på hur relationen ser ut för B- respektive T-lymfocyter i biopsier av rotfyllda tänder med apikal parodontit med bedömd låggradig inflammation. Denna studie kommer även att analysera hur den inflammatoriska bilden ser ut i förhållande till beskrivna symtom i dessa biopsier. Material &amp; metod: En pilotstudie utfördes på 10 biopsier från rotfyllda tänder med apikal parodontit med bedömd låggradig inflammation enligt Danesh et al 2019 klassificeringssystem. Biopsierna hämtades från Malmö universitets biobank. Immunhistokemisk infärgning av antigenerna CD20+ och CD3+ utfördes samt analyserades med hjälp av digitalmikroskop. Jämförelsen av symtomen från remisserna skedde efter att de histologiska resultaten sammanställts. Resultat: Det fanns fler T-lymfocyter än B-lymfocyter i 6 stycken av biopsierna. I de resterande 4 biopsierna var de lika många. I remisserna hade symtombilden inte angetts föralla biopsier. Slutsats: Enligt vår pilotstudie ser vi tendenser till att T-lymfocyter är fler än B-lymfocyter eller att de är lika många. Inga slutsatser kunde dras gällande symtombilden. Ett större material från olika remittenter krävs för definitiva slutsatser. En vidare infärgning av CD4+ samt CD8+ skulle vara intressant. / Aim: To investigate the relation between B- and T- lymphocytes in biopsies of root-filled teeth with apical periodontitis with assessed low-grade inflammation. This study will also analyse what the inflammation looks like in relation to the symptoms described in these biopsies.  Study design: A pilot study was performed on 10 biopsies of root-filled teeth with apical periodontitis with assessed low-grade inflammation according to the classification system of Danesh et al 2019. The biopsies were collected from Malmö University's biobank. An immunohistochemical staining of antigens CD20+ and CD3+ were performed and analysed by a digital microscope. A comparison of the symptoms from the referrals were performed once the histological results were compiled. Results: There were more T-lymphocytes than B-lymphocytes in 6 of the biopsies. In the remaining 4 biopsies there were an equal amount of B- and T-lymphocytes. The symptoms were not stated for all biopsies in the referrals.  Conclusion: According to our pilot study, we see tendencies that T lymphocytes are more than B lymphocytes or that they are equal. No conclusions could be drawn regarding the symptom picture. Larger material from different referrers is required for definitive conclusions. A further staining of CD4 + and CD8 + would be interesting.

Traditional methods for increasing the energy absorption of a structure involve using a stronger material or increasing the volume of the structure, resulting in a higher cost or additional weight. Additive manufacturing (AM) can be used to maximize the energy absorption of materials with the ability to create complex geometries such as cellular structures. Previous work has shown that the energy absorption of additively manufactured parts can be improved through functionally graded cellular structures; however, this strategy has not been applied to ultra-high strength steel materials. This work characterizes the effect of multiple functional-grading strategies (e.g. uniform, rod-graded, size-graded) on the energy absorption to weight ratio of laser powder bed fusion (L-PBF) produced M300 maraging steel lattice structures. Each structure is designed with the same average relative density to analyze the structures on an equal mass basis, to evaluate manufacturability, mechanical response, and compare experimental results with numerical simulation.