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By taking human perception into account in computer graphics, time and processing power may be utilised more efficiently when modelling and rendering scenes. Exploring possibilities for reducing the complexity of forest scenes is particularly interesting because of the geometric complexity of trees, the effects of which are compounded by dense, large-scale forests. Most studies of rendering simplifications for forests concern level-of-detail methods, simplifying scenes in areas where simplifications are less perceptible to the viewer. The present study instead approaches the topic by considering that humans, to certain extents, are insensitive to the exact composition of objects in aggregates. In forest scenes that use a variety of geometrically different trees, this can be utilised to favour the geometrically simpler tree. A perceptual study was conducted to explore how perceptive viewers are to the ratio between trees, in forest scenes that feature two geometrically different tree models. Specifically, the tree models varied in leaf and branch density. The impacts of forest density, layout and camera angle were studied. Overall, it was found that density and layout had significant effects on thresholds measured for participants’ perceptiveness of ratio, while camera angle had little impact. The results indicate that the ratio between two different tree models can be skewed considerably in favour of the geometrically simpler model, without participants detecting changes. These findings provide some guidelines for reducing polygon count in forest scenes while preserving appearance. Motivated by these findings, the educational part of this study considers the role of perceptual topics in computer graphics courses. Specifically, the study focuses on the inclusion of perceptual topics in introductory computer graphics courses at Swedish universities, as well as the attitudes of computer graphics educators toward teaching perception. 22 course syllabuses at 12 Swedish universities were collected and analysed. Interviews were conducted with three computer graphics educators, while 13 educators responded to an online survey. The results present a diverse set of approaches and attitudes toward perception among educators, signifying that the role of perception in computer graphics education is uncertain. Perceptual topics were included in about half of the surveyed courses, with teaching approaches ranging from marginally including perceptual topics, to fully dedicated lectures, though perception was rarely mentioned in the intended learning outcomes of courses. Overall, approaches seemed influenced mainly by the background of the student group, educators’ own biases and experiences, as well as challenges posed by needing to address foundational skills such as programming. By investigating perceptual thresholds through a psychophysical experiment and exploring pedagogical practices in relation to perceptual topics in computer graphics courses, this study links empirical research with pedagogy, highlighting the role of perception in computer graphics from different perspectives. / Genom att ta hänsyn till mänsklig perception i datorgrafik kan tid och processorkraft utnyttjas mer effektivt vid modellering och rendering av scener. Att utforska möjligheter för att minska komplexiteten i skogsscener är särskilt intressant, på grund av den geometriska komplexiteten hos träd, vars effekt förvärras av täta, storskaliga skogar. De flesta studier av renderingsförenklingar för skogar rör detaljnivåmetoder (eng: level-of-detail), förenklingar av scener i områden där ändringar är mindre märkbara för betraktaren. Denna studie närmar sig istället ämnet genom att ta hänsyn till att människor, i viss utsträckning, är okänsliga för den exakta sammansättningen av objekt i aggregat. I skogsscener som använder en mängd geometriskt olika träd kan detta utnyttjas för att gynna det geometriskt enklare trädet. En perceptuell studie genomfördes för att undersöka hur medvetna personer är om förhållandet mellan träd i virtuella skogsscener betraktat ovanifrån, där två geometriskt olika trädmodeller använts. Specifikt studerades effekterna av skogstäthet, trädplacering och kameravinkel på uppfattningsförmåga. Det visade sig att täthet och placering hade betydande effekter på tröskelvärden som mättes för deltagarnas uppfattning om förhållandet, medan kameravinkeln hade liten inverkan. Resultaten indikerar att förhållandet kan förskjutas avsevärt till förmån för den geometriskt enklare trädmodellen, utan att deltagarna upptäcker förändringar. Sammantaget erbjuder dessa resultat några riktlinjer för att minska antalet polygoner i storskaliga skogsscener sett från luften, samtidigt som scenernas utseenden bevaras. Motiverad av dessa fynd överväger den pedagogiska delen av denna studie rollen av perceptuella ämnen i datorgrafikkurser. Specifikt fokuserar studien på inkluderingen av perceptuella ämnen i kurser på introduktionsnivå vid svenska universitet, samt attityder till att undervisa om perception bland lärare som undervisar om datorgrafik. 22 kursplaner vid 12 svenska universitet samlades in och analyserades. Intervjuer genomfördes med tre pedagoger, medan 13 pedagoger svarade på en enkät. Resultaten presenterar en mångsidig uppsättning tillvägagångssätt och attityder till perception bland lärare, vilket indikerar att perceptionens roll i datorgrafikutbildning är vag. Perceptuella ämnen inkluderades i ungefär hälften av de undersökta kurserna, även om perception sällan nämns i kursernas lärandemål. Undervisningsmetoderna innefattande perception sträckte sig från marginell inkludering, till dedikerade föreläsningar. Sammantaget verkade tillvägagångssätten främst påverkas av studenternas bakgrund, lärares egna fördomar och erfarenheter, såväl som utmaningar som uppstår genom att behöva ägna tid åt grundläggande färdigheter som programmering.

A theoretical model describing photophysics of π-conjugated aggregates, such as molecular crystals and polymer thin films, is developed. A Holstein-like Hamiltonian expressed with a multi-particle basis set is used to evaluate absorption and photoluminescence (PL) spectra. An analysis with line strength ratio proves to be a powerful diagnostic tool to obtain additional spectral signatures with which to distinguish H- vs. J-aggregation. For the H-aggregates absorption peak ratio, A0-0/A0-1, diminishes as the excitonic coupling increases. Also the PL peak ratio, I0-0/I0-1, is zero at T=0K with no disorder and the value increases as temperature and disorder increase. By contrast the J-aggregates show the opposite trends. Furthermore we will show the PL peak ratio provides a direct measurement of the exciton coherence length for a linear J-aggregate and could be expressed as I0-0/I0-1 = Ncoh/l2. We will also show that it is inversely proportional to square root of temperature (T-1/2). Applying our theory to the herringbone style oligoacene molecular crystals, we show the lowest singlet exciton states are highly influenced by charge transfer (CT) states and the well known energetic gap in two polarized absorption spectra, so called Davydov Splitting (DS), is a product of the interaction. We have successfully reproduced the DS for all three oligoacenes without any free parameters. Inspired by the CT contribution in oligoacene crystals, we further develop Wannier-Mott exciton model and apply to disorder-free polydiacetylene (PDA) quantum wires, which have been shown to be extremely emissive. We will show the quantum wire is a J-aggregate and we once again derive the peak ratio and the coherence size relation, I0-0/I0-1 = kNcoh/l2, where k is a prefactor close to unity. Typical photophysical properties of polymer p-stacks such as those occurring in P3HT films are well explained by the simple linear H-aggregate model. However several groups have started seeing more J-like behaviors amongst “improved” (less disordered) polymer films such as increased values of A0-0/A0-1 and I0-0/I0-1 and higher radiative rates. With the new perception of a single polymer chain being a J-aggregate, we apply our new theory to p-stack of polymer chains. We call this HJ-aggregate model since the interchain interaction induces H-aggregation. In the study we show a competition between intrachain and interchain interactions that leads to unique photophysical features. The new model is capable of explaining a wide range of polymer systems and most importantly the theory uncovers the mechanism of the improved polymer films; reducing disorder urges increasing intrachain reactions within each chain, thus enhancing more J-like spectral features. / Chemistry

This thesis evaluates the organization of the structural proteins, Human Gamma D crystallin and Collagen type II, into higher-order structures using light scattering. Specifically, it evaluates the natures of incipient aggregation in Human Gamma D crystallin and the nature of its interactions with CAPEGn, an electrostatic blocker. Additionally, this thesis evaluates whether Collagen type II growth kinetics follows Classical nucleation theory.

In this thesis we investigate concepts associated with aggregation. The basic idea of aggregation is that there exists a reduced order model such that, for an appropriate initial condition, the trajectories of the reduced-order model are linear combinations of the trajectories of the ful 1-order model. We study systems which do not aggregate exactly, but which "nearly aggregate". It is shown that for "nearly aggregable" systems there exists a reduced-order model such that, for an appropriate initial condition, the trajectories of the reduced-order model are near a linear combination of the trajectories of the full-order model. Under certain conditions it has also been shown that near-aggregation is equivalent to near-unobservability (roughly, an invariant subspace close to the null space of C). Here we establish a relationship between near-unobservability and modal measures of observability as suggested by Selective Modal Analysis. With this result we then obtain an upper bound on the norm of the transfer function residue using near-unobservability measures. The Generalized Hessenberg Representation (GHR) and Dual GHR are examined throughout this analysis. It is finally shown that for SISO systems, the residue norm may be expressed in terms of certain parameters of the Dual GHR. / M.S.

<p dir="ltr">The construction industry is one of the largest contributors to carbon emissions, abiotic depletion of natural resources, and waste generation due to the vast quantity of concrete produced. Concrete’s main components have a significant environmental impact. The manufacturing of cement is responsible for 8% of global carbon emissions. In 2019, over 45 billion tons of aggregates were produced. Furthermore, the production of concrete generated over 600,000 tons of concrete waste in 2018.</p><p dir="ltr">Conversely, vegetation consumes 30% of the global carbon dioxide emissions. Recent studies indicated that cryptogamic species, and in particular moss, present a CO₂ uptake of 6.43 billion metric tons more than bare soil. Cryptogamic covers, such as moss and other CO₂ sequestering organisms, are key for the global cycles of carbon and nitrogen. By promoting the growth of living cryptogamic organisms in concrete building facades and roofs, the carbon footprint of concrete can greatly decrease, potentially achieving sub-zero carbon footprint. To attain this solution, cementitious composites must be designed to have an improved bio-receptivity, defined as a material's ability to be colonized by living organisms, or as a substrate to grow living organisms.</p><p dir="ltr">Previous studies show that the bio-receptivity of cementitious composites depends on a material’s acidity and ability to capture and retain water. Yet, the inter-relationship between these properties and bio-receptivity is currently not well understood. Additionally, existing methods to achieve enhanced bio-receptivity in cementitious composites in terms of are often either expensive or counterproductive in terms of sustainability.</p><p dir="ltr">This thesis aims to investigate and develop new methods to create ultra-sustainable composites with enhanced bio-receptivity and low abiotic depletion of natural resources. Additionally, this thesis aims to understand the importance, inter-relationship, and influence of the acidity and water storage properties of cementitious composites on their bio-receptivity.</p><p dir="ltr">The first portion of this thesis is focused on proposing a new method to enhance bio-receptivity of precast cementitious composites elements through accelerated CO₂ exposure treatment and elucidating the function of recycled concrete aggregate use to create ultra-sustainable composites with enhanced bio-receptivity and low abiotic depletion of natural resources. Thus, this study simultaneously tackles the reduction of waste generation and abiotic depletion of natural resources, as well as the promotion of bio-receptivity while reducing the net carbon footprint of the cementitious composites. Results suggested that the proposed accelerated CO₂ exposure treatment enhanced the bio-receptivity of mortars, especially in mortars with RCFA. The combined effect of the RCFA’s high porosity plus the effect of accelerated CO₂ exposures decrease on pH drastically enhanced the ability of promoting moss growth on mortars, enabling the production of low carbon bio-receptive cementitious material with a sub-zero abiotic depletion of natural resources.</p><p dir="ltr">The purpose of the second portion of this thesis was focused on understanding of the inter-related role of the mortar’s porosity, water absorption, and surface pH on the bio-receptivity of cementitious composites. This portion of this thesis also focused on creating a predictive model of bio-receptivity of mortars as a function of water storage properties and surface pH. By conducting this study, the extent of importance of the water storage properties and surface pH on bio-receptivity can be determined. Results suggested that w/c ratio heavily influences the bio-receptivity of mortar, in which a higher w/c ratio increases bulk porosity, water absorption, and decreases the average surface pH. The use of accelerated CO₂ exposure improved bio-receptivity due to and decrease in average surface pH. Additionally, the combined effects of high w/c ratio and accelerated exposure CO₂ exhibited even greater improvements in bio-receptivity. Furthermore, the increase in w/c ratio resulted in the mitigation of accelerated CO₂ exposure adverse effects on bulk porosity and absorption. The developed bio-receptive predictive model successfully predicts the bio-receptivity of mortars as a function of the average surface pH and water absorption. This bio-receptivity prediction model provides us with an instrument to assist in engineering concretes with a target bio-receptivity. The results of this study also show that, while previous literature indicated a maximum pH of 5.0-5.5 to produce a bio-receptive cementitious composite, the pH threshold to obtain a bio-receptive cementitious composite depends on other factors such as porosity of the material, and it is possible to create bio-receptive concretes with a surface pH of 6.2-8.3.</p><p dir="ltr">This research will contribute to creating target-by-design living-engineered concrete facades that can capture CO₂ while reducing the consumption of natural resources.</p>

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-09-30T13:20:44Z No. of bitstreams: 1 JOSÉ AFONSO GONÇALVES DE MACÊDO - DISSERTAÇÃO PPGECA 1989..pdf: 62874473 bytes, checksum: fb1fdb8f43a121e308d6bbcf739a30b1 (MD5) / Made available in DSpace on 2018-09-30T13:20:44Z (GMT). No. of bitstreams: 1 JOSÉ AFONSO GONÇALVES DE MACÊDO - DISSERTAÇÃO PPGECA 1989..pdf: 62874473 bytes, checksum: fb1fdb8f43a121e308d6bbcf739a30b1 (MD5) Previous issue date: 1989-08-31 / Este trabalho faz parte de um estudo mais amplo que visa a utilização de agregados graúdos não convencionais para a obtenção de misturas betuminosas e concreto de cimento Portland. Sendo concebido a partir de estudos já iniciados por outros pesquisadores, que estudaram comparativamente agregados graúdos calcários e lateríticos com um agregado graúdo granítico, visando suas utilizações em concreto betuminoso usinado ã quente. Nesta pesquisa os agregados são avaliados em laboratório,a partir de suas características físicas e mecânicas bem como fa zendo parte de um concreto betuminoso fabricado com teores de ligante determinados a partir dos estudos iniciados por Brasileiro, (1983). Também são verificadas as variações ocorridas com a absorção e massa específica dos agregados graúdos, antes e após a confecção dos corpos de prova pelo ensaio Marshall. Os resultados obtidos permiter.; concluir que, embora tenham sido obtidos em laboratório, existem boas perspectivas de utilização dos agregados lateríticos e calcários para fabricação de concreto betuminoso usinado ã quente, restando ainda, entre outras coisas, melhor adaptação da metodologia de ensaio para avaliação destes materiais e, a execução de trechos experimentais para verificar seus comportamentos em serviços. / This research, which is part of a more comprehensive study on non conventional materials, aims to utilize coarse aggregates for bituminous mixtures and concrete of Portland cement. Previous studies carried out by several investigators, have shown thorough comparative studies the feasibility of calcareous, laterite and granite coarse aggregates for hot-mix bituminous concrete. The aggregates utilized in this research are avaluated in the laboratory by its physical and mechanical characteristics.As well as in samples of bituminous concrete with binder contents, as determined by Brasileiro (1983). Also, it has been verified variations on the absorption and specific gravity of coarse aggregates, before and after the compaction of samples for Marshall test. The laboratory test results concluds that, there are good perspectives to utilize lateritic and calcareous aggregates for hot-mix bituminous concrete. Further research is needed to find the best testing methodology in order to evaluate these materials, and to construct trial pavements to verify its field behaviour.