Rapporten presenterar en studie där tre trätyper, balsa, ask och björk, fabriceras genom en förutbestämd metod till transparent trä. Detta material har många möjliga applikationer, inklusive energieffektiva byggnader, förpackningar, solceller och elektroniska apparater. Syftet med studien är att jämföra de erhållna proverna av transparent trä utifrån morfologi och optiska egenskaper samt koppla dessa resultat till mikrostruktur. Detta för att avgöra huruvida den specifika fabriceringsmetoden lämpar sig för trätyperna och vilken som är mest lämpad. Den valda fabriceringsmetoden består av tre steg, delignifiering, tvätt med lösningsmedel samt polymerinfiltration. Syftet med det första steget i processen, delignifieringen, är att ta bort lignin, beståndsdelen i trä som ger träet dess färg. Detta skedde genom kemikaliebehandling med acetatbuffer och natriumklorit i sur miljö under uppvärmning, varvid träproverna blev vita. Proverna placerades därefter i en vakuumdesickator där de tvättades med etanol och därefter aceton. Etanol hindrar fibrerna från att krympa och acetonet tar bort de sista kemikalieresterna i trästrukturen. Inför det sista steget, polymerinfiltrationen, polymeriserades monomerer av metylmetakrylat till oligomerer, varpå dessa pressades in i träproverna med vakuum där de polymeriserades till polymetylmetakrylat (PMMA). PMMA har ett liknande brytningsindex till trä, vilket minskar ljusspridningen och ökar transparensen i provet. Vidare placerades träproverna mellan två glasplattor och lindades in i aluminiumfolie. Proverna värmdes i ugn där polymeriseringen slutfördes och det transparenta träet erhölls. Träprovernas optiska egenskaper och morfologi karakteriserades. För att bestämma optiska egenskaper uppmättes transmittans och haze. Transmittansen anger hur mycket ljus som kan passera genom provet, medan haze anger hur mycket ljusspridning som sker i förhållande till transmittansen. Dessa parametrar uppmättes enligt ASTM D1003 “Standard Method for Haze and Luminous Transmittance of Transparent Plastics”. Provernas morfologi karakteriserades med ett svepelektronmikroskop (SEM) och resultaten presenterades med högupplösta bilder. Från dessaanalyserades mikrostrukturen i träproverna och graden av delignifiering och polymerinfiltration bedömdes. Resultaten från mätningarna av de optiska egenskaperna visade att balsa har den högsta transmittansen (81–87%), följt av björk (74–83%) och sedan ask (66–78% för sommarved och 74–83% för vårved). Vidare uppmättes haze till ca 65–70% för balsa, ca 70–75% för björk och 74-80% för ask. Genom analys av SEM-bilderna bedömdes graden av delignifiering som högst i balsaträet. För att avgöra detta studerades mellanrummet mellan fibrerna som i obehandlat trä är ligninfyllda. Det observerades då att dessa mellanrum var mest tomma i det delignifierade balsaträt, vilket antydde på att graden av delignifiering var högst för denna trätyp. Graden av polymerinfiltrering ansågs likvärdig för de tre träsorterna då det förekom luftfickor i samtliga träprov. Sammanlagt ledde detta till att balsa blev mest transparent av de tre träsorterna, och är den mest lämpade träsorten för denna fabriceringsmetod.

Motivation In the upcoming decades, traditional firms will transition to becoming a more regenerative version, with a socio-ecological purpose at the core of the firm. In this transition phase, regenerative firms, with a focus on impact maximisation of the socio-ecological purpose and traditional firms, with a focus rather on profit maximisation, need to coexist and be resilient somehow. While in the coming decades the number of regenerative firms will grow, it is important to understand how these regenerative firms can enable organisational resilience. Yet, prior research neglects how especially inter-organisational collaboration could enhance the organisational resilience of regenerative firms. Therefore, the context of this study is within the consumer goods industry in the Netherlands and the United Kingdom, focusing on regenerative firms. Purpose This study aims to shed light on how inter-organisational collaboration can strengthen the organisational resilience of regenerative firms. The first part of the research will mostly address the question how regenerative firms can strengthen organisational resilience with a focus on the capabilities needed. In addition, the study will demonstrate how regenerative firms approach and use inter-organisational collaboration. Methodology The study, with a qualitative approach, used a multi-case study design. Various people were interviewed, such as CEOs, founders, quality managers, consultants, impact officers, following a semi-structured interview design. For transcription purposes, the interviews were audio-recorded and the results from the interviews were labelled, following an open coding process. The results, with matching open codes, were then connected back to the theoretical framework. Results The results of this study indicated how inter-organisational collaboration is used to strengthen the organisational resilience of regenerative firms. Contradicting prior research about traditional firms, regenerative firms do not fear competition, yet these firms rather achieve system resilience by being resilient as a collective. Regenerative firms realise this by being transparent, absorbing and sharing knowledge to achieve success for the system they are embedded in. Sharing knowledge in a transparent manner and aiming for reciprocity among inter-organisational collaboration actors contributes positively to their system resilience. Thus, inter-organisational collaboration is a powerful tool for regenerative firms to enhance this system resilience and consequently maximising the impact of their collective socio-ecological purpose.

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<p>The development of nanocomposite materials has had significant influence on modern material design. Novel properties can be achieved and controlled for a diverse range of applications. The work presented here focused on characterization of polyurethane based coatings with ITO nano-inclusions. The coatings displayed high transparency in the visible range, and UV/IR shielding properties when studied with UV-Vis spectroscopy. UV/IR shielding improved with greater ITO density, with minor affect on visible transmittance. The effective medium approximation was successfully applied to ellipsometry modeling. Coatings with varying fractions of nanoparticles were analyzed. The modeled volume percent of the nanoparticles followed a strong linear trend with the known weight percentages. SEM and TEM imaging determined that majority of the particles existed in clusters. The nanoparticles were oblong shaped, 10-20nm big, randomly distributed, with no segregation to interfaces. Agglomerates varied in size, with the largest observed agglomerate being 250nm.</p> <p>Thermal stability was studied by TGA and DSC. No degradation occurred until 238°C. DSC revealed that the matrix continued to undergo modifications with consecutive runs. It was inconclusive whether the changes were from the polyurethane or dispersive agents in the system. Electron micrographs showed that segregation did not occur post-annealing. Average surface roughness increased from 3.5nm to 5nm after annealing at 120°C for several weeks. Ellipsometry results showed that film thickness decreased 20nm and 50nm before equilibriating for the 80°C and 120°C anneals respectively. The optical and thermal measurements demonstrated that the coating has great potential for improving the PV performance.</p> / Master of Applied Science (MASc)

Microphone arrays are becoming increasingly integrated into every facet of life. From sonar to gunshot detection systems to hearing aids, the performance of each system is enhanced when multi-sensor processing is implemented in lieu of single sensor processing. Head mounted microphone arrays have a broad spectrum of uses that follow the rigorous demands of human hearing. From noise cancellation to focused listening, from localization to classification of sound sources, any and all attributes of human hearing may be augmented through the use of microphone arrays and signal processing algorithms. Placing a set of headphones on a human provides several desirable features such as hearing protection, control over the acoustic environment (via headphone speakers), and a means of communication. The shortcoming of headphones is the complete occlusion of the pinnae (the ears), disrupting auditory cues utilized by humans for sound localization. This thesis presents the underlying theory in designing microphone arrays placed on diffracting bodies, specifically the human head. A progression from simple to complex geometries chronicles the effect of diffracting structures on array manifold matrices. Experimental results validate theoretical and computational models showing that arrays mounted on diffracting structures provide better beamforming and localization performance than arrays mounted in the free field. Data independent, statistically optimal, and adaptive beamforming methods are presented to cover a broad range of goals present in array applications. A framework is developed to determine the performance potential of microphone array designs regardless of geometric complexity. Directivity index, white noise gain, and singular value decomposition are all utilized as performance metrics for array comparisons. The biological basis for human hearing is presented as a fundamental attribute of headset array optimization methods. A method for optimizing microphone locations for the purpose of the recreation of HRTFs is presented, allowing transparent hearing (also called natural hearing restoration) to be performed. Results of psychoacoustic testing with a prototype headset array are presented and examined. Subjective testing shows statistically significant improvements over occluded localization when equipped with this new transparent hearing system prototype. / Ph. D.

The temperature and thermal stress distributions in a semi-transparent solid of flat plate geometry exposed to a collimated radiative source for various angles of incidence is investigated. This plate is convectively insulated on the surface where the radiation is incident while the rear surface is convectively cooled. Tile effective internal heat generation term is rederived so as to take into account the internal specular reflections (diffuse reflections were not considered) in the plate when the source is present. The newly-derived effective internal heat generation term allows for variations in the angle of incidence of the collimated source. This one-dimensional analysis investigates the importance of the incoming radiation wavelength, and the angle of incidence, on the behavior of the temperature and stress distributions. The nature of the concavity of the temperature distribution in relation to the stress distribution is also studied. The heating of the plate by a single pulsed source (laser) for a duration of 0.001 seconds followed by the subsequent cooling of the plate is examined by numerical example using Corning Glass Works #7940 Fused Silica glass as the semitransparent material. / Master of Science

In the dynamic arena of display technology, augmented reality (AR) displays represent a pivotal advancement, seamlessly bridging the digital and physical worlds. This dissertation delves into the realm of AR display technologies, spotlighting the challenges and limitations of current systems, including transparent and near-eye displays, and proposes innovative solutions to enhance user experience and display performance. With a focus on overcoming issues such as diffraction-induced image blur, the trade-off between resolution and field of view (FoV) in near-eye displays, and FoV constraints in waveguide-based displays, this research introduces new evaluation methods, optimization techniques, and system designs. First, the dissertation presents a quantitative evaluation of diffraction effects on background objects, leading to the development of a pixel structure optimization method aimed at reducing diffraction in transparent displays with small aperture ratios. This advancement promises to enhance image clarity and visibility, addressing one of the key challenges in the deployment of AR technology for transparent displays. Next, we introduce a novel Maxwellian-type foveated AR system that leverages a single light engine. This system employs a temporal polarization-multiplexing method to encode both high-resolution foveal and low-resolution peripheral images through the same light engine. With the aid of polarization-selective lenses, this system effectively separates the two views, delivering a wide FoV and high angular resolution in the foveal region, effectively minimizing the resolution-FoV compromise in near-eye displays. Furthermore, the dissertation conducts a detailed analysis of FoV limitations in single-layer waveguides, proposing a strategic combination of a gradient-pitch polarization volume grating (PVG) with a butterfly exit-pupil expansion (EPE) scheme. This approach aims to extend the FoV in single-layer waveguides towards the theoretical full-color limit. This research addresses pivotal challenges in waveguide-based AR technology, marking a significant step towards realizing more immersive and user-friendly AR systems.

Functional materials are essential to human welfare and to provide foundations for emerging industries. As an alternative route to experimental materials discovery, computational materials designs are playing an increasingly significant role in the whole discovery process. In this work, we use an in-house developed python utility: PAOFLOW, which generates finite basis Hamiltonians from the projection of first principles plane-wave pseudopotential wavefunctions on pseudo atomic orbitals(PAO) for post-process calculation on various properties such as the band structures, density of states, complex dielectric constants, diffusive and anomalous spin and charge transport coefficients. In particular, we calculated the dielectric function of Sr-, Pb-, and Bi-substituted BaSnO3 over wide concentration ranges. Together with some high-throughput experimental study, our result indicates the importance of considering the mixed-valence nature and clustering effects upon substitution of BaSnO3 with Pb and Bi. We also studied two prototype ferroelectric rashba semiconductors, GeTe and SnTe, and found the spin Hall conductivity(SHC) can be large either in ferroelectric or paraelectric structure phase. Upon doping, the polar displacements in GeTe can be sustained up to a critical hole concentration while the tiny distortions in SnTe vanish at a minimal level of doping. Moreover, we investigated the sensitivity of two dimensional group-IV monochalcogenides to external strain and doping, which reveal for the first time giant intrinsic SHC in these materials, providing a new route for the design of highly tunable spintronics devices based on two-dimensional materials.