Global ETD Search

1	A study of rare-earth doped silicon based films as a luminescent downshifting layer for cadmium telluride photovoltaics Bernard, Sneha 11 1900 (has links) The peak efficiency range for CdTe solar cells is between 500-700nm; however efficiencies are limited at wavelengths shorter than 500nm due to the fact that at higher energies, most photons are absorbed in the CdS layer of the module and cannot contribute to the cell current. This means that incident photons with higher energies are ‘wasted’ as they are not efficiently absorbed by the cell. Luminescent downshifting (LDS) is a third-generation photovoltaic technology in which an external layer applied to the front surface of the cell absorbs high energy photons and re-emits them towards the cell at energies where they are more efficiently absorbed, thus avoiding front surface loss mechanisms. This research project investigates the use of cerium and terbium co-doped silicon oxide thin films grown using electron cyclotron resonance plasma enhanced chemical vapour deposition (ECR PECVD) as a luminescent down-shifting layer. Post-deposition annealing in a quartz tube furnace caused the formation of cerium disilicate (Ce2Si2O7) nanocrystallites, which were found to strongly absorb incident light at wavelengths below 360 nm and efficiently sensitize Tb3+ ions in the film for re-emission. The effect of annealing time and sample composition on physical and optical properties was studied. Film compositions were determined through Rutherford backscattering spectrometry, revealing an incremental increase in rare earth concentration. Photoluminescence measurements showed a distinct Tb3+ peak around 550nm, which is close to the ideal efficiency wavelength for CdTe photovoltaics. Variable Angle Spectroscopic Ellipsometry measurements were used to determine the index of refraction of as-deposited and annealed films. UV-Visible absorption spectroscopy and transmission ellipsometry measurements showed a sharp increase in absorption around 400nm confirming wide separation between absorption and emission bands. When LDS films were coupled with thin film CdTe, subsequent absorption spectroscopy and transmission measurements showed stronger absorption at short wavelengths, as anticipated. / Thesis / Master of Applied Science (MASc)
2	Downshifting och livsstilsmigration till landsbygden : En kvalitativ studie om kvinnors flyttmotiv till den svenska landsbygden / Downshifting and lifestyle migration to the countryside : A qualitative study about women's moving motives to rural Sweden Salehi, Marzieh, Palm, Elinor January 2019 (has links) Denna uppsats har syftat till att undersöka downshifting som en livsstilsmigration till landsbygden samt belysa downshiftares flyttmotiv till landsbygden i förhållande till deras valda livsstil. Frågeställningar som uppsatsen har utgått ifrån är: vilka motiv påverkar downshiftare att flytta till landsbygden? samt hur upplever downshiftarna landsbygden som plats och hur möjliggör landsbygden deras livsstil? Forskningen beskriver downshiftning som en motrörelse till ett högt livstempo där det förespråkas att “växla ner”. Vi har uppmärksammat en trend där människor som downshiftar ofta flyttar till landsbygden som följd av sin livsstil och vi ville därför fördjupa oss i ämnet utifrån ett kulturgeografiskt perspektiv då detta inte undersökts tidigare. Vi har även uppmärksammat att det finns mindre forskning som rör intern livsstilsmigration inom Sverige och specifikt om livsstilsmigration till landsbygden. En stor del av forskningen kring livsstilsmigration har hittills behandlat internationell migration. I förhållande till de nämnda observationerna syftar därför studien till att undersöka downshifting som en livsstilsmigration. Tidigare forskning kring downshifting, livsstilsmigration och plats utgör den teoretiska referensramen. Uppsatsen har utgått ifrån en kvalitativ undersökning med semistrukturerade intervjuer med downshiftare som flyttat från en större stad till landsbygden. Sammanfattningsvis genomfördes åtta intervjuer med endast kvinnliga respondenter, detta eftersom vi använde oss av snöbollsurvalet som uteslutande länkade till kvinnliga nätverk. Resultaten visar bland annat att de flesta flyttar till landsbygden för att kunna växla ner och hoppa av “ekorrhjulet” som de upplever är påtagligt i storstaden. I studiens slutsats har vi kommit fram till att flyttmotiv till landsbygden bygger på flera olika motiv som inte skiljer sig nämnvärt från de motiv som framkommit i tidigare forskning. Att flytta till landsbygden har fungerat som strategi för att kunna styra över sin egen tid eftersom de låga boendekostnaderna möjliggör för downshiftaren att kunna gå ner i arbetstid. Downshifting Rural Lifestyle Migration Place Sense of place Downshifting Landsbygd Livsstil Migration Plats Platskänsla Human Geography Kulturgeografi
3	Can we slow down? Challenges and possibilities of living slowerand simpler in Sweden Österlund, Sandra January 2020 (has links) This thesis takes its departure in the view of modern society as being characterised by a heavy focus on efficiency and economic growth, and perception that everything is moving faster and faster in line with Hartmut Rosa´s theory of social acceleration. The effects of this can be seen in rising numbers of stress related sicknesses and mental health problems, as well as a heavy pressure on the earths resources to facilitate continued growth. The aim of the thesis is to investigate the challenges and possibilities for individuals in Sweden to slow down and live a simpler life in this context. Previous research suggests that slower lifestyles can be beneficial both for well-being and environmental sustainability reasons, so understanding the preconditions of this to be possible can be an important aspect when trying to plan for a sustainable future. The theoretical framework consists of the model of voluntary simplicity lifestyle by Osikominu and Bocken (2020), the theory of social acceleration by Rosa (2009) and selected writings on Social Change. The thesis is based on a thematic analysis of empiric material from individuals in Sweden who has transitioned to a slower and more simple lifestyle, generally in terms of working less, reducing their consumption and living closer no nature, and also are visible on social media, reaching out to many others as inspiration. The material consists of writings and recordings from the study-persons in the form of blog-posts and podcasts. The study could confirm that many parts of the VSL-model also were applicable and experienced in the Swedish context. Most participants had in common that their previous lifestyle was characterised by stress, pressure, and living according to others expectations, in line with Rosa´s theory of social acceleration. Their new slower and simpler lifestyles were a decision to follow their own path in life and start to value their time more. The challenges that could be recognised was the norm of working full-time, achievement values, living outside the norm, ethical dilemmas regarding consumption and, for those living on the countryside, transport and infrastructure. The possibilities most recognised were concerning their wellbeing, closely related to their possibility of finding time for recovery, as well as living more in contact with the environment. Social life appeared both as a challenge and a possibility. Slow living voluntary simplicity downshifting minimalism sustainability social acceleration social change Sociology Sociologi
4	Microwave-Assisted Solvothermal Synthesis and Optical Characterization of M(RE)F4 (M – Alkali Metal; RE – Rare-Earth Metal) Nano- and Microscale Particles Panov, Nikita 04 June 2020 (has links) Interest in rare-earth-doped crystalline materials, e.g., M(RE)F4 (M – alkali metal, RE – rare-earth metal), featuring unique optical properties such as light upconversion and downshifting is experiencing a surge due to the broad spectrum of applications that these photonic systems are facilitating. The development of reliable synthetic methods that grant rapid access to these materials is therefore of great importance. Microwave-assisted synthesis is appealing in this regard, because microwave radiation enables rapid and uniform heating of the reaction mixture and allows for rigid control of the reaction conditions, factors that facilitate the production of high-quality materials within minutes. Surprisingly, the investigation around microwave-assisted synthesis of M(RE)F4 materials featuring upconversion and downshifting luminescence is limited. Methods that have already been developed predominately target Na-based systems, despite the evidence that the Li-based analogues also display excellent optical properties. In fact, only a single microwave-assisted approach toward a nanoscale Li-based system has been reported to date, while to my knowledge, no report of a microwave-assisted synthesis of a microscale Li-based system existed prior to the commencement of the work presented in this thesis. The challenge lies in the fact that access to Li(RE)F4 is not easily achieved through a simple substitution of the alkali metal source in the established protocols that yield Na(RE)F4; rather, a complete re-optimization of the synthesis method is required. This particular challenge was successfully addressed in this work. Presented and discussed in Chapter 3 of this thesis is a rapid microwave-assisted solvothermal synthesis approach toward both upconverting and downshifting LiYF4:RE3+ microparticle systems. More specifically, it is detailed how the rigorous optimization of the reaction temperature/duration profile, initial reaction mixture pH, and ratio of the metal precursors was necessary in gaining control over the crystalline phase, morphology, and size of the microparticles under microwave-induced solvothermal conditions. Importantly, a materials growth mechanism involving the depletion of a Li-free crystal phase, followed by a particle ripening process is also proposed. Moreover, the versatility of the developed method is highlighted by showcasing how it can be extended toward the synthesis of other relevant Li- and Na-based M(RE)F4 nano- and microscale materials (i.e., LiYbF4, NaYF4, and NaGdF4) featuring upconversion luminescence. Lastly, potential challenges associated with microwave-assisted synthesis are discussed, and appropriate solutions are proposed. The upconversion and downshifting luminescence of the M(RE)F4 materials attained via the developed synthesis approach is investigated in Chapter 4. The first part of the chapter provides a general assessment of the characteristic luminescence generated by the M(RE)F4 materials featuring various RE3+ dopant systems. The second part of the chapter is devoted to a much more thorough single-particle investigation of the anisotropic luminescence behaviour exhibited by the LiYF4:RE3+ microparticles via hyperspectral imaging, polarized emission spectroscopy, and optical trapping. It is my hope that you, the reader, will find the work presented in this thesis stimulating from two vantage points – from the development of the most rapid microwave-assisted solvothermal synthesis of upconverting and downshifting M(RE)F4 nano/microscale materials reported to date, as well as from the utilization of specialized luminescence characterization techniques to provide fundamental insight into a seldom-considered luminescence property of crystalline materials such as LiYF4. LiYF4 microparticles Microwave-assisted synthesis Polarized emission spectroscopy Optical trapping
5	Dinosaurier, drakar, vapen, rymdskepp, aliens, eld, monster, farliga djur : Om att passa in i samhället eller hitta hem utanför. / Dinosaurs, dragons, weapons, spaceships, aliens, fire, monsters, dangerous animals : To fit into society or to find your home outside. Pettersson, Mattias January 2019 (has links) I denna text vill jag, som undertiteln skvallrar, prata om att passa in i samhället eller hitta hem utanför. Arbetet har den enkla strukturen att det börjar med att prata om hinder man kan ha för att ”passa in”, såsom att inte klara prestations-pressen man känner från en osynlig makt, eller helt enkelt av att bryta från normen (här med fokus på att vara bög eller queer). Vidare via min och andras historier kring att ha sitt psyke eller sina känslor som en grundläggande parameter i sitt konstnärskap, och går sen avslutningsvis ut i några andra alternativa vägar att hitta hem utanför; drag och frivillig enkelhet. Varsågod. / Dinosaurs, dragons, weapons, spaceships, aliens, fire, monsters, dangerous animals. Never interested me. That's why they interest me. Through intuitive sculpting, stories about my traumas, lusts and needs are formed, and about the society they exist in. I can see a tension towards the boy I never was/the man I never became, and a longing after to now approach him om my own terms. The sculptures are crooked, weak, broken, naive and weird, and in this becomes a vital space where that is allowed. The pieces are standing with the underdogs. In a movement upwards. fit in queer gay men feminine men drag straight acting downshifting dragons spaceship alien gender roles ceramics sculpture safe space naivism outsider art mental illness working class anxiety depression stress norms emotions straight acting scew masculinity masc for masc fantasy mcqueen rupauls dragrace blue abstract art passa in hitta hem queer bögar feminina killar drag frivillig enkelhet drakar rymdskepp aliens könsroller keramik skulptur trygga rum tryggt rum naivism outsiderart psykisk ohälsa arbetarklass ångest depression stress normer känslostyrd straightacting skevhet manlighet fantasy mcqueen rupauls dragrace blå abstrakt konst Arts Konst

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