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Plasma Nanotexturing of Silicon for Photovoltaic Applications : Tailoring Plasma-Surface Interactions for Improved Light Management / Nanotexturation du silicium par gravure plasma pour applications photovoltaïques : Optimisation des interactions plasma-surface pour l'amélioration des propriétés optiquesFischer, Guillaume 26 November 2018 (has links)
Cette thèse est dédiée à l’étude de la texturation de surface du silicium cristallin (c-Si) à l’échelle nanométrique (nanotexturation) par un procédé de gravure ionique réactive en chimie SF6/O2 et en réacteur plasma à couplage capacitif à excitation radiofréquence. Ce travail a pour objectif générique l’optimisation du procédé de nanotexturation de surface en vue d’une intégration pour le traitement de la face avant de l’absorbeur de cellules photovoltaïques c-Si. A cette fin, une étude des interactions plasma-surface est menée dans le cas d’une excitation plasma par tension simple fréquence, ou par tension multifréquence générant des asymétries électriques dans le plasma (méthode des « forme d’ondes sur mesure », abrégé TVW, de l’anglais "Tailored Voltage Waveforms").L’étude se porte premièrement sur les différents mécanismes de chauffage électronique dans le plasma. Les modes de chauffage électronique dominants sont déterminés pour un plasma SF6/O2 à faible pression grâce à l’utilisation de l’excitation TVW. En contrepartie, ce mode d’excitation permet de générer des asymétries électriques variables dans le plasma, affectant ainsi le flux et l’énergie de bombardement ioniques sur l’électrode porte-substrats. Dans les conditions étudiées, l’excitation TVW permet d’élargir la gamme de conditions disponible pour la gravure (en termes de flux et d’énergie de bombardement ioniques) par rapport à une excitation simple fréquence.Deuxièmement, les interactions plasma-surface lors de la gravure du c-Si en chimie SF6/O2 sont étudiées. Une fenêtre process permettant d’obtenir une nanotexturation efficace de la surface de c-Si – à température ambiante – est identifiée. Il est ainsi possible de diminuer drastiquement la réflexion de la lumière en surface du c-Si (dans la gamme de longueurs d’ondes [250,1000nm]) : du « silicium noir » est obtenu. Les conditions de nanotexturation (flux et énergie des d’ions) sont variées expérimentalement grâce à l’excitation TVW. Un modèle phénoménologique de gravure est proposé : le rendement de gravure augmente en fonction avec l’énergie des ions, au-dessus d’un seuil de gravure d’environ 13eV. Grâce à ce modèle, il est démontré que la hauteur moyenne des nanostructures formées est directement (positivement) liée à la fluence ionique, pondérée par l’énergie de bombardement.Les propriétés optiques des surfaces nanotexturées sont ensuite étudiées. Lorsque la largeur des nanostructures est petite devant la longueur d’onde de la lumière (dans le c-Si), la surface nanotexturée agit comme une couche antireflet à gradient d’indice de réfraction : un lien direct entre la hauteur des nanostructures et la réflectance totale de la surface est déterminé. Une très faible réflectance (de l’ordre de 2% en incidence normale) dans une large gamme spectrale (approximativement [250,1000nm]) est atteinte. De plus, une forte diffusion de la lumière est engendrée lorsque la largeur des nanostructures dépasse un seuil déterminé expérimentalement. En conséquence, la lumière est plus efficacement piégée dans le c-Si, améliorant l’absorption dans la gamme [1000,1200nm].Les propriétés optiques des surfaces nanotexturées sont intéressantes pour améliorer la photogénération de charges électriques dans les cellules photovoltaïques c-Si. Cependant, les dommages induits en surface du c-Si par bombardement ionique (lors de la nanotexturation plasma) sont responsables d’une augmentation de la recombinaison des charges électriques en surface. Cet effet est atténué par l’application d’une faible énergie de bombardement ionique. Des conditions optimales de nanotexturation du c-Si par plasma SF6/O2 peuvent être obtenues par la maximisation du flux d’ions, en maintenant l’énergie de bombardement faible. Ces spécifications se révèlent antagonistes dans le cas d’une décharge plasma à couplage capacitif à excitation simple fréquence, mais le conflit peut être (en partie) levé par l’utilisation de l'excitation TVW. / This thesis is dedicated to the study of crystalline silicon (c-Si) surface texturing at the nanoscale (nanotexturing) using capacitively coupled plasma reactive ion etching (CCP-RIE). The general objective consists in tuning the nanotextured surface properties to improve light-management in c-Si solar cells through front surface texturing. To this aim, plasma-surface interactions during etching in a SF6/O2 discharge are investigated using both single-frequency excitation and Tailored Voltage Waveforms (TVWs), i.e. a multifrequency approach triggering electrical asymmetries in the plasma.To gain a full picture of the achievable processing range, the electron heating mechanisms and ion bombardment energy on the surface are first studied. An identification of the dominant electron heating mechanisms in low pressure SF6/O2 plasma is demonstrated using TVWs as an innovative probing tool. Different electrical asymmetry effects are shown to arise depending on the dominant heating mode, which therefore affects both the ion flux and bombardment energy on the etched surface. Although a complete decoupling between ion energy and flux cannot be achieved in the investigated discharge conditions, TVWs do lead to an extended playground for SF6/O2 plasma etching of c-Si surfaces in CCP-RIE.The plasma-surface interaction mechanisms during SF6/O2 plasma etching and texturing of c-Si surfaces are then investigated. A processing window to achieve nanotextured anti-reflective c-Si surfaces (“black silicon”) at room temperature is delimited. Building on the work from the first section, the ion flux and bombardment energy on the c-Si surface are varied independently in this process window. A phenomenological model (etching yield varying with the square root of the ion energy above a threshold around 13 eV) is proposed. From this model, a direct (positive) link between the energy weighted ion fluence and the nanostructure height is identified. Importantly, the final nanostructure average width is shown to also weakly depend on the instantaneous ion flux during the process.Subsequently, anti-reflection and light scattering properties of plasma nanotextured c-Si surfaces are studied. Regarding anti-reflection, when the nanostructure average width is small compared to the wavelength (in c-Si), the nanotextured surface acts as an anti-reflective graded refractive index layer and a direct link between the nanostructure average height and the reflectance can be derived. Very low reflectance (in the order of 2% at normal incidence) on a broad wavelength range (approximately [250, 1000nm]) can be achieved, and the improved anti-reflective properties extend to high angles of incidence. Additionally, strong light scattering is shown to arise when the nanostructure average width overcomes a given threshold determined experimentally. Consequently, light is more efficiently trapped in the c-Si substrate, leading to superior absorption in the range [1000, 1200nm].The aforementioned optical properties of nanotextured c-Si surfaces are of practical interest for improved light management in c-Si photovoltaic devices. However, plasma induced damages (during plasma nanotexturing), as well as enlarged surface area, are responsible for increased carrier recombination. The contribution to recombination from plasma induced defects is shown to be mitigated when ion bombardment energy is kept low. Design rules are consequently proposed: optimized conditions for c-Si nanotexturing in SF6/O2 plasma can be achieved by maximizing the ion flux while keeping ion energy low (but above the etching threshold). These requirements are conflicting in the case of a single frequency CCP discharge, but the trade-off may be (at least partly) resolved using TVWs.
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From photovoltaics to microgrids : A case study on Loccioni and how its tailored solutions compete with standardized products in the energy utility industryMehlig, Jakob, Rosén, Simon January 2023 (has links)
Global industries are undergoing significant sustainability transitions, presenting new opportunities for R&D and innovation-driven companies. Rather than competing in large markets, these companies thrive in specialized niches. In the energy utility sector, which is experiencing rapid growth and the emergence of new niches, uncertainty surrounding future market dynamics and technology poses challenges for large-scale infrastructure investments. However, this uncertainty opens doors for smaller niche actors that prioritize innovation over mass production of standardized products. This study focuses on the challenges and benefits faced by small innovation-based companies as they offer tailored solutions in the face of growing standardization within emerging industries. To address this topic, the researchers conducted a case study at Loccioni, an Italian engineering firm involved in the energy utility industry. Loccioni has positioned itself as a niche player, emphasizing strong customer relationships, differentiation, and research and development to gain a competitive edge. During a two-month period in Italy, the authors conducted nine semi- structured interviews, engaging seven Loccioni collaborators and two customer representatives. Thematic analysis of the interview data revealed three key themes: Customer Relationship Management, Dominant Logic, and Loccioni's position in the energy market. The thesis concludes that Loccioni cannot effectively compete with standardization solely by developing components; instead, they must focus on designing integrated systems. This approach allows Loccioni to simultaneously compete in the present market and drive innovation for the future. Moreover, it enables the continuous development of core competencies, vital for the long-term survival of the company. To achieve this, small innovation-based companies must adopt a business strategy centered around flexibility and customer satisfaction, leveraging their customers' resources. However, it is crucial for these companies to utilize flexibility wisely, as it can hinder growth and innovation if mismanaged. Loccioni's dominant logic, which prioritizes customer contentment and investment in uncertain technologies and opportunities, positions them as a significant contributor to the global green transition.
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Vilka behandlingsmetoder finns för våldsutövande män? : En litteraturstudie om behandlingsmetoder för män som utövat våld i nära relationGailany, Lara, Lahdo, Gabriella January 2024 (has links)
Syftet med studien är sammanställa forskning om behandlingsmetoder för män som utövat våld mot kvinnor i nära relation. I syftet ligger även att granska vilka metoder som anses vara framgångsrika i detta behandlingsarbete. Åtta artiklar utgör studiens empiri. Vi har gjort en tematisk analys som därefter analyserats utifrån studiens teoretiska utgångspunkter: professionsteorin, arbetsallians, klientorientering och yrkeskompetens. Resultaten visar att individanpassade behandlingsmetoder är avgörande i arbetet med våldsutövare och att ett holistiskt synsätt behöver tillämpas i arbetet. Våra slutsatser är att de som arbetar med behandlingsområdet behöver utgå från individanpassade behandlingsmetoder och upprätthålla en stark arbetsallians med våldsutövare. I enighet med forskningen om behandlingsmetoder ser vi också att det behövs mer forskning inom området. De behandlingsmetoder som har identifierats är duluth-modellen, kognitivbeteende- och psykodynamisk terapi samt motiverande samtal. Resultatet visar att motiverande strategier samt individanpassade metoder är de mest effektiva i behandlingsarbetet / The purpose of this study is to assemble research on treatment methods for men who have perpetrated violence against women in intimate relationships. The aim is also to examine which methods are considered successful in the treatment work. The empirical foundation consists eight articles. We have done a thematic analysis which has been analyzed based on the theoretical framework of the study: profession theory, working alliance, client orientation and professional competence. The results show that individual adapted treatment methods are crucial in working with perpetrators of domestic violence and that holistic approach needs to be applied in the work. Our conclusions are that those who work in the area treatment need to apply individually adapted treatment methods and maintain a strong working alliance with perpetrators of violence. In agreement with the research on treatment methods, we also see that more research is needed in the area. The treatment methods that have been identified are the Duluth model, cognitive behavioral and psychodynamic therapy, and motivational interviewing. The results show that motivational strategies and individually adapted methods are the most effective in treatment work.
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Evaluating An Online Personalized Family-based Intervention To Promote Healthy Lifestyle ChangesHayes, Sharon 01 January 2010 (has links)
The current study evaluated the initial feasibility, efficacy, and acceptability of a motivationally-tailored family-based intervention designed to promote the adoption of healthy lifestyle behaviors associated with physical activity and nutrition. Parents (N=132) of children 6 to 11 years old were randomly assigned to the intervention or control condition, and they completed a series of online questionnaires. Intervention participants (n=61) received a single motivationally-tailored feedback report via e-mail. Control participants (n=71) completed measures and immediately received information about a free online resource that provides information about healthy lifestyle behaviors (www.mypyramid.gov). Feasibility data indicate that an online feedback program has high dissemination potential (parents from 31 states participated). However, the current methodology is not sufficient in reaching families who are at greatest risk for developing chronic health conditions associated with obesity or low activity level. In general, the intervention was acceptable to parents. Outcome data revealed that the intervention and control groups did not differ significantly on most variables at one month follow-up. Exploratory analyses provided additional evidence for the importance of including parents and targeting parent-child interactions in the context of pediatric nutrition and physical activity interventions. Limitations and future directions are discussed.
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Impact of Tailored Messages to Change Towards a Plant-Based Diet: Media Effects, Behavioral Change and Practical ImplicationsWiemer, Lena 01 October 2018 (has links)
No description available.
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Beyond the Office Walls: Understanding Organizational Belonging in the Era of Remote Work : Exploring the Dynamics of Managerial Interactions and Their Impact on Remote Workers' Organizational BelongingWilliam, Philip, Davidovic, Nemanja January 2024 (has links)
The present-day working setting has endured many developments over a couple of centuries.These developments have provided us with new working settings, concepts, and roles. Withthe advancements in technology and the underlying instigator of COVID-19, the remotesetting has become a commonality for many organizations. Concepts such as organizationalbelonging have grown to become a vital focus for companies and a necessity for employees.The role of the manager which was once simple and direct has become complex andmultidimensional. The rise in remote workers, full-time and hybrid, during and post-COVID19 has caught the attention of many researchers. Yet, the profound implications surroundingremote workers have been neglected. This study wants to shed light on remote workers’ senseof belonging and the factors regarding the managerial role that interplays into the mentioned.The purpose is to unfold how to effectively utilize the remote setting while creating apleasant environment for the employees. An environment directed by managerial support,interactions, and culture transmission will foster productivity, motivation, job satisfaction,and finally the sense of belonging of the employees. Lastly, this exploratory qualitative studywill through a combination of the abductive and inductive approach and a thematic analysisfathom the managerial role in remote working employees’ sense of belonging. In conclusion,this study argues that managers do have the power to shape the remote working environmentand thus, strengthen employees’ sense of belonging. Tailored supportive practices, supportiveleadership approaches, more engagement, deeper relationships, and consistent feedback andrecognition would improve the remote setting experience and belonging for the employees.
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Optomechanics in hybrid fully-integrated two-dimensional photonic crystal resonators / Optomécanique dans les résonateurs intégrés et hybrides à cristal photonique bi-dimensionelTsvirkun, Viktor 15 September 2015 (has links)
Les systèmes optomécaniques, dans lesquels les vibrations d'un résonateur mécanique sont couplées à un rayonnement électromagnétique, ont permis l'examen de multiples nouveaux effets physiques. Afin d'exploiter pleinement ces phénomènes dans des circuits réalistes et d'obtenir différentes fonctionnalités sur une seule puce, l'intégration des résonateurs optomécaniques est obligatoire. Ici nous proposons une nouvelle approche pour la réalisation de systèmes intégrés et hétérogènes comportant des cavités à cristaux photoniques bidimensionnels au-dessus de guides d'ondes en silicium-sur-isolant. La réponse optomécanique de ces dispositifs est étudiée et atteste d'un couplage optomécanique impliquant à la fois les mécanismes dispersifs et dissipatifs. En contrôlant le couplage optique entre le guide d'onde intégré et le cristal photonique, nous avons pu varier et comprendre la contribution relative de ces couplages. Cette plateforme évolutive permet un contrôle sans précédent sur les mécanismes de couplage optomécanique, avec un avantage potentiel dans des expériences de refroidissement et pour le développement de circuits optomécaniques multi-éléments pour des applications tels que le traitement du signal par effets optomécaniques. / Optomechanical systems, in which the vibrations of a mechanical resonator are coupled to an electromagnetic radiation, have permitted the investigation of a wealth of novel physical effects. To fully exploit these phenomena in realistic circuits and to achieve different functionalities on a single chip, the integration of optomechanical resonators is mandatory. Here, we propose a novel approach to heterogeneously integrated arrays of two-dimensional photonic crystal defect cavities on top of silicon-on-insulator waveguides. The optomechanical response of these devices is investigated and evidences an optomechanical coupling involving both dispersive and dissipative mechanisms. By controlling optical coupling between the waveguide and the photonic crystal, we were able to vary and understand the relative strength of these couplings. This scalable platform allows for unprecedented control on the optomechanical coupling mechanisms, with a potential benefit in cooling experiments, and for the development of multi-element optomechanical circuits in the frame of optomechanically-driven signal-processing applications.
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Análise dos eventos de aceleração dos motores e dissipação de energia na fase de descida das aeronaves Boeing 737NG da VRG Linhas AéreasScorza, Pedro Rodrigo January 2010 (has links)
Esta dissertação propõe um método de análise dos eventos de aceleração dos motores e dissipação de energia através do uso dos freios aerodinâmicos na fase de descida das aeronaves Boeing 737 NG da VRG Linhas Aéreas, baseando-se nos conceitos de energia, de aproximações em descidas contínuas e desenho dos procedimentos de chegadas, revisando as bases das práticas de conservação de combustível e dos sistemas de garantia da qualidade das operações de vôo. Foram analisadas mais de 130.000 descidas em um período de nove meses, durante a operação normal da empresa, através de leitura de dados dos gravadores de vôo que resultaram, após aplicação de algoritmos matemáticos simples e filtros, em mais de 314.000 eventos isolados. Estes eventos foram tratados com uma visão estatística, permitindo a quantificação financeira dos eventos através da proporcionalidade da variação de combustível consumido e energia agregada ou dissipada da aeronave. Os resultados obtidos através do método apresentado permitiram apontar as famílias, séries e prefixos de aeronaves com diferentes desempenhos nas descidas, as cidades de destino e rotas com desempenho baixo quanto a conservação de combustível e energia, assim apontando os possíveis caminhos para a empresa focar esforços na redução do custo de combustível. / This paper proposes a method of analysis of fuel consumption and energy dissipation events, as a consequence of engines acceleration and the use of speed brakes during the Boeing 737 NG descent segment of VRG Linhas Aéreas, based on the concepts of energy, continuous descent approaches and design of arrivals procedures, reviewing the basics of fuel conservation practices and flight operations quality assurance systems.There were analyzed more than 130,000 descents in a period of nine months, during the company normal operation, by reading data from flight recorders that resulted in, after the application of simple mathematical algorithms and filters, more than 314,000 individual events. These events were treated with a statistical view, to quantify the financial impact of this events through the proportionality of the variation in fuel consumption and energy added or dissipated by the aircraft.The results obtained using this method allowed to understand families, series and tail numbers of aircrafts with different performances on the descent phase, the destination cities and routes with poor performance in energy and fuel conservation, thus indicating a possible focus to enhance efforts to reduce total fuel costs.
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Self-regulation and quality of life after a heart attack : a cross-cultural studyNayoan, Johana January 2010 (has links)
Objective. Coronary heart disease has been on the rise in poorer countries and decreasing in developed countries over the last twenty years. However, the cardiac-related health-related quality of life (HRQOL) in poorer countries has not been studied. This study aimed to compare HRQOL following heart attack in a developing country in the East with that of a developed country in the West. Using the self-regulation of health and illness behaviour, the relationships between illness beliefs, coping cognitions and HRQOL are studied. Design. This study was a cross-sectional correlational survey and data were collected shortly before myocardial infarction patients were discharged from hospital. Methods. A sample of 243 individuals from the UK and Indonesia were recruited. Illness beliefs were assessed with the B-IPQ, along with coping cognitions (Brief-COPE) and health-related quality of life (MacNew questionnaire). Results. Illness beliefs and coping cognitions predicted HRQOL in the combined sample. Some aspects of socio-demographic and clinical variables were concurrently associated with HRQOL. Conclusion. The results demonstrate that people in the East have low illness beliefs and these are associated with worse HRQOL compared with those in the West. The findings suggest that there is an urgent need for smoking cessation campaigns in the East, while the West could benefit more from tailored-cardiac rehabilitation programme.
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Développement d’une approche de prévention nutritionnelle sur-mesure à destination des individus, prenant en compte différentes dimensions de l’alimentation durable / Development of a tailored nutrition counselling approach for individuals, taking into account several dimensions of diet sustainabilityGazan, Rozenn 13 July 2018 (has links)
Promouvoir des choix alimentaires en accord avec les quatre dimensions de l’alimentation durable, à savoir la nutrition (en lien avec la santé), l’économie, le socio-culturel et l’environnement, est une priorité nationale et mondiale.L’objectif de cette thèse était de proposer une approche de prévention nutritionnelle sur-mesure, à destination des individus, prenant en compte différentes dimensions de l’alimentation durable. Pour cela, nous avons i) compilé des données hétérogènes issues de sources variées ; ii) proposé une méthode d’analyse multicritère ; iii) réalisé un outil permettant de générer des conseils en accord avec les préférences de chacun.Nous avons réalisé une revue de la littérature, qui souligne l’intérêt d’utiliser l’optimisation des consommations alimentaires pour identifier des régimes durables. Une méthodologie reproductible de compilation de données a été développée et appliquée à la construction d’une base de données unique, nommée « SUStable », intégrant les métriques associées à chaque dimension de la durabilité pour plus de 200 aliments couramment consommés en France.Sur la base de théories du changement de comportement, nous avons développé « Mon Alimentation Sur-Mesure », un prototype d’application web de conseils alimentaires sur-mesure. Un questionnaire de fréquence alimentaire de 94 items, intégré dans l’application, a été validé théoriquement afin d’estimer l’erreur de mesure induite par la structure du questionnaire (utilisation d’une liste finie d’items et de tailles de portions). Avec « Mon Alimentation Sur-Mesure », l’utilisateur peut connaitre la qualité de ses consommations alimentaires, le coût de son alimentation et son niveau d’activité physique. L’utilisateur est acteur de son changement : il précise ses préférences alimentaires ; il choisit, parmi trois modèles d’optimisation des consommations alimentaires, celui qui correspond le mieux à ses attentes ; il choisit les conseils qui lui semblent réalistes.Le prototype d’application développé est innovant dans la mesure où il considère l’alimentation dans sa globalité et rend l’utilisateur actif pour générer les conseils qui lui conviennent le mieux. Cette application pourrait être un futur outil de prévention en santé qui contribuerait à la reprise en main des individus sur leur alimentation. / Promoting food choices in line with the four dimensions of diet sustainability, namely nutrition related to health, economy, socio-cultural and environment, is a national and global priority.The aim of this thesis was to develop a tailored nutrition counselling approach for individuals, taking into account several dimensions of diet sustainability. To achieve this, we have: i) compiled heterogeneous data from various sources; ii) proposed a method for multi-criteria assessment; iii) developed a tool to provide dietary advices which are in accordance with individual’s preferences.We have written a narrative review that demonstrates the added value of diet optimization to identify sustainable diets. A reproducible methodology was developed and applied to the creation of a unique food database, named SUStable, integrating metrics associated with each dimension of diet sustainability for more than 200 foods representative of the French food consumption.We developed a theory-based web application, named “Mon Alimentation Sur-Mesure”, which provides tailored dietary advices. A food frequency questionnaire of 94 items was validated theoretically in order to estimate the error due to the inherent structure of the questionnaire (use of a finite list of items and portion sizes). With “Mon Alimentation Sur-Mesure”, the user can obtain a picture of the nutritional quality of her/his diet, her/his diet cost and her/his level of physical activity. The user is actor in her/his own dietary changes: she/he specifies her/his food preferences; she/he selects, among three diet optimization models, the one that best suits her/his expectations; she/he chooses dietary advices that she/he considers achievable.The application prototype is innovative: it uses a whole-diet approach and allows the user to act to choose her/his advices. This prototype could be a future online health promotion tool which could help individuals to take in hand their diet.
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