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Etude des mécanismes physico-chimiques impliqués dans la dévolatilisation et l’oxydation de combustibles solides pulvérisés sous atmosphères plus ou moins riches en oxygène / Study of physical-chemical mechanisms involved in pulverized fuels devolatilization and oxidation under oxygen enriched atmospheresBruhier, Cyril 06 December 2013 (has links)
Le charbon demeure à l’heure actuelle l’un des combustibles fossiles les plus couramment employés afin de produire de l’énergie. Son utilisation accrue dans le futur devra toutefois être conciliée avec la problématique de réduction des émissions de gaz à effet de serre. Des procédés permettant de limiter les émissions de CO2 ou de faciliter son captage, à l’image de l’oxycombustion, sont de fait actuellement développés. Leur implémentation à l’échelle industrielle implique toutefois de lever un certain nombre de verrous scientifiques liés à la compréhension des mécanismes physico-chimiques d’oxydation du charbon pulvérisé sous atmosphères plus ou moins riches en oxygène. Ce travail de thèse a de fait porté sur la mise au point d’un banc d’essais de laboratoire permettant d’étudier la combustion du charbon en reproduisant des conditions de chauffe analogues à celles rencontrées industriellement. Le brûleur hybride qui a été mis au point lors de ce travail a permis d’analyser des flammes jets de combustible solide sous atmosphères O2/N2 et O2/CO2 contenant des teneurs variables en oxygène. Une caractérisation détaillée des champs de vitesse et de température dans la chambre réactionnelle a été opérée. Des mesures de température des semi-cokes dans les flammes et de concentrations d’espèces gazeuses (CO, CO2, O2, NO, NOx et SOx) ont également été réalisées tout au long de la combustion. Des prélèvements de semi-cokes à différents temps de séjour ont enfin été opérés de sorte à obtenir des profils de dévolatilisation qui ont pu être confrontés à divers modèles empiriques issus de la littérature. L’ensemble des données que nous avons obtenues nous a permis de mettre en évidence l’impact d’un enrichissement en oxygène du milieu réactionnel sur les cinétiques de dévolatilisation et sur les mécanismes de formation de polluants tels que les NOx et les SOx. Les travaux menés sous oxycombustion ont pour leur part permis de mieux appréhender les différences fondamentales entre la combustion du charbon pulvérisé sous air et sous atmosphères O2/CO2. Pour terminer, des essais préliminaires de combustion de mélanges à base de charbon et de bois ont également été menés, la co-combustion de charbon et de biomasse constituant un autre moyen de limiter les quantités nettes de CO2 émises dans l’atmosphère. / Coal is currently one of the most widely used fossil-fuel for energy production applications. Its increasing use in the near future will have to face the greenhouse gas reduction objectives. Different processes have thus been developed to reduce CO2 emissions or ease their capture as oxy-fuel combustion for instance. The implementation of such techniques at industrial scale implies fundamental works to be undertaken to better understand the physical-chemical processes involved in the oxidation of pulverized coal under oxygen enriched environments. The present work has thus focused on the development of a lab-scale test bench allowing the study of coal combustion with heating rates similar to those met in industrial combustors. The hybrid burner that has been set up allowed the analysis of different solid fuels jet-flames under O2/N2 and O2/CO2 atmospheres containing various amounts of oxygen. A detailed characterization of the velocity and temperature fields has been carried out in the combustion chamber. Char temperatures and gaseous species concentrations (CO, CO2, O2, NO, NOx and SOx) have also been monitored during the combustion. Char samples at different residence times have finally been collected to derive devolatilization profiles that have been compared to simulated data issued from various empirical models from the literature. Obtained results clearly illustrate the impact of an oxygen enrichment of the reaction medium on devolatilization kinetics and pollutants formation including NOx and SOx. Works conducted in the fields of oxy-fuel combustion allowed to better understand the fundamental differences between pulverized coal combustion under air and O2/CO2 environment. Finally, preliminary experiments have been conducted using coal and wood blends since coal co-combustion with biomass appears to be another interesting mean to reduce net CO2 emissions into the atmosphere.
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Optimisation of shrinkage in the design of compaction tooling for WC-CoBlaski, Krzysztof 29 February 2008 (has links)
Abstract
Tungsten carbide-cobalt powder is pressed before sintering into a compacted form using
punches and a die cavity. After the powder has been pressed to a specific shape, it is
sintered and shrinks a certain amount to a final size. To accommodate this shrinkage, the
pressing tools are designed to a certain “shrinkage percentage” and thus the pressed
component or compact is larger than the sintered component by that percentage amount.
During the pressing process, there is a large amount of friction between the powder being
compacted and the die cavity wall. To counter pressing friction, a lubricant is pre-mixed
with the tungsten carbide powder. In the past at Powder Industries, the powder was
mixed with wax and all of the tools were designed to a 20% shrinkage. In recent times,
the wax in the powder has been replaced by PEG (polyethylene glycol) by most
manufacturers as this increases the quality of the final product and is easier to remove in
the furnaces. As a result of the new PEG lubricant, the tool wear rate at Powder
Industries increased and because a higher pressure had been necessary to achieve powder
pressing to the same shape and form, often the pressed components exhibited cracks or
were not pressed ideally.
On account of the problems introduced by PEG, correct tool design for the shrinkage was
obtained by a ‘trial & error’ process. This project has been motivated by the need of
establishing pressing and/or design ‘rules’ that would do away with trial and error when
designing compaction tooling.
The project has consisted of investigating the physical properties of 23 grades of WC-Co
powder (with or without TiC and TaC) and of performing a series of pressing tests for
each grade. A relationship between the apparent density of a powder and the ideal green
density of the green compact pressed from the same powder has been found. Using this
relationship, an equation has been derived between ideal shrinkage, powder apparent
density, component sintered density and powder volatile content. Since the last three
parameters are known to the tool designer, this equation can be used to calculate the ideal
shrinkage when designing new compaction tooling. This method of calculating shrinkage
is now in general use at Powder Industries and many successful sets of compaction
tooling have already been manufactured
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Is there a mortality differential by marital status among women in South Africa? a study on a rural sub-district of Mpumalanga Province in the North-East South AfricaShoko, Mercy 22 September 2009 (has links)
Abstract Using longitudinal data collected between 1999 and 2007, for Agincourt Demographic
Surveillance Area, the paper examines the effect of marital status and co-residence on
mortality of women who are aged between 20 and 80. The Cox Proportional Hazard
Model is used to investigate the relationship between mortality and the covariates; marital
status, co-residence, woman’s country of origin and marital duration for married women.
The number of months the husband was resident in the ADSA is used as a proxy for coresidence.
After controlling for women migration, marital status and co-residence were
significant. The divorced/separated and widowed women had a higher probability of
dying compared to the married. In addition, being married to a migrant partner increased
the woman’s probability of dying. Thus the study concludes that marital status and coresidence
affects mortality.
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Co-writes : En studie av den musikaliska processen i låtskrivning tillsammans med andra.Wallentén, Siri January 2018 (has links)
Att skriva musik med andra personer påverkar mig både som musiker, låtskrivare och personligt. Efter ett samtal med producenten och låtskrivaren Max Thulin föddes en nyfikenhet i mig kring låtskrivning med andra personer, både okända och för mig kända personer. Jag ville genom mitt arbete undersöka hur den musikaliska processen påverkades av vem jag skrev med och vad det skulle få för effekter på mitt initiativtagande, textförfattande, melodiskrivande och producerande av en låt. Jag har i mitt arbete skrivit musik tillsammans med fyra andra musiker, två vänner och två för mig okända personer. Låtskrivningssessionerna har varit under begränsad tid och allt material har skapats på plats under sessionerna. Arbetet har resulterat i fyra låtar av olika karaktär och genre. Efter genomlyssning och analysering av låtskrivningssessionerna kan jag dra slutsatsen att mitt musikaliska initiativtagande påverkas starkt av vem jag skriver med. Jag har fått utveckla nya verktyg och tankebanor för att bland annat arbeta med textförfattande tillsammans med en annan låtskrivare, jobba med stämföring där två röster ska sjunga parallellt och bli medveten i vilka musikaliska val jag väljer att ta under en låtskrivningssession.
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Pais que retornam a residir com os filhos na velhice: novas ou velhas parcerias?Santos, Valeria Lima Antunes dos 07 April 2005 (has links)
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Previous issue date: 2005-04-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The increase in longevity in Brazil has repercussions on all the social layers; there has been a growing concern about aging. Medical sciences and technology have been offering a better quality of life to the aging being. However, how can one live these extra years with dignity, having their rights guaranteed? In our society, the family still is the link between the individual and the community in which this subject is inserted. Therefore, it is the main spring that launches the subject to life. Consequently, it is responsible for the being that is formed. It is necessary to think about the cares that are the responsibility of that institution towards its older members, when these affective bonds remain strong.
The present work aimed to investigate how the elderly person perceives the family institution nowadays, how he relates to the different generations, what difficulties he encounters in this relationship, and how he organizes himself internally before the contradictions.
To achieve this, the qualitative analysis allowed to understand, through the look of this old subject, how he faces this new transition period and the way in which he continues the life projects that had been postponed. It was possible to identify an increasing commitment of this age segment to taking into their own hands the success for achieving what they consider significant. Although living with the family, the elderly person demonstrates that he preserves the autonomy and responsibility for his choices. / O aumento da longevidade no Brasil repercute em todas as camadas sociais; há uma crescente preocupação diante do envelhecer. As ciências médicas e a tecnologia vêm proporcionando ao ser que envelhece maior qualidade de vida. Mas, como viver estes anos a mais, com dignidade e ter os direitos garantidos? Em nossa sociedade, a família ainda é o elo entre o indivíduo e a comunidade na qual esse sujeito se insere. Portanto, é a mola mestra que lança o sujeito para a vida. Conseqüentemente, é responsável pelo ser que se forma. Há que se pensar a respeito dos cuidados que cabem a essa instituição, para com os seus membros mais velhos, quando esses vínculos afetivos permanecem fortes.
O trabalho aqui realizado procurou conhecer como o idoso percebe a instituição família na atualidade, como se relaciona com as diferentes gerações, quais são as dificuldades nesse convívio e como se organiza internamente diante das contradições.
Para tanto, a análise qualitativa permitiu, mediante o olhar desse sujeito velho, compreender como enfrenta esse novo período de transição e a maneira como dá continuidade aos projetos de vida que foram postergados. Foi possível identificar um crescente comprometimento desse segmento etário em tomar para si a conquista do que considera significativo. Mesmo residindo com a família, demonstra que preserva a autonomia e a responsabilidade por suas escolhas.
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Epidemiology of infections and co-infections : impact on survival and growth of zebu cattle under one yearMwangi, Samuel Thumbi January 2012 (has links)
In any host population, individuals may be infected with multiple pathogens concurrently or in sequence. The direction and strength of pathogen-pathogen interactions are often unknown and dependent on the mechanism of interaction. This thesis is concerned with the epidemiology of infections and coinfections in zebu cattle during their first year of life, and the consequences they have for hosts’ survival probabilities and growth rates. Specifically, the study aims to: a) identify the many different pathogen infections occurring in zebu cattle under one year old, b) identify the main causes of mortality and reduced growth rates, c) test for evidence of effects of pathogen-pathogen interactions on mortality and growth, and d) determine the risk factors for infections with pathogens associated with increased mortality and reduced growth rates in zebu calves. To achieve these aims data collected from an epidemiological follow-up study of a cohort of 548 indigenous zebu cattle, recruited at birth and followed for the entire first year of life was used. Growth rates were enormously variable (52 to 704% of birth-weight) and 88 (16%) of the calves died during the first year, most from infectious disease. In total, 25,104 calf weeks of observation and data from 5,337 individual calf visits were analysed. Over 50 different pathogens were identified in the cohort. The thesis begins by providing an overview of zebu cattle and the importance of cattle diseases relevant to Sub-Saharan Africa, emphasising the importance of epidemiological studies taking into account co-infections, which are common in the natural populations, as opposed to a single-pathogen focus. A detailed description of the study design, data collection and descriptive analysis of non-infectious factors, including management and environmental factors, and a descriptive analysis of all pathogens screened for in the study are provided. Using Cox proportional models with frailty terms, the study then identifies infectious and non-infectious risk factors associated with mortality. Further, the role co-infections play in decreasing survival probabilities are investigated, revealing that the hazard for death from East Coast Fever (ECF) - the single most important disease associated with 40% of all deaths - increases 10 times in animals co-infected with Trypanosoma species, and 1.3 times for every 1000 eggs per gram faeces increase in strongyle egg count. Mixed-effect models are used to study growth rates and the impact of coinfections, revealing both synergistic interactions (lower host growth rates) of T. parva and A. marginale co-infections, and antagonistic interactions (relatively higher host growth rates) of T. parva and T. mutans co-infections compared to single infections with T. parva. Further, this work shows that helminth infections can have a strong negative effect on the growth rates but this is burden-dependent. These findings provide baseline epidemiological data on the diseases with greatest impact on health and performance of young zebu cattle, information that is valuable in the prioritisation and control of diseases. Additionally, they provide evidence of co-infections affecting host growth and survival, and have important implications on disease control strategies, suggesting benefits of aan integrated approach to control of worm, tick and tsetse-borne diseases.
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Engagement du consommateur dans la co-création de valeur : rôle des motivations et conséquences sur l'empowerment psychologique, la satisfaction et le bien-être subjectif / Consumer engagement in value co-creation : role of motivations and consequences on psychological emporwerment, satisfaction and subjective well-beingThion, Stéphane 03 April 2018 (has links)
Dans un contexte de forte compétition et d’accélération des processus d’innovation, la co-création de valeur entre l’entreprise et les consommateurs devient un avantage compétitif. Encore faut-il que le consommateur accepte de s’engager dans les interactions qui sous-tendent cette co-création de valeur. Pourquoi les consommateurs sont-ils prêts à s’engager dans la co-création de valeur ? Quelles sont les conséquences de cet engagement ? Trois études quantitatives ont été menées afin de répondre à cette problématique. Cette recherche contribue à la littérature en révélant plusieurs mécanismes : la motivation intrinsèque (plaisir d’interagir) et la motivation extrinsèque introjectée (implication de l’ego) sont les principaux moteurs de l’engagement dans des interactions co-créatrices de valeur alors que la motivation extrinsèque internalisée (sentiment de compétence) renforce la motivation intrinsèque. Cet engagement a un effet positif sur l’empowerment psychologique du consommateur. De façon surprenante, l’effet de cet engagement sur le bien-être subjectif du consommateur dépend du produit utilisé. Ces résultats contribuent à donner aux managers marketing des leviers d’actions qui leur permettront d’améliorer leur connaissance des usages afin d’adapter leur offre et innover. / In a context of strong competition and acceleration of innovation processes, value co-creation between the company and consumers becomes a competitive advantage. However, the consumer must still agree to engage in the interactions underlying value co-creation. Why are consumers willing to engage in value co-creation? What are the consequences of such engagement? Three quantitative studies were conducted to address this issue. This research contributes to the literature by revealing several mechanisms: intrinsic motivation (pleasure of interacting) and introjected extrinsic motivation (ego involvement) are the main drivers of engagement in value co-creating interactions while internalized extrinsic motivation (feeling of competence) reinforces intrinsic motivation. This engagement has a positive effect on consumer’s psychological empowerment. Surprisingly, the effect of this engagement on their subjective well-being depends on the product used. These results contribute to give levers for action to marketing managers that will improve their knowledge of uses in order to adapt their offer and innovate.
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Skrivsamarbete och produktion av elektroniska dokument i studiesammanhang / Collaborative writing and production of electronic documents in a study contextPalmquist, Jonas January 2009 (has links)
<p>This thesis paper presents experiences and views on collaborative writing from interviews with university students. Analysis of these interviews, focusing on problems with coordination and technological tools, shows that problems to some extent can be avoided with knowledge of the tools used and knowledge of coordination.</p>
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The relations between sleeping arrangements, and cultural values and beliefs in first generation Chinese immigrants in CanadaSong, Jianhui 11 1900 (has links)
The purpose of this study was to examine the relations between cultural values, social norms, and beliefs related to co-sleeping with the sleeping arrangements of first generation Chinese immigrants in Canada. The participants were 162 first generation Chinese immigrants from four Canadian cities who had children ranging from 2 months to 71 months (M = 37.9, SD = 18.06). Participants completed a questionnaire measuring their cultural values and beliefs, value of parenting roles and family, value of romantic relationships, and beliefs of sleeping arrangements. Parents indicated their sleeping arrangements (i.e. where child slept and with whom the child slept). Participants were also asked to draw a picture of their bedroom(s) which indicated the location of the childs and/or parents bed, and the distance between the two beds. Results indicated that 77% Chinese parents in this study co-slept with their pre-school aged child, whereas only 23% parents let their child sleep in their own bedroom. Among the co-sleepers, half of the children slept in their parents bed, and half of them slept in their own bed, which was either attached to the parents bed or separated from the parents bed. The mean distance between the parents bed and the childs bed was 21.15cm (SD = 42.74) for co-sleeping families, and 502.8 cm (SD = 188.69) for solitary sleeping families.
Using stepwise regression analysis, the relations between demographic factor, space availability, values, norms, and beliefs, on the one hand, and sleeping arrangements, on the other, were examined. Personal beliefs about sleeping arrangements, including cultural beliefs of independence and interdependence, beliefs of marital quality, and beliefs of solitary sleeping, influence sleeping arrangements. Parents length of residency in Canada, childs age, and bedroom numbers also influence sleeping arrangements. The findings have important implications for researchers and health professionals in terms of sleeping arrangements in the larger socio-cultural context.
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Co-branding ur ett konsumentperspektiv : En fallstudie av företaget Sony EricssonThomas, Elias, Wahlén, Jenny January 2006 (has links)
Syftet med uppsatsen har varit att undersöka hur konsumenterna uppfattar varumärkesutvidgningen. Studien har haft fokus på ett fallföretag, Sony Ericsson samt de varumärken (Walkman och Cyber-shot från Sony) som de använder på deras produkter. Vi har samlat in data med konsumenters uppfattningar om co-branding och deras brukande av produkter ur den kategori där de co-brandade varumärkena finns. Vidare har vi sökt efter förklaringar till huruvida det finns någon koppling mellan användandet av Mp3-spelare och digitalkamera i förhållande till betydelsen av varumärkena. Undersökningen har varit helt webbaserad och samlat in över 200 svar varvid 197 har använts i sammanställningen av enkätsvaren. Vi har använt oss av rådande teorier inom varumärken, varumärkeshantering, varumärkesvärdering och varumärkesfusioner. De teorier som ligger till grund för uppsatsen är Brand Management, Brand Equity, och Co-branding. Detta har tillåtit oss att gå från generella beskrivningar om varumärken fram till hantering och värdering av varumärken för att slutligen nå kärnan av uppsatsens tema det vill säga co-branding. Resultatet av undersökningen blev att det råder hög kännedom om Mp3-varumärket Walkman med en kännedom på nio av tio tillfrågade, medan drygt fyra av tio kände till digitalkamera- varumärket Cyber-shot. Av de tillfrågade som dessutom använder sig av någon av de respektive produkterna är kännedomen om förknippat varumärke ännu högre. Betydelsen av varumärkena har trots olika kännedom varit ungefär lika stora och legat under det godkända värdet på tre i den femgradiga skalan. Män har prioriterat och värderat Mp3-spelarfunktionen och Walkman högre än motsvarigheten till digitalkamera, medan kvinnornas prioritet har varit hos kamerafunktionen och Cyber-shot varumärket. Vi har kunnat dra slutsatserna att två starka varumärken som kombineras inte bidrar med lika stor synergi som ett lågvärdesvarumärke får när det kombineras med ett högvärdesvarumärke. Då varumärkena Walkman och Cyber-shot visat sig vara starka som enskilda varumärken samtidigt som Sony Ericsson är ett företag med högt anseende innebär varumärkesutvidgningen för Sony Ericssons mobiltelefoner inga ökade fördelar för Sony Ericsson. Hos dem som använder Mp3-spelare och digitalkameror har vi kommit fram till att det finns en högre kännedom om varumärkena samt att varumärkena är av större vikt när de co-brandats. Detta tycks bero på att ökad kännedom ger mer kunskap om alternativen på marknaden och skapar därför medvetenhet och preferenser hos konsumenterna. Slutligen har vi i denna undersökning upptäckt ett samband där de konsumenter som prioriterat funktionerna högt även har haft en hög prioritering av förknippat varumärke.
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