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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Early Childhood Caries in children 12-24 months old in Mitchell's Plain, South Africa.

Ali, Mustafa. January 2008 (has links)
<p>The American Academy of Pediatric Dentistry (2005/06) defines Early Childhood Caries (ECC) as the presence of 1 or more decayed (noncavitated or cavitated lesions), missing (due to caries), or filled tooth surfaces in any primary tooth in a child 71 months of age or younger. ECC can cause significant problems in preschool children and is a source of considerable societal costs. The South African national oral health survey conducted between the year 1999 and 2002 reported on the caries prevalence in young children. The caries prevalence was 50% in 4-5 year old children with a mean dmft of 2.4 (van Wyk and van Wyk, 2004).The aim of the study is to assess early childhood caries in children 12-24 months in the Mitchell's Plain district of the Western Cape.Objectives are to determine: a) The prevalence and pattern of early childhood caries. b) The relation between early childhood caries and infant feeding practices. c) The relation between early childhood caries and oral hygiene practices of the child.</p> <p>This study is a cross sectional study of ECC of children 12-24 months of age. Parent/child pair attending the Well Baby Clinic at Eastridge/Mitchell's Plain were informed about the study and invited to participate on a voluntary basis. The data collected consisted of a dental examination of 120 children (stratified by age: 60 in 12-18 months age group and 60 in 19-24 months age group) and a questionnaire completed by the accompanying parent/guardian. The dental examination was conducted using the WHO guidelines (Geneva 1997). Child age, tooth status (sound, decayed, filled, extracted, unerupted), and visible dental plaque on maxillary incisors (Spitz et al, 2006) were recorded.The prevalence of ECC for the sample was 23.3% (dmft =0.88). The maxillary incisors had the highest prevalence of decay (14%) followed by the maxillary molars (4%). There was a significant association (p=.006) between duration (12 months and more) of bottle use and presence of caries (40% caries prevalence). There is no significant difference between the different feeding practices (breast, bottle or both) and the presence of caries. There is a high prevalence of Early Childhood Caries (23.3%) in the 12-24 month age group. Early Childhood Caries was related to prolonged (&gt / 12 months) bottle feeding. The association between the presence of dental plaque and ECC was the most significant factor (p= .000).</p>
122

Processamento e caracteriza??o da blenda poli (metacrilato de metila) (PMMA) elastomerico e poli (tereftalato de etileno) (PET) p?s-consumo

Reinaldo, Jucikl?cia da Silva 23 August 2013 (has links)
Made available in DSpace on 2014-12-17T14:07:12Z (GMT). No. of bitstreams: 1 JucikleciaSR_DISSERT.pdf: 18878091 bytes, checksum: 13af0d90d6b4b0980975e46b7393cd8c (MD5) Previous issue date: 2013-08-23 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This work studied the immiscible blend of elastomeric poly(methyl methacrylate) (PMMA) with poly(ethylene terephthalate) (PET) bottle grade with and without the use of compatibilizer agent, poly(methyl methacrylate-co-glycidyl methacrylate - co-ethyl acrylate) (MGE). The characterizations of torque rheometry, melt flow index measurement (MFI), measuring the density and the degree of cristallinity by pycnometry, tensile testing, method of work essential fracture (EWF), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were performed in pure polymer and blends PMMA/PET. The rheological results showed evidence of signs of chemical reaction between the epoxy group MGE with the end groups of the PET chains and also to the elastomeric phase of PMMA. The increase in the concentration of PET reduced torque and adding MGE increased the torque of the blend of PMMA/PET. The results of the MFI also show that elastomeric PMMA showed lower flow and thus higher viscosity than PET. In the results of picnometry observed that increasing the percentage of PET resulted in an increase in density and degree crystallinity of the blends PMMA/PET. The tensile test showed that increasing the percentage of PET resulted in an increase in ultimate strength and elastic modulus and decrease in elongation at break. However, in the phase inversion, where the blend showed evidence of a co-continuous morphology and also, with 30% PET dispersed phase and compatibilized with 5% MGE, there were significant results elongation at break compared to elastomeric PMMA. The applicability of the method of essential work of fracture was shown to be possible for most formulations. And it was observed that with increasing elastomeric PMMA in the formulations of the blends there was an improvement in specific amounts of essential work of fracture (We) and a decrease in the values of specific non-essential work of fracture (&#946;Wp) / Neste trabalho ? estudada a blenda imisc?vel poli(metacrilato de metila) (PMMA) elastom?rico com poli(tereftalato de etileno) (PET) grau garrafa com e sem o uso do agente compatibilizante, poli(metacrilato de metila-co-metacrilato de glicidilaco- acrilato de etila) (MGE). As caracteriza??es de reometria de torque, medida de ?ndice de fluidez (MFI), determina??o da densidade e do grau de cristalinidade por picnometria, ensaio de tra??o uniaxial, m?todo do trabalho essencial fratura (EWF), microscopia eletr?nica de varredura (MEV) e microscopia eletr?nica de transmiss?o (MET), foram realizadas nos pol?meros puros e nas blendas PMMA/PET. Os resultados reol?gicos apresentaram ind?cios de rea??o qu?mica entre o grupo ep?xi do MGE com os grupos finais de cadeias do PET e, tamb?m, com a fase elastom?rica do PMMA. O aumento na concentra??o de PET reduziu o torque e a adi??o do MGE aumentou o torque da blenda PMMA/PET. Os resultados de MFI mostraram tamb?m que, o PMMA elastom?rico apresentou menor fluidez e, consequentemente, maior viscosidade que o PET. Nos resultados de picnometria observou-se que, o aumento da porcentagem de PET proporcionou um aumento na densidade e no grau de cristalinidade das blendas PMMA/PET. Os ensaios de tra??o mostraram que, o aumento da porcentagem de PET proporcionou um aumento na resist?ncia m?xima e no m?dulo de elasticidade e uma diminui??o no alongamento na ruptura. Entretanto, na invers?o de fase, onde a blenda apresentou ind?cios de uma morfologia cocont?nua e tamb?m, com 30% de fase dispersa PET e compatibilizada com 5% de MGE, verificaram-se resultados expressivos de alongamento na ruptura em rela??o ao PMMA elastom?rico. A aplicabilidade do m?todo do trabalho essencial de fratura mostrou-se poss?vel para a maioria das formula??es. Observou-se ainda que, com o aumento do PMMA elastom?rico nas formula??es das blendas, ocorreu uma melhoria nos valores do trabalho essencial espec?fico de fratura (We) e uma redu??o nos valores do trabalho n?o essencial espec?fico de fratura (&#946;Wp)
123

Lévi-Strauss e a tríade da estrutura: a linguagem, o simbólico e o inconsciente

Mendes, Tássia Nogueira Eid 10 April 2014 (has links)
Made available in DSpace on 2016-06-02T20:13:15Z (GMT). No. of bitstreams: 1 5889.pdf: 1158628 bytes, checksum: eb3e8512fbb67f17e03cf8a0d7697ebe (MD5) Previous issue date: 2014-04-10 / Universidade Federal de Sao Carlos / This research had as a goal a better definition of the notion of unconscious in the work of Claude Lévi-Strauss. In the early texts, such as The Symbolic Efficacy (1949), this concept is introduced as a set of structural laws, named Symbolic function. Nevertheless, throughout the path of the levi-straussian work, this terminology fades bit-by-bit, making room for concepts like the symbolic thought. In its turn, this concept imprints the determination of symbolism, characteristic that defines mankind, and thus, the unconscious defines humanity itself. Placed between nature and culture, the unconscious therefore is paradoxically plural and universal, allowing the apprehension of an integrated reality. The pair unconscious/ conscious characterizes the different levels of the phenomenon that Lévi-Strauss analyses in his anthropology, granting two types of investigation: inductive and deductive. The proposal of an unconscious facet of the social phenomenon made possible the prescription of two discontinued methods. The exam of the empirical and transcendental realities is orchestrated in a way of establishing, at the same time, an irreducibly statement between nature and culture and a refusal to old-fashioned dualisms. In this work, throughout the developments of the notion unconscious in the work of Lévi-Strauss, we hope to demonstrate that this concept is symbolic, and that such an analysis implies the investigation of the passage between nature and culture. Therefore, we hope to set the implications of this notion to the definition of mankind in the work of Lévi- Strauss. / Esse trabalho teve como objetivo melhor definir a noção de inconsciente na obra de Lévi-Strauss. Em textos iniciais, como a A eficácia simbólica (1949), esse conceito é apresentado como um conjunto de leis estruturais, nomeado função simbólica. Não obstante, ao longo do percurso da obra levistraussiana, pouco a pouco, o termo função simbólica se desvanece, dando lugar a conceitos como: pensamento simbólico. Este, por sua vez, marca a determinação do simbolismo na obra do antropólogo, noção, esta, que define o estatuto de humanidade. Desse modo, o inconsciente passa a caracterizar não só o pensamento simbólico, mas a própria definição da humanidade (LÉVI-STRAUSS, 2012). Situado entre natureza e cultura tal qual o homem e, portanto, paradoxalmente plural e universal, o inconsciente levistraussiano permite a apreensão de uma realidade integrada. O par consciente/inconsciente, ao qualificar os diferentes níveis dos fenômenos aos quais se dedica Lévi-Strauss, operacionaliza o uso tanto da indução quanto da dedução na investigação a que se propôs. A postulação de uma faceta inconsciente dos fenômenos sociais foi o que permitiu uma abordagem completa da realidade, prescrevendo métodos aparentemente descontínuos.. Desse modo, a abordagem do empírico e do transcendental é orquestrada de maneira a prescrever uma irredutibilidade entre as ordens natureza e cultura, ao mesmo tempo, uma recusa à antigos dualismos (sensível/inteligível, corpo/espírito, natureza/cultura). Neste texto, esperamos, através da marcha demonstrativa da função simbólica ao longo dos desenvolvimentos da obra do antropólogo, ter contribuído para uma compreensão do inconsciente, na antropologia estrutural, como simbólico. Ordem que subjaz a pluralidade cultural, assim como confere o universal almejado pela cientificidade esquadrinhada por Lévi-Strauss. A análise do conceito de função simbólica implica, inelutavelmente, o exame da passagem entre natureza e cultura, bem como o lugar que cabe a humanidade mediante estas duas esferas.
124

Prevalência de cárie em bebês com fissuras labiopalatinas e sua correlação com fatores socioeconômicos e hábitos de higiene bucal

Thaieny Ribeiro da Silva 27 July 2015 (has links)
Este trabalho analisou a prevalência de cárie e sua correlação com fatores sociodemográficos e cuidados de higiene bucal em 145 crianças com fissura labiopalatina (GF) na faixa etária de 7 a 66 meses, comparando os resultados com 130 crianças sem fissura (GC), na mesma faixa etária. A prevalência de cárie foi avaliada pelo índice ceo-d, e as famílias responderam um questionário contendo perguntas sobre hábitos dietéticos e de higiene bucal e fatores sociodemográficos. Os resultados foram avaliados por estatística descritiva e comparados pelos testes qui-quadrado, Mann-Whitney, Kruskal-Wallis e coeficiente de correlação de Spearman. O índice ceo-d médio foi 1,5 para o GF e 0,8 para o GC, sem diferença estatística (p=0,072). A maioria (99% no GF e 98,5% no GC) relatou realizar higiene bucal na criança, havendo receio em realizar este procedimento por 26,6% no GF e 6,3% no GC (p<0,001). A introdução de açúcar foi mais precoce no GF (p<0,001), enquanto a mamadeira de madrugada após os seis meses de idade foi mais frequente no GC (p=0,023). A higiene bucal foi iniciada mais precocemente no GF (p<0,001). A análise da ocorrência de cárie por dente revelou maior prevalência no GF para os dentes 55 (p=0,025), 52 (p<0,001), 51 (p=0,022), 62 (p<0,001) e 65 (p=0,006). Foi observada correlação significativa entre cárie e o aumento da idade e número de dentes presentes para o GF (p<0,001 para ambos) e GC (p=0,002 e p=0,004, respectivamente). Foi observada associação significativa entre cárie e renda familiar apenas para o GC (p=0,028). / This study analyzed the prevalence of dental caries and its correlation with sociodemographic factors and oral hygiene care in 145 children with cleft lip and palate (GF) aged 7 to 66 months, compared to 130 children without clefts (GC), at the same age range. The caries prevalence was analyzed by the dmft index, and the families responded to a questionnaire containing questions on dietary and oral hygiene habits and sociodemographic factors. The results were assessed by descriptive statistics and compared by the chi-square, Mann- Whitney and Kruskal-Wallis tests and Spearmans correlation coefficient. The mean dmft was 1.5 for GF and 0.8 for GC, without statistical difference (p=0.072). Most individuals (99% in GF and 98.5% in GC) reported performing oral hygiene in the child, with fear to perform this procedure by 26.6% in GF and 6.3% in GC (p<0.001). The introduction of sugar occurred earlier in GF (p<0.001), while bottle feeding at night after six months of age was more frequent in GC (p=0.023). The oral hygiene was initiated earlier in GF (p<0.001). Analysis of the occurrence of caries per tooth revealed higher prevalence in GF for the teeth 55 (p=0.025), 52 (p<0.001), 51 (p=0.022), 62 (p<0.001) and 65 (p=0.006). Significant correlation was observed between dental caries and increase in age and in number of present teeth for GF (p<0.001 for both) and GC (p=0.002 and p=0.004, respectively). Significant association between dental caries and family income was only observed for GC (p=0.028).
125

O Teorema de Poincaré-Bendixson para campos vetoriais contínuos na garrafa de Klein / The Poincaré-Bendixson Theorem for continuous vector fields on the Klein bottle

Daniela Paula Demuner 05 February 2009 (has links)
Neste trabalho apresentamos uma versão do Teorema de Poincaré-Bendixson para campos vetoriais contínuos na garrafa de Klein. Como conseqüência, mostramos que a garrafa de Klein não possui campo vetorial contínuo com trajetória injetiva recorrente / We present a version of the Poincaré-Bendixson Theorem on the Klein bottle for continuous vector fields. As a consequence, we obtain the fact that the Klein bottle does not admit continuous vector fields having a recurrent injective trajectory
126

Estudo das características da oclusão na dentição decídua e na mista e fatores associados / Study of the characteristics of occlusion in deciduous dentition and mixed and associated factors

Costa, Catiara Terra da 09 August 2013 (has links)
Made available in DSpace on 2014-08-20T14:30:10Z (GMT). No. of bitstreams: 1 tese_catiara_terra_costa.pdf: 2345268 bytes, checksum: 562e208284c988b88f8298b81b142463 (MD5) Previous issue date: 2013-08-09 / Knowing the occlusal characteristics of deciduous and mixed dentition, its development, changes and possible influencing factors is important for prevention and interception of malocclusion, being it of great epidemiological value. For this,longitudinal studies are appropriate because they observe the same population in different time points. This study consisted of two parts: cross-sectional and longitudinal study. The cross-sectional study investigated the influence of demographic, behavioral and socioeconomic factors at time breastfeeding of the child and the influence of the same in occlusal characteristics of primary dentition. It was found that the statistically significant factors for breastfeeding were time use of baby bottle (p<0.001) and time-use of pacifier (p<0.001), moreover, in relation to dental occlusion were associated the relation of canines (p=0.002), the midline deviation (p=0.013), anterior open bite (p<0.000), overjet (p<0.001), posterior crossbite (p=0.006) and presence of malocclusion (p<0.001). The longitudinal study compared occlusal characteristics present in children in primary dentition and mixed dentition, six years after. Were eligible all children examined in 2007 that, after contact with the mother, were reassessed and were in the mixed dentition. For data collection was performed clinical evaluation, by only one specialized and calibrated examiner, comprising occlusion, presence of visible plaque, dental trauma and experience of dental caries. After, interview was applied to mother investigating age and schooling, current income, child's oral habits, among others, and questioning the child about dietary habits, hygiene habits and selfperception. Descriptive analyzes were performed and to test the influence of the variables on the outcomes were used chi-10 square test, Fisher exact test and McNemar test. It was found that the anterior open bite (p<0.001), spacing (p=0.001), overjet (p=0.012), crowding (p<0.001) and malocclusion (p<0.001) presented association between deciduous and mixed dentition. And veryfing the factors that influence the crowding in the mixed dentition it was found the deciduous arch type (p<0.001), primate spaces (p=0.050) and the presence of crowding in primary dentition (p=0.014). The follow up of occlusion development showed that the presence of malocclusion is associated between deciduous and mixed dentition and thus, prevent or intercept these types of malocclusions in the primary dentition can improve the occlusion in mixed dentition. / Conhecer as características oclusais das dentições decídua e mista, seu desenvolvimento, alterações e possíveis fatores influentes é importante para a prevenção e interceptação das maloclusões, tornando-se de grande valor epidemiológico. Para isto, estudos longitudinais são apropriados, pois observam a mesma população em momentos temporais diferentes. Este estudo foi constituído de duas partes: estudo transversal e estudo longitudinal. O estudo transversal investigou a influência dos fatores demográficos, comportamentais e socioeconômicos no tempo de aleitamento materno da criança e a influência do mesmo em características oclusais da dentição decídua. Identificou-se que os fatores estatisticamente significantes para o aleitamento natural foram o tempo de uso da mamadeira (p<0,001) e o tempo de uso da chupeta (p<0,001), além do que, em relação à oclusão dentária apresentaram associação a relação de caninos (p=0,002), o desvio da linha média (p=0,013), a mordida aberta anterior (p<0,001), a sobressaliência (p<0,001), a mordida cruzada posterior (p=0,006) e a presença de maloclusão (p<0,001). O estudo longitudinal comparou características oclusais presentes nas crianças na dentição decídua e na dentição mista, seis anos após. Foram elegíveis todas as crianças examinadas em 2007 que, após contato com a mãe, foram reavaliadas e estavam na dentição mista. Para a coleta dos dados foi realizada a avaliação clínica, por única examinadora especializada e calibrada, englobando oclusão, presença de placa visível, traumatismo dentário e experiência de cárie dentária. Após, foi aplicada entrevista à mãe investigando idade e escolaridade, renda atual, hábitos bucais da criança, dentre outros e à criança questionando sobre hábitos de dieta, de higiene e autopercepção. Foram realizadas análises descritivas e para testar a influência das variáveis sobre os desfechos foram utilizados os testes: qui-quadrado, exato de Fischer e de McNemar. Constatou-se 8 que a mordida aberta anterior (p<0,001), o espaçamento (p=0,001), a sobressaliência (p=0,012), o apinhamento dentário (p<0,001) e a presença de maloclusão (p<0,001) apresentaram associação entre as dentições decídua e mista. E, verificando-se os fatores que influenciam no apinhamento dentário na dentição mista encontrou-se o tipo de arco decíduo (p<0,001), espaços primata (p=0,050) e a presença de apinhamento na dentição decídua (p=0,014). O acompanhamento longitudinal do desenvolvimento da oclusão mostrou que a presença de maloclusões está associada entre as dentições decídua e mista e, portanto, prevenir ou interceptar estes tipos de maloclusões na dentição decídua pode melhorar as condições de oclusão na dentição mista.
127

Early Childhood Caries in children 12-24 months old in Mitchell's Plain, South Africa

Ali, Mustafa January 2008 (has links)
Magister Scientiae Dentium - MSc(Dent) / The American Academy of Pediatric Dentistry (2005/06) defines Early Childhood Caries (ECC) as the presence of 1 or more decayed (noncavitated or cavitated lesions), missing (due to caries), or filled tooth surfaces in any primary tooth in a child 71 months of age or younger. ECC can cause significant problems in preschool children and is a source of considerable societal costs. The South African national oral health survey conducted between the year 1999 and 2002 reported on the caries prevalence in young children. The caries prevalence was 50% in 4-5 year old children with a mean dmft of 2.4 (van Wyk and van Wyk, 2004).The aim of the study is to assess early childhood caries in children 12-24 months in the Mitchell's Plain district of the Western Cape.Objectives are to determine: a) The prevalence and pattern of early childhood caries. b) The relation between early childhood caries and infant feeding practices. c) The relation between early childhood caries and oral hygiene practices of the child.This study is a cross sectional study of ECC of children 12-24 months of age. Parent/child pair attending the Well Baby Clinic at Eastridge/Mitchell's Plain were informed about the study and invited to participate on a voluntary basis. The data collected consisted of a dental examination of 120 children (stratified by age: 60 in 12-18 months age group and 60 in 19-24 months age group) and a questionnaire completed by the accompanying parent/guardian. The dental examination was conducted using the WHO guidelines (Geneva 1997). Child age, tooth status (sound, decayed, filled, extracted, unerupted), and visible dental plaque on maxillary incisors (Spitz et al, 2006) were recorded.The prevalence of ECC for the sample was 23.3% (dmft =0.88). The maxillary incisors had the highest prevalence of decay (14%) followed by the maxillary molars (4%). There was a significant association (p=.006) between duration (12 months and more) of bottle use and presence of caries (40% caries prevalence). There is no significant difference between the different feeding practices (breast, bottle or both) and the presence of caries. There is a high prevalence of Early Childhood Caries (23.3%) in the 12-24 month age group. Early Childhood Caries was related to prolonged (12 months) bottle feeding. The association between the presence of dental plaque and ECC was the most significant factor (p= .000). / South Africa
128

Géométrie systolique extrémale sur les surfaces / Extremal systolic geometry on surfaces

Yassine, Zeina 16 June 2016 (has links)
En 1949, C. Loewner a demontré dans un travail non publié l'inégalité systolique optimale du tore T reliant l'aire au carré de la systole. Par la systole on désigne la longueur du plus court lacet non contractile de T. De plus, l' égalité est atteinte si et seulement si le tore est plat hexagonal. Ce résultat a donné naissance à la géométrie systolique. Dans cette thèse, nous étudions des inégalités de type systolique portant sur les longueurs minimales de différentes courbes et pas seulement la systole.Dans un premier temps, nous démontrons trois inégalités géométriques optimales conformes sur la bouteille de Klein reliant l'aire au produit des longueurs des plus courts lacets noncontractiles dans des classes d'homotopie libres différentes. Pour chaque classe conforme, nous décrivons la métrique extrémale réalisant le cas d'égalité.Nous établissons ensuite des inégalités géométriques optimales sur le ruban deMobius muni d'une métrique de Finsler. Ces inégalités géométriques relient la systole et la hauteur du ruban de Mobius à son volume de Holmes-Thompson. Nous en déduisons une inégalité systolique optimale sur la bouteille de Klein munie d'une métrique de Finsler avec des symétries. Nous décrivons également une famille de métriques extrémales dans les deux cas.Dans le troisième travail, nous démontrons une inégalité systolique critique sur la surface de genre deux. Plus précisément, il est connu que la surface de genre deux admet une métrique Riemannienne plate à singularités coniques qui est extrémale parmi les métriques à courbure nonpositive pour l' inégalité systolique. Nous montrons que cette métrique est en fait critique pour des variations lentes de métriques, cette fois-ci sans hypothèse de courbure, pour un autre problème systolique portant sur les longueurs des plus courts lacets non contractiles dans certaines classes d'homotopie libres données. Ces classes d'homotopie correspondent aux lacets systoliques et deux-systoliques de la surface extrémale / In 1949, C. Loewner proved in an unpublished work that the two-torus T satisfies an optimal systolic inequality relating the area of the torus to the square of its systole. By a systole here we mean the smallest length of a noncontractible loop in T. Furthermore, the equality is attained if and only if the torus is flat hexagonal. This result led to whatwas called later systolic geometry. In this thesis, we study several systolic-like inequalities. These inequalities involve the minimal length of various curves and not merely the systole.First we obtain three optimal conformal geometric inequalities on Riemannian Klein bottles relating the area to the product of the lengths of the shortest noncontractible loops in different free homotopy classes. We describe the extremal metrics in each conformal class.Then we prove optimal systolic inequalities on Finsler Mobius bands relating the systoleand the height of the Mobius band to its Holmes-Thompson volume. We also establish an optimalsystolic inequality for Finsler Klein bottles with symmetries. We describe extremal metric families in both cases.Finally, we prove a critical systolic inequality on genus two surface. More precisely, it is known that the genus two surface admits a piecewise flat metric with conical singularities which is extremal for the systolic inequality among all nonpositively curved Riemannian metrics. We show that this piecewise flat metric is also critical for slow metric variations, this time without curvature restrictions, for another type of systolic inequality involving the lengths of the shortest noncontractible loops in different free homotopy classes. The free homotopy classes considered correspond to those of the systolic loops and the second-systolic loops of the extremal surface
129

Revêtements barrière d'alumine amorphe appliqués à l’intérieur de flacons pharmaceutiques en verre, par le procédé de dépôt chimique en phase vapeur. / Amorphous alumina barrier coatings applied by chemical vapor deposition on the inner surface of pharmaceutical glass bottles.

Etchepare, Pierre-Luc 23 July 2015 (has links)
Les matériaux utilisés dans le domaine de l’emballage sont parfois revêtus d’une couche barrière afin de réduire les interactions entre le contenant et son contenu. Sur les flacons en verre, le dépôt de ces couches permet de limiter la dégradation de leur surface interne, de réduire le lessivage des cations du verre et d’améliorer la stabilité des propriétés du produit au contact. Dans ce contexte, un procédé de dépôt chimique en phase vapeur (CVD) à partir de tri-isopropoxyde d’aluminium (TIA) par injection liquide directe est mis en œuvre pour appliquer des revêtements d’alumine amorphe sur les parois internes de flacons en verre. Etant donné le nombre important de paramètres expérimentaux et la complexité de la géométrie à revêtir (une cavité avec un seul orifice étroit), le procédé de dépôt est modélisé avec le code de Mécanique des Fluides Numériques Fluent. Le modèle représente les profils locaux de vitesse d’écoulement, de température et de concentration des espèces gazeuses dans l’enceinte réactionnelle, ainsi que les vitesses locales de croissance, s’appuyant sur une loi cinétique hétérogène apparente de décomposition du TIA en alumine. Il permet une meilleure compréhension des phénomènes physico-chimiques se produisant à l’intérieur du corps creux et conduit ainsi à l’amélioration de la configuration du réacteur pour obtenir une couche mince transparente et d’épaisseur relativement uniforme. Le modèle est ensuite utilisé comme guide dans le choix des conditions opératoires pour revêtir la surface interne du flacon à pressions élevées, se rapprochant des conditions de fonctionnement à pression atmosphérique sur les lignes de production industrielle. Une interaction entre expériences et simulations est nécessaire pour adapter la configuration du réacteur aux dépôts à hautes pressions. Des films submicroniques sont déposés à différentes pressions de 666 Pa àt 97,3 kPa, pour un profil prédéterminé de températures le long des parois du flacon comprises entre 480 et 650 °C. Les films obtenus sont amorphes, stœchiométriques, sans traces de carbone et présentent une microstructure dense et légèrement rugueuse. Les flacons revêtus sont soumis à un essai de vieillissement hydrothermal lors d’un cycle de stérilisation pendant une heure à 121 °C et 200 kPa en contact avec de l’eau ultra-pure. La résistance hydrolytique, qui correspond à la résistance du verre à la cession de substances minérales solubles au contact de l’eau est évaluée pour des revêtements de différentes épaisseurs comprises entre 45 et 650 nm en moyenne. Les mécanismes de diffusion et d’extraction des cations sont analysés par spectroscopie de photoélectrons induits par rayons X et spectrométrie par torche plasma. Les effets du vieillissement sur l’adhérence, la nature et la microstructure en surface de la couche d’alumine amorphe sont étudiés. Une synthèse évaluant entre autre la robustesse du procédé, les vitesses de dépôt, les performances barrières et la résistance au vieillissement hydrothermal des couches minces d’alumine, en vis-à-vis des solutions de traitements de surface sur flacon déjà existantes, permet de conclure sur la maturité industrielle et la valeur ajoutée de ce procédé. / Materials for packaging applications are sometimes coated with a barrier film in order to decrease the interactions between the content and the container. Deposition of such coatings on glass bottles allows limiting the deterioration of the internal surface, decreasing the leaching of cations from the glass and improving the stability of the properties of the liquid content. In this context, a chemical vapor deposition (CVD) process has been designed for the deposition of amorphous alumina thin films on the inner walls of a glass container. The process involves aluminum tri-isopropoxide (ATI), which is fed to the deposition volume by a direct liquid injection (DLI) technology. Given the number of experimental parameters and the complexity of the substrate (a hollow body with a unique narrow entrance), a model of the process has been developed with the Computational Fluid Dynamics code Fluent. The model displays the local profiles of mass flow, temperature and gas species concentrations in the reactor, and the local growth rates based on the kinetic law of the apparent heterogeneous reaction of ATI decomposition to alumina. A good agreement has been found between the experimental and the calculated growth rates. The model allowed gaining a better insight into the physic-chemical phenomena occurring inside the hollow body and thus improving the reactor configuration to obtain transparent and relatively uniform thin films. Following, the model was used as a guide for the choice of the operating conditions of the depositions at higher pressure. An interplay between experimental and simulated results was used to adapt the reactor configuration for depositions at atmospheric pressure. Submicronic films were performed for several pressures between 666 Pa and 97.3 kPa, for thermal profiles along the bottle walls ranging from 753K to 923K. The deposited films are amorphous, stoichiometric without carbon residues, dense and slightly rough. The coated bottles underwent a test of hydrothermal ageing with a cycle of sterilization filled with ultra-pure water during one hour at 121°C and 200 kPa. The hydrolytic resistance, which is the resistance of the glass to the release of soluble mineral substances into water, is measured for films with several thicknesses ranging from 45 to 650 nm on average. The mechanisms of diffusion and extraction for the alkali ions have been analyzed by X-ray photoelectron spectroscopy and inductively coupled plasma spectrometry. The impacts of ageing on the adhesion, the nature and the surface microstructure of the amorphous alumina films have been studied. The robustness of the process, the growth rate, barrier performances and resistance to the hydrothermal ageing of thin films, and the comparison of the above with the scarce existing solutions of surface treatments on glass bottles, allows concluding on the industrial viability and the added value of the process.
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Identifiering av flaskhalsar på ett pappersbruk : En tidsstudie på produktionsavdelningens förpackningsmaskiner. / Identification of bottle necks in a paper mill. : A time study on the production department’s packaging machines.

Karlsson, Emelie January 2020 (has links)
För att Nordic Paper Seffle AB i framtiden ska kunna utöka sin produktion eller byta ut nuvarande komponenter behöver de grunda sina beslut i fakta. På produktionsavdelningen finns idag varken dokumenterad cykeltid eller aktiviteter noterade för deras tre förpackningsmaskiner. Genom detta examensarbete kommer en tidsstudie genomföras i syfte att dokumentera maskinernas aktiviteter och identifiera flaskhalsar i flödena. Metoden som arbetet bygger på, har en grund inom Lean med verktyg och begrepp som beskrivs inom filosofin. Arbetet kommer inte involvera någon tidsstudie för operatörerna på något sätt vilket betyder att endast förpackningsmaskinerna kommer studeras. Kringarbete kommer nämnas för att ge en klarare bild på förloppet. De noterade aktiviteterna redovisas i löpande tabeller tillsammans med deras cykeltider. Efter vardera förpackningsmaskinen följer analys för hela grupper eller enskilda aktiviteter som flaskhalsar. Analysen för resultatet kommer ses ur ett effektivitetsperspektiv och liknas med bland annat de punkter som Lean presenterar för slöserier. Här kommer flaskhalsarna beskrivas samt varför de anses vara flaskhalsar för förpackningsmaskinerna. I samband redogörs även en trolig anledning och lösning för problemet. Resultatet beräknas hjälpa företaget att växa samt lägga en grund för framtida studier inom relaterade områden som kommer beskrivas ytterligare i arbetets slutsats. / If Nordic Paper Seffle AB is going to expand or exchange parts in their production in the future, they have to base their decisions in facts. Today, the production department doesn’t have any cycle times, or activities documented for their three packaging machines. By doing this thesis a time study will be performed with the purpose of documenting the machines activities and to identify bottle necks in the value stream. The thesis has its’ roots in Lean, with tools and concepts profound to the philosophy. The work won’t involve any time studies of the operators in any way. This means that it’s only the packaging machines which will be studied. Circular work will be mentioned to give a clearer picture of the process. The listed activities will be reported in tables together with their cycle times. An analysis will follow each packaging machine for whole groups or single activities, presented as bottle necks. The results will be analyzed and viewed from an efficiency perspective and will be compared to, among other things, the points Lean presents for waste. Here, the bottle necks will be described alongside why they are considered bottle necks for the packaging machines. In connection to this a probable reason and solution is presented. The result is expected to help the company grow and lay a foundation for future studies in related areas that will be further described in the conclusion.

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