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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.
71

Mécanismes de dégradation des enveloppes barrières pour application panneaux isolants sous vide / Vacuum insulation panels (VIPs) : defects identification on the multilayer in order to investigate the effect of hygrothermal ageing in severe conditions

Dubelley, Florence 06 April 2016 (has links)
Le panneau isolant sous vide, PIV est principalement constitué d’un matériau de cœur nano-poreux encapsulé sous vide par une enveloppe barrière multicouche polymère-métal. Dans l’objectif d’étendre le domaine d’emploi des PIV sur le marché de l’isolation thermique du bâtiment, il est nécessaire d’améliorer les performances d’étanchéités et la résistance en température et humidité des complexes barrières métallisés, ces derniers représentant le point faible des PIV. Ce travail a pour objectif d’identifier les différentes modifications subies par ces complexes au cours de leurs fonctionnement et de déterminer les mécanismes à l’origine de leur dégradation prématurée. Des vieillissements à 70 °C et 90 %RH (conditions maximales d’utilisations identifiées pour le bâtiment français) ont été réalisés à la fois sur les composants, sur les complexes et sur les PIV pour des temps compris entre 1 et 870 jours. A l’échelle microscopique, la dégradation chimique du polyéthylène téréphtalate (PET) et de l’adhésif polyuréthane (PU) ont été étudiées par spectroscopie IR. Des marqueurs de l’hydrolyse ont ainsi pu être identifiés et ont permis de mettre en évidence la dégradation de ces deux composants au sein du complexe. L’hydrolyse ayant des répercussions directes sur les propriétés mécaniques des polymères explique la fragilisation à long terme de l’enveloppe. L’action de l’eau entraine également un gonflement et une plastification du PET, mis en évidence par mesure gravimétrique. Ces derniers peuvent entrainer des modifications de microstructure ayant des répercussions directes sur les mécanismes de transports des molécules d’eau et ainsi participer à la fragilisation du complexe. A l’échelle macroscopique, des mesures fines de retrait des films polymères ont été réalisées. Ces dernières ont été corrélées aux différentes délaminations de l’enveloppe barrière. Des analyses aux interfaces ont permis de déterminer le mode de rupture, adhésif ou cohésif. / Vacuum Insulation Panels (VIPs) were already developed some time ago for low-temperature applications such as refrigerators. More recently, they have been used for the building application. They consist of a fine powder or fiber core material (fumed silica, glass fiber, PU foam) enveloped by a polymer-metal. The latter is responsible for preventing gas and water molecules from breaking the vacuum. Nevertheless, the use of VIPs for this application was limited for applications in severe conditions as for example: temperature, humidity and mechanical load. At high temperature and/or humidity, the most critical component of a VIP is the envelope: both for the tightness point of view and for its degradation. Consequently in these conditions, the vacuum was degraded and durability of the panel performance was decreased sharply.This work focuses on the degradation mechanisms of the polymer-metal envelope. The effect of hygrothermal ageing (70 °C and 90 %RH) on envelope was investigated at different scales: Microscopic: High humidity is at the origin of the hydrolysis of some components such as Polyethylene terephthalate (PET) and polyurethane adhesive (PU). Hydrolysis is directly at the origin of the changes mechanical properties, leading to embrittlement of the complex. An additional microstructural modifications was evidence in PET at high humidity and also contributes to embrittlement of the complex. Macroscopic: shrinkage of polymer film seems to be the origin of debonding in polymer-metal multilayer.
72

Modélisation des modifications structurales, électroniques et thermodynamiques induites par les défauts ponctuels dans les oxydes mixtes à base d'actinides (U,Pu)O2 / First-principles modeling of the structural, electronic and thermodynamic modifications induced by point defects in actinide mixed oxides (U,Pu)O2

Cheik Njifon, Ibrahim 06 November 2018 (has links)
(U,Pu)O2 (aussi appelé MOX) est actuellement utilisé comme combustible dans les réacteurs nucléaires à eau pressurisée (REP) avec une teneur massique en Pu d’environ 10 %. Il est également envisagé comme combustible de référence pour les réacteurs à neutrons rapides à caloporteur sodium, avec une teneur massique en Pu d’environ 25 %. En conditions opérationnelles, (U,Pu)O2 est soumis à des réactions de fission qui génèrent une grande quantité de défauts et de produits de fission. Par migration, ces défauts et produits de fission gazeux peuvent s'agréger en nano-cavités, dislocations et bulles de gaz, conduisant à une modification de la microstructure. Une meilleure description du comportement du combustible à l’échelle atomique, notamment des mécanismes élémentaires impliqués dans la diffusion des défauts et des produits de fission, est donc nécessaire pour affiner les modèles utilisés dans les codes de performance des combustibles. Pour l’étude des propriétés de (U,Pu)O2, nous avons effectué des calculs de structure électronique basés sur la méthode DFT+U combinée au contrôle des matrices d’occupation des orbitales corrélées. Des minimisations d’énergie ainsi que la dynamique moléculaire ab initio ont été utilisées. Nous avons étudié dans un premier temps les propriétés du cristal de (U,Pu)O2 pour différentes teneurs en Pu. Nous avons ensuite étudié la stabilité des défauts ponctuels ainsi que les modifications structurales et électroniques induites par ces défauts ponctuels dans (U,Pu)O2 et (U,Ce)O2, matériau utilisé comme simulant de (U,Pu)O2. Enfin, nous avons étudié le piégeage et la solubilité des gaz de fission (Kr, Xe) et de l’hélium dans la matrice de (U,Pu)O2 / (U,Pu)O2 (commonly called MOX) is currently used as nuclear fuel in pressurized water reactors with a Pu content of around 10 wt.%, and is envisaged as the reference fuel in Generation IV sodium fast reactors (SFR) with a Pu content of around 25 wt.%. Under operation, (U,Pu)O2 is submitted to fission reactions which generate a large quantity and variety of point defects, as well as fission products. By migrating, point defects and gaseous fission products can aggregate into nano-voids, dislocations and fission gas bubbles, which lead to the modification of the fuel microstructure. Therefore, a better description of the fuel behaviour at the atomic scale, and especially of the elementary mechanisms involved in the diffusion of point defects and fission products, is necessary to refine the models used in the fuel performance codes used to simulate the behaviour of fuels at the macroscopic scale. We use electronic structure calculations based on the DFT+U method combined with the occupation matrix control scheme (OMC) to investigate (U,Pu)O2 properties for various Pu contents. Static energy minimizations and ab initio molecular dynamics were used. We have first determined bulk structural, electronic and thermodynamics properties of (U,Pu)O2. We then studied the stability of point defects in (U,Pu)O2 and (U,Ce)O2, as well as the structural and electronic modifications induced by these point defects, in (U,Pu)O2 and the common experimental surrogate (U,Ce)O2. Finally, the fission gas (Kr and Xe) and helium (He) trapping and solubility in (U,Pu)O2 matrix are investigated
73

[en] SYNTHESIS AND CHARACTERIZATION OF MIXED MATRIX MEMBRANES BASED ON IONIC LIQUID DISPERSION IN POLYURETHANE OR PEBAX FOR CO2/N2 SEPARATION / [pt] SÍNTESE E CARACTERIZAÇÃO DE MEMBRANAS DE MATRIZES MISTAS BASEADAS EM DISPERSÃO DE LÍQUIDO IÔNICO EM POLIURETANO OU PEBAX PARA SEPARAÇÃO DE CO2/N2

ANA CAROLINE ALVES FELIPE 22 August 2022 (has links)
[pt] A implementação de medidas que reduzam as emissões de gases de efeito estufa ganha importância no cenário atual. Um importante método para captura de CO2 consiste nos processos de separação por membranas. Visando melhorar a eficiência seletiva na separação de gases, este trabalho estudou a síntese de membranas poliméricas de matrizes mistas a fim de aumentar os valores de permeabilidade, utilizando líquidos iônicos em sua estrutura, que apresentam elevada solubilidade de CO2 e seletividade. A síntese do líquido iônico foi realizada a partir do cátion imidazólico e do ânion NTf2(-) , em reações de 3 etapas. Os filmes poliméricos de matrizes mistas foram sintetizados por diferentes tipos de polímeros comerciais, PEBAX 1657, PEBAX2533 e PU 1185A10; com concentrações de 0 por cento, 20 por cento e 60 por cento (m/m) do líquido iônico. A técnica de ressonância magnética nuclear (RMN) de (1)H e (13)C foi utilizada para validar a composição do líquido iônico. As caracterizações de membranas compósitas se deram pelas técnicas de microscopia eletrônica de varredura (MEV), análise termogravimétrica (TGA) e espectroscopia de infravermelho com transformada de Fourier (FTIR). Na presença do líquido iônico, a seletividade relativa de CO2/N2 apresentou um aumento considerável para as membranas de PU e PEBAX2533, enquanto a permeabilidade de CO2 aumentou nas membranas de PU e PEBAX1657. / [en] The measures to reduce greenhouse gas emissions, gains more importance in the current scenario. Processes involving membrane separation are an important method for CO2 capture which are widely used. In order to improve the selective efficient in the gas separation this paper studies the development and synthesis of composite polymeric membranes that will be able to increase the permeability using ionic liquids in your structure, which have high CO2 solubility and selectivity. The ionic liquid synthesis was obtained using imidazolium cation and the NTf2(-) anion, on 3 steps reactions. The composite polymeric membranes were synthesized by different types of commercial polymers, PEBAX1657, PEBAX2533 and PU 1185A10; with 0 percent, 20 percent and 60 percent (wt.) concentrations of ionic liquid. The nuclear magnetic resonance (NMR) technique for 1H and 13C was used to validate the ionic liquid structure. The composite membrane characterizations were obtained by those techniques: scanning electron microscope (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR). In the presence of ionic liquid, the selectivity of CO2/N2 increased for the PU and PEBAX2533 membranes, and the permeability of CO2 increased for the PU and PEBAX1657 membranes.
74

Clustering and Anomaly detection using Medical Enterprise system Logs (CAMEL) / Klustring av och anomalidetektering på systemloggar

Ahlinder, Henrik, Kylesten, Tiger January 2023 (has links)
Research on automated anomaly detection in complex systems by using log files has been on an upswing with the introduction of new deep-learning natural language processing methods. However, manually identifying and labelling anomalous logs is time-consuming, error-prone, and labor-intensive. This thesis instead uses an existing state-of-the-art method which learns from PU data as a baseline and evaluates three extensions to it. The first extension provides insight into the performance of the choice of word em-beddings on the downstream task. The second extension applies a re-labelling strategy to reduce problems from pseudo-labelling. The final extension removes the need for pseudo-labelling by applying a state-of-the-art loss function from the field of PU learning. The findings show that FastText and GloVe embeddings are viable options, with FastText providing faster training times but mixed results in terms of performance. It is shown that several of the methods studied in this thesis suffer from sporadically poor performances on one of the datasets studied. Finally, it is shown that using modified risk functions from the field of PU learning provides new state-of-the-art performances on the datasets considered in this thesis.
75

Caracterização e utilização do resíduo da borracha de pneus inservíveis em compósitos aplicáveis na construção civil / Caracterization and utilization of the waste rubber from scrap tires in composites to use in the civil construction

Rodrigues, Mara Regina Pagliuso 29 August 2008 (has links)
Este trabalho tem como objetivo o desenvolvimento de uma tecnologia para a atenuação do impacto provocado pelo passivo ambiental gerado por pneus inservíveis, conjuntamente ao desenvolvimento de novos materiais compostos para uso na construção.Os pneus têm uma estrutura física especial, com grande resistência e durabilidade, mesmo ao término de sua vida útil e, por isso, sua deposição em aterros sanitários é inadequada, já que eles não permitem compactação, tornando-se favoráveis para a criação de agentes causadores de enfermidades e oferecem grandes riscos de incêndios, o que acarreta sérios danos ao meio ambiente. A tecnologia desenvolvida utilizou a borracha de pneus inservíveis, após serem picados por processo mecânico, segundo diferentes tamanhos, para a composição de produtos de baixo custo e utilizáveis na construção civil em elementos construtivos, placas de amortecimento sonoro e de revestimento de pisos para edificações, sinalização horizontal em vias públicas, absorvedores de impacto em estradas,etc. O agente de aglomeração utilizado foi a resina poliuretânica derivada do óleo de mamona (Ricinus communis), uma fonte renovável, que também apresenta estabilidade física e química, e um excelente desempenho como aglomerante. O composto obtido foi testado com relação à durabilidade, às propriedades mecânicas como resistência à compressão e tração, módulo de elasticidade e fluência por meio da termo análise, demonstrando resultados satisfatórios e confirmada sua aplicação em vários campos da construção civil. / The objective of this work is to develop a technology for the impact attenuation caused by the passive environmental generated by scrap tires, jointly to the development of new composites for being used in construction. The tires have a special physical structure, with great resistance and durability, also in the term of their useful life, therefore, their deposit in landing fields are inadequate, once they do not allow compacting, becoming favorable for the creation of causes of diseases and they offer great fires risks, what causes serious damages to the environment. The developed technology used the rubber of useless tires, after being fragmented by mechanic process, according to different sizes, for the composition of products of low cost to be used in the civil construction in constructive elements, noise reduction plates and lining of floors for constructions, horizontal signaling in public ways, impact insulating in highways, and so on. The agent of mass used was the polyurethane resin, derived of the castor oil (Ricinus communis), a renewable source that also presents physical and chemical stability, and a good bonding behavior. The obtained composite was tested in relation to durability behavior, mechanical properties which the compression forces and tension, and also its modulus of elasticity and creep by use of thermo analisys, demonstrated satisfactory results and confirmed its application in a many fields of the civil construction.
76

Arbeitnehmerbeteiligung an der Corporate Governance

Zhang, Haichen 07 February 2013 (has links)
In der vorliegenden Arbeit werden die Rechtsordnungen der Arbeitnehmerbeteiligung an der Corporate Governance jeweils in Deutschland und China miteinander verglichen. Neben der historischen Entwicklung wird der Rechtsvergleich vor allem unter vier Aspekten geführt: Arbeitnehmerbeteiligung an der Geschäftsführung, deren Bestellung, deren Beratung und deren Überwachung. Insgesamt ist festzustellen, dass es sowohl in der deutschen als auch in der chinesischen Rechtsordnung Organe bzw. Mechanismen zur Arbeitnehmerbeteiligung an der Corporate Governance auf der unternehmerischen wie der betrieblichen Ebene gibt. Allerdings fehlt es in China insbesondere an detaillierten Rechtsvorschriften zur Durchführung und dem Schutz der Beteiligungsrechte der Arbeitnehmer, so dass viele Beteiligungsrechte, wie ähnlich sie auch wie in der deutschen Rechtsordnung aussieht, nur auf dem Papier bleiben. / The dissertation compares the German and Chinese legal systems for employee´s participation in corporate governance. Besides the historic development of the both systems, the comparison is mainly focused on four aspects: employees´ participation in management issues, in appointing the board, in consultation for the board and in supervising the board. In general, both the German and Chinese legal systems have organs and mechanism for employees to participate in corporate governance both on the corporate level and the shop-floor level. However, the Chinese system is still lack of legal regulations to implement and protect the participation rights. Hence, quite a few participation rights still stay on paper, although they look very similar as in the German system.
77

Development of solar water heating system

Magnusson, Erik, Schedwin, Johan January 2010 (has links)
This report includes development of an already designed solar water heater. The product shall be constructed in a way that it will suit a manufacturing line in Kampala, Uganda. To find the most suitable design for each area a research was carried out which included study visits, interviews and background reading. It provided the following results: Regarding the attachment of in- and outgoing pipes from the water tank many methods were taken into consideration and it was found that the best and most suitable way for this case is to weld the fittings using a weld robot. Regarding the fitting of the acrylic, a suitable solution is to make a flange when vacuum forming the plastic casing to further support the design. This could also be used to waterproof the case by using a sealing material. A suggestion of using pre-molded PU-foam is also presented. Regarding the ability to open the case for maintenance, two solutions were recommended. Either the use of spire clips or having the clips integrated into the casing. Regarding the calculation of material usage when deep drawing the tank and collector, it is possible to do a reasonably accurate assumption. The complicated design in this product makes the estimation less accurate. It is recommended that test draws are done and often the machine producer has more precise numbers. Regarding the coloring of the collector; chemical coloration is not possible on a galvanized surface. The method used is painting, either with powder coating or with wet paint.
78

Efeito do estado nutricional bioqu?mico de retinol e alfatocoferol sobre seus n?veis em lactantes

Lira, Larissa Queiroz de 01 April 2011 (has links)
Made available in DSpace on 2014-12-17T14:03:37Z (GMT). No. of bitstreams: 1 LarissaQL_DISSERT.pdf: 2541848 bytes, checksum: 732cfe4b835f5fc4a48b57022760627a (MD5) Previous issue date: 2011-04-01 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Vitamins A and E are essential nutrients in many biological processes, so that their adequate supply to the neonate is crucial. However, the bioavailability of vitamins may be limited by factors such as maternal nutritional status and the interaction between nutrients. This study aimed to investigate the effect of biochemical nutritional status of retinol and alpha-tocopherol levels in serum and colostrum. The study included 103 healthy puerperal women treated at the reference state maternity hospital (Natal-RN). Colostrum and serum samples were collected fasting in the immediate postpartum period and the analysis of retinol and alpha-tocopherol were determined by high-performance liquid chromatography. Specific cutoff points were adopted to characterize the biochemical status of vitamins A and E. For the total group of lactanting women the average concentration of retinol in serum (1.49 ? 0.4 &#956;mol/L-1) and colostrum (2.18 ? 0.8 &#956;mol/L-1), as well as alpha-tocopherol in serum (26.4 ? 8.0 &#956;mol/L-1) and colostrum (26.1 ? 12.8 &#956;mol/L-1), indicated adequate biochemical state. However, when evaluating the individual, was found a high prevalence of deficient serum (15%) and colostrum retinol (50%), and also alphatocopherol in serum (16%) and colostrum (61%). In women with serum retinol &#8805; 1.05 &#956;mol/L-1, found an inverse correlation between serum retinol and alpha-tocopherol in colostrum (p = 0.008, r = -0.28). This association was not observed in women with serum retinol <1.05 &#956;mol/L-1. This situation demonstrates for the first time in humans that high physiological levels of serum retinol, without supplementation, can negatively influence the transfer of alpha-tocopherol in breast milk. Although the diagnosis of satisfactory nutritional status lactanting women showed high risk of subclinical deficiency of vitamins A and E from measurements made in the colostrum / As vitaminas A e E s?o nutrientes essenciais em muitos processos biol?gicos, de modo que seu adequado fornecimento ao neonato ? fundamental. No entanto, a biodisponibilidade dessas vitaminas pode ser limitada por fatores como o estado nutricional materno e a intera??o entre nutrientes. Este trabalho teve como objetivo investigar o efeito do estado nutricional bioqu?mico de retinol e de alfa-tocoferol sobre seus n?veis no soro e no colostro materno. Participaram do estudo 103 pu?rperas saud?veis atendidas em maternidade p?blica de refer?ncia estadual (Natal-RN). Amostras de soro e colostro foram coletadas em jejum no p?s-parto imediato e as an?lises de retinol e alfa-tocoferol foram feitas por cromatografia l?quida de alta efici?ncia. Os valores de 1,05 &#956;mol/L-1 de retinol no soro e de 2,09 &#956;mol/L-1 de retinol no colostro foram adotados como pontos de cortes para caracterizar a condi??o bioqu?mica referente ? vitamina A. Valores de 11,6 &#956;mol/L-1 de alfa-tocoferol no soro e de 26,1 &#956;mol/L-1 de alfa-tocoferol no colostro foram adotados como pontos de cortes para caracterizar a condi??o bioqu?mica referente ? vitamina E. No grupo total de lactantes, a concentra??o m?dia de retinol no soro (1,49 ? 0,4 &#956;mol/L-1) e no colostro (2,18 ? 0,8 &#956;mol/L-1), assim como, de alfatocoferol no soro (26,4 ? 8,0 &#956;mol/L-1) e no colostro (26,1 ? 12,8 &#956;mol/L-1) indicou adequado estado bioqu?mico. No entanto, ao se avaliar o indiv?duo, foi constatada elevada preval?ncia de defici?ncia de retinol no soro (15%) e no colostro (50%), como tamb?m, de alfa-tocoferol no soro (16%) e no colostro (61%). Em mulheres com retinol s?rico &#8805; 1,05 &#956;mol/L-1, foi encontrado correla??o inversa entre retinol s?rico e alfa-tocoferol do colostro (p = 0.008, r = -0.28). Esta associa??o n?o foi observada em mulheres com retinol s?rico < 1,05 &#956;mol/L-1. Tal situa??o evidencia pela primeira vez em humanos, que n?veis fisiol?gicos adequados de retinol s?rico podem influenciar negativamente a passagem de alfa-tocoferol para o leite materno. Apesar do diagn?stico de satisfat?rio estado nutricional do grupo total de lactantes, ao se avaliar o indiv?duo, foi constatado elevado risco de defici?ncia subcl?nica para as vitaminas A e E a partir das dosagens feitas no colostro
79

Influ?ncia da suplementa??o de retinol palmitato sobre os n?veis de vitamina A no leite de pu?rperas saud?veis

Louren?o, Raquel Maria da Silva 19 May 2006 (has links)
Made available in DSpace on 2014-12-17T14:03:45Z (GMT). No. of bitstreams: 1 RaquelMSL.pdf: 657503 bytes, checksum: b03819bd313909e18887cde152d23958 (MD5) Previous issue date: 2006-05-19 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The tendency towards reduction of serum retinol levels, an existing placental barrier and the increase of retinol demand, are factors that place puerperal and lactating women at risk for Vitamin A deficiency. This micronutrient is an essential component of vital processes such as differentiation, cellular proliferation, and apoptosis. The objective of this study is to evaluate the effect of palmitate retinol supplementation (100.000UI) upon the milk retinollevels in puerperal women at the Janu?rio Cicco University Maternity Hospital. This intervention has been adopted by the Ministry of Health since 2002. The longitudinal experiment was conducted with 106 puerperal women (68 comprised the supplemented group and 38 the control group). The High Performance Liquid Chromatography (HPLC) method was used to dose the retinol of the milk and serum samples, and the creamtocrit method to determine the milk fat levels. The retinol means for the colostrums were 99.0 ? 64.4 ug/dL and 160.1 ? 94,4 ug/dl 6 hours afier supplementation; 68.9 ? 33.5 ug/dL for the transitional milk, and 30.6 ? 15.2 ug/dL for the mature milk of the supplemented group. Ali the difterences between means were statistically significant. The difterence between retinol means in the control group were also significant, with these being greater in the colostrum, 88.6 ? 62.1 ug/dL with 61.9 ? 30.1 ug/dl in the transition milk and 32.9 ?32.9 ? 17.6 ug/dL in the mature milk. No significant difference was observed in the retinol means of the three types ot milk in the supplemented group when compared to their respective means in the control group. The prevalence in serum (35.1 % and 81.1 % for the cutting point 20 ug/dL, respectively) and in milk (51.4%) revealed vitamin A deficiency as a public health problem. COlostrum, transition, and mature milk tats varied similarly in the supplemented group (1,92 ? 0,96; 3,25 ? 1,27 and 3,31 ? 1,36 grams) and in the control group (1,87 ? 1,14; 3,25 ? 1,31 and 3,36 ? 1,67 grams), with an observed difference between the colostrum/transition milk and the colostrum/mature milk fats. No difference was observed between the groups. The study showed that the 200.000UI supplementation was not sufficient to increase the milk retinol to the desired levels nor to meet the demands of the mothers with deprived hepatic reserves. It is suggested that another similar dose be offered within 30 days or less, and within 2 months post-partum, while continual/y monitoring for possible pregnancy / Fatores como a tend?ncia ? diminui??o dos n?veis de retinol s?rico das gestantes, barreira placent?ria e aumento da demanda de retinol, fazem com que pu?rperas e lactentes representem grupos de risco de defici?ncia em vitamina A, nutriente que participa de processos vitais, como a diferencia??o, prolifera??o celular e apoptose. O objetivo do presente trabalho foi avaliar o efeito da suplementa??o de retinol palmitato (200.000 UI) sobre os n?veis de retinol no leite de pu?rperas da Maternidade Escola Janu?rio Cicco (MEJC), interven??o que vem sendo adotada pelo Minist?rio da Sa?de desde 2002. O experimento do tipo longitudinal teve como participantes 106 pu?rperas (68 do grupo suplementado e 38 do grupo controle). A Cromatografia L?quida de Alta Efici?ncia (CLAE) foi o m?todo utilizado para dosar retinol das amostras de leite e soro; e o cremat?crito para determinar os n?veis de gordura no leite. A quantifica??o do retinol apresentou m?dias de 99,0 ? 64,4 ug/dl para o colostro; 160,1 ? 94,4 ug/dl para o colostro 6 horas ap?s suplementa??o; 68,9 ? 33,S ug/dl para o leite de transi??o e 30,6 ?15,2 ug/dl para o leite maduro do grupo suplementado. As diferen?as foram significativas entre todas as m?dias. O grupo controle tamb?m demonstrou m?dias de retinol significativamente diferentes, sendo estas superiores no colostro 88,6 ? 62,1 ug/dl, reduzindo para 61,9 ? 30,1 ug/dl no leite de transi??o e 32,9 ? 17,6 ug/dl no leite maduro. Nenhuma diferen?a significativa foi observada quando as m?dias do retinol referentes aos tr?s tipos de leite do grupo suplementado foram comparadas com as respectivas m?dias do grupo controle. A preval?ncia encontrada no soro (35,1% e 81,1 % para o ponto de corte 20 ug/dl e 30 ug/dl, respectivamente) e no leite (51,4%) revelou a defici?ncia de vitamina A como problema de sa?de p?blica. A gordura do leite colostro, transi??o e maduro variou de forma semelhante no grupo suplementado (1,92 ? 0,96; 3,25 ?1,27 e 3,31 ? 1,36 gramas) e controle (1,87 ? 1,14; 3,25 ? 1,31 e 3,36 ? 1,67 gramas), ocorrendo diferen?a entre colostroltransi??o e colostro/maduro. N?o houve diferen?a entre os grupos. O seguinte trabalho demonstrou que a suplementa??o utilizando 200.000 UI n?o foi capaz de elevar os n?veis de retinol no leite at? o momento esperado e, provavelmente, n?o foi fornecida em quantidade suficiente para satisfazer as demandas das m?es com reservas hep?ticas mais espoliadas. ? vi?vel sugerir que uma outra dose de igual valor seja ofertada, num intervalo de 30 dias a 60 dias p?s-parto, verificando sempre a possibilidade de gravidez
80

Acceptance and impact of social networks marketing using extended technology acceptance model

Mulero, Senikat Olumayowa January 2012 (has links)
Thesis (MTech (Information Technology)--)Cape Peninsula University of Technology, 2012 / Includes bibliographical references (leaves 127) / In rapid advances in marketing strategies, Social Networks Marketing (SNM) is dramatically becoming an important aspect in promoting businesses. Social networks marketing has been found as one of the most effective tool used in businesses today, by most business owners in South Africa, to expand, and flourish their businesses. The explosion of Internet usage has drawn the attention of researchers towards social networks marketing. Research has shown that potential Internet users are doubtful, and indecisive to use, and accept SNM system in spite of their availability. Therefore, there is a need for researchers to identify some of the factors that determine user’s unwillingness to accept and use the system. According to the Technology Acceptance Model (TAM), Perceived Ease of Use (PEOU), and Perceived Usefulness (PU) are the two major constructs in determining the use and acceptance of various information systems. These beliefs may not fully explain the user’s behaviour towards newly introduced system, such as social networks marketing. Hence, this study had successfully implemented TAM to the newly proposed information system (social networks marketing system). Using TAM as a theoretical framework, the study added two new constructs “perceived credibility” and “awareness” as part of the factors influencing user’s acceptance of social networks marketing. The purpose of the study was to explore the impact of social networks marketing system by SMEs in South Africa, and perception of consumers. In addition, this research investigated factors that influence users’ acceptance of social networks marketing using TAM as the basis for the theoretical framework. Questionnaire-based study done in 2 groups; consumers and small and medium-scale enterprises (SMEs), in this work, represent the major users of social networks marketing in South Africa. The research model was tested using data collected from 143 questionnaires and analysed using linear regression. The results show that user’s intentions to use SNM are strongly and positively correlated with user acceptance. The empirical results confirmed that perceived credibility and perceived usefulness are the strongest determinant in predicting user’s intention to use SNM. In addition, many of the South African SMEs using SNM, have presumed that SNM has positively and negatively impacted their businesses.

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