O objetivo deste trabalho é controlar a incidência de fissuras em fibrocimentos aplicando o conceito de materiais com gradação funcional através da protensão química gerada pela aplicação de silicato de sódio alcalino entre as camadas dos fibrocimentos. Atualmente é bastante comum os fibrocimentos apresentarem fissuras ao longo das bordas devido aos gradientes de umidade gerados durante a estocagem das pilhas de telhas no pátio das indústrias. O potencial da protensão química foi avaliado através da porosidade total, da quantificação das fases hidratadas, da retração por secagem e do desempenho mecânico. A aplicação de silicato de sódio alcalino no ligante CPII F provocou retração por secagem 1,5 vezes maior que a referência aos 91 dias. O módulo de ruptura (MOR) não sofreu alteração, mas o limite de proporcionalidade da matriz (LOP) aumentou em torno de 95%. O módulo de elasticidade dinâmico foi 13 % maior. O aumento da retração por secagem e o ganho de desempenho mecânico apontam o potencial da protensão química para o controle da fissuração em fibrocimentos produzidos pelo processo Hatschek. / The objective of this work is controlling the incidence of cracks in fiber cement, using the concept of functionally graded materials through the chemical prestressing, generated by application of alkaline sodium silicate among fiber cement layers. Currently, its very common the fiber cements present cracks along the edges due to moisture gradients, caused during storage of piles of tiles in the courtyard of the industry. The chemical prestressing potential was evaluated through of the total porosity, the quantification of hydrate phases, the drying shrinkage and the mechanical performance. The application of alkaline sodium silicate in the cement CPII F caused drying shrinkage 1,5 times greater than the reference to 91 days. The modulus of rupture (MOR) didnt suffer change, but the proportional limit of matrix (LOP) increased by around 95%. The dynamic modulus of elasticity was 13% higher. The increase of drying shrinkage and the mechanical performance gain indicate the chemical prestressing potential to control the cracking in fiber cement produced by the process Hatschek.

Proposição: O objetivo deste estudo foi avaliar como a contração volumétrica (CV), o grau de conversão (GC), a taxa máxima de polimerização (RPmax) e a tensão de polimerização (TPmax) de dois compósitos experimentais são influenciados pela concentração de fotoiniciadores na matriz e pela irradiância aplicada na fotopolimerização. Material e métodos: Duas séries de monômeros foram formuladas, com partes iguais em peso dos seguintes monômeros: série B= Bis-GMA/ TEGDMA; série U= Bis-GMA/ UDMA / TEGDMA. Essas séries foram combinadas a três níveis de fotoiniciadores, num total de seis materiais experimentais, com a concentração em porcentagem de peso de uma amina terciária (EDMAB) e canforoquinona (CQ), respectivamente: alta (H)= 0,8 / 1,6; intermediária (M)= 0,4 / 0,8 e baixa (L)= 0,2 / 0,4. A todas as misturas, 75% e peso de vidro de estrôncio e 5% em peso de OX-50 (sílica coloidal) foram adicionados. O estudo foi dividido em três módulos: no primeiro, os seis compósitos foram testados quanto aos parâmetros descritos acima para a mesma dose de energia aplicada. No segundo, os mesmos materiais foram testados com a dose de energia ajustada de acordo com a concentração de fotoiniciadores de modo que todos os níveis atingissem graus de conversão semelhantes. No terceiro módulo, os materiais com a concentração \"M\" de fotoiniciadores foram submetidos a uma de três irradiâncias: 200, 400 ou 600 mW/cm2, com o tempo de exposição ajustado para que a dose de energia fosse mantida constante. CV foi registrada em um dilatômetro de mercúrio, GC foi avaliado através de FTIR, RPmax foi obtida através de um DSC 7 e a TP foi avaliada em um aparato de compliance controlado, descrito por Sakaguchi et al., 2004. Resultados: Em todos os módulos, não houve interação entre os fatores e assim, as médias foram agrupadas por série de monômeros e nível de fotoiniciadores (módulos 1 e 2) ou nível de irradiância (módulo 3). No módulo 1, as concentrações \"H\" e \"M\" apresentaram GC semelhante, ambas estatisticamente superiores à apresentada pelo grupo com o menor conteúdo de CQ/amina. A série U apresentou GC superior à da série B. RPmax aumentou significantemente com a concentração de fotoiniciadores entre cada um dos níveis estudados (p<0,001), e foi maior para a série U (p<0,05). O grupo de concentração \"H\" apresentou valores de TPmax maiores do que os grupos de concentração \"L\", enquanto que \"M\" apresentou valores de TPmax semelhantes aos dos outros dois (p<0,001). As séries B e U apresentaram TPmax equivalente (p>0,05). CV foi maior para \"L\", estatisticamente diferente das outras duas. A série B apresentou maior CV (p<0,05 para ambos os fatores). No módulo 2, o GC não foi influenciado pela concentração de fotoiniciadores (p>0,05). A série U apresentou maior GC comparado com a série B (p<0,001). RPmax aumentou com a concentração de fotoiniciadores entre cada um dos níveis estudados e foi maior para a série U (p<0,001 para ambos). TPmax não foi influenciada pela concentração de fotoiniciadores (p>0,05). A série B apresentou maior TPmax comparado com a série U (p<0,001). CV foi maior para \"L\", estatisticamente diferente das outras duas. A série B apresentou maiores valores de CV (p<0,001 para ambos os fatores). No módulo 3, GC variou significantemente apenas com a irradiância (p<0,001), sendo que os grupos de alta irradiância apresentaram valores estatisticamente mais baixos comparados aos níveis de irradiância médio e baixo. RPmax, aumentou com a irradiância e foi maior para a série U (p<0,001 para ambos). A série B apresentou valores de TPmax do que os da série U. CV não foi influenciada pela irradiância (p=0,442). A série B apresentou CV estatisticamente maior que a série U (p<0,001). Conclusões: De maneira geral, podemos dizer que CV, GC e RPmax mostraram uma interação bastante complexa e, nas condições deste estudo, não foi possível determinar a contribuição relativa de cada um destes fatores no desenvolvimento da tensão de polimerização. No entanto, parece haver uma tendência de TPmax ser influenciada mais pronunciadamente pelo GC ou CV do que pela RPmax, como demonstrado nos módulos 2 e 3. / Proposition: The objective of this study was to evaluate how the volumetric shrinkage (VS), degree of conversion (DC), maximum rate of reaction (RPmax), polymerization stress (PSmax) and maximum rate of stress development (RSmax) of two experimental composites are influenced by the photoinitiator concentration ([photo]) and by the irradiance. Methods and materials: Bis-GMA/TEGDMA (B series) and Bis GMA/UDMA/TEGDMA (U series) were mixed in equal parts in weight. A tertiary amine (EDMAB) and camphoroquinone (CQ), respectively, were added in three concentrations: high (H)= 0.8/1.6; intermediate (M)= 0.4/0.8 and low (L)= 0.2/0.4 (in wt%). In all mixtures, 80 wt% filler was added. The study was divided in three sections: I) composites were photoactivated with 13 J/cm2. II) radiant exposure was adjusted so that all [photo] would achieve similar DC. III) [photo] \"M\" materials were submitted to three irradiances: 200 (L), 400 (I) or 600 (H) mW/cm2, with exposure time adjusted to convey the same radiant exposure. VS was registered in a mercury dilatometer, DC was evaluated by FTIR spectroscopy, RPmax was obtained in a DSC 7 and PSmax was evaluated in a controlled compliance device, described previously (SAKAGUCHI; WILTBANK; MURCHISON, 2004a). Results: Because no interaction between the factors was observed (except for RSmax in sections I and III), means were pooled for monomer series and [photo] (sections I and II) or irradiance (section III). I) concentrations \"H\" and \"M\" presented similar DC, both statistically superior to \"L\" (p<0.001). U series presented higher DC compared to B series. RPmax increased significantly with photoinitiator concentration between each of the studied levels (p<0.001), and was higher for U series (p<0.05). VS was higher for \"L\", statistically different than the other two (p<0.05). B series presented higher VS (p<0.05). The group with \"H\" concentration presented PSmax higher than \"L\", while \"M\" presented values similar to both (p<0.001). B and U series presented equivalent PSmax (p=0.284). For B series, RSmax increased 100% between the lower e intermediate [photo]. For U series, this increase was only around 50%. II) DC was not influenced by [photo] (p=0.388). U series presented higher DC compared to B series (p<0.001). RPmax increased with [photo] between all studied levels and was higher for U series (p<0.001 for both). VS was higher for \"L\", statistically different from the other two (p<0.001). B series presented higher VS (p<0.001). PSmax was not influenced by the photoinitiator concentration (p=0119). B series presented higher PSmax compared to U series (p<0.001). RSmax increased with [photo] and was higher for U series (p<0.001). III) High irradiance groups presented statistically lower DC compared to the other irradiance levels (p<0.001). Monomer series did not influence DC (p=0.793). RPmax increased with the irradiance and was higher for U series (p<0.001 for both). VS was not influenced by the irradiance (p=0.442). B series presented VS statistically higher than U series (p<0.001). \"H\" groups presented higher PSmax compared to \"L\". \"M\" presented PSmax similar to both (p<0.001). B series presented PSmax higher than U series. While no difference in RSmax between irradiance leves was observed for B series, RSmax increased with the irradiance for U series. Conclusions: There seems to be a trend for PSmax to be influenced more markedly by DC or VS than by RPmax. However, VS, DC and RPmax showed a quite complex interaction and, in the conditions of the present study, it was not possible to determine the relative contribution of each of these factors on stress development.

For usual concrete structure built in several phases, concrete deformations are restrained during the hardening process. When shrinkage is restrained, tensile stresses are induced and a cracking risk occurs. Modelling the evolution of an early age set of parameters on concrete is necessary to predict the early age behaviour of concrete structures. The difficulty lies in the fact that the modelling of concrete properties must be based on experimental data at early age and this data must be obtained automatically because the hardening process of the concrete takes place rapidly during the first hours and also the first days. The thesis deals with experimental and numerical study of the early age properties of cement based materials and more specifically the development of the autogenous deformation, the coefficient of thermal expansion, the E-modulus and the basic creep in compression and tension. For this purpose, a comprehensive work was carried out at ULB and Ifsttar involving the development of a new approach with new test procedures and the design of new testing devices to generate experimental data since the setting of the material. The methodology is based on two repeated testing methods. For the characterization of the viscoelastic behaviour of a concrete since setting, a permanent loading coupled to a test with repeated minute-long loadings is needed. Whereas, the autogenous strain, the coefficient of thermal expansion and the setting are characterized with repeated thermal variations on a concrete sample. The new approach was defined on an ordinary concrete and then extended to the study of the following parameters: the water-cement ratio, the restrained effect of aggregate on the cement paste in the development of concrete properties at early age, the substitution of cement by mineral addition and the difference of behaviour in tension and in compression. Based on these experimental results, new models were developed for the characterization of the early age properties of cement based materials since setting time. An adapted version of the Model Code 2010 for modelling of basic creep is also proposed. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

We provide a flexible means of estimating time-varying parameter models in a Bayesian framework. By specifying the state innovations to be characterized trough a threshold process that is driven by the absolute size of parameter changes, our model detects at each point in time whether a given regression coefficient is constant or time-varying. Moreover, our framework accounts for model uncertainty in a data-based fashion through Bayesian shrinkage priors on the initial values of the states. In a simulation, we show that our model reliably identifies regime shifts in cases where the data generating processes display high, moderate, and low numbers of movements in the regression parameters. Finally, we illustrate the merits of our approach by means of two applications. In the first application we forecast the US equity premium and in the second application we investigate the macroeconomic effects of a US monetary policy shock. / Series: Department of Economics Working Paper Series

We assess the relationship between model size and complexity in the time-varying parameter VAR framework via thorough predictive exercises for the Euro Area, the United Kingdom and the United States. It turns out that sophisticated dynamics through drifting coefficients are important in small data sets while simpler models tend to perform better in sizeable data sets. To combine best of both worlds, novel shrinkage priors help to mitigate the curse of dimensionality, resulting in competitive forecasts for all scenarios considered. Furthermore, we discuss dynamic model selection to improve upon the best performing individual model for each point in time. / Series: Department of Economics Working Paper Series

Les résines composites à base de polymères diméthacrylates sont des biomatériaux fréquemment employés en dentisterie où la matrice est synthétisée in vivo par photopolymérisation en chaîne radicalaire. En Odontologie Conservatrice, la contraction volumique dont cette matrice est le siège au cours de sa synthèse est un inconvénient majeur. Elle est, en effet, à l’origine de contraintes physiques souvent néfastes et mal contrôlées dès lors que le matériau, collé aux murs cavitaires, est élaboré en milieu confiné. Aucune étude n'a permis à ce jour d’analyser de manière approfondie ce phénomène de contraintes de contraction au regard des conditions opératoires de la synthèse de la matrice. Le but de ce travail est donc d'isoler la problématique des contraintes internes en orientant exclusivement l’étude vers l'analyse de la matrice. En élaborant des prototypes à base de Bis-GMA et d’UEDMA et après caractérisation de certaines propriétés physico-chimiques, rhéologiques et thermodynamiques des mélanges de ces comonomères et des copolymères résultants, ce travail a permis de contribuer à une meilleure compréhension de la phénoménologie de la relaxation viscoélastique qui gouverne la dissipation des contraintes de contraction / Composite materials containing polymers are biomaterials frequently employed in dentistry where the matrix is synthesized in vivo by photocured radical chain. In Operative Dentistry, the resulting shrinkage strain produced during the synthesis of this matrix is a major disadvantage. It is, indeed, at the origin of often harmful and badly controlled physical stresses since the material, stuck to the cavity walls, is elaborated in confined surroundings. No study to date allowed analyzing thoroughly this phenomenon of contraction taking into consideration the operating conditions of the synthesis of the matrix. The goal of this work is thus to exclusively isolate the set of problems of the internal stresses by directing the study towards the matrix analysis. By elaborating prototypes based on Bis-GMA and UEDMA and after characterization of certain physicochemical, rheological and thermodynamic properties of mixtures of these comonomers and of the resulting copolymers, this work made it possible to contribute to a better understanding of the phenomenology of the viscoelastic relaxation which governs the dissipation of the shrinkage stress

La gran parte de productos de consumo contienen partes realizadas a través del proceso de inyección de termoplásticos, esto constata la importancia de este proceso de conformado con respecto a otros procesos de transformación de plástico. La minimización de los costes para ser más competitivos así como la eliminación o reducción de defectos en las piezas inyectadas, han sido los motivos principales para controlar el proceso a través de la optimización de las variables que entran en juego en este proceso, es por ello que se han realizado numerosos estudios referentes a obtener las relaciones existentes entre las variables del proceso y los aspectos de rentabilidad, estética y defectología de las piezas inyectadas. Modelizar dichas relaciones a través de algoritmos matemáticos con el fin de optimizar los resultados obtenidos y predecir el estado final de las piezas inyectadas han sido los objetivos de la mayoría de estudios. Uno de los efectos intrínsecos a la inyección es la deformación de la pieza, esta deformación tiene lugar debido a distintos factores que intervienen en el diseño del proceso en su conjunto, diferencias en la contracción, diferencias en la refrigeración, las esquinas de la pieza, la orientación molecular, etc son elementos condicionantes de la deformación que se han estudiado en infinidad de artículos, en esta divulgación científica se estudiará la deformación bajo aspectos dimensionales de la pieza con la finalidad de intentar descubrir y optimizar las condiciones de entrada que en este caso serían las dimensiones de la pieza a través de la observación y modelización de las variables de salida que seria la deformación. Y la pregunta que nos realizamos es ¿Cómo varían las deformaciones modificando las dimensiones de la pieza? ¿Cuáles son las dimensiones de la pieza a estudio que minimizan los efectos negativos de la deformación? ¿se puede predecir la deformación que obtendremos en una pieza solo con las dimensiones de una pieza? A todas estas preguntas intentamos dar respuesta en el estudio siguiente. / Gámez Martínez, JL. (2014). ANÁLISIS DE LA DEFORMACIÓN EN LA INYECCIÓN DE TERMOPLÁSTICOS BAJO VARIABLES DE FORMA DE LA PIEZA MEDIANTE RED NEURONAL Y SUPERFICIES RESPUESTA [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/39350 / TESIS

Content: Tannery effluent with high salinity and chromium have a serious environmental impact. The traditional chrome tannage that involved the use of sodium chloride, acid and chromium is one of the main origins of salt and chromium pollution. In this study, a non-pickling, low-chrome tanning technology was developed. The novel Chrome-free agent SL can be directly employed to tan bated cattle pelts and the wet white was obtained. Then the shaved wet white was pre-treated by Poly-carboxylate auxiliary agent and tanned by chrome powder. It was tested that the shrinkage temperature of the wet white, the initial pH of chrome tanning, the consumption of chrome powder, the shrinkage temperature of the chrome-tanned leather, the content of Cr2O3 in effluent, the absorption of chromium and the other properties of the chrome-tanned leather. It was found that the shrinkage temperature of the wet white tanned by SL reached over 80oC, the optimal consumption of Poly-carboxylate auxiliary agent was 2wt% based on the weight of the shaved wet white, the better low-chrome tanning conditions were that the wet white was tanned by 4wt% chromium powder for 150～180min at room temperature when the initial pH value was 3.5. The next processes were same as traditional chrome tannage. Meanwhile, the shrinkage temperature of the leather tanned by the low-chrome tannage reached more than 95oC, the absorption of chromium was 96%, the content of Cr2O3 in the effluent was under 200mg/L. For the low-chrome tanned leather, the absorption of dyestuff, fat-liquor reached 99.5%, 82.5% respectively. Compared with the traditional chrome tanned process, not only the conventional pickling process was eliminated, the process was been shorten and reduce the pollution of sodium chloride, but it can reduce 50% of the consumption of Chrome powder, improve the absorption of chromium and can reduce content of Cr2O3 in effluent. Take-Away: 1. LUO JIAN-XUN, LI JING, LIAO XUE-PIN,etc.Cleaner Chrome Tanning – A Non-Pickling Process Using an Aliphatic Aldehyde as Pre-tanning Agent. J. Soc. Leather. Technol.Chem. 2012,96 (1):21-26. 2.LUO JIAN-XUN,FENG YANJUAN.Cleaner Processing of Bovine Wet-white: Synthesis and Application of a Novel Chrome-free Tanning Agent Based on an Amphoteric Organic Compound. J. Soc. Leather. Technol.Chem. 2015,99 (4):190-195. 3.XU JIA-LI, LUO JIAN-XUN.Synthesis and application of a polycarboxylate auxiliary agent. China Leather.2017,46(3):35-41.

The thesis deals with the design and assessment of all supporting parts of a cast-in-place reinforced concrete sewage tank in a wastewater treatment plant. The thesis includes a technical report, static analysis, drawing documentations, construction process and visualization. The drawing documentation consists of shape and reinforcement drawings of supporting parts.

The thesis deals with the study of magnesium oxide burned by various burning regimes and his possibilities of its usage as potential expansion additive. The theoretical part of the thesis concerns mainly the volume changes and how they can be influenced. The practical part focuses on monitoring morphology, phase composition and the hydration process of magnesium oxide.