Influence des caractéristiques rhéologiques des bétons autoplaçants sur leur durabilité

Résumé : De même degré d’importance que les paramètres de formulation, les conditions de consolidation sont des facteurs déterminants pour la durabilité des bétons conventionnels vibrés. Dans le cas des bétons autoplaçants (BAP), grâce à leur grande fluidité, la mise en place dans les coffrages a lieu par écoulement libre sous l’effet de leur poids propre. Leur consolidation se fait sans vibration grâce à leurs caractéristiques rhéologiques. Il est donc légitime de penser que les caractéristiques rhéologiques des BAP peuvent avoir une influence importante sur les propriétés qui déterminent la durabilité. Cette thèse étudie les liens possibles entre les caractéristiques rhéologiques des BAP et leur durabilité vis-à-vis du transport des agents agressifs. Dix-sept formulations de BAP couvrant une large gamme de caractéristiques rhéologiques et se différenciant uniquement par leur dosage en adjuvants ont été étudiées à cet effet. Trois modèles rhéologiques classiques ont été mis en œuvre pour la détermination des paramètres rhéologiques des bétons étudiés. L’essai de sorptivité et dans une moindre mesure l’essai de carbonatation accélérée ont été utilisés comme indicateur de durabilité vis-à-vis du transport des agressifs. La durabilité de la couche superficielle au contact respectivement avec le coffrage en bois et en PVC a été étudiée et les résultats ont été comparés à la durabilité du béton à cœur. Cette étude a été faite en tenant compte des échanges hydriques et de l’arrangement granulaire au droit du coffrage. D’autre part, l’étude de la durabilité de la couche superficielle dans des conditions de mise en place proches du chantier a été faite sur 6 poutres partiellement armées longues de 2 m ainsi que sur 3 bétons semi-autoplaçants légèrement vibrés. Les résultats montrent qu’il existe une corrélation forte entre la viscosité plastique du modèle Bingham modifié ou le coefficient de consistance du modèle Herschel-Bulkley et la sorptivité. Très probablement, la viscosité agit sur le volume relatif des pores capillaires de gros diamètres. L’étude spécifique de la couche superficielle a montré que sa sorptivité dépend du type de coffrage utilisé à cause des éventuels échanges hydriques opérés entre le béton et la surface du coffrage. De plus, l’arrangement granulaire au droit du coffrage est également influencé. Ainsi, la sorptivité de la couche superficielle au contact du PVC est proche mais inférieure à celle du béton à cœur. La sorptivité de la couche superficielle au contact du bois est significativement inférieure à celle de la couche superficielle au contact du PVC tout en restant corrélé avec la viscosité plastique du modèle Bingham modifié ou le coefficient de consistance du modèle Herschel-Bulkley.

A microelectrode impedance method to measure interaction of cells

An impedance method was developed to determine how immune system cells (hemocyte) interact with intruder cells (parasites). When the hemocyte cells interact with the parasites, they cause a defensive reaction and the parasites start to aggregate in clusters. The level of aggregation is a measure of the host-parasite interaction, and provides information about the efficiency of the immune system response. The cell aggregation is monitored using a set of microelectrodes. The impedance spectrum is measured between each individual microelectrode and a large reference electrode. As the cells starts to aggregate and settle down towards the microelectrode array the impedance of the system is changed. It is shown that the system impedance is very sensitive to the level of cell aggregation and can be used to monitor in real time the interaction between hemocyte cells and parasites.

Generate disaggregated soil allocation data using a Minimum Cross Entropy Model

Montado ecosystem in the Alentejo Region, south of Portugal, has enormous agro-ecological and economics heterogeneities. A definition of homogeneous sub-units among this heterogeneous ecosystem was made, but for them is disposal only partial statistical information about soil allocation agro-forestry activities. The paper proposal is to recover the unknown soil allocation at each homogeneous sub-unit, disaggregating a complete data set for the Montado ecosystem area using incomplete information at sub-units level. The methodological framework is based on a Generalized Maximum Entropy approach, which is developed in thee steps concerning the specification of a r order Markov process, the estimates of aggregate transition probabilities and the disaggregation data to recover the unknown soil allocation at each homogeneous sub-units. The results quality is evaluated using the predicted absolute deviation (PAD) and the "Disagegation Information Gain" (DIG) and shows very acceptable estimation errors.

Limited Partnerships and Reputation Formation

This paper analyzes the optimal quality decision of a producer in a multi-period setting with reputation effects. Using a unique database of returns on real estate limited partnerships (RELPs), we empirically examine alternative theoretical predictions of optimal producer strategy. In particular, we test whether the producers in our market invest in reputation building by initially selling high quality goods and then lowering quality. Using a variety of statistical tests, we find evidence consistent with reputation building, both in the aggregate and for individual developers.

A promoção da motivação pela competição : área disciplinar não curricular, área de projecto do 12º ano

Relatório da prática de ensino supervisionada, Mestrado em Ensino da Informática, Universidade de Lisboa, Instituto de Educação, 2011

Cystathionine beta-synthase variants : identification, characterization and modulation by thiol compounds

Tese de doutoramento, Farmácia (Bioquímica), Universidade de Lisboa, Faculdade de Farmácia, 2014

Ficção e encenação : o desenho como narrativa visual

Tese de doutoramento, Belas-Artes (Ciências da Arte), Universidade de Lisboa, Faculdade de Belas-Artes, 2014

Essays on Applications of the Factor Model

Thesis (Ph.D.)--University of Washington, 2013

Programa Mais Educação : um instrumento para uma política educativa integral no Brasil

Tese de mestrado, Ciências da Educação (Área de especialidade em Administração Educacional), Universidade de Lisboa, Instituto de Educação, 2015

Validating A knowledge transfer framework in health services

The study of knowledge transfer (KT) has been proceeding in parallel but independently in health services and in business, presenting an opportunity for synergy and sharing. This paper uses a survey of 32 empirical KT studies with their 96 uniquely named determinants of KT success to identify ten unique determinants for horizontal knowledge transfer success. These determinants, the outcome measure of Knowledge Use, and separate explicit and tacit transfer flows constitute the KT Framework, extending the work of previous KT framework authors. Our Framework was validated through a case study of the transfer of clinical practice guideline knowledge between the cardiac teams of selected Ontario hospitals, using a survey of senders and receivers developed from the KT literature. The study findings were: 8 of 10 determinants were supported by the Successful Transfer Hospitals; and 4 of 10 determinants were found to a higher degree in the Successful than non-Successful transfer hospitals. Taken together, the results show substantive support for the KT Framework determinants, indicating aggregate support of 9 of these determinants, but not the 10th - Knowledge Complexity. The transfer of tacit knowledge was found to be related to the transfer of the explicit knowledge and expressed as the transfer or recreation of resource profile and internal process tacit knowledge, where this tacit transfer did not require interactions between Sender and Receiver. This study provides managers with the building blocks to assess and improve the success rates of their knowledge transfers.

Impact of energy-using product policies

Energy-using products (EuPs), such as domestic appliances, audio-visual and ICT equipment contribute significantly to CO2 emissions, both in the domestic and non-domestic sectors. Policies that encourage the use of more energy efficient products can therefore generate significant reductions in overall energy consumption and hence, CO2 emissions. To the extent that these policies cause an increase the average production cost of EuPs, they may impose economic costs on producers, or on consumers, or on both. In this theoretical paper, an adaptation of a simple vertical product differentiation model – in which products are characterised in terms of their quality and their energy consumption – is used to analyse the impact of the different EuP polices on product innovation and to assess the resultant economic impacts on producers and consumers. It is shown that whereas the imposition of a binding product standard for energy efficiency unambiguously reduces aggregate profit and increases the average market price in the absence of any learning effects, the introduction or strengthening of demand-side measures (such as energy labelling) may reduce, or increase, aggregate profit. Even in the case where the overall impact is unambiguously negative, the effects of product innovation and learning can be in either direction.

Aggregation Limits Surface Expression of Homomeric GluA3 Receptors

AMPA receptors are glutamate-gated cation channels assembled from GluA1-4 subunits and have properties that are strongly dependent on the subunit composition. The subunits have different propensities to form homomeric or various heteromeric receptors expressed on cell surface, but the underlying mechanisms are still poorly understood. Here, we examined the biochemical basis for the poor ability of GluA3 subunits to form homomeric receptors, linked previously to two amino acid residues, Y454 and R461, in its ligand-binding domain (LBD). Surface expression of GluA3 was improved by co-assembly with GluA2 but not with stargazin, a trafficking chaperone and modulator of AMPA receptors. The secretion efficiency of GluA2 and GluA3 LBDs paralleled the transport difference between the respective full-length receptors and was similarly dependent on Y454/R461, but not on LBD stability. In comparison to GluA2, GluA3 homomeric receptors showed a strong and Y454/R461-dependent tendency to aggregate both in the macroscopic scale measured as lower solubility in nonionic detergent and in the microscopic scale evident as the preponderance of hydrodynamically large structures in density gradient centrifugation and native gel electrophoresis. We conclude that the impaired surface expression of homomeric GluA3 receptors is caused by nonproductive assembly and aggregation to which LBD residues Y454 and R461 strongly contribute. This aggregation inhibits the entry of newly synthesized GluA3 receptors to the secretory pathway.

Accessibility Planning tools for sustainable and integrated Land Use/Transport (LUT) development: an application to Rome

The paper fits into the themes of sustainable accessibility planning in urban areas, that can be defined as the integration of transport and land use planning to achieve sustainable development. In particular the study proposes a tool to support the choices of activities location, which is based on a new aggregate (zone-specific) indicator: the ‘Marginal Activity Access Cost’, providing estimation in monetary terms of the impacts on mobility and on the environment of locating one new activity in a specific zone of the urban area. The proposed indicator is validated through an application to the urban area of Rome.

Virtual power players demand response programs management based on locational marginal prices

Power systems have been suffering huge changes mainly due to the substantial increase of distributed generation and to the operation in competitive environments. Virtual power players can aggregate a diversity of players, namely generators and consumers, and a diversity of energy resources, including electricity generation based on several technologies, storage and demand response. Resource management gains an increasing relevance in this competitive context, while demand side active role provides managers with increased demand elasticity. This makes demand response use more interesting and flexible, giving rise to a wide range of new opportunities.This paper proposes a methodology for managing demand response programs in the scope of virtual power players. The proposed method is based on the calculation of locational marginal prices (LMP). The evaluation of the impact of using demand response specific programs on the LMP value supports the manager decision concerning demand response use. The proposed method has been computationally implemented and its application is illustrated in this paper using a 32 bus network with intensive use of distributed generation.

LMP triggered real time demand response events

Recent changes in power systems mainly due to the substantial increase of distributed generation and to the operation in competitive environments has created new challenges to operation and planning. In this context, Virtual Power Players (VPP) can aggregate a diversity of players, namely generators and consumers, and a diversity of energy resources, including electricity generation based on several technologies, storage and demand response. Demand response market implementation has been done in recent years. Several implementation models have been considered. An important characteristic of a demand response program is the trigger criterion. A program for which the event trigger depends on the Locational Marginal Price (LMP) used by the New England Independent System operator (ISO-NE) inspired the present paper. This paper proposes a methodology to support VPP demand response programs management. The proposed method has been computationally implemented and its application is illustrated using a 32 bus network with intensive use of distributed generation. Results concerning the evaluation of the impact of using demand response events are also presented.