Thèse (Ph. D.)--Université Laval, 2002. / Dans le titre le signe "1" est souscrit. Bibliogr.: f. 175-202. Publié aussi en version électronique.

Thèse (M.Sc.)--Université Laval, 2003. / Bibliogr.: f. 123-142. Publié aussi en version électronique.

Organizational support for cooperative work has been shifted from using Face-to-Face (FTF) communication in collocated groups to using Communication-Mediated-Communication (CMC) in dispersed groups. This new and growing form of communication has stimulated scholars to study the differences of group performance between FTF and CMC. Task categorization has been the methodology chosen for several empirical research studies. These studies conclude that the effectiveness of a communication medium for a given task depends on the degree to which there is a fit between the richness of information that can be transmitted via a system’s technology and the information richness requirements of that task. However, there are numerous problems associated with using task categorization in such studies. One of these limitations is that categorization forces the researcher to enclose a task situation into a general predetermined category that may not describe the real nature of the activity. For instance, task categorization does not capture the dynamic interaction of groups performing tasks that involve variation. This thesis discusses the weakness and limitations of this approach and, using conclusions drawn from experimental results, propose the adoption of a more systematic approach based on the concept of Ashby’s law of requisite variety. Findings on the differences in performance of FTF groups versus CMC groups of 39 three-person groups of engineering undergraduate students revealed that the group performance was not affected by the communication medium but rather by variation in the task (low and high complexity).

Organizational support for cooperative work has been shifted from using Face-to-Face (FTF) communication in collocated groups to using Communication-Mediated-Communication (CMC) in dispersed groups. This new and growing form of communication has stimulated scholars to study the differences of group performance between FTF and CMC. Task categorization has been the methodology chosen for several empirical research studies. These studies conclude that the effectiveness of a communication medium for a given task depends on the degree to which there is a fit between the richness of information that can be transmitted via a system’s technology and the information richness requirements of that task. However, there are numerous problems associated with using task categorization in such studies. One of these limitations is that categorization forces the researcher to enclose a task situation into a general predetermined category that may not describe the real nature of the activity. For instance, task categorization does not capture the dynamic interaction of groups performing tasks that involve variation. This thesis discusses the weakness and limitations of this approach and, using conclusions drawn from experimental results, propose the adoption of a more systematic approach based on the concept of Ashby’s law of requisite variety. Findings on the differences in performance of FTF groups versus CMC groups of 39 three-person groups of engineering undergraduate students revealed that the group performance was not affected by the communication medium but rather by variation in the task (low and high complexity).

Thèse (M.Sc.)--Université Laval, 2002. / Dans le titre le signe "1" est souscrit. Bibliogr.: f. 66-79. Publié aussi en version électronique.

Les instabilités thermoacoustiques, également appelées instabilités de combustion, sont un problème majeur pour la production d’électricité ainsi que dans l’industrie aérospatiale. Ces instabilités sont dues à un transfert d’énergie entre une source chaude, le plus souvent une flamme stabilisée dans un brûleur, et le champ acoustique environnant. Les instabilités de combustion peuvent avoir de nombreuses conséquences délétères telles que l’extinction de la flamme, l’augmentation des flux de chaleur pariétaux, l’émission d’ondes sonores de grande amplitude à certaines fréquences, des vibrations importantes, des dégâts structurels et même l’explosion du moteur dans certains cas. Étant donné les conséquences potentielles de tels phénomènes, d’importants moyens de recherche ont été consacrés à la prédiction de l’apparition d’instabilités de combustion dans les chaudières, les moteurs de fusée et les turbines à gaz ces dernières décennies. Néanmoins, le cadre théorique associé à l’étude de ces instabilités est complexe et nécessite l’emploi de nombreuses disciplines de la physique. De plus, les brûleurs industriels sont constitués de nombreuses cavités tridimensionnelles interagissant entre elles d’un point de vue acoustique. Pour toutes ces raisons, la prédiction de la stabilité thermoacoustique d’un brûleur demeure une tâche ardue à ce jour... (Voir le texte de la thèse pour la suite du résumé) / Thermoacoustic instabilities, also known as combustion instabilities, are a major concern in the aerospace and energy production industries. They are due to an energy transfer that occurs between a heat source, usually a flame stabilized inside a combustor, and the surrounding acoustic field and may lead to undesirable phenomena such as flame extinction, increased heat fluxes, very large sound emissions at certain frequencies, vibration, structural damage and even catastrophic failure in some cases. Given the potential consequences of such phenomena, a large research effort has been devoted to predicting the onset of combustion instabilities in modern boilers, rocket engines and gas turbines during the past few decades. Unfortunately, the theoretical framework associated with the study of thermoacoustic instabilities is complex and multi-physics and the geometry of practical combustors is an intricate arrangement of 3D cavities. As a consequence, predicting the thermoacoustic stability of a combustor at an early design stage is a challenging task to date... (See inside the manuscript for the remainder of the abstract)

Bile acids regulate their own synthesis through a feedback regulatory mechanism of mainly two enzymes in the classic pathway, the 7α-hydroxylase and the 12α-hydroxylase. In the early 1990's it was shown that the regulatory responses of 7α-hydroxylase are mediated at the transcriptional level and since then many positive and negative transcription factors that mediate regulatory response have been identified. An important finding was that the transcription factors regulating the expression of 7α- and 12α-hydroxylase genes are nuclear receptors.One of the first nuclear receptors identified to play a role in the transcription of the 7α-hydroxylase gene was HNF-4 since then many nuclear receptors have been identified that are involved in regulating the 7α- and 12α-hydroxylase genes. Among them the most important ones are FTF and HNF-4 which has been shown to play crucial roles in the transcription and regulation by bile acids. In this study we demonstrate the importance of FTF and HNF-4 independent of each other in the transcription and bile acid-mediated regulation of the 7α- and 12α-hydroxylase enzymes by creating promoter mutants that would either bind FTF or HNF- 4. Once the binding studies were established we performed tissue culture experiments to confirm the promoter activity and bile acid-mediated regulation with the respective promoter mutant constructs. The data from this study shows that HNF-4 is important for 7α-hydroxylase promoter activity but is not required and importantly we show that HNF-4 is not a required for the bile acid-mediated regulation of the 7α-hydroxylase. We present data which suggests that FTF is absolutely required for the promoter activity and bile acid-mediated regulation of 7α-hydroxylase. With respect to the 12α-hydroxylases how that both FTF and HNF-4 are absolutely required for promoter activity. In this study we present evidence that since the bile acid responsive elements (BARE) are similar within both the 7α- and 12α-hydroxylase promoters one can be exchanged for the other maintaining both activity and bile acid-mediated regulation.

Le récepteur nucléaire Fetoprotein Transcription Factor (FTF) identifié par notre laboratoire et exprimé principalement dans le système digestif est un régulateur important du métabolisme des lipides et des stéroïdes, de la prolifération cellulaire et du développement embryonnaire. Plusieurs groupes ont constaté que l’influence du récepteur FTF sur la synthèse de stéroïdes et la régulation du cycle cellulaire stimule la prolifération tumorale de cellules d’origine tissulaire diverse. Mes études de doctorat ont porté sur l’expression tissulaire de FTF, sur la caractérisation d’un nouvel élément régulateur de son promoteur et sur l’identification par immunoprécipitation de chromatine (ChIP-chip) des cibles transcriptionnelles de FTF dans le foie de souris fœtale et adulte et dans les cellules d’hépatome humain. Ces études ont permis de mieux définir le rôle métabolique de FTF ainsi que son rôle développemental et son implication potentielle dans la carcinogenèse hépatique. L’expression de FTF par les organes du système digestif et par certaines structures nerveuses, sa régulation par des récepteurs nucléaires métaboliques et sa liaison aux promoteurs de multiples enzymes et transporteurs impliqués dans le métabolisme énergétique placent FTF dans une position clé dans l’homéostasie métabolique et énergétique de l’organisme. Le facteur de transcription C/EBPpartenaire de FTF au promoteur de l’AFP et impliqué lui aussi dans le développement hépatique et le métabolisme énergétique, est lié au promoteur de 20% des cibles transcriptionnelles de FTF. De plus, C/EBP lie le promoteur de FTF formant ainsi une autre boucle activatrice s’ajoutant au réseau transcriptionnel hépatique. Dans les cellules d’hépatome, FTF lie les promoteurs de plusieurs gènes impliqués dans la prolifération et le maintien des cellules tumorales, soit des régulateurs de la réplication, de la croissance et de l’apoptose cellulaire. FTF fait donc partie intégrante du réseau transcriptionnel hépatique régissant le développement et la différenciation hépatique et le maintien du métabolisme énergétique chez l’adulte et est vraisemblablement impliqué dans la promotion de la cancérogenèse hépatique. / FTF is a nuclear receptor principally expressed in adult digestive organs that has been shown to act as a major regulator of lipids and steroids metabolism, cellular proliferation and embryonic development. FTF involvement in steroid synthesis and cell cycle regulation tends toward the stimulation of tumor proliferation in neoplasic tissues in which FTF is expressed. However, more studies of FTF function in normal and disease states and on its regulation are needed to draw a complete picture of FTF activity in cell physiology. Within the context of my studies, I delineated the FTF adult and fetal tissular expression, characterized a novel Ftf promoter element and identified FTF direct hepatic transcriptional targets in fetal, adult and tumor cell lines by using chromatin immunoprecipitation (ChIP-on-chip). These studies defined new FTF functions in metabolism, fetal development and hepatic carcinogenesis. FTF expression in digestive system and in neural structures controlling eating behavior, its transcriptional regulation by metabolic nuclear receptors and its binding to enzyme and transporter gene promoters driving energy metabolism, puts FTF in a key location for governing cellular and organismal energy metabolism. C/EBP, a transcriptional FTF partner on the Afp gene promoter and also involved in energy metabolism, is bound to 20% of the FTF targets including FTF itself thus adding branches to the complex hepatic transcriptional network. In hepatoma cells, FTF binds to proliferation and tumor cell maintenance genes like replication, growth and apoptosis regulators. Therefore, FTF belongs to the hepatic transcription network that governs hepatic development, differentiation and adult energy metabolism and is likely to be involved in promoting hepatic tumorogenesis.

<p>Combustion instability, a complex phenomenon observed in combustion chambers is due to the coupling between heat release and other unsteady flow processes. Combustion instability has long been a topic of interest to rocket scientists and has been extensively investigated experimentally and computationally. However, to date, there is no computational tool that can accurately predict the combustion instabilities in full-size combustors because of the amount of computational power required to perform a high-fidelity simulation of a multi-element chamber. Hence, the focus is shifted to reduced fidelity computational tools which may accurately predict the instability by using the information available from the high-fidelity simulations or experiments of single or few-element combustors. One way of developing reduced fidelity computational tools involves using a reduced fidelity solver together with the flame transfer functions that carry important information about the flame behavior from a high-fidelity simulation or experiment to a reduced fidelity simulation.</p> <p> </p> <p>To date, research has been focused mainly on premixed flames and using acoustic solvers together with the global flame transfer functions that were obtained by integrating over a region. However, in the case of rockets, the flame is non-premixed and distributed in space and time. Further, the mixing of propellants is impacted by the level of flow fluctuations and can lead to non-uniform mean properties and hence, there is a need for reduced fidelity solver that can capture the gas dynamics, nonlinearities and steep-fronted waves accurately. Nonlinear Euler equations have all the required capabilities and are at the bottom of the list in terms of the computational cost among the solvers that can solve for mean flow and allow multi-dimensional modeling of combustion instabilities. Hence, in the current work, nonlinear Euler solver together with the spatially distributed local flame transfer functions that capture the coupling between flame, acoustics, and hydrodynamics is explored.</p> <p> </p> <p>In this thesis, the approach to extract flame transfer functions from high-fidelity simulations and their integration with nonlinear Euler solver is presented. The dynamic mode decomposition (DMD) was used to extract spatially distributed flame transfer function (FTF) from high fidelity simulation of a single element non-premixed flame. Once extracted, the FTF was integrated with nonlinear Euler equations as a fluctuating source term of the energy equation. The time-averaged species destruction rates from the high-fidelity simulation were used as the mean source terms of the species equations. Following a variable gain approach, the local species destruction rates were modified to account for local cell constituents and maintain correct mean conditions at every time step of the nonlinear Euler simulation. The proposed reduced fidelity model was verified using a Rijke tube test case and to further assess the capabilities of the proposed model it was applied to a single element model rocket combustor, the Continuously Variable Resonance Combustor (CVRC), that exhibited self-excited combustion instabilities that are on the order of 10% of the mean pressure. The results showed that the proposed model could reproduce the unsteady behavior of the CVRC predicted by the high-fidelity simulation reasonably well. The effects of control parameters such as the number of modes included in the FTF, the number of sampling points used in the Fourier transform of the unsteady heat release, and mesh size are also studied. The reduced fidelity model could reproduce the limit cycle amplitude within a few percent of the mean pressure. The successful constraints on the model include good spatial resolution and FTF with all modes up to at least one dominant frequency higher than the frequencies of interest. Furthermore, the reduced fidelity model reproduced consistent mode shapes and linear growth rates that reasonably matched the experimental observations, although the apparent ability to match growth rates needs to be better understood. However, the presence of significant heat release near a pressure node of a higher harmonic mode was found to be an issue. This issue was rectified by expanding the pressure node of the higher frequency mode. Analysis of two-dimensional effects and coupling between the local pressure and heat release fluctuations showed that it may be necessary to use two dimensional spatially distributed local FTFs for accurate prediction of combustion instabilities in high energy devices such as rocket combustors. Hybrid RANS/LES-FTF simulation of the CVRC revealed that it might be necessary to use Flame Describing Function (FDF) to capture the growth of pressure fluctuations to limit cycle when Navier-Stokes solver is used.</p> <p> </p> <p>The main objectives of this thesis are:</p> <p>1. Extraction of spatially distributed local flame transfer function from the high fidelity simulation using dynamic mode decomposition and its integration with nonlinear Euler solver</p> <p>2. Verification of the proposed approach and its application to the Continuously Variable Resonance Combustor (CVRC).</p> <p>3. Sensitivity analysis of the reduced fidelity model to control parameters such as the number of modes included in the FTF, the number of sampling points used in the Fourier transform of the unsteady heat release, and mesh size.</p> <p> </p> <p>The goal of this thesis is to contribute towards a reduced fidelity computational tool which can accurately predict the combustion instabilities in practical systems using flame transfer functions, by providing a path way for reduced fidelity multi-element simulation, and by defining the limitations associated with using flame transfer functions and nonlinear Euler equations for non-premixed flames.</p> <p> </p><br>

Denna studie undersöker hur fyra gymnasielärare i svenska arbetade med formativ bedömning samt examination under utbrottet av Covid-19 våren 2020. Studien består av fyra nätbaserade intervjuer med verksamma svenskämneslärare i syfte att ta reda på hur de upplevde sin hantering av formativ bedömning och examination av elever i samband med den rådande coronakrisen. Studien delar upp den formativa bedömningsprocessen efter följande kategorier: Muntlig produktion, skriftlig produktion, grupparbeten, lärarrespons, självbedömning, kamratrespons samt examination. Resultatet indikerar bland annat att bristande möjligheter till fysisk kontakt har påverkat den formativa bedömningen samt examinationen, exempelvis genom att ställa högre krav på tydlighet och insyn. Resultaten pekar även på att rättssäkerheten är en utmaning med examinationen, medan behovet av att fortsätta utveckla nättjänster som Urkund eller Exam.net lyfts fram. Studiens resultat indikerar också att det har ställts högre krav på lärares prestationer gällande formativ bedömning, främst på grund av bristen på fysisk kontakt mellan lärare och elev. Därigenom bidrar denna studie till förståelse för användandet av formativ bedömning i svenskämnet via distansundervisning, samt för betydelsen av att rusta framtidens lärare inför liknande situationer i framtiden.