Effet de l'aération d'appoint, de la saison et de l'espèce de macrophytes dans le traitement d'un effluent piscicole par marais artificiel

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

MAT-701: PREDICTING THE COMPRESSIVE STRENGTH OF ULTRA-LIGHTWEIGHT CONCRETE BY AN ARTIFICIAL NEURAL NETWORK

Ultra-lightweight concrete (ULWC) has potential applications for floating structures and architectural elements because of its dry density coming in at under 1000 kg/m3. The objective was to develop an artificial neural network (ANN) to aid the ULWC designer according to his needs. Boundary conditions were set for each material and 13 constraints based on the water binder ratio, density, air content, binder and aggregate content. The ANN predicted the compressive strength with a comfortable margin of error, with the gap encountered being attributed to variability in workability. Precise constraints and boundary conditions are needed to ensure a lower variability in workability. The ANN, coupled with a genetic algorithm, can generate millions of mixes for a given compressive strength in a short amount of time. The designer is able to choose mixes according to additional needs, such as the carbon footprint, absolute density, polymer content, cost, etc

A unified moment tensor potential for silicon, oxygen, and silica

Si and its oxides have been extensively explored in theoretical research due to their technological and industrial importance. Simultaneously describing interatomic interactions within both Si and SiO$_2$ without the use of \textit{ab initio} methods is considered challenging, given the charge transfers involved. Herein, this challenge is overcome by developing a unified machine learning interatomic potentials describing the Si/ SiO$_2$/ O system, based on the moment tensor potential (MTP) framework. This MTP is trained using a comprehensive database generated using density functional theory simulations, encompassing a wide range of crystal structures, point defects, extended defects, and disordered structure. Extensive testing of the MTP is performed, indicating it can describe static and dynamic features of very diverse Si, O, and SiO$_2$ atomic structures with a degree of fidelity approaching that of DF

Nanocrystalline Cellulose as Effect Pigment in Clear Coatings for Wood

Nanocrystalline cellulose (CNC) is a renewable material with high potential in many applications. Due to its unique self-assembly and optical properties, CNC tends to behave as an iridescent pigment. The aim of this research was to explore the potential of CNC as an effect pigment in wood coatings. CNC-based coatings were developed from an aqueous CNC solution, a UV-curable water-based clear coating formulation, several colorants, and specialized additives. In this paper, the morphology of the resulting CNC films was investigated through circular dichroism and optical microscopy under polarized light. The effect of the CNC surface charge changes was monitored through zeta potential measurements. Color changes, or travel, and flop index were used to assess the iridescent effect of the coatings containing CNC. The experimental wood coatings contained CNC showed that the enhancement of the iridescent effect depends on the distribution and alignment of the CNC rod-like particles in order to generate the right pitch in the helical structure and their interaction with the polymer matrix as well with the additives. In conclusion, CNC could be successfully used as effect pigment in finishing systems, which can enhance the attractiveness and bring out the special grain of various types of wood.ISSN:2090-874

Effect Of Additives On Cutting Temperature Of Glass Fibers Reinforced Polymers

Composites are abrasive materials that generate heat during machining operations. This heat generates thermal damage locally and may severely alter the mechanical properties of the components if it exceeds the glass transition temperature of the matrix. This research studies the influence of additives, mixed to the epoxy matrix of Glass Fiber Reinforced Polymer (GFRP), on the cutting temperature. The results show that wax together with clay and a wetting agent, contribute to reduce the maximum cutting temperature, on a 300mm length of cut, a value up to 28% as compared to a plain epoxy matrix

Stressed and distressed: how is the COVID-19 pandemic associated with sexual frequency, sexual satisfaction, and relationship satisfaction?

Background: The Canadian government’s response to the ongoing COVID-19 pandemic included the implementation of several restrictive measures since March 2020. These actions sought to decrease social contact and increase physical distancing, including that within universities. Such constraints were required to impede the transmission of the virus; however, concerns remain about their impact on the sexual and intimate relationships of university employees and students. Aim: This study examined the associations between COVID-19–related stress and sexual frequency, sexual satisfaction, and relationship satisfaction, also testing the mediating role of psychological distress. Methods: The models were tested with Canadian data collected from university employees and students in 2 phases: the first wave in April-May 2020 (T1; n = 2754) and the second wave in November-December 2021 (T2; n = 1430), 18 months afterward. Participants completed self-report questionnaires online. Path analyses were performed to test the associations of the mediation models. Outcomes: The principal outcomes included psychological distress determined via the Patient Health Questionnaire–4, relationship satisfaction measured via the Dyadic Adjustment Scale, and sexual satisfaction and sexual frequency ascertained through a single item each. Results: Overall, COVID-19–related stress was associated with higher psychological distress, which in turn was related to lower sexual frequency, sexual satisfaction, and relationship satisfaction. Similar results were obtained with T1 and T2 data, indicating the mediating effect of psychological distress. Clinical implications: These findings increase scholarly comprehension of the negative associations between stress/distress and sexual and romantic relationships. Sexuality and close relationships are vital to the quality of human life; thus, targeted interventions should be developed to reduce COVID-19–related stress and its impact on sexual and romantic relationships to mitigate the long-term influences of this unique global challenge. Strengths & Limitations: To our knowledge, this study is the first to use a large sample size and replicate findings in 2 waves. Nonetheless, it is limited by the use of cross-sectional data. Longitudinal studies with the same participants are mandated to better understand the evolution of these outcomes. Conclusion: COVID-19–related stress and psychological distress were found among participating university students and employees and were associated with lower sexual satisfaction, sexual frequency, and intimate relationship satisfaction. These results were observed at the early onset of the pandemic and 18 months afterward, suggesting that the stress generated by the pandemic were not mere reactions to the onset of the pandemic but persisted over time