In the present PhD work, three sophisticated models based on the "Engineering" modeling approach have been utilized to conveniently describe and thoroughly analyze details of Lightning events at the CN Tower. Both the CN Tower and the Lightning Channel are represented by a number of connected in series Transmission Line sections in order to account for the variations in the shape of the tower and for plasma processes that take place within the Lightning Channel. A sum of two Heidler functions is used to describe the "uncontaminated" Return Stroke current, which is injected at the attachment point between the CN Tower and the Lightning Channel. Reflections and refractions at all points of mismatched impedances are considered until their contribution becomes less than 1% of the originally injected current wave. In the proposed models, the problem with the current discontinuity at the Lightning Channel front, commonly taken care of by introducing a "turn-on" term when computing radiation fields, is uniquely treated by introducing reflected and transmitted components. For the first time, variable speed of propagation of the Return Stroke current front has been considered and its influence upon the predicted current distributions along the whole Lightning Channel path and upon the radiated distant fields analyzed. Furthermore, as another novelty, computation of the electromagnetic field is accomplished in Cartesian Coordinates. This fact permits to relax the requirement on the verticality of the Lightning Channel, normally imposed in Cylindrical Coordinates. Therefore, it becomes possible to study without difficulty the influence of a slanted Lightning Channel upon the surrounding electromagnetic field. Since the proposed sophisticated Five-Section Model has the capability to represent very closely the structure of the CN Tower and to emulate faithfully the shape of, as well as physical processes within the Lightning Channel, it is believed to have the potential of truthfully reproducing observed fields. The developed modeling approach can be easily adapted to study the anticipated radiated fields at tall structures even before construction.

Frequent climatic shocks have presented challenges for rainfed agriculture in sub-Saharan Africa. Appropriate water management practices are among the solutions to the challenges. The role of water harvesting in achieving sustainable agricultural intensification and specified resilience was explored. Suitable areas for water harvesting in the Upper Blue Nile basin were identified. The usefulness of the Curve Number method for surface runoff estimation was evaluated, and was found to perform satisfactorily. The impact of climate change in the Lake Tana sub-basin was studied. A decision support system was developed for locating and sizing of water harvesting ponds in the SWAT model. Methodological developments enabled analysis of the implications of water harvesting intensification in a meso-scale watershed in the Lake Tana sub-basin. Results suggest that water harvesting can increase agricultural productivity, sustain ecosystems and build specified resilience, and thereby contribute to sustainable agricultural intensification. There is considerable potential for water harvesting in the Upper Blue Nile Basin. Rainfall may increase in the Lake Tana sub-basin due to climate change. Supplementary irrigation from water harvesting ponds and better nutrient application increased staple crop production by up to three-fold. Moreover, a substantial amount of cash crop was produced using dry seasonal irrigation. Water harvesting altered the streamflow regime, and reduced sediment loss from the watershed.       Water harvesting can play an important role in food security. It showed potential to buffer climatic variability. In the watershed studied, water harvesting will not compromise the environmental water requirements. Instead, increased low flows, and reduced flooding and sediment loss may benefit the social-ecological systems. The adverse effects of disturbance of the natural flow variability and sediment influx to certain riverine ecosystems warrant detailed investigation. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 5: Epub ahead of print. Paper 6: Manuscript.</p> / Water resources management and social-ecological resilience

<p>Society-induced changes to the environment are altering the effectiveness of existing management strategies for sustaining natural and agricultural ecosystem productivity. At the watershed scale, natural and agro-ecosystems represent complex spatiotemporal stochastic processes. In time, they respond to random rainfall events, evapotranspiration and other losses that are spatially variable because of heterogeneities in soil properties, root distributions, topography, and other factors. To quantify the environmental impact of anthropogenic activities, it is essential that we characterize the evolution of space and time patterns of ecosystem fluxes (e.g., energy, water, and nutrients). Such a characterization then provides a basis for assessing and managing future anthropogenic risks to the sustainability of ecosystem productivity.</p><p>To characterize the space and time evolution of watershed scale processes, this dissertation introduces a mean field approach to watershed hydrology. Mean field theory (also known as self-consistent field theory) is commonly used in statistical physics when modeling the space-time behavior of complex systems. The mean field theory approximates a complex multi-component system by considering a lumped (or average) effect of all individual components acting on a single component. Thus, the many body problem is reduced to a one body problem. For watershed hydrology, a mean field theory reduces the numerous point component effects to more tractable watershed averages resulting in a consistent method for linking the average watershed fluxes (evapotranspiration, runoff, etc.) to the local fluxes at each point.</p><p>The starting point for this work is a general point description of the soil moisture, rainfall, and runoff system. For this system, we find the joint PDF that describes the temporal variability of the soil water, rainfall, and runoff processes. Since this approach does not account for the spatial variability of runoff, we introduce a probabilistic storage (ProStor) framework for constructing a lumped (unit area) rainfall-runoff response from the spatial distribution of watershed storage. This framework provides a basis for unifying and extending common event-based hydrology models (e.g. Soil Conservation Service curve number (SCS-CN) method) with more modern semi-distributed models (e.g. Variable Infiltration Capacity (VIC) model, the Probability Distributed (PDM) model, and TOPMODEL). In each case, we obtain simple equations for the fractions of the different source areas of runoff, the spatial variability of runoff and soil moisture, and the average runoff value (i.e., the so-called runoff curve). Finally, we link the temporal and spatial descriptions with a mean field approach for watershed hydrology. By applying this mean field approach, we upscale the point description with the spatial distribution of soil moisture and parameterize the numerous local interactions related to lateral fluxes of soil water in terms of its average. With this approach, we then derive PDFs that represent the space and time distribution of soil water and associated watershed fluxes such as evapotranspiration and runoff.</p> / Dissertation

Les codes correcteurs d’erreurs Non-Binaires Low Density Parity Check (NB-LDPC) sont connus pour avoir de meilleure performance que les codes LDPC binaires. Toutefois, la complexité de décodage des codes non-binaires est bien supérieure à celle des codes binaires. L’objectif de cette thèse est de proposer de nouveaux algorithmes et de nouvelles architectures matérielles de code NB-LDPC pour le décodage des NBLDPC. La première contribution de cette thèse consiste à réduire la complexité du nœud de parité en triant en amont ses messages d’entrées. Ce tri initial permet de rendre certains états très improbables et le matériel requis pour les traiter peut tout simplement être supprimé. Cette suppression se traduit directement par une réduction de la complexité du décodeur NB-LDPC, et ce, sans affecter significativement les performances de décodage. Un modèle d’architecture, appelée "architecture hybride" qui combine deux algorithmes de l’état de l’art ("l’Extended Min Sum" et le "Syndrome Based") a été proposé afin d’exploiter au maximum le pré-tri. La thèse propose aussi de nouvelles méthodes pour traiter les nœuds de variable dans le contexte d’une architecture pré-tri. Différents exemples d’implémentations sont donnés pour des codes NB-LDPC sur GF(64) et GF(256). En particulier, une architecture très efficace de décodeur pour un code de rendement 5/6 sur GF(64) est présentée. Cette architecture se caractérise par une architecture de check node nœud de parité entièrement parallèle. Enfin, une problématique récurrente dans les architectures NB-LDPC, qui est la recherche des P minimums parmi une liste de taille Ns, est abordée. La thèse propose une architecture originale appelée first-then-second minimum pour une implantation efficace de cette tâche. / The Non-Binary Low Density Parity Check (NB-LDPC) codes constitutes an interesting category of error correction codes, and are well known to outperform their binary counterparts. However, their non-binary nature makes their decoding process of higher complexity. This PhD thesis aims at proposing new decoding algorithms for NB-LDPC codes that will be shaping the resultant hardware architectures expected to be of low complexity and high throughput rate. The first contribution of this thesis is to reduce the complexity of the Check Node (CN) by minimizing the number of messages being processed. This is done thanks to a pre-sorting process that sorts the messages intending to enter the CN based on their reliability values, where the less likely messages will be omitted and consequently their dedicated hardware part will be simply removed. This reliability-based sorting enabling the processing of only the highly reliable messages induces a high reduction of the hardware complexity of the NB-LDPC decoder. Clearly, this hardware reduction must come at no significant performance degradation. A new Hybrid architectural CN model (H-CN) combining two state-of-the-art algorithms - Forward-Backward CN (FB-CN) and Syndrome Based CN (SB-CN) - has been proposed. This hybrid model permits to effectively exploit the advantages of pre-sorting. This thesis proposes also new methods to perform the Variable Node (VN) processing in the context of pre-sorting-based architecture. Different examples of implementation of NB-LDPC codes defined over GF(64) and GF(256) are presented. For decoder to run faster, it must become parallel. From this perspective, we have proposed a new efficient parallel decoder architecture for a 5/6 rate NB-LDPC code defined over GF(64). This architecture is characterized by its fully parallel CN architecture receiving all the input messages in only one clock cycle. The proposed new methodology of parallel implementation of NB-LDPC decoders constitutes a new vein in the hardware conception of ultra-high throughput rate decoders. Finally, since the NB-LDPC decoders requires the implementation of a sorting function to extract P minimum values among a list of size Ns, a chapter is dedicated to this problematic where an original architecture called First-Then-Second-Extrema-Selection (FTSES) has been proposed.

Le résultat principal de cette thèse est l'étude de l'ampleur dans des expansions des structures géométriques et de SU-rang oméga par un prédicat dense/codense indépendant. De plus, nous étudions le rapport entre l'ampleur et l'équationalite, donnant une preuve directe de l'équationalite de certaines théories CM-triviales. Enfin, nous considérons la topologie indiscernable et son lien avec l'équationalite et calculons la complexité indiscernable du pseudoplan libre / The main result of this thesis is the study of how ampleness grows in geometric and SU-rank omega structures when adding a new independent dense/codense subset. In another direction, we explore relations of ampleness with equational theories; there, we give a direct proof of the equationality of certain CM-trivial theories. Finally, we study indiscernible closed sets—which are closely related with equations—and measure their complexity in the free pseudoplane

Reducing the time spent by experts on the process of cuneiform fragment reconstruction means that more time can be spent on the translation and interpretation of the information that the cuneiform fragments contain. Modern computers and ancillary technologies such as 3D printing have the power to simplify the process of cuneiform reconstruction, and open up the field of reconstruction to non-experts through the use of virtual fragments and new reconstruction methods. In order for computers to be effective in this context, it is important to understand the current state of available technology, and to understand the behaviours and strategies of individuals attempting to reconstruct cuneiform fragments. This thesis presents the results of experiments to determine the behaviours and actions of participants reconstructing cuneiform tablets in the real and virtual world, and then assesses tools developed specifically to facilitate the virtual reconstruction process. The thesis also explores the contemporary and historical state of relevant technologies. The results of experiments show several interesting behaviours and strategies that participants use when reconstructing cuneiform fragments. The experiments include an analysis of the ratio between rotation and movement that show a significant difference between the actions of successful and unsuccessful participants, and an unexpected behaviour that the majority of participants adopted to work with the largest fragments first. It was also observed that the areas of the virtual workspace used by successful participants was different from the areas used by unsuccessful participants. The work further contributes to the field of reconstruction through the development of appropriate tools that have been experimentally proved to dramatically increase the number of potential joins that an individual is able to make over period of time.

Low relief, heavily human-impacted landscapes like those of the Prairies in south-central Canada have received little attention in previous hydrological research. Here, the rainfall-runoff relationship in the context of both a field-based investigation and an empirical model is examined in an effort to provide insight into Prairie hydrology. Rainfall and water level data were collected for nested sub-watersheds of the Catfish Creek watershed, a 642 km2, near-level, mixed land use and engineered Prairie watershed. First, the dataset is examined for runoff controls. Second, the history of the United States Curve Number Method is reviewed and its initial abstraction ratio examined against collected field data to determine the applicability of a single, constant ratio to Prairie landscapes. Overall, the results indicate that Prairie runoff generation processes differ significantly from those of humid, pristine catchments of higher relief and a conceptual model is proposed with that regards.

This Thesis researches, explains and provides conclusions for the question of correlation between data and criteria used by Environment Canada (EC) and Lightning Studies Research Group (LSG) of University of Toronto. The necessity of such correlation arises from the question of common criteria between severe weather, as it shown in graphical data from EC, and intense lighting storms, recorded by LSG, despite deep differences in area, time scale and object of observation used by those two organizations. The objective of the Thesis is not only to compare those two, very different sets of data and criteria and find out the common ground between them, but also to provide in-depth explanation of criteria, used by Lighting Studies Research Group, along with revisiting and establishing some of them. Eight storm cases, taken from years 2005-2008 provide cases for practical research, which affects intermediate Greater Toronto Area.

This thesis presents the first modeling study on long-term carbon dynamics for the University of Guelph Elora Agricultural Research Station and the Environment Canada Borden Forest Research Station at the daily and half-hourly time-step. The daily version of the CENTURY (DayCENT) model and the Carbon- and Nitrogen-coupled Canadian Land Surface Scheme (CN-CLASS) model were validated for quantifying the effects of agricultural management and component respiration on the carbon budget. DayCENT indicated that conventional tillage (CT) enhanced the annual heterotrophic respiration relative to no-till (NT) by 38.4, 93.7 and 64.2 g C m-2 yr-1 for corn, soybean and winter wheat, respectively. The seasonal variation of total soil organic carbon (SOC) pool was greater in CT than NT due to tillage effects on carbon transfer from the active surface SOC pool to the active soil SOC pool at a rate of 50-100 g C m-2 yr-1. NT accounted for a 10.7 g C m-2 yr-1 increase in the slow SOC pool (20-year turnover time) at a site in Elora, Ontario, Canada. I found that the plant phenology algorithms used in CN-CLASS were not constructed and validated for crop growth, resulting in a high degree of uncertainty in the simulations. Therefore, I designed and tested a new agricultural module for CN-CLASS. The regression analysis indicated that the new crop module improved the net ecosystem productivity (NEP) simulation for a cornfield, with the coefficient of determination (r2) of annual NEP increasing from 0.51 in the original CN-CLASS to 0.78 in the modified version of the model. I verified CN-CLASS to simulate the dynamics of component respiration for tracing the contributions from litterfall, SOC and root respiration in a deciduous mixedwood forest in Borden, Ontario, Canada. The model estimated that the annual ecosystem CO2 respiration was 1366 g C m-2 yr-1, contributed by heterotrophic respiration (57%), maintenance respiration (37%) and growth respiration (6%). The annual accumulated soil respiration was estimated at 782 g C m-2 yr-1, which was dominated by CO2 emissions from soil organic matter (60%). The base respiration rates required further verification based on field measurements. Based on the verified modeling approach in this thesis, the modeling core of DayCENT can be constructed as an integral platform for Agriculture and Agri-Food Canada National Carbon and Greenhouse Gas Accounting and Verification System. The crop phenological module in CN-CLASS allows us to conduct further agricultural studies concerning global carbon budget and environmental change. The validated respiration algorithms in CN-CLASS would be helpful in developing global biological CO2 transport model for tracing emission sources. / Natural Science and Engineering Research Council of Canada

In the present PhD work, three sophisticated models based on the "Engineering" modeling approach have been utilized to conveniently describe and thoroughly analyze details of Lightning events at the CN Tower. Both the CN Tower and the Lightning Channel are represented by a number of connected in series Transmission Line sections in order to account for the variations in the shape of the tower and for plasma processes that take place within the Lightning Channel. A sum of two Heidler functions is used to describe the "uncontaminated" Return Stroke current, which is injected at the attachment point between the CN Tower and the Lightning Channel. Reflections and refractions at all points of mismatched impedances are considered until their contribution becomes less than 1% of the originally injected current wave. In the proposed models, the problem with the current discontinuity at the Lightning Channel front, commonly taken care of by introducing a "turn-on" term when computing radiation fields, is uniquely treated by introducing reflected and transmitted components. For the first time, variable speed of propagation of the Return Stroke current front has been considered and its influence upon the predicted current distributions along the whole Lightning Channel path and upon the radiated distant fields analyzed. Furthermore, as another novelty, computation of the electromagnetic field is accomplished in Cartesian Coordinates. This fact permits to relax the requirement on the verticality of the Lightning Channel, normally imposed in Cylindrical Coordinates. Therefore, it becomes possible to study without difficulty the influence of a slanted Lightning Channel upon the surrounding electromagnetic field. Since the proposed sophisticated Five-Section Model has the capability to represent very closely the structure of the CN Tower and to emulate faithfully the shape of, as well as physical processes within the Lightning Channel, it is believed to have the potential of truthfully reproducing observed fields. The developed modeling approach can be easily adapted to study the anticipated radiated fields at tall structures even before construction.