Magister Scientiae - MSc / High-spin states in the oblate deformed odd-odd thallium nucleus ( ) 109 190 81 Tl have been investigated through the reaction 175Lu(20Ne, 5n)190Tl at a beam energy of 115 MeV. The gamma rays emitted from 190Tl nucleus were detected with Ge detectors using the AFRODITE array at iThemba LABS, South Africa. Gamma-gamma coincidence data were obtained and used to construct the level scheme. In this work, Directional Correlations from Oriented (DCO) state ratios and linear polarization anisotropies were measured in order to deduce spin and parity of energy levels in the decay scheme. It was possible to determine the spin and parity of two additional signature-partner bands which decay to the ground-state band. / South Africa

Ce projet adresse le problème de détection des structures directionnelles précises dans les champs de courant. L'accent est mis surtout sur la détection des structures tourbillonnaires, puisque les chercheurs dans le domaine de la dynamique des fluides considèrent ces structures comme étant particulièrement importantes. Chapitre 1 présente la motivation de ce projet et fournit les détails du contexte environnemental et mathématique du problème en soulignant les parties essentielles de la théorie qu'on utilise après pour la solution. Chapitre 2 propose une méthode statistique, basée sur la proportion des vraisemblances, pour adresser le problème particulier de la détection des tourbillons et montre l'efficacité de cette méthode sur les données simulées et réelles en discutant aussi les limitations. Chapitre 3 développe les idées discutées dans les chapitres 1 et 2 pour trouver un outil statistique plus général qui répare les défauts de la première méthode et permet la détection de toutes les structures directionnelles qui peuvent intéresser les chercheurs. Tous les outils nécessaires pour l'analyse des données en utilisant les deux méthodes développées dans ce projet se trouvent dans les annexes A et B de la thèse. / This work addresses the problem of detecting specific directional structures in flows of current. Specific emphasis is placed on vortex detection, as scientists studying fluid dynamics consider this structure to be of particular importance. Chapter 1 presents the motivation behind the project and provides details about the environmental and, subsequently, the mathematical context of the problem, highlighting the essential parts of the theory that is later used to propose the solution. Chapter 2 offers a statistical approach, based on a likelihood ratio, to solving the specific problem of vortex detection and demonstrates the effectiveness of the method on simulated and real data, also discussing the limitations of the approach. Chapter 3 expands on the ideas discussed in Chapters 1 and 2 to derive a generalized statistical test that remedies the flaws of the first approach and extends to the problem of detecting any directional structure of interest. All necessary tools for the analysis of data using the two methods developed in this project are given in Appendix A and B.

Endemic species flocks inhabiting ancient lakes, oceanic islands and other long-lived isolated habitats are often interpreted as adaptive radiations. Yet molecular evidence for directional selection during species flocks radiation is scarce. Using partial transcriptomes of 64 species of Lake Baikal (Siberia, Russia) endemic amphipods and two nonendemic outgroups, we report a revised phylogeny of this species flock and analyse evidence for positive selection within the endemic lineages. We confirm two independent invasions of amphipods into Baikal and demonstrate that several morphological features of Baikal amphipods, such as body armour and reduction in appendages and sensory organs, evolved in several lineages in parallel. Radiation of Baikal amphipods has been characterized by short phylogenetic branches and frequent episodes of positive selection which tended to be more frequent in the early phase of the second invasion of amphipods into Baikal when the most intensive diversification occurred. Notably, signatures of positive selection are frequent in genes encoding mitochondrial membrane proteins with electron transfer chain and ATP synthesis functionality. In particular, subunits of both the membrane and substrate-level ATP synthases show evidence of positive selection in the plankton species Macrohectopus branickii, possibly indicating adaptation to active plankton lifestyle and to survival under conditions of low temperature and high hydrostatic pressures known to affect membranes functioning. Other functional categories represented among genes likely to be under positive selection include Ca-binding muscle-related proteins, possibly indicating adaptation to Ca-deficient low mineralization Baikal waters.

A two-dimensional, finite-element, porous-media flow model is developed to simulate stratified bi-directional flow of brine through the earth embankment carrying the Southern Pacific Railroad across Great Salt Lake. The model is part of a two-year research program whose objective is to develop a computer model of circulation in Great Salt Lake. This overall model is to be used as a predictive device for salinity distributions and circulation patterns in the lake. The porous media flow model is designed to establish flow rates through the Southern Pacific Railroad causeway embankment which traverses the north central part of he lake and divides it into two bodies of water. The study first develops the mathematical equations which describe two-dimensional stratified bi-directional flow of a fluid through porous media. Next , the problem is numerically posed as a boundary value problem in terms of pressure. This formulation is then solved by an iterative finite element scheme which employs quadratic, isoparametric, quadrilateral elements. The study also investigates two possible means of performing an analysis of stratified bi-directional flow with a pressure formulation by either posing the problem as a single boundary value problem with two densities of fluid within, or as two single-density boundary value problems coupled at the density interface. The single boundary formulation did not converge with the techniques attempted due to numerical instability at the density interface. The numerical model developed enables one to calculate fluid flow rates as well as the locations of the free surface and density-interface. The model simulation investigates many lake variables which affect brine flows through the embankment. Realistic model parameters are used which cover the range of actual values observed on the lake for the years 1968 through 1972. The numerical results presented in the study are given in terms of generalized dimensionless variables. The numerical results appeared to be in agreement with previously performed stratified bi-directional Hele-Shaw model studies. The major lake parameters affecting flow rates through the causeway were the free surface head difference, the southside lake surface elevation and the difference in fluid densities between the upper and lower layers of the embankment . The southward density flow was found to be completely cut off for certain combinations of lake parameters. Lack of adequate field data collected on the embankment has left both the geometry and the coefficient of permeability of the fill in question, preventing a rigorous verification of the model' s ability to predict actual flows. More field data are also necessary to establish whether there is stratification on the north side of the embankment which can greatly affect flow calculations. A high Reynold's number was found for flow through the embankment, raising a question as to the validity of the Darcian flow assumption used in the analysis. However, the establishment of the true Reynold's number can only be verified through the collection of more empirical data.

Complete coverage relies on a path planning algorithm that will move one or more robots, including the actuator, sensor, or body of the robot, over the entire environment. Complete coverage of an unknown environment is used in applications like automated vacuum cleaning, carpet cleaning, lawn mowing, chemical or radioactive spill detection and cleanup, and humanitarian de-mining. The environment is typically decomposed into smaller areas and then assigned to individual robots to cover. The robots typically use the Boustrophedon motion to cover the cells. The location and size of obstacles in the environment are unknown beforehand. An online algorithm using sensor-based coverage with unlimited communication is typically used to plan the path for the robots. For certain applications, like robotic lawn mowing, a pattern might be desirable over a random irregular pattern for the coverage operation. Assigning directional constraints to the cells can help achieve the desired pattern if the path planning part of the algorithm takes the directional constraints into account. The goal of this dissertation is to adapt the distributed coverage algorithm with unrestricted communication developed by Rekleitis et al. (2008) so that it can be used to solve the complete coverage problem with directional constraints in unknown environments while minimizing repeat coverage. It is a sensor-based approach that constructs a cellular decomposition while covering the unknown environment. The new algorithm takes directional constraints into account during the path planning phase. An implementation of the algorithm was evaluated in simulation software and the results from these experiments were compared against experiments conducted by Rekleitis et al. (2008) and with an implementation of their distributed coverage algorithm. The results of this study confirm that directional constraints can be added to the complete coverage algorithm using multiple robots without any significant impact on performance. The high-level goals of complete coverage were still achieved. The work was evenly distributed between the robots to reduce the time required to cover the cells.

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Highly directive loudspeakers have long been important tools for sound system designers, experimental acousticians, and many other professionals in the audio industry. They allow sound engineers to more easily manipulate the radiation pattern of their loudspeakers to accommodate the purpose of the venue. Many commercially available products, while exhibiting good directivity at mid and high frequencies, generally lack control in the low frequency range. A new method for controlling the radiation pattern of a loudspeaker at low frequencies has been developed and modeled extensively. Prototypes have been built and tested in an anechoic chamber. Results from computer modeling and experimental measurements will be presented and compared in this thesis.

Nonsmoothness appears in various applications in chemical engineering, including multi-stream heat exchangers, nonsmooth flash calculation, process integration. In terms of numerical approaches, convex/concave relaxations of static and dynamic systems may also exhibit nonsmoothness. These relaxations are used in deterministic methods for global optimization. This thesis presents several new theoretical results for nonsmooth sensitivity analysis, with an emphasis on convex relaxations. Firstly, the "compass difference" and established ODE results by Pang and Stewart are used to describe a correct subgradient for a nonsmooth dynamic system with two parameters. This sensitivity information can be computed using standard ODE solvers. Next, this thesis also uses the compass difference to obtain a subgradient for the Tsoukalas-Mitsos convex relaxations of composite functions of two variables. Lastly, this thesis develops a new general subgradient result for Tsoukalas-Mitsos convex relaxations of composite functions. This result does not limit on the dimensions of input variables. It gives the whole subdifferential of Tsoukalas-Mitsos convex relaxations. Compare to Tsoukalas-Mitsos’ previous subdifferential results, it does not require additionally solving a dual optimization problem as well. The new subgradient results are extended to obtain directional derivatives for Tsoukalas-Mitsos convex relaxations. The new subgradient results and directional derivative results are computationally approachable: subgradients in this article can be calculated both by the vector forward AD mode and reverse AD mode. A proof-of-concept implementation in Matlab is discussed. / Thesis / Master of Applied Science (MASc)

The growth of Distributed Energy Resources is accelerating, causing significant changes in utility distribution systems due to the bidirectionality of power flow. As a result, protection systems will require upgrades to operate with these new requirements. The current-only directional relay (CODR) is a novel proposal that detects the direction of fault currents without the need for new devices, but instead upgrades the software logic of existing devices, making it a cost-effective solution. This work provides a complete description of how to implement a hardware testbed to review the CODR method. Findings show that CODR performs successfully in a real environment, but its algorithm needs to be upgraded if used in distribution systems where lines have a non-negligible resistive component. / Master of Science / The use of renewable energy sources, such as solar panels and wind turbines, is growing rapidly. This is causing changes in the way electricity is distributed, as power can now flow in both directions. To keep up with these changes, the systems that protect the electricity grid need to be updated. One cost-effective solution is to use a new type of relay, called the current-only directional relay (CODR), which can detect the direction of fault currents without the need for new devices. This work describes how to test the CODR method using a hardware testbed. The results show that the CODR performs well in a real environment, but its algorithm needs to be updated for use in certain types of distribution systems.