The provision of decent, affordable and well-located housing for low-income communities has been an intractable problem, especially for developing countries. The empirical puzzle that motivated this study is that, despite the adverse macro environment in Zimbabwe, there appears to be private-sector developers who are successfully developing housing benefiting the low-income group. This is so, despite numerous studies that claim that given the magnitude of the housing challenge, a neoliberal doxa in a developing country context as a solution is a fallacy. Working on the broad premise that these developments represent a successful adaptation to the structural environment, the main question guiding the study was - what accounts for the success of market provided low-income housing developments in Zimbabwe despite the environment not being conducive for it? The two sub-questions flowing from this main question were firstly, how does the structural environment enable and/or constrain private sector low-income developments in Zimbabwe? Secondly, what strategies do developers adopt in response to the structural enablers and/or constraints to develop low-income housing in Zimbabwe? From these questions, the study has two hypotheses – the first hypothesis is that despite the adverse environment there exists in Zimbabwe structural enablers that make market solutions to the low-income housing challenge possible. The second hypothesis states that developers have specific discernible strategies that they employ in response to the adverse operating environment to reduce development costs to levels that enable them to provide low-income housing successfully. Using the Structure-Agency model, which is a theoretical framework rooted in institutional economics, a conceptual model to study the development process was developed and used to theorise the impact of structure on agency in the development process. Empirical evidence was gathered using observation, household surveys, and semi-structured interviews. This evidence was obtained from five housing schemes, the local authority, central government, financiers and the developers of the housing schemes, and then processed using NVIVO and SPSS. The study finds that most challenges faced by developers emanate from the institutional environment and access to resources. These challenges are namely central-local government dynamics fuelled by political undertones, lack of access to land suitable for the target group, a bureaucratic and stiff regulatory framework as well as a lack of market provided developer and end-user finance. Enabling factors were mainly the withdrawal of the government in the provision of housing in line with World-Bank neoliberal orthodoxy and incapacitation of the local authority, which eliminated alternative sources of housing for the low income group other than market provided housing, thus widening the market base for the developers. Strategies used by the developers include developer provided finance to the target group, preselling developments, sidestepping the local authority through buying land at the periphery of the local authority boundary, sidestepping regulatory barriers through engaging in corruption, backward integration to promote efficient resource allocation, and an innovative approach to risk management that caters for the low-income group. The study concludes that all these strategies have one overriding objective of cost containment. The findings indicate that there is potential, appetite and scope for more private-sector engagement. On this basis, it is recommended that the key to unlocking this potential lies with the state, as there are several policy implications that flow from these findings if the highlighted constraints are to be addressed. The study makes a number of key contributions to knowledge on market solutions to the low-income housing challenge in the area of theory, methodology, policy and empirical data.

Nous nous intéressons à estimer la moyenne d'une variable aléatoire de loi à queue lourde. Nous adoptons une approche plus robuste que la moyenne empirique classique communément utilisée. L'objectif est de développer des inégalités de concentration de type sous-gaussien sur l'erreur d'estimation. En d'autres termes, nous cherchons à garantir une forte concentration sous une hypothèse plus faible que la bornitude : une variance finie. Deux estimateurs de la moyenne pour une loi à support réel sont invoqués et leurs résultats de concentration sont rappelés. Plusieurs adaptations en dimension supérieure sont envisagées. L'utilisation appropriée de ces estimateurs nous permet d'introduire une nouvelle technique de minimisation du risque empirique pour des variables aléatoires à queue lourde. Quelques applications de cette technique sont développées. Nous appuyons ces résultats sur des simulations sur des jeux de données simulées. Dans un troisième temps, nous étudions un problème d'estimation multivarié dans le cadre des U-statistiques où les estimateurs précédents offrent, là aussi, une généralisation naturelle d'estimateurs présents dans la littérature. / In this thesis, we are interested in estimating the mean of heavy-tailed random variables. We focus on a robust estimation of the mean approach as an alternative to the classical empirical mean estimation. The goal is to develop sub-Gaussian concentration inequalities for the estimating error. In other words, we seek strong concentration results usually obtained for bounded random variables, in the context where the bounded condition is replaced by a finite variance condition. Two existing estimators of the mean of a real-valued random variable are invoked and their concentration results are recalled. Several new higher dimension adaptations are discussed. Using those estimators, we introduce a new version of empirical risk minimization for heavy-tailed random variables. Some applications are developed. These results are illustrated by simulations on artificial data samples. Lastly, we study the multivariate case in the U-statistics context. A natural generalization of existing estimators is offered, once again, by previous estimators.

The classic flow shop problem assumes that jobs make only single passes through the processing machines and that the processing times are not affected by the length of the delay before jobs are processed. These assumptions are being relaxed in recent papers that consider reentrance problems and those with schedule deterioration. In this study, these two assumptions are both relaxed, and a model of a reentrant flowshop with a deteriorating schedule is considered. A linear programming formulation of the problem is first presented. Three solution heuristics are considered under different deterioration scenarios. It was observed that both Nawaz Enscor and Ham (NEH) algorithm and Genetic Algorithm (GA) performed much better than the Campbell Dudek and Smith (CDS) algorithm. Overall, when considering both the quality of solution and computational time together, the NEH algorithm seems to have performed much better than the others as the size of problems increases. This model would find useful applications in some metallurgical and manufacturing processes where such problems are usually encountered. / Dissertation (MEng (Industrial Engineering))--University of Pretoria, 2021. / Industrial and Systems Engineering / MEng (Industrial Engineering) / Unrestricted

Dans ce travail, on s'intéresse à des outils mathématiques spéciaux appelés tenseurs qui sont formellement définis comme des tableaux multidimensionnels définis sur le produit tensoriel d'espaces vectoriels (chaque espace vectoriel étant muni de son système de coordonnées), le nombre d'espaces vectoriels impliqués dans ce produit étant l'ordre du tenseur. L'intérêt pour les tenseurs est motivé par certains travaux expérimentaux qui ont prouvé, dans divers contextes, que traiter des données multidimensionnelles avec des tenseurs plutôt que des matrices donne un meilleur résultat aussi bien pour des tâches de régression que de classification. Dans le cadre de la thèse, nous nous sommes focalisés sur une décomposition dite de Tucker et avons mis en place une méthode pour l'apprentissage de dictionnaires, une technique pour l'apprentissage en ligne de dictionnaires, une approche pour la décomposition d'un tenseur de grandes tailles et enfin une méthodologie pour la décomposition d'un tenseur qui croît par rapport à tous les modes. De nouveaux résultats théoriques concernant la convergence et la vitesse de convergence sont établis et l'efficacité des algorithmes proposés, reposant soit sur la minimisation alternée, soit sur la descente de gradients par coordonnées, est démontrée sur des problèmes réels / In this work, we are interested in special mathematical tools called tensors, that are multidimensional arrays defined on tensor product of some vector spaces, each of which has its own coordinate system and the number of spaces involved in this product is generally referred to as order. The interest for these tools stem from some empirical works (for a range of applications encompassing both classification and regression) that prove the superiority of tensor processing with respect to matrix decomposition techniques. In this thesis framework, we focused on specific tensor model named Tucker and established new approaches for miscellaneous tasks such as dictionary learning, online dictionary learning, large-scale processing as well as the decomposition of a tensor evolving with respect to each of its modes. New theoretical results are established and the efficiency of the different algorithms, which are based either on alternate minimization or coordinate gradient descent, is proven via real-world problems.

Alors que l’on utilise couramment de nombreux modèles numériques différents pour la description statique des réservoirs souterrains et des incertitudes associées, les incertitudes sur les écoulements des fluides à l’intérieur de ces réservoirs ne peuvent, pour des raisons de performance, que s’appuyer que sur quelques simulations d’écoulements. Les travaux de cette thèse ont donc pour objectif d’améliorer la transmission de l’impact des incertitudes statiques sur les réponses du simulateur dynamique d’écoulements sans augmenter le temps de calcul, grâce à des modèles approchés (proxy). Pour cela deux axes de recherche ont été menés : - L’implémentation de nouveaux proxys basés sur le Fast Marching, afin de modéliser la propagation d’un fluide dans un réservoir avec seulement quelques paramètres. Cela permet d’obtenir des courbes de réponse similaires à celles fournit par le simulateur d’écoulement pour un temps de calcul très court ; - La mise en place d’une procédure de minimisation mathématique afin de prédire les courbes de réponses du simulateur d’écoulement à partir d’un modèle analytique et des distances entre les modèles calculées avec les réponses des proxys. Les méthodes développées ont été appliquées sur deux cas d’études réels afin de les valider face aux données disponibles dans l’industrie. Les résultats ont montrés que les proxys que nous avons implémentés apportent de meilleures informations que les proxys disponibles bien que les nôtres soient toujours perfectibles. Nous avons aussi mis en évidence l’intérêt de notre procédure de minimisation pour mieux évaluer les incertitudes dynamiques à partir du moment où le proxy utilisé est suffisamment fiable / Although it is common to use many different numerical models for the static description of underground reservoirs and their associated uncertainties, for fluid flow uncertainties through these reservoirs only few dynamic simulations can be used due to performance reasons. The objective of this thesis’ work is to better transmit the impact of static uncertainties on flow simulator’s responses without increasing computation time, using approximated models (proxies). Research has been undertaken in 2 directions: - Implementation of new proxies based on Fast Marching in order to better approach fluid propagation behavior in a reservoir using only a few parameters. This allows to obtain response curves close to those provided by the flow simulator in a very short period of time - Set up a mathematical minimization’s procedure in order to predict flow simulator’s response curves using an analytical model and distances between proxy responses computed on every model. The methods developed during this PhD have been applied on two different real cases in order to validate them with industry data. Results have shown that our new proxy improve the quality of the information about fluid behavior compared to the available proxy even though ours can still be improved. We also highlight that our minimization procedure better assesses dynamic uncertainties if the proxy used is reliable enough

Municipal solid waste management (MSWM) is a global problem as most local authorities fail to dispose MSW safely. In view of this, the study was aimed at evaluating environmental and health risks associated with municipal solid waste (MSW) illegal disposal as well as constraints faced by Masvingo City in MSWM, with a view to developing an alternative sustainable management model. The study, informed by the philosophy of pragmatism, employed a mixed methods design in which quantitative and qualitative data werecollected concurrently. Questionnaires comprising both close and open-ended questions, semi-structured interviews and site visits were used to collect data. The study population comprised participants from Masvingo City’s residential areas, Masvingo City Council employees, Environmental Management Agency (EMA) officials and informal waste pickers. A sample of 406 participants, comprising 354 residents from high-density, 16 residents from medium-density, 24 residents from low-density suburbs, six council employees, two EMA officials and four informal waste collectors participated in the survey. Concurrent triangulation was employed to analyse data. Basic numerical analysis was used for quantitative data while thematic data analysis was employed for qualitative data. Three main findings which emerged from the study were (a) Land pollution, air pollution, surface water pollution and loss of urban beauty, were the main environmental risks as at least 59 % of the respondents noted the four as environmental risks associated with illegal municipal solid waste disposal (b) Cholera, skin problems and malaria were the main health risks; and, (c) The main constraints related to MSW management were inadequate environmental education, lack of cooperation and participation from waste generatorsand lack of resources by Masvingo City . From the findings, 66 %, 52 % and 49 % of participants noted inadequate environmental education, lack of cooperation and participation, and lack of resources respectively as constraints faced by Masvingo City in MSWM. Basing on the findings of the study, it can be concluded that MSW disposal in Masvingo was a threat to the environment and human health and, as a result, a sustainable MSWM model was developed for Masvingo City. / Environmental Sciences

The aim of this study is to examine the main reasons for and obstacles to single family households sorting household waste. Focusing on a population between ages 35 and 45 and 65+, it also examines motivating factors, reasons, and obstacles to reduce total household waste. Worldwide, the problem of greenhouse gases and dioxins because of waste is still unresolved. The national environmental legislation state that everyone is responsible to handle their waste in a way that does not harm people or the environment. Previous investigations regarding waste, conducted by waste company Miva, situated in municipality of Örnsköldsvik, show that improvements can be done by the citizens. The current project involves a survey sent to 789 households and answered by 302. Results from the survey combined with eight telephone interviews showed the following: people sort their waste mainly for environmental reasons but sometimes they find it easier not to sort at all, often because of very dirty packaging or simply convenience. Both age groups have the will but do not experience the possibility to reduce their overall waste. Higher waste management cost does not motivate people to improve their recycling habits, but personal feedback seems to be an effective way to reach higher motivation. To reach further improvements and reduce waste the citizens of Örnsköldsvik might need to change their consumption habits and producers take their responsibility regarding packaging. Further research to what impacts consumer behaviour is needed.

Autonomous driving systems are rapidly improving and may have the ability to change society in the coming decade. One important part of these systems is the interpretation of sensor information into trajectories of objects. In this master’s thesis, we study an energy minimisation method with radar and camera measurements as inputs. An energy is associated with the trajectories; this takes the measurements, the objects’ dynamics and more factors into consideration. The trajectories are chosen to minimise this energy, using a gradient descent method. The lower the energy, the better the trajectories are expected to match the real world. The processing is performed offline, as opposed to in real time. Offline tracking can be used in the evaluation of the sensors’ and the real time tracker’s performance. Offline processing allows for the use of more computer power. It also gives the possibility to use data that was collected after the considered point in time. A study of the parameters of the used energy minimisation method is presented, along with variations of the initial method. The results of the method is an improvement over the individual inputs, as well as over the real time processing used in the cars currently. In the parameter study it is shown which components of the energy function are improving the results. / Mycket resurser läggs på utveckling av självkörande bilsystem. Dessa kan komma att förändra samhället under det kommande decenniet. En viktig del av dessa system är behandling och tolkning av sensordata och skapande av banor för objekt i omgivningen. I detta examensarbete studeras en energiminimeringsmetod tillsammans med radar- och kameramätningar. En energi beräknas för banorna. Denna tar mätningarna, objektets dynamik och fler faktorer i beaktande. Banorna väljs för att minimera denna energi med hjälp av gradientmetoden. Ju lägre energi, desto bättre förväntas banorna att matcha verkligheten. Bearbetning sker offline i motsats till i realtid; offline-bearbetning kan användas då prestandan för sensorer och realtidsbehandlingen utvärderas. Detta möjliggör användning av mer datorkraft och ger möjlighet att använda data som samlats in efter den aktuella tidpunkten. En studie av de ingående parametrarna i den använda energiminimeringsmetoden presenteras, tillsammans med justeringar av den ursprungliga metoden. Metoden ger ett förbättrat resultat jämfört med de enskilda sensormätningarna, och även jämfört med den realtidsmetod som används i bilarna för närvarande. I parameterstudien visas vilka komponenter i energifunktionen som förbättrar metodens prestanda.

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Yes / This paper proposes a probabilistic multi-objective optimization method for the operation of three-phase distribution networks incorporating active network management (ANM) schemes including coordinated voltage control and adaptive power factor control. The proposed probabilistic method incorporates detailed modelling of three-phase distribution network components and considers different operational objectives. The method simultaneously minimizes the total energy losses of the lines from the point of view of distribution network operators (DNOs) and maximizes the energy generated by photovoltaic (PV) cells considering ANM schemes and network constraints. Uncertainties related to intermittent generation of PVs and load demands are modelled by probability density functions (PDFs). Monte Carlo simulation method is employed to use the generated PDFs. The problem is solved using ɛ-constraint approach and fuzzy satisfying method is used to select the best solution from the Pareto optimal set. The effectiveness of the proposed probabilistic method is demonstrated with IEEE 13- and 34- bus test feeders.