Cette thèse développe des outils permettant de prouver qu’un système dynamique est sûr. En supposant qu’une partie de l’espace d’état est dangereuse, un système dynamique est dit sûr lorsque son état n’atteint jamais cette partie dangereuse au cours du temps, quel que soit l’état initial appartenant à un ensemble d’états initiaux admissibles et quel que soit le niveau de perturbation restant dans un domaine admissible. Les outils proposés cherchent à établir des preuves de sûreté pour des systèmes décrits par des modèles dynamiques non-linéaires et des modèles dynamiques hybrides. Prouver qu’un système dynamique est sûr en calculant explicitement l’ensemble des trajectoires possibles du système lorsque le modèle dynamique est non-linéaire et perturbé reste une tâche très difficile. C’est pourquoi cette thèse aborde ce problème à l’aide de fonctions barrières paramétrées. Une barrière, lorsqu’elle existe, permet de partitionner l’espace d’état et d’isoler l’ensemble des trajectoires possibles de l’état du système de la partie dangereuse de l’espace d’état. La fonction paramétrique décrivant la barrière doit satisfaire un certain nombre de contraintes impliquant la dynamique du modèle, l’ensemble des états initiaux possibles, et l’ensemble dangereux. Ces contraintes ne sont pas convexes en général, ce qui complique la recherche de fonctions barrières satisfaisantes. Précédemment, seules des fonctions barrières polynomiales ont été considérées pour des modèles dynamiques polynomiaux. Cette thèse considère des systèmes dynamiques relativement généraux avec des barrières paramétriques quelconques. Les solutions présentées exploitent des outils de satisfaction de contraintes sur des domaines continus et des outils issus de l’analyse par intervalles. Dans un premier temps, cette thèse considère des systèmes dynamiques non-linéaires à temps continu. Le problème de conception d’une barrière paramétrique est formulé comme un problème de satisfaction des contraintes sur des domaines réels avec des variables quantifiées de manière existentielle et universelle. L’algorithme CSC-FPS a été adapté afin de résoudre le problème de synthèse de barrière. Cet algorithme combine une exploration de l’espace des paramètres de la barrière et une phase de vérification des propriétés de la barrière. A l’aide de contracteurs, il est possible de significativement accélérer la recherche de solutions. Dans un second temps, ces résultats sont étendus au cas de systèmes décrits par des modèles dynamiques hybrides. La propriété de sûreté doit être prouvée lors de l’évolution à temps continu du système dynamique, mais aussi pendant les transitions du système. Ceci nécessite l’introduction de contraintes supplémentaires qui lient les fonctions barrières associées à chaque mode à temps continu entre elles. Réaliser la synthèse de toutes les fonctions barrières pour les différents modes simultanément n’est envisageable que pour des systèmes de très petite dimension avec peu de modes. Une approche séquentielle a été proposée. Les contraintes liées aux transitions sont introduites progressivement entre les modes pour lesquels une barrière a déjà été obtenue. Lorsque certaines contraintes de transition ne sont pas satisfaites, une méthode de backtracking doit être mise en œuvre afin de synthétiser des barrières offrant une meilleure prise en compte des contraintes de transition non satisfaites. Ces approches ont été évaluées et comparées avec des techniques de l’état de l’art sur des systèmes décrits par des modèles à temps continu et des modèles hybrides. / This thesis addresses the problem of proving the safety of systems described by non-linear dynamical models and hybrid dynamical models. A system is said to be safe if all trajectories of its state do not reach an unsafe region. Proving the safety of systems by explicitly computing all its trajectories when its dynamic is non-linear or when its behavior is described by an hybrid model with non-linear dynamics remains a challenging task. This thesis considers the barrier function approach to prove the safety of a system. A barrier function, when it exists, partitions the state space and isolates the trajectories of the system starting from any possible initial values of the state and the unsafe part of the state space. The set of constraints, which have to be satisfied by a barrier function are usually non-convex, rendering the search of satisfying barrier functions hard. Previously, only polynomial barrier functions were taken in consideration and for systems with polynomial dynamics. This thesis considers relatively general dynamical systems with generic non-linear barrier functions. The solutions presented are based on template barrier functions, constraint satisfaction problems, and interval analysis. The first part of the thesis focuses on non-linear dynamical systems. The barrier function design problem is formulated as a constraint satisfaction problem that can be solved using tools from interval analysis. This formulation allows one to prove the safety of a non-linear dynamical system by finding the parameters of a template barrier function such that all constraints are satisfied using the FPS-CSC algorithm, which has been adapted and supplemented with contractors to improve its efficiency. The second part of the thesis is dedicated to the design of barrier functions for systems described by hybrid dynamical models. Safety properties have to be proven during the continuous-time evolution of the system, but also during transitions. This leads to additional constraints that have to be satisfied by candidate barrier functions. Solving all the constraints simultaneously to find all the barrier functions is usually computationally intractable. In the proposed approach, the algorithm explores all the locations sequentially. Transition constraints are introduced progressively between the already explored locations. Backtracking to previous location is considered when transition constraints are not satisfied. The efficiency of the proposed approaches has been compared with state-of-the-art solutions.

This research project investigates the possibility of a public programme-overlay at the Union Buildings, situated on Meintjieskop on the western edge of the Pretoria inner city. The design of the Buildings was commissioned to Sir Herbert Baker to celebrate the newly formed Union of South Africa in 1910. The buildings were completed in 1913 and this research project attempts to commemorate the centenary of this landmark. The buildings’ current state does not allow for public participation and this seems unfortunate for both the public and the buildings. This dissertation attempts to reintroduce the Union Buildings to South Africans, the Pretoria public as well as international tourists by recording the memory of the buildings. The intervention is an interpretative archive to the life of the Union Buildings. The static, stereotomic nature of the buildings has ironically been shaped and forced into many different symbolic meanings through the ever-changing political and cultural dynamics of South Africa. The life of the buildings has been interpreted into five distinguishing symbolic-eras: Birth, Union, Oppression, Democracy and Power. The new intervention attempts to make these layered eras public. This project will also explore the relationship between architecture and craft. This study understands that architecture is more than ever becoming a two dimensional experience and this is believed to be a direct result of the dimension in which it is explored - between pen and paper. The investigation will contest this current condition in which architecture finds itself. Moreover the focus of this study will be to explore architecture in its final dimension, thus exploring the relationship between architecture and craft. In the true sense this is a study of the tekton. / Dissertation (MArch(Prof))--University of Pretoria 2012. / Architecture / MArch(Prof) / Unrestricted

Thesis title: Evaluation of postural stability and postural strategy in obese people Objectives: The main objective was to evaluate postural stability using computer posturography in obese people and assess whether three-month exercise training with a focus on sensorimotor stimulation has an effect on postural stability. Methods: This is a cross-sectional experimental study. The research group consisted of 20 probands aged 30 to 62 years with BMI values of 31.1-53.5 kg / m2, from which the general posturography was evaluated. The effect of sensorimotor training was subsequently assessed of 13 probands, who were divided into two groups - interventional (n = 6) and control (n = 7). The measurement was performed using static computer posturography and computer goniometry processed by the freeStep software system. To compare the effect of sensorimotor training, measurements were performed twice in the intervention and control groups, over a period of approximately three months. Postural stability was evaluated based on the Sway test. Statistical analysis was performed using IBM SPSS Statistics 24 software. Statistical significance was determined at the level of α = 0.05, the result where p <0.05 was considered statistically significant. Results: General posturography in the research group showed a...

MiniZinc is a modelling language for constraint satisfaction and optimisation problems. It can be used to solve difficult problems by declaratively modelling them and giving them to a generic solver. A linter, a tool for static analysis, is implemented for MiniZinc to provide analysis for improving models. Suggesting rewrites that will speed up solving, removing unnecessary constructs, and pointing out potential problems are examples of the analysis this tool provides. A method for finding points of interest in abstract syntax trees (parsed models) is designed and implemented. The linter is tested and evaluated against models in the MiniZinc Benchmarks, a collection of models used to benchmark solvers. The result from running the linter on one of the models from the benchmarks is more closely inspected and evaluated. The suggestions were correct and made the model simpler, but, unfortunately, there was no noticeable impact on the solving speed.

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The first detected computer virus commenced in the 1970s. Since then, malware infections have grown exponentially along with rapid increases within the digital environment. Malware detection is a challenging task due to the relentless growth in complexity and volume. That is why the need for automated detection arises. Applying machine learning to malware detection is not a new trend, and researchers have been experimenting with since the 1990s. This thesis aims to evaluate classification algorithms to discover malicious Portable Executables by looking at their static features. Six machine learning models were built and tested based on 20,000 malicious and benign files. Random Forest scored the highest cross-validation score of 99.3% amongst the models with 15 features. Selecting the number of features was based on research of previous studies. This thesis confirms that it is possible to use machine learning for static malware detection. It can also help for future automated malware analysis research. / Det första datorviruset upptäcktes på 1970-talet. Sedan dess, har antalet attacker ökat i och med den skenande digitala utvecklingen. Att finna skadlig kod är en utmanade uppgift då de ökar i komplexitet och volym. Därför finns det ett behov att automatisera spårningen. Att använda maskininlärning för upptäckt av skadlig kod är inte en ny trend och forskare har experimenterat med det sedan år 1990. Syftet med denna avhandling är att utvärdera klassificeringsalgortimer för att upptäckta skadlig kod i Portable Executables genom att använda statiska prediktorer. Sex stycken maskininlärnings modeller skapades och testades baserat på 20.000 skadliga och legitima filer. Random Forest uppnådde det högsta korsvalderingsvärdet på 99.3% av dessa modeller med 15 prediktorer. Att använda 15 prediktorer var inspirerat av forskning av tidigare studier. Denna avhandling bevisar att det är möjligt att använda maskininlärning för statisk spårning av skadlig kod. Det kan också användas för framtida automatiserade forskningsstudier om skadlig kod.

This master´s thesis deals with the acoustic emission of the gearbox housing. It contains a description of the procedure of solving individual numerical approaches and their results. Finally, it compares the influence of design modifications on acoustic emission.

The purpose of this study was to examine the relationship between estimated absolute and relative squat strength and a static jump protocol with potential to provide desirable training adaptation data to practitioners in the field of collegiate strength and conditioning. Forty-one young (20.80 ± 2.44 years), healthy volunteers reported estimated back squat 1RM’s based on the most recent training block and completed a static jump protocol. Males (n=19, est. 1RM 141.29 ± 32.02kg) and female (n=22, est. 1RM 71.56 ± 19.64kg) jump data revealed large to very large correlations between squat strength, mean jump heights of jumps and other calculated variables.

This thesis deals with the verification of global transformation key on densification points around Olomouc by selected GNSS methods. The work will be described in GNSS technology, its distribution, measurement methods and services. As part of this work is a description of networks of permanent reference stations. Next, become familiar with the creation of local transformation key to what is used and what is its significance. The measurement was carried out at points densification, described in a separate section. In this thesis is describes surveying methods and principles, the methods of measurement GNSS, equipment, as well as any specific regarding this issue. The result is a clear set of tables with measured values of GNSS equipment and coordinates ZhB, accuracy of the method used (standard deviations), graphical reporting, and comparing the results of the global and local transformation key.

The master thesis deals with the design of geometry of plates of the injection molding unit using the FEM tool Topological Optimization. The reason for this is to reduce the weight of these components, which is beneficial in the transport and assembly of the injection molding machine. However, the final models of geometry of plates must meet certain requirements in terms of the limit state of deformation, the limit state to the critical value of the equivalent stress. This condition involves both limit state of elasticity and limit state of fatigue. Computational modeling and also Topological Optimization are performed in ANSYS Workbench.