The way our brain works is still an open question, but one thing seems to be clear: biological neural systems are computationally powerful, robust and noisy. Natural nervous system are able to control limbs in different scenarios with high precision. As neural networks in living beings communicate through spikes, modern neuromorphic systems try to mimic them by using spike-based neuron models. This thesis is focused on the advancement of neurorobotics or brain inspired robotic arm controllers based on artificial neural network architectures. The architecture chosen to implement those controllers was the spike neuron version of Reservoir Computing framework, called Liquid State Machines. The main goal is to explore the possibility of using brain inspired neural networks to control a robot by demonstration. Moreover, it aims to achieve systems robust to environmental noise and internal structure destruction presenting a graceful degradation. As the validation, a series of action learning experiments are presented where simulated robotic arms are controlled. The investigation starts with a 2 degrees of freedom arm and moves to the research version of the Rethink Robotics Inc. collaborative humanoid robot Baxter. Moreover, a proof-of- concept experiment is also done using the real Baxter robot. The results show Liquid State Machines, when endowed with an extra external feedback loop, can be also employed to control more complex humanoid robotic arms than a simple planar 2 degrees of freedom one. Additionally, the new parallel architecture presented here was capable to withstand noise and internal destruction better than a simple use of multiple columns also presenting a graceful degradation behaviour.

Les modèles de surface continentale (Land Surface Models, LSM) ont été développés pour calculer les bilans d'eau et d'énergie à la surface des continents dans les modèles de climat, ou modèles de circulation générale. Depuis le simple « bucket » de Manabe (1969), la représentation des processus hydrologiques dans les LSM n'a cessé d'évoluer, si bien que les LSM de dernière génération sont employés comme des modèles hydrologiques à part entière. Le travail effectué au cours de cette thèse vise à évaluer les paramétrisations hydrologiques d'un LSM de ce type, le Catchment LSM (CLSM), qui utilise l'information topographique pour calculer le ruissellement de surface et le flux souterrain, ainsi que la variabilité sous-maille de l'humidité du sol. Pour cela, nous présentons trois applications de CLSM :<br><br>– une application au bassin de la Somme (France) qui a permis d'améliorer la prise en compte des écoulements souterrains,<br>– une application à la moraine du Glacier Zongo (Bolivie) pour analyser la relation entre l'albedo et l'humidité du sol nu,<br>– une application dans le cadre du projet ALMIP (Afrique de l'Ouest) pour l'intercomparaison régionale de LSM.<br><br>La diversité de ces contextes jette un éclairage varié sur les forces et les faiblesses de CLSM, et offre la possibilité de mieux appréhender les interactions complexes qui gouvernent les échanges d'eau et d'énergie à la surface des continents. On montre l'importance de considérer l'intégralité du domaine souterrain, depuis les premiers centimètres du sol jusqu'aux aquifères.

Thesis (M.Sc. (Dietetics))--North-West University, Potchefstroom Campus, 2004.

Interfacial polarization resistances limit the performance of many thin film solid-state devices, especially at low temperatures. To improve performance, a fundamental understanding of the electrode kinetics that govern interfacial reaction rates must be developed. The goal of this work is to determine site-specific reaction mechanisms and the relative significance of various reactions in order to quantify optimum structural parameters within the cathode microstructure. Key parameters include the length of triple phase boundary (TPB), the quantity of exposed electrolyte/electrode surface, and the ratio of electrolyte to electrode material. These parameters, when studied in a specific system, can be incorporated into broader models, which will encompass the specific conductivity of each component to develop an optimized three-dimensional network. The emphasis of this work is the systematic control and manipulation of potential cathodic reaction sites in order to develop an understanding of the relative importance of specific reaction sites. Since the physical dimensions of reaction sites are relatively small, an approach has been developed that utilizes micro-fabrication (similar to that used in integrated-circuit fabrication) to produce small and highly controlled microstructures. Investigations were made into the nature and reactivity of Triple Phase Boundaries (hereafter TPB) through the use of patterned platinum electrodes since only the TPBs are active in these electrodes. After the processing details of micro-fabrication were established for the platinum electrodes, patterned Mixed-Ionic/Electronic Conducting (MIEC) electrodes were fabricated and studied using impedance spectroscopy to determine the contributions from the MIEC surface versus the TPB. Systematically changing the geometry of the MIEC electrodes (thickness and line width) allowed for the determination of the effect of ambipolar transport within the MIEC on the activity of MIEC surfaces versus the TPB. This information is critical to rational design of functionally graded electrodes (with optimal particle size, shape, porosity and conductivity). In addition to experimental studies, representative patterned electrode samples were made available for collaborative studies with surface scientists at other institutions to provide additional techniques (such as Raman Spectroscopy) on the carefully designed and controlled cathode surfaces.

A program of study has been established for the quantitative study of electrode reactions in solid oxide fuel cells. The initial focus of the program is the mixed conducting cathode material strontium-doped lanthanum manganate (LSM). A formalism was established treating reactions taking place at the gas-exposed surface of mixed conducting electrodes. This formalism was incorporated into a phenomenological model for oxygen reduction in LSM, which treats the phenomenon of sheet resistance. Patterned electrodes were designed that reduce the dimensionality of the appropriate model, and these electrodes were successfully fabricated using DC sputtering and photolithography. A new model for the bulk defect equilibrium in LSM was proposed and shown to be a better fit to nonstoichiometry data at low temperatures. The fitting was carried out with a particle swarm optimizer and a rigorous method for identification. It was shown that a model for the interface structure between LSM and yttria-stabilized zirconia (YSZ) that assumes free oxygen vacancies in YSZ does not accord with experimental observations. Cluster variation method (CVM) was adapted for analysis of the problem, and a new analytical method combining CVM and electrical contributions to the free energy was proposed.

Extreme hydrological events associated with global warming are likely to produce an increasing number of flooding scenarios resulting in significant bridge inundation and associated damages. During large floods, the presence of a bridge in an open channel triggers a highly turbulent flow field including 3D complex coherent structures around bridge structures. These turbulence structures are highly energetic and possess high sediment entrainment capacity which increases scouring around the bridge foundation and consequently lead to structural stability problems or even failure of the structure. Hence, understanding the complex turbulent flow field for these extreme flow conditions is crucial to estimate the failure risks for existing bridges and better design of future bridges. This research employs the method Large Eddy Simulation (LES) to predict accurately the 3D turbulent flow around bridge structures. The LES code is refined with a novel free surface algorithm based on the Level Set Method (LSM) to determine the complex water surface profiles. The code is used to analyze the hydrodynamics of compound channel flow with deep and shallow overbanks, free flow around a bridge abutment, pressure flow with a partially submerged bridge deck and bridge overtopping flow. All simulations are validated with data from complementary physical model tests under analogous geometrical and flow conditions. Primary velocity, bed shear stress, turbulence characteristics and 3D coherent flow structures are examined thoroughly for each of the flow cases to explain the hydrodynamics of these complex turbulent flows.

Vegetables and fruit appear to confer protection against various diseases, but most adults in South Africa eat substantially less than the recommended amounts. Many barriers and factors that influence vegetable consumption have been identified in the literature. One major barrier is the perishability of vegetables. Frozen vegetables can be a useful way in encouraging greater intakes. Some consumers are, however, of the opinion that processing destroy nutrients to a large extent. There is, therefore, a lack of understanding of the freezing process. Research on the attitudes of consumers towards frozen vegetables in South Africa is limited. Objective: The purpose of this study was to determine the attitudes of consumers regarding the link between frozen and fresh vegetables and health and the attributes of frozen vegetables. Subjects/Setting: One thousand nine hundred and ninety seven South African respondents, representative of the four major race groups of South Africa (whites, blacks, coloureds and Indians) were randomly chosen from metropolitan areas from the nine provinces in South Africa. Questionnaires, existing of 17 food-related sections, including subsections on vegetables and health, were designed by researchers in co-operation with business partners. MARKINOR, a market research company, was contracted to collect the data. Respondents were questioned regarding their attitudes towards the link between frozen and fresh vegetables and health. Statistical analysis performed: The quantitative data produced by the survey was analysed by using the StatisticaⓇ-programme in order to generate the relevant tabulations, descriptive statistics and statistical tests. Results: Overall, the attitudes of consumers towards frozen vegetables were found to be negative. Practical and statistically significant attitude differences towards frozen vegetables were found between most variables. Results from this study revealed that different levels of education, age and gender do not have a big influence on consumer's attitudes towards frozen vegetables. However, practical and statistically significant differences were found between the various LSM (Living Standards Measure) groups, especially with regard to the convenience of frozen vegetables. Results also indicated that Indians, the age group 61+ and males were the most negative towards frozen vegetables. Almost 75% of all consumers indicated that they never eat frozen vegetables. Only 1% of consumers in the LSM group 2 own a fridge/freezer. An alarmingly 26% of all consumers indicated that they are not convinced that vegetables are healthy. Application/Conclusions: Nutrition professionals should use these findings to target messages in health-promotion programmes to increase the overall consumption of vegetables. The use of frozen vegetables by consumers with frozen storage facilities should be promoted aggressively. Consumers also need practical advice on how to overcome the barriers to dietary change. Nutrition counseling efforts should also be aimed specifically at increasing frozen vegetable consumption among targeted subgroups, particularly Indians, males and the age group 61+. It is strongly recommended that suitable measuring instruments be developed for assessing the knowledge and attitude of South Africans towards vegetable and fruit consumption and the ability of individuals to improve their health. The results of this study may prove to be very useful in this regard. / Thesis (M.Sc. (Dietetics))--North-West University, Potchefstroom Campus, 2004.

Vegetables and fruit appear to confer protection against various diseases, but most adults in South Africa eat substantially less than the recommended amounts. Many barriers and factors that influence vegetable consumption have been identified in the literature. One major barrier is the perishability of vegetables. Frozen vegetables can be a useful way in encouraging greater intakes. Some consumers are, however, of the opinion that processing destroy nutrients to a large extent. There is, therefore, a lack of understanding of the freezing process. Research on the attitudes of consumers towards frozen vegetables in South Africa is limited. Objective: The purpose of this study was to determine the attitudes of consumers regarding the link between frozen and fresh vegetables and health and the attributes of frozen vegetables. Subjects/Setting: One thousand nine hundred and ninety seven South African respondents, representative of the four major race groups of South Africa (whites, blacks, coloureds and Indians) were randomly chosen from metropolitan areas from the nine provinces in South Africa. Questionnaires, existing of 17 food-related sections, including subsections on vegetables and health, were designed by researchers in co-operation with business partners. MARKINOR, a market research company, was contracted to collect the data. Respondents were questioned regarding their attitudes towards the link between frozen and fresh vegetables and health. Statistical analysis performed: The quantitative data produced by the survey was analysed by using the StatisticaⓇ-programme in order to generate the relevant tabulations, descriptive statistics and statistical tests. Results: Overall, the attitudes of consumers towards frozen vegetables were found to be negative. Practical and statistically significant attitude differences towards frozen vegetables were found between most variables. Results from this study revealed that different levels of education, age and gender do not have a big influence on consumer's attitudes towards frozen vegetables. However, practical and statistically significant differences were found between the various LSM (Living Standards Measure) groups, especially with regard to the convenience of frozen vegetables. Results also indicated that Indians, the age group 61+ and males were the most negative towards frozen vegetables. Almost 75% of all consumers indicated that they never eat frozen vegetables. Only 1% of consumers in the LSM group 2 own a fridge/freezer. An alarmingly 26% of all consumers indicated that they are not convinced that vegetables are healthy. Application/Conclusions: Nutrition professionals should use these findings to target messages in health-promotion programmes to increase the overall consumption of vegetables. The use of frozen vegetables by consumers with frozen storage facilities should be promoted aggressively. Consumers also need practical advice on how to overcome the barriers to dietary change. Nutrition counseling efforts should also be aimed specifically at increasing frozen vegetable consumption among targeted subgroups, particularly Indians, males and the age group 61+. It is strongly recommended that suitable measuring instruments be developed for assessing the knowledge and attitude of South Africans towards vegetable and fruit consumption and the ability of individuals to improve their health. The results of this study may prove to be very useful in this regard. / Thesis (M.Sc. (Dietetics))--North-West University, Potchefstroom Campus, 2004.

Astrozyten erfüllen unverzichtbare Aufgaben im ZNS. Sie sorgen im Normalfall unter anderem für eine ausgewogene K+/H2O-Clearence, regulieren den Gefäßdurchmesser, bilden die Blut-/Hirnschranke, betreiben “Transmitter-Recycling” und modulieren die interneuronale Signalweitergabe durch prä- und postsynaptische Mechanismen. Die Funktionen und Einflüsse dieser zentralnervösen Gliazellen unter pathologischen Bedingungen im ZNS sind bei weitem nicht so gut untersucht, aber ebenso vielfältig. Eine ganz entscheidende Frage stellt sowohl unter physiologischen wie auch pathologischen Bedingungen das Vorliegen eines Überlappungsfaktors des von benachbarten Astrozyten okkupierten Areals dar. Betrüge ein solcher Faktor ! 1, könnten mehrere Gliazellen das gleiche Areal auch unter pathologischen Bedingungen durch ihre vielfältigen Funktionen unterstützen. Dahingegen würde das Ausbleiben eines Überlappungsgrades ! 1 bedeuten, dass bestimmte Gebiete im Neuropil anfälliger gegen Noxen oder degenerative Veränderungen wären. Um diesen Überlappungsgrad zu untersuchen, wurden Hirnschnitte von Labormäusen mittels einer geeigneten Methodenkombination untersucht. Dabei wurde das durchschnittliche Volumen der Astrozyten im motorischen Kortex durch Golgi- Färbung, sowie deren Zellzahl pro Volumeneinheit durch immunhistochemische Färbungen untersucht und mittels konfokaler Laserscanning-Mikroskopie dokumentiert. Aus diesen Parametern ließ sich ferner der durchschnittliche Überlappungsfaktor im beschriebenen Areal berechnen. Im Interesse dieser Arbeit standen dabei neben dem Unterschied im Überlappungsfaktor der Astrozyten zwischen Wildtyp- und GFAP-/- VIM-/- Knockout- Mäusen, als Beispiel für ein genetisch bedingtes Fehlen dieser Intermediärfilamente, auch der Einfluss des fortschreitenden Lebensalters, so dass für beide Genotypen sowohl junge- als auch alte Tiere untersucht wurden. Folgende Ergebnisse lassen sich zusammenfassen: 1. Das Vorhandensein der Intermediärfilamente GFAP und Vimentin scheint keinen Einfluss auf das Volumen der Astrozyten im motorischen Kortex zu haben. 2. Das Lebensalter der V ersuchstiere steht mit dem V olumen der Astrozyten signifikant in Zusammenhang. Das von Astrozytenfortsätzen der knapp zwei Jahre alten Tiere okkupierte Volumen betrug mit durchschnittlich ca. 61.000 !m3 gut das Doppelte des Volumens in jungen Mäusen (ca. 28.000 !m3). 3. Die Zellzahl der Astrozyten im motorischen Kortex wird offenbar weder vom Lebensalter, noch vom Vorhandensein der Intermediärfilamente GFAP und Vimentin signifikant beeinflusst. 4. Der Überlappungsfaktor der Astrozyten im motorischen Kortex lag bei den jungen Kontroll-Tieren bei 0,87 und bei den jungen DKO-Tieren bei 0,96. 5. Der Überlappungsfaktor der Astrozyten im motorischen Kortex lag bei den alten Kontroll-Tieren bei 2,22 und bei den alten DKO-Tieren bei 2,10. Die Ergebnisse zeigen, dass das Fehlen der Intermediärfilamente GFAP und Vimentin keinen Einfluss auf den Überlappungsgrad der Astrozyten im motorischen Kortex hat. Die Ursache für phänotypisch manifeste Erkrankungen, wie z.B. der Alexander Krankheit, welche durch ein fehlerhaft exprimiertes GFAP in Astrozyten hervorgerufen wird, ist demnach in anderen Mechanismen zu suchen. Großen Einfluss auf den Überlappungsfaktor der Astrozyten hatte dagegen das Lebensalter der Versuchstiere, was sich mit neueren Erkenntnissen zur Funktion der Astrozyten im Hinblick auf Lernvorgänge, aber auch auf degenerative Prozesse, in Zusammenhang bringen lässt.

Solid oxide fuel cell (SOFC) research is currently underway to improve performance, cost and durability by lowering the operating temperature to ~600°C. One approach is to design fabrication processes capable of tailoring desirable cathode microstructures to enhance mass and charge transfer properties through the porous medium. The aim of this study is to develop a cost effective fabrication technique for deposition of novel microstructures, specifically, functionally graded thin films of LSM oxide with porosity graded structure for use as IT- SOFCs cathode. Spray pyrolysis method was chosen as a low-temperature processing technique for deposition of porous LSM films onto dense YSZ substrates. The effort was directed toward the optimization of the processing conditions for deposition of high quality LSM films with variety of morphologies in the range of dense to porous microstructures. Results of optimization studies on spray parameters revealed that the substrate surface temperature is the most critical parameter influencing the roughness and morphology, porosity, cracking and crystallinity of the film. Physical and chemical properties of deposited thin films such as porosity, morphology, phase crystallinity and compositional homogeneity have shown to be extensively dependent on the deposition temperature as well as solution flow rate and the type of precursor solution among other parameters. The LSM film prepared from organo-metallic precursor and organic solvent showed a homogeneous crack-free microstructure before and after heat treatment as opposed to aqueous solution. Also, increasing the deposition temperature and the solution flow rate, in the specific range of 520-580 ℃ and 0.73-1.58 ml/min, respectively, leads to change the microstructure from a dense to a highly porous film. Taking the advantage of simplicity of spray pyrolysis technique combined with using metal-organic compounds, the conventional ultrasonic spray system was modified to a novel system whereby highly crystalline multi-layered porosity graded LSM cathode with columnar morphology and good electrical conductivity in the range of 500-700 °C was fabricated through a multi-step spray and via applying optimum combination of spray parameters. This achievement for the current graded LSM cathode would allow its use in IT-SOFCs.