L'interaction des individus avec l'environnement statique ou dynamique nécessite une exploration détaillée et précise des objets. Pour cela, notre système oculomoteur produit des mouvements oculaires rapides et précis appelés « saccades » afin de ramener l’image des objets d’intérêt sur la petite zone centrale de notre rétine (fovéa). Toutefois, notre système oculomoteur est fréquemment exposé à des perturbations physiologiques ou pathologiques. Ces changements sont contrôlés en permanence par des processus sensori moteurs basés sur la plasticité neuronale et appelés adaptation saccadique. L’objectif de mes travaux de thèse est de mieux comprendre les caractéristiques de cette adaptation et sa rétention à long terme mais aussi les réseaux impliqués dans l’adaptation saccadique. Comme les saccades oculaires ont un lien étroit avec l’attention visuo-spatiale, notre intérêt s’est également porté sur les interactions qui peuvent exister avec les réseaux impliqués dans le contrôle de l’attention visuo-spatiale. Un des principaux résultats est que l’orientation de l’attention exogène covert -sans bouger les yeuxdans des taches de détection et de discrimination est améliorée après l’adaptation des saccades réactives. Ces données fondamentales pourraient mener au développement de nouvelles méthodes de rééducation des déficits visuo-attentionnels / The interaction of human beings with their static or dynamic environment requires detailed and precise exploration of objects. For this, our oculomotor system produces fast and accurate eye movements called "saccades" to bring the image of objects of interest on the small central area of the retina (fovea). However, our oculomotor system is frequently exposed to physiological or pathological disturbances. These changes are continuously monitored by sensorimotor processes based on neuronal plasticity and called "saccadic adaptation". The aim of my thesis is to better understand the characteristics of this adaptation and its long-term retention but also the neural networks involved in saccadic adaptation. As saccadic eye movements are closely related to visuo-spatial attention our work has also addressed the interactions that may exist with the networks involved in the control of visuo-spatial attention. A major result revealed that the orientation of the 'covert' exogenous attention -without moving the eyes- in detection and discrimination tasks is improved after adaptation of reactive saccades. These basic data could give rise to the development of new rehabilitation methods in visual-attention deficits

Cette thèse de doctorat a pour objectif principal d'étudier certaines propriétés probabilistes et statistiques de modèles de volatilité contenant des variables explicatives exogènes. Elle comporte deux parties.Dans une première partie, nous étudions le comportement asymptotique de l'estimation du quasi-maximum de vraisemblance (QMV) pour la classe polyvalente des modèles PGARCH semi-forts augmentés avec des covariables. Les hypothèses principales sur les variables exogènes sont la stationnarité et la non-colinéarité avec les autres variables explicatives de la volatilité. Pour la distribution asymptotique du QMV, nous étudions quatre situations différentes correspondant à des modèles forts ou semi-forts, et des paramètres à l'intérieur ou au bord de l'espace des paramètres. Nous montrons la normalité asymptotique du QMV sans imposer aucune condition de moment sur le processus observé lorsque le paramètre GARCH-X appartient à l'intérieur de l'espace des paramètres. Par contre, quand un ou plusieurs coefficients sont égaux à zéro, les conditions de moment d'ordre 4 sont requises pour que la matrice d'information soit finie et la loi asymptotique est alors la projection d'une loi normale sur un cône convexe . Comme la vraie valeur du paramètre n'est pas contrainte à appartenir à l'intérieur de l'espace des paramètres, nous proposons des tests pour déterminer l'ordre du modèle et vérifier la signification des variables exogènes. La deuxième partie est consacrée à l'étude de l'influence des variables exogènes sur les matrices de covariance conditionnelle de rendements d'actifs. Plus précisément, nous considérons des modèles BEKK avec variables exogènes. Les paramètres sont estimés par deux méthodes qui s'appellent l'estimation par ciblage de la variance et l'estimation équation par équation. Ces deux méthodes nous permettent de réduire la complexité numérique liée à l'estimation d'un nombre élevé des paramètre des modèles GARCH multivariés, en particulier, en présence de variables exogènes. La consistance ainsi que la loi limite de ces estimateurs sont établies pour des hypothèses relativement peu restrictives. En particulier, les innovations sont supposées être une différence de martingales au lieu d'être iid. Nos résultats sont illustrés par des expériences de Monte Carlo et des applications sur séries réelles. / This PhD Dissertation is dedicated to the study of probabilistic and statistical properties of volatility models augmented with exogenous variables. It consists of two parts which are summarized below. In the first part of this work, we study asymptotic behavior of the QMLE for the versatile class of the semi-strong PGARCH models augmented with exogenous variables. The main assumptions on the exogenous variables are the stationarity and the non-colinearity with the other explanatory variables of the volatility. For the asymptotic distribution of the QMLE, we investigated four different situations corresponding to strong or semi-strong models, and to parameters inside or at the boundary of the parameter space. When the GARCH-X parameter belongs to the interior of the parameter space, the asymptotic distribution of the QMLE is normal, whereas it is the projection of a normal distribution on a convex cone when one or several coefficients are equal to zero. For models with positive GARCH coefficients, the asymptotic distribution is obtained under very mild conditions, in particular, without any moment condition on the observed process. When the GARCH parameter stands at the boundary, fourth-order moment conditions are required for the information matrix to be finite. Our asymptotic results are obtained under conditions that are only marginally stronger than these optimal moment conditions, which extends and improves the results that existed for GARCH models without covariables. The second part is devoted to studying the influence of exogenous variables on the conditional covariance matrix of asset returns. Specifically, we consider BEKK models augmented with exogenous variables. The parameters are estimated by two methods which are called the variance targeting estimation and equation by equation estimation. Both methods allow us to reduce the curse of dimensionality which appears when modeling a conditional covariance matrix, particularly in the presence of exogenous variables. The consistency and the asymptotic distribution of these estimators are established under mild assumptions. In particular, the innovation is assumed to be a martingale difference instead of iid. Our results are illustrated by Monte Carlo experiences and the applications on real series.

[pt] O objetivo deste trabalho é inserir variáveis exógenas no modelo Holt-Winters com múltiplos ciclos, genuinamente univariado. Serão usados dados horários de demanda de energia elétrica provenientes de uma cidade da região sudeste do Brasil e dados de temperatura, tanto em sua forma primitiva quanto derivada, por exemplo, indicadores de dias quentes, o chamado cooling degree days (CDD). Com isso, pretende-se melhorar o poder preditivo do modelo, gerando previsões com maior acurácia. / [en] The aim of this thesis is to insert exogenous variables in the model Holt-Winters with multiple cycles, genuinely univariate. Hourly data will be used for electricity demand from a city in southeastern Brazil and temperature data, both in its original form as derived, for example, indicators of hot days, cooling degree days called (CDD). With this, we intend to improve the predictive power of the model, generating predictions with greater accuracy.

MSCAGR (Animal Science) / Department of Animal Science / The study evaluated the nutritive value of orange pulp- buffalo grass (OPBG) silage as a po-tential pig feed. In experiment 1, OPBG was ensiled in 58 one-litre jars, split into Reno-zyme® enzymes (containing α-amylases and β-endo 1, 3; 1, 4 beta glucanase) (denoted OPBGE) and 18 without enzyme (denoted OPBG). Samples were collected from the lab on days 7, 15 and 30 in a three by two factorial design (period by treatment). In Experiment 2, 12 South African Windsnyer-type (SAWIP) (27.2±3.9 kg) and 12 Large White- Landrace crosses (LW x LR) (28±9.8 kg) were fed diets containing different levels of bulk-ensiled OPBG ad libitum for 30 days, in a 2 X 3 (breed by level of OPBG (control, low (15% OPBG) and high (30% OPBG))) factorial arrangement. The apparent total tract digestibility (ATTD) of the pigs was measured during week 3 of feeding. The average body gain ABG average daily feed intake (ADFI), average daily gain (ADG), average gain to feed ratio (AG: F) were measured weekly. Serum glucose (GLU) , blood urea nitrogen (BUN), creatinine (CREAT), cholesterol, (CHOL) and triglycerides (TG) were measured during week 4 of the experiment. The levels of CP, EE, NDF, water soluble carbohydrates (WSC), lactic acid (LA) and pH were different (P<0.05) for OPBGE and OPBG on day 7. However the OPBGE concentra-tions of DM, ASH, CP, NDF, HEMI, WSC, LA and pH were higher (P<0.05) compared to OPBG. The OPBGE was lower (P<0.05) on EE and ADF, compared to OPBG on day 7. The levels of DM, ASH, CP, NDF, ADF, HEMI, LA and WSC were different (P<0.05) for OPBGE and OPBG on day 30. However the OPBGE levels of DM, CP, NDF, ADF, LA and WSC were higher (P<0.05) compared to OPBG. ASH, EE and HEMI were lower (P<0.05) on day 30. There were significant diets x day interactions (P<0.05) for DM, ASH, CP, EE, NDF, ADF, HEMI, WSC, and LA, but not for pH. The aerobic stability study was inconclusive. The digestibility levels of OM and NDF were different (P<0.05) for LW x LR and SAWIP, where LW x LR ATTD on OM and NDF was higher (P<0.05) compared to SAWIP for all diets. The LW x LR ADG was higher (P<0.05) compared to SAWIP for all diets. There was a diet x breed interaction effect (P <0.05) on ADG whereby the BUN and CREAT were different (P <0.05) for LW x LR and SAWIP. The SAWIP BUN was higher (P<0.05), but the CREAT and TG were lower (P<0.05) compared to LW x LR for all diets fed. In conclusion, OPBG inclu-sion in pig feed enhanced the quality of feed, digestibility, performance and blood metabo-lites profile. / NRF

Magister Commercii - MCom / Diversification is one of the more familiar concepts in finance because of its ability to curtail risk towards investors. However, for diversification to be efficient, the assets combined should have inversely related price movements. In the same light, previous research done on international portfolio diversification has consistently found that having investments diversified across different global markets that have low to medium correlations helps to get as close to an optimal portfolio as possible. However, previous research also indicates that both global financial integration and exogenous shocks increase correlations among international markets, hence negating the benefits of international portfolio diversification to an extent. Therefore, with global integration on the rise, coupled with economic and political instability in some BRICS nations, the research examines these factors and gauges the current viability of international portfolio diversification from the perspective of a South African investor.

Infant visual attention develops rapidly over the first year of life, significantly altering the way infants respond to peripheral visual events. Here we present data from 5-, 7- and 10-month-old infants using the Infant Orienting With Attention (IOWA) task, designed to capture developmental changes in visual spatial attention and saccade planning. Results indicate rapid development of spatial attention and visual response competition between 5 and 10 months. We use a dynamic neural field (DNF) model to link behavioral findings to neural population activity, providing a possible mechanistic explanation for observed developmental changes. Together, the behavioral and model simulation results provide new insights into the specific mechanisms that underlie spatial cueing effects, visual competition, and visual interference in infancy.

No description available.

This master thesis report is focused on the development and study of a tendon driven soft actuator for use on the Honda Haru robot. The single degree of freedom actuator will be used to actuate the eyes of the robot. Motivating development of this new actuator is the operational safety of the robot. A soft continuum actuator can provide a higher level of inherent safety as compared with the currently used rigid actuator. After development, a factorial study of the developed actuator was performed in order to understand the effect of velocity, load and material hardness on the actuator motion. The results of this study show that the linearity, hysteresis and current draw of the actuator are all affected by varying material and velocity. No significant effect of actuator load was measured. Data-driven system identification of the actuator was later performed using polynomial models. A relative comparison of standard-, nonlinear- and adaptive ARX models showed that adaptive ARX is most suitable to capture the dynamics of the developed actuator under dynamic conditions. / Denna examesarbetesrapport täcker utveckling samt studie av ett 3d-utskrivet mjukt ställdon. Det vajerdrivna ställdonet är designat för att driva ögonrörelser på den sociala roboten HARU och utvecklingen motiverades av den ökade säkerhet som en mjuk och eftergivlig komponent kan ge robotens användare jämfört med den nuvarande stela mekanismen. Den utvecklade komponenten undersöktes sedan i två faser. Först utfördes en faktorstudie där rörelsehastighets, lastvikts samt materialhårdhets påverkan på ställdonets kinematik undersöktes. Resultaten från denna studie visar att linjäritet, hysteres samt strömförbrukning av det utvecklade ställdonet påverkas av rörelsehastighet samt materialets hårdhet. Ingen signifikant påverkan av lastvikt uppmättes. Utöver faktorstudien undersöktes även förmågan av olika polynomialmodeller att modellera ställdonet med god nogrannhet. Linjära, ickelinjära samt rekursiva linjära modeller utvecklades via systemidentifiering och deras prestanda jämfördes. Resultaten från detta visar att rekursiva linjära modeller är bäst lämpade för att modellera det utvecklade ställdonet under dynamiska förhållanden.

This dissertation is divided into six chapters, as foHows: Chapter 1 of this dissertation discusses the growing significance of FDI for developing countries. It compares FDT in developed and developing countries and analyses recent evidence ofFDI flows to developing countries. Chapter 2 analyses the (endogenous and exogenous) detenninants ofFDI flows into developing countries. Chapter 3 discusses the importance of FDI flows, which are essential for new investments or for financing fortuitous deficits in host countries, and looks at the adjustment mechanisms for the equilibrium of the balance of payments. Chapter 4 gives attention to FDI flows, the liberalisation of financial markets and the financial account of the balance of payments in developing countries in providing more opportunities and mechanisms for development and economic growth. Finally, chapter S examines and compares FDI flows tu South Africa and Angola - the biggest FDI recipients on the African continent. / Economics / MCom (Economics)

Enhanced biological phosphorus removal (EBPR) was researched from the performance of a modified University of Cape Town (UCT), anaerobic-anoxic/nitrifying-aerobic process. The work focussed on high P influent where milk was compared to carbohydrates as exogenous added carbon and typical settled sewage. The results confirmed that at equal COD load in the influent (minimum COD:P (250:5) ratio for EBPR), milk always provided sufficient soluble substrate than the carbohydrate mix, but also improved the EBPR performance. The laboratory scale treated 10L/day where 2 parallel treatment trains for milk and an equivalent carbohydrate mix as supplement to compare and study the P sequestration from hypothesised P ligands in milk and easily assimilable carbon (AOM) after fermentation for biological P uptake. The aerobic bioreactors used submerged flat sheet membranes (AeMBR) to improve the effluent quality and reduce the suspended solid residues. The results suggested extra benefits from adding calcium chloride (CaCl2) (200 ml at 250 mM/day or 200 mg/L treated) to form P complexes both in the anaerobic and aerobic zones (100 ml CaCl2 250mM/zone/day). To complete P removal a calcium phosphate (CaPO4) further treatment stage (post membrane final effluent (F.E.)) was added for nucleation. The combination of, A2O-N, exogenous carbon and calcium addition improved the performance of the EBPR, and enabled the laboratory units to achieve less than the 1 mg/L P required by the EU Directive. The process was tested at higher than normal P loads (maximum 100 mg/L) (domestic wastewater influent 15 mg/L). Experiments with influent P load ≤ 50mg/L, with 1% milk as AOM were compared to the carbohydrate mix and could remove soluble P to less than 1mg/L above 97% and less than 2 mg/L more than 99% of the in the time respectively. With an influent P load of 60mg/L (maximum 100 mg/L), the soluble P in the F.E. with milk was below 5 mg/L and below 8 mg/L with carbohydrates mix. The results showed that most of the phosphorus was retained by the sludge during the anoxic-aerobic phases. The remaining phosphate in the F.E. was able to pass through AeMBR pore size (0.4 μm) and needed to be chelated by the nucleation process. The results indicated this A2O-N modifications achieved stable nutrient removal and also offered the potential for more sustainable phosphorus recovery. The EBPR without AOM was 25% less efficient compared to milk and never achieved the E.U standard of 1mg/L in final effluent. The flat sheet membrane always achieved a NTU final effluent below 1 and the TOC always greater than 90% removal or less than the EU 125 standard regardless of the feeding COD/P ratio.