Soil suction is one of the main state parameters that governs unsaturated soil behaviour. Tensiometers are the only type of probe that can measure soil suction directly, but only up to 90 kPa. In the past two decades, a new type of tensiometer with much greater measurement range (up to 2 MPa) has appeared in the literature. The measurement range (i.e. capacity) of a tensiometer is limited by (i) how well it is saturated, and (ii) the air entry value of its porous interface. In this study, the first high capacity tensiometer of Turkey was designed and built. For the purpose of increasing the measurement capacity of the tensiometers, a novel saturation setup that uses a hydraulic pressurization system with capacity of 10 MPa was designed and built. A vacuum-and-pressure saturation procedure was developed. To calibrate the 10 MPa pressure transducers that form the core of the tensiometers, a high-pressure calibration setup capable of pressurizing up to 11 MPa was designed and built. By varying designs of tensiometer bodies, porous interfaces and seals, ways of increasing the suction capacity are investigated. Over a dozen tensiometer design variations are developed, and tried by exposing to atmospheric evaporation. A maximum suction measurement of 870 kPa was achieved with a conventional design / however, none of the new designs were successful. 3 successful designs were also briefly tried on soil samples

The structural behaviour of pavements in cold regions can considerably be affected by seasonal variation in environmental factors such as temperature and moisture content. Along with the destructive effect of heavy traffic loads, climatic and environmental factors can considerably contribute to pavement deterioration. These factors can influence the structural and functional capacity of the pavement structures which, as a result, can trigger and accelerate pavement deterioration mechanisms. Studies on the influence of variation of the environmental factors on the response and behaviour of pavement materials have shown that proper consideration to these factors must be given in realistic pavement design and analysis. In flexible pavement structures, particularly with a thin hot mix asphalt (HMA) layer, unbound materials and subgrade soil largely contribute to the overall structural behaviour of the pavement system. In unbound materials, moisture content and its variation can significantly affect pavement layer stiffness and permanent deformation characteristics. Therefore, the moisture condition of pavements and its influence on the mechanical behaviour of pavement materials has been of interest among the pavement research community. A proper understanding of moisture transformation in pavement systems and its effects on pavement performance are important for mechanistic pavement design. The present summary of this doctoral thesis is based on four main parts. The first part of the thesis covers field measurements and findings from a test section along county road 126 in southern Sweden and consists of two journal papers (paper I and II) tackling different aspects of the research topic. This test section is located in a relatively wet ground condition and consists of a thin flexible pavement structure with a deep drainage system. It is instrumented with subsurface temperature, volumetric moisture content and groundwater probes. The mechanical response of the pavement structure was investigated using Falling Weight Deflectometer (FWD) measurements. The second part of the thesis (paper III and IV) are based on laboratory experiments and investigates different recent approaches that have been proposed to apply principles of unsaturated soil mechanics for incorporating seasonal variation of moisture content into the resilient modulus models using matric suction. The third part of the thesis (paper V) builds a bridge that spans between the laboratory and field investigations with an attempt to evaluate one of the predictive models presented in Paper III. The fourth part of the thesis (paper VI) mainly focuses on the laboratory-based investigation of the permanent deformation characteristic of subgrade soils. In this part, the permanent deformation characteristics of two different silty sand subgrade soils were investigated and modelled using the data obtained from repeated load traxial tests. Paper I mainly focuses on the spring-thaw weakening of the pavement structure. The environmental data collected using different sensors and the FWD tests were used to investigate variations in moisture content with thaw penetration and its influence on the stiffness of unbound layers and the pavement’s overall bearing capacity. Using the backcalculated layer stiffness and corresponding in situ moisture measurements in the unbound layers, a degree of saturation-based moisture-stiffness model was developed for the granular material and the subgrade. In Paper II, the drainage system of the structure was manually clogged during a three month period in summer to raise the groundwater level and increase the moisture content of the layers. Along with the subsurface groundwater level and moisture content monitoring, the structural response of the pavement was studied. In this research work, the FWD tests were conducted at three different load levels. The stress dependent behaviour of the unbound granular layer and the subgrade soil were further studied using the multilevel loads FWD test data. Additionally, parameters of a nonlinear stress-dependent stiffness model were backcalculated and their sensitivity to in situ moisture content was studied. In Paper III and IV, series of suction-controlled repeated load triaxial (RLT) tests were conducted on two silty sand (SM) subgrade materials. Several resilient modulus prediction models that account for seasonal moisture content variation through matric suction were summarized and after optimizing the model parameters, the capability of the prediction models in capturing the material response were evaluated. In Paper V, an attempt was made to evaluate the proficiency of one of the suction-resilient modulus models using the field moisture content and FWD measurements from the Torpsbruk test site. The backcalculated subgrade stiffness dataset at different moisture contents were compared with resilient modulus models obtained from the suction-resilient modulus predictive model. Paper VI presents an evaluation of several permanent deformation models for unbound pavement materials that incorporate the time-hardening concept using a series of multistage repeated load triaxial (RLT) tests conducted on silty sand subgrade materials. The permanent deformation tests were conducted at four different moisture contents with pore suctions measurement throughout the test. The effect of moisture content (matric suction) on the permanent deformation characteristics of the materials and the predictive model parameters were further investigated. / <p>QC 20150324</p>

The aim of the study was to establish the possible causes of poor Grade 12 results in physical science in South Africa and to apply a total quality management (TQM) approach to suggest a solution. The literature study indicates that resources, preparation or subject knowledge, commitment and support affect the quality of performance. The research was done in one school district (cluster). Following the literature study a questionnaire was distributed to 150 science teachers from 31 schools and the response rate was 73% (113 responses). The questionnaire tested the respondents' perception on the availability of resources and the support received by them, the support given to learners and their level of preparation and subject knowledge. From this, as well as from the biographical information from the questionnaire, certain conclusions were made about the reasons for poor performance of learners in science examinations. It could be concluded from the analysis of the results that limited support to teachers and support to learners are important factors contributing to a poor Grade 12 pass rate. The pass rate also correlates positively with experience levels of teachers. Although 39% of teachers are unqualified or under-qualified, no significant correlation could be found between pass rate and level of qualification. Analysis of the effect of commitment on pass rate was inconclusive. / Thesis (M.B.A.)--North-West University, Potchefstroom Campus, 2011.

The aim of the study was to establish the possible causes of poor Grade 12 results in physical science in South Africa and to apply a total quality management (TQM) approach to suggest a solution. The literature study indicates that resources, preparation or subject knowledge, commitment and support affect the quality of performance. The research was done in one school district (cluster). Following the literature study a questionnaire was distributed to 150 science teachers from 31 schools and the response rate was 73% (113 responses). The questionnaire tested the respondents' perception on the availability of resources and the support received by them, the support given to learners and their level of preparation and subject knowledge. From this, as well as from the biographical information from the questionnaire, certain conclusions were made about the reasons for poor performance of learners in science examinations. It could be concluded from the analysis of the results that limited support to teachers and support to learners are important factors contributing to a poor Grade 12 pass rate. The pass rate also correlates positively with experience levels of teachers. Although 39% of teachers are unqualified or under-qualified, no significant correlation could be found between pass rate and level of qualification. Analysis of the effect of commitment on pass rate was inconclusive. / Thesis (M.B.A.)--North-West University, Potchefstroom Campus, 2011.

Les matériaux granulaires sont souvent utilisés dans les chaussées à faible trafic, pour la réalisation des couches d'assise non liées. L'objectif de la thèse est une meilleure compréhension du comportement hydromécanique des matériaux granulaires insaturés sous charge répétée en tenant compte des différents effets couplés: teneur en eau et teneur en fines. Une série d'essais triaxiaux à chargements répétés (TCR) est réalisée avec les différents échantillons de sable de Missillac remodelés à différentes teneurs en eau et en fines pour caractériser les comportements de déformation permanent et résilient. En outre, les courbes de rétention sont obtenues par des essais de succion. Puis, sur la base des résultats expérimentaux, les modèles de déformations permanentes et réversibles existants sont améliorés pour prendre en compte les teneurs en fines et en eau variables. Finalement, le comportement de l'état limite du sable Missillac est estimé avec les effets des teneurs en fines et en eau. / Granular materials are often used in low traffic pavement structures as unbound granular base and sub-base layers. The objective of this context is a better understanding of hydromechanical behaviour (deformation behaviour mainly) of the unsaturated granular materials under repeated loading taking into account the various coupled effects: water content and fine content. A series of RLTTs are conducted with the different remolded Missillac sand samples at different water contents and fine contents to characterize the permanent and resilient deformation behaviour. Besides, the soil water retention curves (SWRCs) are obtained by suction measurement. Then, based on the experimental results, the existing permanent and resilient deformation models are improved to accommodate to the changeable fine content and water content. In the end, the shakedown behaviour of Missillac sand is estimated with the effects of fine content and water content.

La réduction de la consommation de l’eau dans les serres agricoles représente un grand intérêt ne serait-ce que pour accroitre l’efficience d’utilisation de l’eau par les cultures et rendre les professionnelsdu secteur horticole plus compétitifs. La thèse vise à apporter des réponses concernant la gestion optimale de l’eau. Ceci passe par la mise en place d’un modèle capable de prédire les bilans demasse et d’énergie sur l’ensemble du continuum substrat-planteatmosphère en régimes de confort et de restriction hydrique. La plupart des modèles de transfert existants se focalisent soit surle système sol-plante, soit sur le système plante-atmosphère. Ils ont de plus été établis principalement pour les systèmes de grandes cultures, alors que les cultures en pot sous serre possèdent desspécifi cités liées au confi nement tant aérien que racinaire. L’enjeu est de bâtir une approche intégrée du continuum substrat-planteatmosphère pour modéliser le fonctionnement de plantes en pots sousserre. La thèse s’appuie sur une double approche expérimentale et numérique. Une campagne expérimentale a été lancée en 2014 puis en 2015 sous serre et une autre en chambre climatique en 2014,en utilisant l’Impatiens de Nouvelle Guinée comme plante modèle. Il s’agissait d’abord d’élaborer un modèle de la résistance stomatique, élément clef de la transpiration en s’appuyant sur le modèleméthode multiplicatif de Jarvis puis sur la méthode des plans d’expérience en confort et en restriction hydrique. Les données acquises ont permis de caler/valider ces modèles de résistance,qui ont pu êtr / In greenhouses, reducing water consumption is of high interest, not only to increase water effi ciency, but also to maintain competitiveness of the growers. The aim of this thesis is to provideanswers regarding the optimal water management. To reach this goal, predictive models water and energy transfers through the substrate-plant-atmosphere are implemented, considering wellwatered plants and plants under water restriction. Most existing models of water and energy transfers have benne established either on the soil-plants system, or on theplant-atmosphere system. Moreover, such models were mainly developed for open fi eld conditions, although plants grown in pots have specifi cities linked to the aerial and root confi nement.The challenge is therefore to develop an integrated soil-plantatmosphere model for greenhouse plants grown in pot. The thesis was based on a combined experimental and numerical approach.A field survey was conducted in 2014 and then in 2015 inside a greenhouse, and another one in a growth chamber in 2014. The New Guinea Impatiens was used as a plant model. The stomatal resistance was fi rst modeled, as a key factor impacting the transpiration, by using the multiplicative Jarvis model, andthen the design of experiments method for plants under wellwatered and water restriction conditions. The collected data was used to calibrate/validate the aforementioned stomatalresistance models; the obtained models could then be tested to evaluate transpiration with the Penman Monteith model and the direct method. Finally, these models were integrated in

Gas turbine engine efficiency needs to be raised in order to decrease fuel consumption, greenhouse gas emissions, and expenses. Efficiency may be improved in two ways: by reducing engine weight and raising intake temperatures. At intake temperature, conventional nickel-based alloys are already on the verge of failure, meaning there is a need and demand of materials which can withstand higher temperatures. Silicon Carbide Ceramic Matrix Composites (SiC CMCs) are being investigated as a potential replacement for superalloys due to their superior physical properties, such as their low weight and high melting point (approximately one-third of superalloys' weight). However, using SiC CMCs has a serious disadvantage. The mass recession of the SiC is caused by the volatilization of silicon hydroxide, which is caused by oxidation and reactivity with water vapor under the working conditions of gas turbine engines. Therefore, a shielding layer is used to prevent oxidation of the SiC CMCs. This protective coating (EBC) goes by the name of Environmental Barrier Coating. Thermal spray techniques such as atmospheric plasma spray and suspension plasma spray, which employ powder as the feedstock, are used to deposit EBC on SiC CMCs. For EBC to perform well, the coating must be crystalline, reasonably thick to sustain harsh environment, and devoid of cracks. EBC was deposited in order to look at how the spray parameters affected the microstructure. SEM pictures were used to quantify the coating's porosity and the severity of the cracks. To investigate the production of thermally grown oxide (TGO) in the coating and substrate and check how EBCs perform under thermal cyclic fatigue loading, a thermal cyclic fatigue test was conducted. The XRD analysis is performed to ascertain the proportion of crystalline and amorphous phases in the coating, which unfortunately is still in the process to be completed. In the as-sprayed coating samples we can see that when there are more amount and larger pores, we see less number of cracks and vice versa. The effect of spray parameters can be seen on the coatings. Comparing to SPS trial 1, the SPS trial 2 coatings are denser with less number of cracks and has good adhesion. Still the SPS trial 2 coating did not achieve better microstructure in terms of density, and cracks compared to the APS coatings but further looking into the parameters, more desirable coatings can be achieved. After TCF testing, a layer of TGO was seen at the bond coat/topcoat interface, and there was no failure of the coating seen.

Student selection is particularly challenging in South Africa. Heterogeneous educational backgrounds require that it is necessary to assess prospective students' potential rather than their current abilities that crystallised from inadequate school education. Dynamic assessment assesses learning potential versus traditional psychometric measures, which are static measures of cognitive ability, measuring what a person has already learned. The aim was to determine the predictive validity of a selection battery. The following predictors were included in the study; matric results, Potential Index Battery, LPCAT, bridging course status and gender. The results confirmed that static measures of intelligence and matric results showed lower predictive validity than learning potential tests. The learning potential measure appeared to be a more valid predictor of academic performance and is suitable to include in a selection battery. Gender and bridging course factors did not reflect significant differences in academic performance. There were indications that students perform better in successive years of study, once they have adjusted to tertiary education. / Industrial and Organisational Psychology / M. Comm. (Industrial and Organisational Psychology)

Student selection is particularly challenging in South Africa. Heterogeneous educational backgrounds require that it is necessary to assess prospective students' potential rather than their current abilities that crystallised from inadequate school education. Dynamic assessment assesses learning potential versus traditional psychometric measures, which are static measures of cognitive ability, measuring what a person has already learned. The aim was to determine the predictive validity of a selection battery. The following predictors were included in the study; matric results, Potential Index Battery, LPCAT, bridging course status and gender. The results confirmed that static measures of intelligence and matric results showed lower predictive validity than learning potential tests. The learning potential measure appeared to be a more valid predictor of academic performance and is suitable to include in a selection battery. Gender and bridging course factors did not reflect significant differences in academic performance. There were indications that students perform better in successive years of study, once they have adjusted to tertiary education. / Industrial and Organisational Psychology / M. Comm. (Industrial and Organisational Psychology)

In 2009, of the 68,129 learners who wrote Matric, only 34,731 learners passed. In 2010, there was an increase in the provincial pass rate causing much excitement across the board. The reality was that of the 64,090 learners who wrote, only 37,345 learners passed. In 2010, a result below 50% was recorded for Mathematics and Physical Science nationally (DBE; 2011). Despite efforts by the Education Department to support MSTE; establishing Mathematics and Science schools, NGOs and HEIs giving extra Mathematics and Science support to students and teachers, the offering of Saturday classes and incubation camps, we still get minimal return on investment. This thesis analyses these results against the backdrop of language planning theory, particularly language-in-education policies, pre and post-apartheid. The correlation between language medium and academic performance in language (LoLT) and Mathematics of Grade 12 learners is explored. Worldwide the issue of low achievement in Mathematics by ESL students is of great concern (Cuevas, 1984). The 2004 Systemic Evaluation sample of learners was in Grade 6 then; in 2010 they wrote Grade 12. The purpose of the systemic evaluation was to provide an insight into the levels of learner performance in Maths, Natural Science and LoLT in Grade 6 (IPSER, 2006). A major finding of the IPSER was that language was an important factor related to learner achievement. A major disparity was observed in this research, that although the Eastern Cape performed below the national average in the three subjects evaluated, the learners for whom LoLT was the same as their home language obtained scores that were significantly higher than those whose home language was different from the LoLT. The provincial average for Mathematics was 23.40% compared to the national average of 27.80%. For LoLT the province scored 30.16 against the national score of 38.03%. Of interest in this study is a juxtaposition of the Matric results of this same group of learners in 2010 and see whether issues that came up then are still significant in mitigating achievement in Mathematics and Language (LoLT). Some research studies have been conducted in South Africa (Adler, 1998; Setati, 1996-2002; Moloi, 2006) identifying the vital role language plays in learning Mathematics, especially for English L2 learners. Building on research and findings of academics such as the late Alexander, Ramani, Joseph, Hendricks, Heugh, Dalvit, Webb and Murray, this thesis suggests that a mother-tongue-based-bilingual approach to education should be adopted as a matter of urgency