Master of Science / Department of Grain Science and Industry / Yong-Cheng Shi / Sorghum flour is a gluten-free ingredient and can be used to prepare foods for celiac patients. In addition, sorghum flour is a good source of fiber in the form of resistant starch. The objectives of this research were to develop an effective process to increase resistant starch content of sorghum flour and investigate the effects of sorghum protein matrix on starch digestibility. Samples of white sorghum flour (28.9% amylose content) with different moisture contents (0%, 12.5%, 20%, and 30%) were treated at different temperatures (100, 120, and 140 [degrees]C) for different times (1, 2, and 4 h). Samples after heat treatments were tested for starch digestibility, protein digestibility, differential scanning calorimetry (DSC), size-exclusion chromatography (SEC), and X-ray diffraction. The sample treated with 20% moisture at 100[degrees]C for 4 h had high resistant starch (RS) content (22.1% compared with 5.6% of the native sample) and low protein digestibility (8.4% compared with 68.3% of the native sample). The same heat-moisture treatment on isolated sorghum starch showed no significant change in RS content. DSC showed a very low degree of gelatinization for samples treated at moisture contents 20% and below. X-ray diffraction also suggested minimal change in starch crystallinity after heat treatment at low moisture contents (20% and below). Sorghum protein solubility after heat treatment was reduced, suggesting that protein structure was altered during the heat treatments. In conclusion, heat-moisture treatments were successful in increasing resistant starch content of sorghum flour by altering sorghum protein without gelatinizing the starch to retain starch functionality in food product applications. Sorghum flour with increased resistant starch content after heat treatment was evaluated and compared with normal sorghum flour for starch digestibility using the Integrated Total Dietary Fiber method, and for food applications in tortillas.

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Sobre opiso desenvolvem-se todas as atividades a que se destina a edificação. Falhas Em sua execução, tais como, empenamentos, placas soltas, bolhas e manchas têm como conseqüências, desde o desconforto pessoal de andar em uma superfícieirregular, ao risco de acidentes de trabalho, contaminação de produtos por poeira, de salinhamento de equipamentos ou até mesmo a interferência no processo de produção, podendo provocar a paralisação parcial ou total da atividade produtiva da empresa.Tais problemas, muitas vezes são decorrentes do excesso de umidade do substrato de concreto, quando da aplicação do revestimento, por não ter tido o tempo de secagem adequado, de maneira a atingir o nível de umidade ideal. O excesso de água residual decorrente da umidade do substrato é uma das principais causas geradoras de patologias nos pisos de concreto quando utilizados revestimentos suscetíveis à presença de água. O comportamento da umidade do concreto é resultado de uma complexa ação entre a quantidade de água física e quimicamente ligada, durante a hidratação do cimento e a capacidade de transporte de água do sistema de poros do concreto. Neste contexto, o presente trabalho procura contribuir na sistematização do conhecimento sobre o assunto, descrevendo, inicialmente, o comportamento de bases de concreto frente à ação da água e os fatores que a influenciam: grau de hidratação, condições de equilíbrio e fluxo de umidade. É mostrado como ocorre a secagem do concreto e a influencia do tempo de cura, relação água/cimento do concreto e condições ambientes sobre o tempo necessário para que a umidade do concreto atinja o nível ideal para o início do revestimento do piso. São descritos os testes utilizados para a medição do nível de umidade do concreto, enfatizando os de caráter quantitativo, baseados na medição do teor de umidade, taxa de emissão de vapor de água e umidade relativa interna do concreto. Valores dos níveis ideais de umidade, em conformidade com o tipo de teste aplicado e materiais empregados, estabelecidos por entidades representativas de fabricantes de revestimentos para pisos de concreto, são apresentados como referências. O texto é finalizado com a apresentação das recomendações que visam facilitar a secagem do concreto e aspectos a serem observados quando da realização da medição do nível de umidade. / On the floor are developed all the activities the building is destined to. Faults in its execution, such as warping, loose plates, bubbles and stains, bring about from the personal discomfort of walking on an irregular surface, to the risk of workplace accidents, contamination of product due to dust, misalignment of equipment or even the interference in the production process, which may cause a partial or total stalling of the company productive activity. Such problems often derive from excess moisture in the concrete substrate, when the lining is applied, for not having been dried long enough, so as to attain the ideal moisture level. The excess residual water deriving from substrate moisture is one of the main causes generating pathologies on concrete floors when linings susceptible to the presence of water are used. The moisture behavior of concrete derives from a complex action between the amount of physical and chemically related water, during the hydration of the cement and the water transport capacity of the concrete pore system. In thisn context, the present work aims to contribute in systematizing the knowledge on the matter, initially describing the behavior of the concrete bases concerning the action of water and the factors influencing this: degree of hydration, balance conditions and humidity. The work shows how the drying of concrete occurs and the influence of the curing time flux, concrete water/cement ratio and ambient conditions on the time required for the concrete moisture to attain the ideal level to start the floor lining. The tests used to measure the concrete moisture level are described, emphasizing those of quantitative character, based on the measurement of the moisture content, water vapor emission rate and the concrete relative internal humidity. Values of the ideal levels of moisture, in accordance with the type of test applied and materials employed, established by representative manufacturer entities for concrete floors linings, are presented as references. The text concludes with the presentation of recommendations that aim to make the drying of concrete easier and aspects to be observed when the measurement of the moisture level is performed.

In all harvesting operations, minimized risks for soil damage combined with short forwarding mileage are desirable in order to achive cost efficient work. This study examined how forwarding mileage are influenced by the time of the year a harvesting operation is conducted. Two scenarios that corresponded to the terrain water conditions during wet and drier periods of the year were created. Twenty harvesting sites were simulated with these scenarios. The results showed that the forwarder’s mileage was reduced in the dry conditions, and that even the forwarder’s mileage over wet areas was reduced under these conditions. This means that there is a potential for productivity increase as well as to reduce the risk of soil damage in wet areas.

Though heating, insulation, wall claddings and cavity-wall construction are considered as measures for remediating moisture and condensation in buildings, ventilation of wall cavities has however become a mantra among architects and other building professionals. Holes of any size and shape are made and located on building facades based on the accepted wisdom that a little air movement will keep the wall cavities dry. Whilst ventilation has been found to be successful in the control of moisture and condensation in rooms and larger enclosures, there is however insufficient understanding of how it works in thin spaces with high aspect ratios, such as the wall cavities studied in this thesis.In order to put in place good control and management practices in the remediation of moisture and condensation in vertical wall cavities by natural ventilation, it is vital to understand the dynamics of airflow in these cavities. In this thesis therefore, different size and shape of slots were employed to numerically investigate the effects of size, spacing and number of the slots on the characteristics of the velocity fields (patterns of airflow and distributions of velocity) in different cavity models. The Reynolds-Averaged-Navier-Stokes (RANS) methodology was employed to simulate the cavity flows under different modelling conditions using FLUENT. The BS 5925 model, an empirical relation for predicting ventilation rates in rooms and other larger enclosures, was employed and modified to predict ventilation rates in these cavities. Experimentally, the mapping of the airstreams in these cavities was obtained under similar reference (inlet) wind speeds employed for the numerical investigations.The results of this study show that there exists a potential at higher wind speeds for natural ventilation in the remediation of moisture and condensation in the cavities of vertical walls. The steady state approach employed in the RANS-based computation of cavity flows in this thesis averages out the peak values of air velocities and therefore gives no information about regions of maxima or minima velocity values even at higher wind speeds. This makes the predicted air change rates insensitive to the inlet air velocities from the ventilation slots and therefore makes the results more applicable for long term control and management of moisture in these cavities. In order to therefore put in place short, medium and long term plans for remediation of moisture in these wall cavities, a time-dependent computation is required. This will also allow the efficiency of the cavity ventilation to be properly assessed. Using the modified BS 5925 model, reasonable predictions were obtained for the air change rates of the wall cavities with the different size of ventilation slots employed. Close agreements are also obtained at lower and higher wind speeds between the predicted ventilation rates from the modified BS 5925 model and the experimental results employed as benchmark for validating the results.

Soil Water Balance (SWB), is a generic and mechanistic crop growth model that has been successfully used to model the water balance of several crops. Its ability to combine crop water modelling and irrigation scheduling approaches allows it to be used as a research tool and an irrigation management tool. Since SWB is a tool that could be used as decision making tool for farmers, its accuracy in simulating crop growth, development and soil water balance should be high. To highlight the importance of improved irrigation management for potato crop by the means of a mechanistic soil water balance model and the importance of the photoperiod factor in potato modelling in sub-tropical region, two potato experiments were carried out in two contrasting seasons, namely, spring and autumn. Growth and development responses of potato under both well irrigated and water stressed conditions for spring and autumn plantings were examined. This study successfully quantified the water use and potato growth responses to water stress. The water use efficiency varied with irrigation treatments and planting time, and autumn experiment had generally higher values than spring. Unstressed treatment gave the highest tuber yields irrespective of planting season and marketable tuber yield was higher in autumn than spring. Water stress imposed at tuber initiation until end of tuber bulking was revealed to be the most detrimental to biomass and tuber production. This suggests that water stress at tuber initiation and bulking stage should be avoided if high tuber yield is the target. Growth analysis data were used to determine crop parameters for SWB calibration and validation. The model simulated reasonably well growth, development and soil water balance in both unstressed and stressed conditions. However, simulations results of total and harvestable dry matter towards the end of the exponential tuber bulking stage (50 - 65 DAP) were deteriorated. As a result, the model did not simulate accurately the final yield. This is an indication that the model fails to simulate the size of the canopy and its duration. The time at which tuber initiation commences appeared not be affected by the planting seasons since variation of the duration between emergence and tuber initiation in different seasons was small. This small variation could be attributed to the fact that the potato growing season in South Africa (Pretoria) in spring 2004 and autumn 2005 experiences minimum and maximum temperatures which are acceptable for the growth of potato. In Pretoria, emergence and tuberisation take place under relatively cool temperatures late in September and also early in April when temperatures are relatively cool. Consequently, potato grown in this period may escape the early autumn and late spring high temperatures. However, autumn planting experiences an abrupt change of day lengths from long days to short days towards tuber initiation. This brusque change of day length may change the crop physiology and affect the subsequent normal course of plant growth. If the day length factor could be integrated into SWB, it appears that the model will better simulate potato growth and development. The poor simulation results of total dry matter and harvestable dry matter early in the growing season suggest that the model should be improved by allowing it to simulate the start of tuber initiation. A linear function of average temperature between a base and an optimal temperature corrected with photoperiod factor was found to be the most appropriate method to estimate thermal time required for tuber initiation. This method suggests that the time of tuber initiation can be estimated from its thermal time within two days. / Dissertation (MSc (Soil Science))--University of Pretoria, 2007. / Plant Production and Soil Science / MSc / unrestricted

In arid lands, a major contribution to water loss is by soil water evaporation. Desert sand dunes in arid regions are devoid of runoff and have high rates of infiltration. Rainwater is commonly stored within them because of the low permeability soils in the underlying desert pavement. In such cases, moisture is confined in the sand dune below a depth, termed as the “extinction depth”, where it is protected from evaporation during long dry periods. Moreover, desert sand dunes have sparse vegetation, which results in low transpiration losses from the stored water. The water accumulated below the extinction depth of the sand dunes can be utilized for various purposes such as in irrigation to support desert agriculture. In this study, field experiments were conducted in Western Saudi Arabia to monitor the soil moisture gradients and determine the diffusive extinction depth of dune sand. The dune sand was saturated with water and was exposed to natural conditions (evaporation and precipitation). The decline of the water level in the sand column was continuously recorded using transducers and sensors installed at different depths monitored the temporal variation of temperature and moisture content within the sand. The hydrological simulator HYDRUS-1D was used to construct the vertical profiles of soil water content and temperature and the results obtained from HYDRUS-1D were compared to the gradients monitored by the sensors.

Organic conducting polymer, poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS), is widely recognized for its electro-actuation mechanism and is used in flexible electronics. Its high potential as actuator is based on a strong coupling between chemical, mechanical and electrical properties which directly depends on external stimuli. There is no model today to describe the interplay between moisture absorption, mechanical expansion and electrical stimulus. Elucidating the role of each component in the effective actuation properties is needed to further optimize and tailor such materials. The objective of this thesis is to develop a macroscopic model to describe water sorption kinetics of the PEDOT:PSS film. We used gravimetric analysis of pure PEDOT:PSS film of three different thicknesses to investigate absorption kinetics over a broad range of temperatures and relative humidity. Our results revealed that the moisture uptake of PEDOT:PSS film does not follow Fickian diffusion law due to the retained amount of water after desorption process. We used an existing diffusionreaction model to describe this behavior, and COMSOL Multiphysics and MATLAB software programs to implement it. We observed that the generic model we used in our work could predict polymer behavior with 95% accuracy. However, our model was not able to properly represent the data at very high relative humidity at low temperature, which was attributed to the excessive swelling of the film. Also, we examined a relation between the moisture content of PEDOT:PSS and its mechanical strain and electrical conductivity. The results presented here are the first step towards a general multiphysics electro-thermo-mechanical description of PEDOT:PSS based actuators.

The thesis is focused on analysis of damage extent of dry floors in case of a flood. In the first part it deals with problems of buildings´ stress factors in the point of view of building physics, floor composition and its connection to constructions of timber houses. In the second part it describes testing of three experimental floor samples during simulated flood. It examines and evaluates the behavior and the way of spreading of the leaking water and the effect of moisture on the materials.

Please read the abstract in the section 00front of this document / Dissertation (M Inst Agrar (Horticulture Science))--University of Pretoria, 2000. / Plant Production and Soil Science / unrestricted