Thesis (MScIng)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

The north and south polar layered deposits (NPLD and SPLD respectively) of Mars are 2 – 3 km thick and mostly ice, comprising nearly all of the known water reserves on Mars. They are commonly believed to hold a detailed record of recent (~10 – 100 Myr) climate within their layers. Dominating the surface of the NPLD, intriguing spiral depressions called troughs, exhibit a pinwheel appearance. In late 2006, the Shallow Radar (SHARAD) instrument began making observations. SHARAD can detect internal structure within the PLD, making observations that are impossible with instruments that only inspect the surface. SHARAD data reveals a unique stratigraphic record associated with trough formation and migration. The troughs did not exist during deposition of the first half of NPLD accumulation but initiated some 1000 m below the current surface and have migrated as much as 100 km northward. Three processes are responsible for this migration: wind transport, insolation induced sublimation, and atmospheric deposition. I synthesize work from ground penetrating radar, optical imagery, established analogs, and atmospheric modeling in order to derive a process model that describes trough formation and evolution, including migration. The NPLD spiral troughs belong to a larger classification of features called cyclic steps, which can exist in either erosional or depositional environments. On the SPLD, troughs and a variety of other features exist. While SPLD features are more complex than NPLD troughs, they exist due to the same three processes. / text

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves [71]-74). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves [71]-74). Also available on the Internet.

Thesis (Ph. D.)--University of Melbourne, 2002. / Title from PDF title page (viewed on May 6, 2005). Includes bibliographical references (p. 108-125).

A Tropical Temperate Trough (TTT) is a type of weather system that links the tropics and the extra-tropics across southern Africa. TTT events have been studied statistically in detail, but very little research has been done to study this phenomenon dynamically and especially on a seasonal scale. This study therefore focuses on the predictability of the characteristics of TTTs across southern Africa on a seasonal scale, by using a state-of-the-art seasonal forecasting model, namely the GloSea5 developed by the UK Met Office. Gridded hindcast data for the months of November, December, January and February from 1996/1997 to 2009/2010 are compared to observed data. The different ensemble members of the GloSea5 model (with lead-times of 1 week up to 2 months) are first compared separately to the observed data, after which the model average, with a 0-month, a 1-month and a 2-month lead-time, is calculated and also compared to the observed dataset. TTT events have distinctive characteristics during the formation and the development phases. Most prominent of these characteristics are the cloud bands associated with these weather systems, which have a north-west to south-east orientation and move from west to east across southern Africa. To identify the TTTs, daily outgoing long-wave radiation values are processed by a Meteorological Robot (MetBot), with a strict criterion to identify the cloud bands that characterise these systems. The MetBot’s algorithm produces the information needed to further investigate the different characteristics of TTTs, such as the frequency, the location and the intensity of these systems. Analysis of the MetBot output includes calculating the Root Mean Square Error, the percentage error and in some cases the percentage deviation of the number of cloud bands, as well as the anchor point, the centroid position, the area, the tilt and the minimum and maximum OLR values of the cloud bands. This investigation revealed that the characteristics of TTT events can to some extent be predicted on a seasonal scale for the summer rainfall season of southern Africa. The model used in this study fared particularly well with a 1-month lead-time forecast (compared to a 0-month and a 2-month lead-time forecast). The intensity and the location of the cloud bands associated with TTT events are forecast with a smaller percentage error than the frequency of these systems, as the frequency of TTTs tend to be significantly under-predicted by the model. For some predicted quantities, such as the area of the cloud bands, a bias-adjustment is necessary which produces significantly better results with smaller percentage errors. In the conclusions, suggestions are made on possible future studies, and how to develop this study further to create seasonal forecasts with higher skill with special regards to TTT events. / Dissertation (MSc)--University of Pretoria, 2019. / Geography, Geoinformatics and Meteorology / MSc / Unrestricted

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2005. / Parabolic trough solar collectors (PTSCs) constitute a proven source of thermal energy for industrial process heat and power generation, although their implementation has been strongly influenced by economics. In recent years, environmental concerns and other geopolitical factors have focused attention on renewable energy resources, improving the prospects for PTSC deployment. Further work is needed to improve system efficiencies and active areas of research include development of advanced heat collecting elements and working fluids, optimisation of collector structures, thermal storage and direct steam generation (DSG). A parabolic trough collector, similar in size to smaller-scale commercial modules, has been developed locally for use in an ongoing PTSC research programme. The aim of this study was to test and fully characterise the performance of the collector. Specialised logging software was developed to record test data and monitor PTSC performance in real-time. Two heat collecting elements were tested with the collector, one unshielded and the other with an evacuated glass cover. Testing was carried out according to the ASHRAE 93-1986 (RA 91) standard, yielding results for the thermal efficiency, collector acceptance angle, incidence angle modifier and collector time constant. Peak thermal efficiency was 55.2 % with the unshielded receiver and 53.8 % with the glass-shielded unit. The evacuated glass shield offered superior performance overall, reducing the receiver heat loss coefficient by 50.2 % at maximum test temperature. The collector time constant was less than 30 s for both receivers, indicating low thermal inertia. Thermal loss tests were conducted and performance of the trough’s tracking system was evaluated. The measured acceptance angles of 0.43° (unshielded) and 0.52° (shielded) both exceeded the tracking accuracy of the PTSC, ensuring that the collector operated within 2 % of its optimal efficiency at all times. Additionally, experimental results were compared with a finite-volume thermal model, which showed potential for predicting trough performance under forced convection conditions.

M.Sc. / Boreholes in the Kruger National Park (KNP) was at first developed to increase the number of animals that were at low densities because of poaching, diseases, fencing and low permanent water availability. This development of artificial waterholes without managerial measures or knowledge of possible consequence led to negative impacts on the environment. These included that the higher concentration of herbivores around artificial waterholes led to a change in vegetation; secondary vegetation growth did not support the feeding habits of water dependent species; the infiltration rate of water in the soil surrounding waterholes changed and animal distribution patterns also changed, in turn changing the predatory base. Due to the above the KNP developed a new water policy. The policy states that all artificial waterholes that are open should be part of natural ecosystem principles. This led to the closure of many artificial waterholes that did not conform to the requirements of the new water policy. This study aimed to determine the ecological implications of artificial waterholes and whether tourism will be affected by the closure of these artificial waterholes. The following two hypothesis were thus tested in this project: i) Artificial waterholes have ecological implications on the environment. ii) The closure of artificial waterholes will have a negative response from tourists and thus affect tourism to the KNP. The results from this project indicated that both these hypothesises can be accepted as the available literature clearly showed that artificial waterholes do have a negative impact on the environment and that the majority of the tourist questioned asked for the waterholes to be opened again. The latter reaction was mainly due to the tourist‟s concern that the animals will suffer and die without water. Furthermore the visitors are concerned they won‟t see animals anymore. This result can partly be due to the low awareness of the visitors on the subject. No effort was made to communicate these decisions, and the reasons it‟s based on, to the public. Although a certain number of artificial waterholes were closed according to the new KNP policy, it is still important to keep a number open due to fact that KNP is not a natural system. It is suggested however that the closure of the artificial waterholes take place differently, following a principle of rotational opening and closing of patches of waterholes to allow recovery of vegetation and facilitate migration between waterholes.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Sheldon Jeter; Committee Member: Sam Shelton; Committee Member: Srinivas Garimella

Submitted by Gabriela Lopes (gmachadolopesufpel@gmail.com) on 2017-07-05T14:11:03Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação Final.pdf: 2449316 bytes, checksum: 3ddf1827ab91a2c84692f64d9ae89d4b (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2017-07-11T20:58:59Z (GMT) No. of bitstreams: 2 Dissertação Final.pdf: 2449316 bytes, checksum: 3ddf1827ab91a2c84692f64d9ae89d4b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-07-11T20:58:59Z (GMT). No. of bitstreams: 2 Dissertação Final.pdf: 2449316 bytes, checksum: 3ddf1827ab91a2c84692f64d9ae89d4b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-03-21 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Os minitomates têm conquistado espaço no mercado devido a sua aptidão para o consumo in natura. No entanto, estudos acerca da melhor forma de condução das plantas, sistemas de cultivo, práticas de manejo e seus efeitos sobre a produtividade, necessidades climáticas, e normas de classificação dos frutos são assuntos a serem esclarecidos. A adoção de técnicas de cultivo de baixo custo e baixo impacto ambiental são preconizadas, e os sistemas de cultivo sem solo com recirculação da solução nutritiva drenada são os mais adequados. Diante disto dois experimentos foram conduzidos em estufa, no Campo Didático do Departamento de Fitotecnia, da Faculdade de Agronomia Eliseu Maciel, da Universidade Federal de Pelotas, nos anos de 2015 e 2016. O primeiro experimento teve como objetivos avaliar o crescimento, o comportamento produtivo e a qualidade de frutos de minitomates dos tipos Grape e Cereja cultivados em dois sistemas fechados de cultivo (vasos e calhas), em substrato de casca de arroz in natura sob diferentes intensidades de desfolha (sem desfolha, uma e duas folhas removidas por simpódio). Também foi realizada a classificação dos frutos por tamanho, empregando-se um grupo de cinco peneiras com perfurações específicas para cada cultivar. O segundo experimento objetivou definir a influência da temperatura e da radiação solar sobre o crescimento das plantas de minitomateiro em estufa em ciclo de outono-inverno, bem como, encontrar o menor valor de radiação solar em que houvesse acúmulo significativo de massa seca pelas plantas. A cultivar Cereja apresentou maior crescimento com acúmulo de massa seca total entre 958 e 1623 g planta-1 , produção entre 7 e 11 kg planta-1 , e tamanho médio de frutos entre 9,7 e 12,0 g. A cultivar Grape acumulou entre 728 e 1015 g planta-1 de massa seca total, teve produção entre 4,62 e 5,84 kg planta-1 , e entre 6 e 7 g fruto-1 de peso médio. Os valores variaram conforme o nível de desfolha. A cultivar Grape apresenta frutos com maior concentração de açúcares, e a retirada de uma folha do simpódio não afeta as respostas produtivas. Entretanto, para cultivar Cereja é necessária a manutenção do simpódio completo. O sistema de cultivo em calhas melhora o crescimento e eleva as respostas produtivas, enquanto que o sistema de vasos aumenta a concentração de açúcares dos frutos. A desfolha diminui a quantidade de frutos classificados como grandes para ambas as cultivares. O sistema de calhas favorece a produção de frutos da cultivar Grape classificados como grandes. As peneiras 1, 2 e 3 são adequadas para a classificação de frutos. É possível classificar frutos de minitomates com o uso de peneiras específicas para cada tipo de fruto. As cultivares apresentam respostas semelhantes à variação da radiação solar e da temperatura. Porém, a cultivar Cereja apresenta maior área foliar e crescimento. A temperatura apresenta influência indireta sobre o metabolismo das plantas, enquanto a radiação solar exerce influência direta sobre todas as variáveis de crescimento. O limiar de radiação solar para as cultivares Cereja e Grape de minitomateiro é de aproximadamente 3,63 MJ m-2 d-1. / Mini tomatoes have gained space in the market due to their flavor for in natura consumption. However, studies on the best way of conducting plants, cropping systems, management practices and their effects on yield, climatic requirements, and fruit grading standards are matters to be clarified. The adoptions of low cost and low environmental impact techniques are recommended, and soilless cropping systems with recirculation of the nutrient solution drained are the most appropriate. Before this, two experiments were conducted in greenhouse, at the Campo Didático do Departamento de Fitotecnia, of Faculdade de Agronomia Eliseu Maciel, in Universidade Federal de Pelotas during 2015 and 2016. The first experiment had as objectives to evaluate the growth, productive behavior and fruit quality of Grape and Cherry mini tomatoes cultivated in two closed growing systems (pots and troughs), in substrate of raw rice husk under different intensities of defoliation (without defoliation, removal of one and two leaves of the sympodium). The classification of fruits by size was also performed, using a group of five sieves with specific drilling for each cultivar. The second experiment aimed to define the influence of temperature and solar radiation on the growth of mini tomato plants in a greenhouse in autumn-winter cycle, as well as to find the lowest value of solar radiation in which there is a significant accumulation of dry matter by the plants. Cherry cultivar presented the highest growth with total dry matter accumulation between 958 and 1623 g plant-1 , production between 7 and 11 kg plant-1 , and mean fruit size between 9.7 and 12.0 g. Grape cultivar accumulated between 728 and 1015 g plant-1 of total dry matter, had production between 4.62 and 5.84 kg plant-1 , and between 6 and 7 g fruit-1 of mean weight. Values varied according to the level of defoliation. Grape cultivar presented fruits with higher sugar concentration, and the removal of one leaf of the sympodium did not affect the productive responses. However, for Cherry cultivar it is necessary to maintain the complete sympodium. The troughs system improved growth and increased productive responses, while the pots growing system increased the sugar concentration of the fruits. Defoliation decreases the amount of fruits grading as large for both cultivars. Troughs system favored the production of Grape cultivars grading as large. Sieves 1, 2 and 3 are suitable for the grading of fruits. It is possible to grading fruits of mini tomatoes with the use of specific sieves for each type of fruit. Cultivars presented responses similar to the variation of solar radiation and temperature. However, Cherry cultivar presented greater leaf area and growth. The temperature had an indirect influence on the plant metabolism, while the solar radiation exerted a direct influence on all the growth variables. The solar radiation threshold for cultivars Cherry and Grape of mini tomato plant is around 3.63 MJ m-2 d-1.