This thesis presents and demonstrates procedures to model and optimize the collector field of a parabolic trough solar thermal power plant. The collector field of such a plant is universally organized into parallel loops of solar collectors. Heat transfer fluid returning from the energy conversion plant is heated to a moderately high temperature in the field. Typically fluid enters a collector loop around 270 °C and leaves at 380 °C. The fluid is then returned to the plant to generate steam. In the first part of this thesis, the collector field and the energy conversion system of a typical parabolic trough solar thermal power plant are modeled. The model is compared with actual performance data and is enhanced and verified as necessary. Originally, the collectors in the plants under consideration were provided with evacuated tube receivers of the highest feasible efficiency without much regard for cost effectiveness. In practice, these receivers have failed at an unexpected rate and need replacement. It is unlikely that a very expensive evacuated tube receiver is now the most cost effective for every location in a collector loop. In particular, a receiver optimized for 270 °C operation may not be optimal at 380 °C. For example, a relatively inexpensive receiver with a flat black absorber and no vacuum may be more cost effective in the lower temperature segments of a loop. In the second part of this thesis, a procedure for the optimum deployment of collectors is developed and demonstrated. The results of this research should be directly applicable to the refurbishment and upgrading of several of the largest solar energy plants in the world.

Absolicon Solar Collector AB in Härnösand, Sweden, develops concentrating solar collectors with a parabolic trough. In the solar collector trough, there is thermal loss due to convection. A convection suppressor was made and used as a method to reduce thermal loss due to convection in the trough. The objective of the project was to evaluate the convection suppressor for solar collectors with a parabolic trough and its impact on the performance (thermal loss characteristics) in two different orientations of the trough, horizontal and inclined. The performance of the solar collector was first measured without the convection suppressor; these results were compared to two previous quasi-dynamical tests of the solar collector performance made by two different institutes, Research Institute of Sweden and SPF Institut für Solartechnik (Switzerland). The comparison was made to validate the test results from the tests without the convection suppressor, which matched. Secondly, when the convection suppressor was made and tested in the two different orientations, the results of the performance with and without the convection suppressor was evaluated as well as the convection suppressor itself. The results showed a significant improvement of the solar collector performance in the aspect of reduced thermal loss when the convection suppressor was used, hence higher efficiency. / Absolicon Solar Collector AB I Härnösand, Sverige, utvecklar koncentrerande solfångare med ett paraboliskt tråg. I solfångarens tråg uppstår termiska förluster som en följd av konvektion. En konvektionsreducerare tillverkades och användes som metod för att minska de termiska förlusterna i tråget. Målet med projektet var att testa och utvärdera konvektionsreduceraren för koncentrerande solfångare med ett paraboliskt tråg samt dess inverkan på verkningsgraden i två olika positioner för tråget, horisontell och lutande. För att kunna mäta konvektionsreducerarens inverkan på solfångaren mättes först solfångarens prestanda utan konvektionsreduceraren i de två olika positionerna, detta resultat användes som referens efter validering. Valideringen gjordes genom att resultatet jämfördes sedan med två andra prestandamätningar (quasi-dynamical test) av solfångaren gjorda av två olika institut, Research Institute of Sweden och SPF Institut für Solartechnik (Schweiz). Därefter, när konvektionsreduceraren var tillverkat och testad i de olika positionerna på samma sätt som mätningarna utan konvektionsreducerare, jämfördes resultaten med och utan konvektionsreducerareet samt att en utvärdering gjordes av dess inverkan. Resultatet visade en signifikant förbättring av solfångarens prestanda i form av minskade termiska förluster när konvektionsreduceraren användes och därav ökad verkningsgrad.

Round Island is a small (208 ha) islet of volcanic origin located 22.5 km north east of mainland Mauritius and has been classified as a nature reserve since 1957. Two sites were chosen for the installation of environmental monitoring equipment. A series of Gerlach troughs were installed to capture surface sediment transported by runoff, which were used to document sediment yields and determine the particle size distribution. Overall, rainfall and erosivity on Round Island is far less, when compared to mainland Mauritius. However, erosivity from Round Island (2,314.76 MJ.mm.ha-1.h-1.yr-1) is slightly above the global average of 2,190 MJ.mm.ha-1.h-1.yr-1. In terms of sediment transport, the annual sediment movement rates for Round Island were established during this study (0.1248 t.ha-1.yr-1) and were found to be considerably lower than Mauritius (10 t.ha-1.yr-1), as well as other tropical island such as Kauai (0.86 t.ha-1.yr-1) and O’ahu (0.6 t.ha-1.yr-1). Thus, although the estimated rates of soil erosion are very low for humid tropical regions, these rates only reflect the contemporary environmental conditions and cognisance of the landscape history should be incorporated into assessments of soil erosion / Geography / M. Sc. (Geography)

Revitalization generally are activities leading to the recovery of ecosystems in the landscape and their stabilization. In this thesis are proposed changes for revitalization of small agro-forestry basin stream called Branná significantly disrupted trough conditions, the banks and a river basin, including throughput migration of aquatic animals.

>Magister Scientiae - MSc / The aim of this study was to compare the trough plasma levels of Aspen-Vancomycin® (AV); and Sandoz-Vancocin CP® (SV) in premature infants with suspected Methicillin Resistant Staphylococcus aureus (MRSA) infection. The study was designed as a prospective, double blind, randomised trial involving male and female premature infants admitted in the Neonatal Intensive care Unit (NICU) at Netcare Blaauwberg and N1-city Hospitals for treatment of suspected MRSA-infection between April 2012 and June 2013. The inclusion criteria were: 29-35 weeks postmenstrual age (PMA), informed and written consent from parents of each premature infant enrolled in the study. Blood samples (0.3-0.4ml) were collected for renal function test and vancomycin trough levels determination. Blood samples for vancomycin trough level assay were collected thirty minutes prior to the administration of the third dose of vancomycin. Statistical analysis was performed and estimation was made giving an indication of how many infants will be needed to make the study statistically significant. Wilcoxon Two-Sample test was performed to determine the p-values and Spearman correlation coefficients were used to determine the correlation between trough levels and variables. P-values < 0.05 were considered significant. A total of 19 premature infants met with study criteria, 10 (5 females and 5 males) received AV and 9 (6 females and 3 males) receive d SV. There was no statistical significant difference between the demographic (GA, BW, PMA, PNA, weight at trial entry, height at trial entry) and biological (albumin, serum creatinine concentration and glomerular filtration rate) parameters of the premature infants in the AV and SV group. There were no statistical significant difference between trough level 1 of AV and SV, although trough level 1 had a lower trend in the SV group (p=0.118). No AV trough level 1 was below the minimum effective concentration (<5μg/ml). It was found that 30% of AV trough level 1 was within the therapeutic range (5-10μg/ml) and 70% of AV trough level 1, were above minimum toxic concentration (>10mg/l). It was found that 22.2% of SV trough level 1 was below minimum effective concentration, 44.4% of SV trough level 1 was within therapeutic range and 33.3% of trough level 1 was above minimum toxic concentration. No correlation was found between trough level 1 and the demographic and biological parameters of the premature infants in the AV group. SV had a positive correlation with GA, BBW, PMA and a negative correlation with PNA

The United Arab Emirates is a new country that has had little time to accumulate a scientific heritage. Meteorologically researched and documented weather material for forecasters is virtually non-existent and that available is fragmented and anecdotal. The thesis tackles this problem by identifying weather phenomena significant to aviation in the Emirates and particularly at Abu Dhabi International Airport (ADIA). Mechanisms responsible for their development are described and applicable forecasting rules and principles are derived. Surface and upper air observation data at ADIA from 1983 to 2002 were analysed to identify the weather phenomena, their associated weather systems and for statistical analyses. When relevant, observation data at Al Ain was also used. Post-processed numerical weather prediction Global Forecast Service Eta model data are used and when and where possible radar and satellite imagery. A secondary aim is to provide information of the general seasonal climate. This was achieved by means of a literature study of the dominating weather systems and the presentation of surface and upper air mean circulation charts. Fog is the most important weather phenomenon and serious disrupter of aviation at ADIA throughout the year. It does not occur during Shamal conditions, but fog can form well inland on the edge of the Empty Quarter at the Liwa Oasis when the Shamal wind becomes light. Contrary to local belief, fog is unlikely to occur on two, or more, consecutive nights. The Shamal can last for several days and disrupt helicopter flights to the oil rigs, while anabatic and katabatic effects often make it gustier and stronger inland at Al Ain than ADIA. While dust storms occur in strong southerly winds off the desert, the Shamal can bring dust from further afield from the north as can the previously unreported Nashi wind. The sea breeze can extend about 150 km inland to Al Ain and the Liwa Oasis. Thunderstorms associated with winter upper air troughs from the west, are the main producers of rain, while occasional thunderstorms off the Hajar Mountains in the east bring some rain in summer. Tropical depressions are a rare event. / Thesis (PhD)--University of Pretoria, 2010. / Geography, Geoinformatics and Meteorology / PhD / Unrestricted

The diploma thesis is focused on the design of an industrial planetary mixer with a volume of 40 liters. The goal is to create a design that takes account of ergonomics and design and technology requirements.

In Sweden, the residential and industrial energy demand is provided by a significant part of district heating. In a decarbonization plan to reduce the CO2 emissions, the integration of a large-scale solar system in the district heating can be a suitable option. The most used types of collectors are flat plate collectors (FPC), for which efficiency drops at high temperature levels. Parabolic through collectors (PTC) have seen increased interest in later years, due to their higher efficiency at higher temperature levels, which could improve system performance both energetically and economically. A hybrid concept using a combination of FPC and PTC for a solar thermal system has previously been studied for a solar district heating system in Denmark, with the aim to maximize the solar production by operating the solar collectors in the temperature ranges where they excel. The first aim of this thesis was to adapt the hybrid solar system in a district heating system for a Swedish case study and to evaluate if the hybrid optimization studied has similar positive effects in the overall thermal production of the system in Sweden, as it did in Denmark. The second aim of this thesis was to investigate the use of photovoltaic thermal collectors (PVT) instead of FPC for parts of the solar thermal system. With PVT, a single solar collector module allows for simultaneous production of heat and electricity and integration of photovoltaic thermal collectors in the solar assisted district heating could improve the overall performance of the system, both in terms of energy production and economical gain.The study was performed using the simulation tool TRNSYS based on a model developed in a danish case study. It was performed a parametric analysis on the percentage of share of the different types of solar collectors in the total area. The results given from the simulations have been used to carry out an economic evaluation based on the levelized cost of substituted energy, the annual operation and maintenance costs, and the marginal operational cost difference between a conventional district heating system supplied by a boiler only and a solar assisted district heating system. Based on the results found, it has been proved that a greater proportion of parabolic trough collectors in the solar field contribute to a greater production of thermal energy but also to higher expenses in the economy of the project. The best configuration which balanced these two factors was composed by 70 % of flat plate collectors and 30 % of parabolic trough collectors, based on the total area. The integration of photovoltaic thermal has been demonstrated to be not cost-effective for the studied location compared to the optimized ratio of FPC to PTC, mainly due to the high and uncertain price of the new technology. The use of photovoltaic thermal system is not yet widely developed in projects and there are only a few existing projects in operation today. In the future, the development of photovoltaic thermal in solar assisted district heating projects might have a higher realizable economic potential due to the industry learning curve, but more studies will need to be performed on this.

This thesis deals with the flood control. In particular, the design of a set of small water reservoirs with retention effect (polders) and their effect on flood flows. The work is divided into two parts, the first part refers to the bachelor thesis. In this thesis is description of the catchment, rainfall-runoff process and the evaluation of the ratio. That was got the necessary information for the design of polders. This is an abbreviated repetition of the contents of the thesis, which is a continuation of this work. The second part deals with the specific design of two reservoirs, including hydro calculations and drawings. For this work were used ArcGIS - ArcMap, Hydrog and to create drawings AutoCAD 2010.

This thesis deals with the solution of numerical modeling. Consequently problems associated with the flow of the water over spillway of the specific water structure. In this case numerical modeling means modeling of fluid movement, which is described by mathematical means. Especially nowadays, when a lot of spillways need to be recalculated, whether it meets the capacity demands, or there is no need to tackle reconstruction. With today's software capabilities there is a wide range of commercial and freeware resources. The numerical model, compared to physical model is less accurate which is, on the otherhand, physical model is usually financially and time-consuming. The following work simulates the behavior of water on the edge of the spillway, in the trough and then behind the trough. The result is a comparison of the water depth in the trough calculated by the numerical and the physical model.